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Eucalyptus-based materials as adsorbents for heavy metals and dyes removal from (waste)waters
Abstract
Eucalyptus is the most widely planted type of hardwood trees. It considers as a cheap, renewable, and ecofriendly biomass source for the production of high value materials. In this context, Eucalyptus-based adsorbents in raw, modified, and carbonaceous forms have been efficiently applied to remove a variety of toxic and carcinogenic aquatic pollutants. This article provides a comprehensive review on the application of Eucalyptus-based adsorbents for the removal of heavy metal and dye pollutants from waste(water). The use of Eucalyptus residues such as bark, leaves, wood or sawdust, and seeds to prepare adsorbents is considered. The performance of Eucalyptus-based adsorbents towards the tested pollutants, as well as their reuse after regeneration is discussed. Furthermore, the adsorption isotherms, kinetics, thermodynamics, and mechanisms are also considered. Finally, the findings and future prospects for the Eucalyptus- based materials and their use as adsorbents for water treatment are presented.
... Biaya penggunaan karbon aktif yang mahal serta sulitnya proses regenerasi maka pada beberapa penelitian terdahulu memanfaatkan bahan yang lebih murah sebagai alternatif baru bahan pembuatan adsorben 8 . Mereka menggunakan bahan murah tersebut secara langsung atau dimodifikasi dengan larutan kimia maupun aktivasi secara termal untuk membuat alternatif karbon aktif 9 . Beberapa bahan murah diambil dari bahan limbah pertanian, limbah industri, maupun bahan alam (bentonite, clay). ...
... Beberapa bahan dari limbah tersebut dianggap ideal untuk diproduksi sebagai adsorben 9 . Adsorben dapat dikatakan baik apabila memiliki sifat struktur permukaan yang stabil pada bahan kimia 11 . ...
Latar belakang: Penggunaan adsorben bahan limbah dari limbah pertanian, industri maupun bahan alam menjadi alternatif baru dalam pengolahan air limbah yang mengandung zat warna. Limbah ini dapat menyebabkan berbagai masalah kesehatan bagi makhluk hidup mulai dari alergi, cidera permanen, asma, bahkan kanker. Tujuan review artikel ini adalah untuk memberikan informasi tren penelitian penggunaan adsorben dari bahan limbah dalam penyisihan zat warna serta informasi mengenai komposisi bahan, dan pengaplikasiannya sebagai potensi alternatif baru bahan adsorben dalam pengolahan limbah.Metode: Metode dalam penulisan review artikel ini dengan metode PRISMA 2020 menggunakan PRISMA checklist melalui 27 identifikator yang telah disediakan. Seleksi artikel dilakukan dengan beberapa kriteria dari tahun publikasi, kata kunci, klasifikasi bahan adsorben, serta artikel tentang adsorpsi secara umum sebagai pendukung. Artikel jurnal terpilih dan sesuai dengan kebutuhan sebanyak 28 artikel kemudian dilakukan pengkajian serta pembahasan lebih lanjut.Hasil: Hasil review artikel yang dikaji sebanyak 50% artikel yang memanfaatkan limbah pertanian sebagai adsorben, 18% artikel memanfaatkan limbah industri, dan 32% artikel memanfaatkan bahan alam. Pengkajian dilakukan menyeluruh mengenai metode pembuatan adsorben, komposisi bahan adsorben, kemampuan adsorpsi, studi kinetika dan studi isotherm adsorpsi. Hasil kajian menunjukkan kemampuan adsorben bahan limbah sangat baik dengan efisiensi tertinggi hingga 99,95%. Metode pembuatan adsorben yang paling umum digunakan dengan aktivasi fisika. Model isotherm yang digunakan sebagian besar adalah Langmuir dengan kinetika adsorpsi pseudo orde kedua.Simpulan: Potensi pemanfaatan adsorben dari bahan limbah sangat besar, ditinjau dari persentase efisiensinya dan kelimpahan bahan baku. Dalam proses adsorpsinya dipengaruhi oleh kandungan bahan, luas permukaan, dan metode pembuatan adsorben. ABSTRACT Title: Literature Review: The Use of Waste Materials as Adsorbent for Degradation Dyes in WastewaterBackground: Industrial, agricultural, and natural dyes can now be treated with adsorbents. This wastewater can cause allergies, serious wounds, asthma, and cancer. This article review discusses current research trends in using waste materials as dye removal adsorbents and their composition and possible usage as new, alternative adsorbents in the waste treatment sector.Method: This article review used PRISMA 2020 with 27 identifiers and the checklist. Articles were selected by year, keywords, adsorbent material categorization, and adsorption in general. Following 28 article requirements, selected journal articles were researched and discussed.Result: The analysis of the articles found that 32% of the articles used natural materials, 18% of the articles used industrial waste, and 50% of the articles used agricultural waste as an adsorbent. The process for creating adsorbents, the make-up of adsorbent materials, adsorption capacity, kinetic studies, and adsorption isotherm studies were all thoroughly evaluated. The study's findings demonstrate that waste materials have excellent adsorbent properties, with the highest efficiency reaching up to 99.95%. Physical activation is the most widely used adsorbent preparation technique. Most of the isotherm models in use have pseudo-second order adsorption kinetics and are Langmuir.Conclusion: Given the percentage of efficiency and the abundance of raw materials, there is a very large potential for using adsorbents made from waste materials. The adsorbent's surface area, material composition, and manufacturing process all have an impact on the adsorption process.
... According to the World Health Organization (WHO), over five hundred million people have been infected, with over six million deaths since the beginning of the COVID-19 pandemic in 2019 [6]. Notably, during the pandemic, many countries like India, France, and Brazil started randomly testing several possible new treatments, including chloroquine (CQN), due to its probable benefits in controlling the disease according to early studies, later proved to be ineffective for the prophylactic treatment of COVID- 19. ...
... Amongst remediation technologies, adsorption has been widely proposed due to the low initial cost of implementation, high efficiency, and simple operational design. Therefore, the search for highly efficient, safe, and economically viable adsorbents has intensified [17][18][19][20][21]. ...
This study aimed at emerging contaminant chloroquine (CQN) removal, widely used in the COVID-19 pandemic through adsorption and employing a low-cost activated biochar from açai fruit endocarp. Two different adsorbents from the same precursor were applied. The first (CAA) was activated at a high temperature using ZnCl2, and the second (CA) was obtained by physical activation. The adsorbents were characterized through BET, FTIR, DRX, TG/DTG, and SEM. The results showed that zinc chloride activation furnished a material with a high specific surface area (SBET) and pore volume of 762 m² g⁻¹ and 0.098 cm³ g⁻¹, respectively. Adsorption kinetics and isotherm were best adjusted through the pseudo-second-order (PSO) and Freundlich for both biochars. The process was thermodynamically favorable, occurring spontaneously without energy request. Additionally, the maximum adsorption capacity for CQN was 15.56 and 40.31 mg g⁻¹ for CA and CAA, respectively, in pH 6.84, at a temperature of 25 °C, 50 mL solution and with 0.05 and 0.02 g of adsorbent. Those results are congruent with the literature showing the versatility of the material and the efficiency of the applied adsorption process.
... In general, the application of available and renewable wastes in the field of adsorption has environmental and economic benefits. In this regard, agricultural wastes gain great importance due to their large availability, low cost, and renewable property [6]. These wastes are basically consisted of lignocellulosic structure with a variety of functional groups which have ability to attract aquatic contaminants through different interaction mechanisms [7]. ...
... Corn wastes-based materials were extensively addressed in the literature as highly efficient adsorbents for aquatic contaminants. Nevertheless, some points are still not considered like (1) optimizing the preparation conditions of corn wastes-based adsorbents, (2) carrying out more studies about anionic and reactive dyes, iron, arsenic, and silver metal ions, fluorides, oils, sulfate, perchlorate, iodate, etc., (3) exploring the dependence of adsorption performance on agitating speed and particle size of adsorbent, (4) performing adsorption experiment in more realistic conditions, including column studies, multi-component systems, and real wastewater, and (5) testing the regeneration performance of adsorbents in fixed-bed units, (6) considering the cost analysis and the disposal of the pollutant-loaded waste, as produced from adsorption for sustainability and environmental point issues of the production and application of these adsorbents, and (7) adopting blends of corn wastes and other materials such as sewage sludge, plastic, coal, etc. as synergetic precursors for adsorbents. ...
Adsorption is a low-cost, efficient and flexible method that can be applied to decontaminate polluted (waste)water. Among other materials, agricultural biomass/waste can be satisfactorily used in raw or modified form as adsorbent for the aforementioned purpose. Corn (Zea mays L.) is the most significant grain crop worldwide after wheat and rice. It is widely cultivated and consumed as food, feed, and industrial raw material, along with the release of a large quantity of corn wastes. Such abundant, renewable, and cheap wastes with unique chemical compositions can be efficiently converted into adsorbents for various aquatic contaminants thus supporting the concept of circular economy and green chemistry. This article represents an extensive review on the use of corn biomass/waste to produce adsorbents (raw, chemically modified, carbonaceous, and composites) for the elimination of metal ions, dyes, pharmaceuticals, pesticides, inorganic ions, phenols and other contaminants. The maximum adsorption capacities for most studied pollutants were 227.27 and 158.7 mg/g for chromium and cadmium, 1301.10 and 512.80 mg/g for methylene blue and malachite green, and 612.38, 201.56, 102.041, and 221.89 mg/g for tetracycline, atrazine, nitrate, and phosphate, respectively. The adsorption behavior, mechanism, and regeneration of the studied adsorbate/adsorbent systems are identified. Special emphasis is also given to other adsorption parameters (pH, adsorbent dose, initial concentration, temperature, etc.). Isotherm, kinetic and thermodynamic studies are also discussed in detail. Important findings and future ideas are finally mentioned.
... Eggs are one of the most important Food incomes in the framework of world-wide feeding, they are important as a source of vital nutrients to human food such as Proteins, fatsoluble vitamins (A, D, E and K) and trace-minerals like iron and zinc [12]. The shell of the hen egg formed from ceramic molecules that have threelayered structure, called cuticle on the outer shell surface, a spongy or (calcareous) layer and an inner mammillary layer [13]. ...
... The outer surface is covered with Mucin protein that considered as a soluble plug for the holes in the shell, also the cuticle is permeable. The percentage (by weight) of the by-product eggshell's chemical components was MgCO3 (1%), Ca3(PO4)2 (1%), Organic Material (4%) and CaCO3 (94%) [13]. The eggshell by-product is about 11% of the egg's whole weight (60g) [16]. ...
... The transformation of residual biomass, such as edible fruit residues, into activated carbons, has been constantly used as adsorbents, as they have favorable properties, such as large pore volume and high surface area, in addition to enabling the conversion of these residues into sustainable sources for the removal of emerging pollutants [11,12]. Among the residues used as adsorbents in the removal of emerging pollutants are: avocado seeds [13], rice and coffee husk wastes [14], Elm tree sawdust [15], corn cob [16], Butia capitata endocarp [17], peanut husk [18,19], waste murumuru [20], mangosteen peel waste [21], coconut Shell [22], agriculture waste [23][24][25][26], fruit shells [27]), Moringa oleifera leaf [28], malt bagasse [29], pumpkin seed Shell [30], eucalyptus residue [31], banana tree pseudo-stem fibers [32], pecan nutshell and palm cactus [33], seeds powder [34], pine [35], Luffa biomass [36], and eucalyptus residue [25]. ...
... The transformation of residual biomass, such as edible fruit residues, into activated carbons, has been constantly used as adsorbents, as they have favorable properties, such as large pore volume and high surface area, in addition to enabling the conversion of these residues into sustainable sources for the removal of emerging pollutants [11,12]. Among the residues used as adsorbents in the removal of emerging pollutants are: avocado seeds [13], rice and coffee husk wastes [14], Elm tree sawdust [15], corn cob [16], Butia capitata endocarp [17], peanut husk [18,19], waste murumuru [20], mangosteen peel waste [21], coconut Shell [22], agriculture waste [23][24][25][26], fruit shells [27]), Moringa oleifera leaf [28], malt bagasse [29], pumpkin seed Shell [30], eucalyptus residue [31], banana tree pseudo-stem fibers [32], pecan nutshell and palm cactus [33], seeds powder [34], pine [35], Luffa biomass [36], and eucalyptus residue [25]. ...
In this work, physical statistical models were employed to provide reasonable information regarding the adsorption of naproxen onto different activated carbons. The activated carbons were prepared from different biomasses (pitaya peels, jabuticaba peels, or grape residues from the winery process) using ZnCl2 as an activator. All the adsorbents were characterized regarding their functional groups and morphological surfaces. The maximum capacity obtained for the activated carbons (at 328 K) was found to be: 167.0 mg g⁻¹ for jabuticaba peels at pH 4; 158.81 mg g⁻¹ for pitaya peels at pH 6.7; and last., grape residues the capacity was 176.0 mg g⁻¹ at pH 7. The equilibrium data of the three adsorbents were well fitted to the monolayer with two energy sites adsorption model, assuming that NPX adsorption on the carbon surfaces occurs via two different functional groups. This statistical physics model calculated the number of NPX molecules bound on the surface and the saturated adsorption capacity for both functional groups at different temperatures. The obtained results indicate that the naproxen molecules can be adsorbed in a parallel and horizontal manner according to the material employed. The receptor density tends to increase with the temperature evolution, indicating that thermal energy and solubility play an important role in adsorption. Configurational entropy indicates similar thermodynamic behavior for all materials where higher disorder is found at the early stages of the adsorption, followed by and decrease a possible organization of the molecules on the surface. The Gibbs free energy shows that adsorption of naproxen is spontaneous in all cases and internal energy is proportional to the adsorption capacity indicating that the system releases energy as the adsorption occurs. Therefore, this article reports new findings to understand the adsorption mechanism of naproxen molecules on activated carbons prepared from lignocellulosic biomass.
... A thorough analysis of the effectiveness of several natural materials derived from plants in eliminating heavy metals from tainted water sources has been performed. These include orange peel [27,28], wheat-based materials [29,30], brown algae [31], eucalyptus bark [32,33], sugar beet pulp [34], olive stone [35,36], and papaya seed [37,38]. The bio-adsorbent potential of these materials in addressing heavy metal-induced water contamination has been the subject of extensive investigation. ...
... Eucalyptus is the most extensively planted hardwood tree species. The biomass it generates is used to synthesize porous activated carbon material for dye eviction from wastewater [30]. Apart from the above application, several research groups mentioned later illustrated the application of the biomass derived from eucalyptus to prepare and fabricate metal nanoparticles. ...
Competent treatment techniques were explored to curb the environmental pollution of dye-laden wastewater. In the current study, eucalyptus biomass contemplated as agricultural waste is translated into eucalyptus graphitic activated carbon (EPGAC) using ZnCl2 at 600 °C in the N2 atmosphere. The present investigation illustrated awareness about the nature of EPGAC’s dye elimination by employing Direct Yellow 12 dye (DY12) as a model dye. EPGAC was characterized using multiple characterization tools such as Fourier transform infrared spectroscopy (FTIR), Boehm titrations, pHzpc, X-ray diffraction (XRD), Raman, field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDX), high-resolution transmission electron microscopy (HRTEM), and Brunauer-Emmett-Teller (BET) surface area analysis techniques. Electron micrographs disclosed the availability of high pore density for the adsorption of DY12 dyes. BJH analysis reported the distribution of mesopores having a 3 nm diameter on the EPGAC surface. Further, the surface area available for adsorption per gram of the adsorbent is estimated as 178.35 m² employing BET analysis. XRD and Raman’s data revealed the graphitic nature of EPGAC. Influences of adsorbent parameters such as EPGAC mass, initial dye concentration, contact time, solution pH, and temperature on the eviction of DY12 by EPGAC were examined to achieve a deeper insight into the adsorption mechanism. The optimum EPGAC adsorbent dose was found to be 0.15 g. The equilibrium was attained at 120 min for DY12 dye. Pseudo-second-order kinetics entirely relates to the perfect fit associated with the investigational results. The aptness of the equilibrium data relevant to the Langmuir adsorption isotherm eventually recommends a maximum unilayer adsorption capacity of 42.01 mg/g for EPGAC. Thermodynamic studies further reveal the spontaneous, endothermic, and chemisorption nature of adsorption. Adsorbent viability was established through stability and recyclability studies carried out up to 5 run cycles with 0.15 g of EPGAC. Adsorption mechanisms were explained considering hydrogen bonding, π-π interactions, and electrostatic interactions, ultimately confirming the adsorption tendency displayed by EPGAC for the eviction of DY12 dye present in industrial wastewater.
... The need for effective and affordable technologies has driven ongoing research efforts in water purification. Among the various purification methods, adsorption emerges as a physicochemical separation technique that is both environmentally friendly and highly effective for treating contaminated water [13,14]. This method effectively removes toxic pollutants at low concentrations while remaining economically feasible and producing minimal secondary waste [15]. ...
The presence of organic dyes and heavy metal ions in water sources poses a significant threat to human health and the ecosystem. In this study, hydrogel adsorbents for water pollution remediation were synthesized using Guipi residue (GP), a cellulose material from Chinese herbal medicine, and chitosan (CTS) through radical polymerization with acrylamide (AM) and acrylic acid (AA). The characteristics of the hydrogels were analyzed from a physicochemical perspective, and their ability to adsorb was tested using model pollutants such as Pb2+, Cd2+, Rhodamine B (RhB), and methyl orange (MO). The outcomes revealed that GP/CTS/AA-co-AM, which has improved mechanical attributes, effectively eliminated these pollutants. At a pH of 4.0, a contact duration of 120 min, and an initial concentration of 600 mg/L for Pb2+ and 500 mg/L for Cd2+, the highest adsorption capabilities were 314.6 mg/g for Pb2+ and 289.1 mg/g for Cd2+. Regarding the dyes, the GP/CTS/AA-co-AM hydrogel displayed adsorption capacities of 106.4 mg/g for RhB and 94.8 mg/g for MO, maintaining a stable adsorption capacity at different pHs. Compared with other competitive pollutants, GP/CTS/AA-co-AM demonstrated a higher absorption capability, mainly targeted toward Pb2+. The adsorption processes for the pollutants conformed to pseudo-second-order kinetics models and adhered to the Langmuir models. Even after undergoing five consecutive adsorption and desorption cycles, the adsorption capacities for heavy metals and dyes remained above 70% and 80%. In summary, this study effectively suggested the potential of the innovative GP/CTS/AA-co-AM hydrogel as a practical and feasible approach for eliminating heavy metals and dyes from water solutions.
... Moreover, the utilization of such wastes in the adsorption field has many advantages in terms of producing cost-effective adsorbents relative to expensive commercial adsorbents like activated carbon and also solving the problem of agricultural waste disposal (Tokula et al., 2023). Many reviews have considered the utilization of agro-wastes such as bamboo (Kalderis et al., 2023), rice husk (Shamsollahi and Partovinia, 2019), corn (Ahmed et al., 2023), eucalyptus (Anastopoulos et al., 2022), peanut husk (Aryee et al., 2021), walnut shell (Albatrni et al., 2022), rice straw (Foong et al., 2022), banana waste (Ahmad and Danish, 2018), and coconut residues (Ighalo et al., 2023;Khan et al., 2023;James and Yadav, 2021) as precursors for adsorbents. ...
Wheat is a major grain crop of the world that provides a stable food for human consumption. Large amounts of by-products /waste materials are produced after the harvesting and processing of wheat crop. Such materials can cause an environmental issue if not disposed of properly. Several studies have shown that wheat residues can be efficient precursors for adsorbents because of their availability, renewability, lignocellulosic composition, and surface active groups enriched structure. In the literature, there are few review articles that address wheat residues-based adsorbents. However, these reviews were specific in terms of adsorbate or adsorbent and did not provide detailed information about the modification, properties, and regeneration of these adsorbents. This article extensively reviews the utilization of wheat biomass/waste including straw, bran, husk, and stalk as precursors for raw or untreated, chemically treated, carbonaceous, and composite adsorbents against various environmental pollutants. The influences of inlet pollutant amount, adsorbent dose, pH, temperature, and time on the performance of adsorbents against pollutants were considered. The maximum uptakes, equilibrium time, and adsorption nature were identified from isotherms, kinetic, and thermodynamic studies. The highest adsorbed amounts of most tested contaminants were 448.20, 322.58, and 578.13 mg/g for lead, chromium, and copper, 1374.6 and 1449.4 mg/g for methylene blue and malachite green, and 854.75, 179.21, and 107.77 mg/g for tetracycline, phosphate, and nitrate, respectively. For the studied adsorbate/adsorbent systems the adsorption mechanism and regeneration were also discussed. Significant results and future directions are finally presented.
... [49] In general, as the pH of a solution increases, cation adsorption increases. [50] The pore volume of the adsorbent, surface area, and the particle size, have large impact on the adsorption. [51] Adsorption removal depends on number of parameters as given in Figure 8. [36] There are variety of adsorbents for the removal of HMs as given below. ...
Because of the growing population and the industrial revolution, a significant number of toxic materials including heavy metals (HMs) are being released into the environment, posing harm to humans, the environment, and other living organisms. When these HMs find their way into water sources, they cause water pollution and pose a threat to the ecosystem. As a result, there is an imperative need to eliminate these HMs from the water. Numerous techniques are being employed for water purification, but adsorption is the most economical and efficient method. The present article critically discussed the applications of different adsorbents including agricultural wastes, industrial wastes, biochar, chitosan, aerogel‐based adsorbents, geopolymer cement/concrete, carbon‐based nanomaterials (NMs), and polymer‐supported nanocomposites (NCs) for removal of HMs from wastewater. Removal capacity of some of the adsorbents are tabulated. Effects of dose of adsorbent, contact time, pH, temperature, initial ion concentration and ionic strength on the removal of HMs from water have been explored. Various adsorption isotherm and kinetic models have also been discussed, including the modeling using artificial neural networks.
... The structure of these wastes poses favorable lignocellulose content with high surface functionality which enables them to interact with pollutant molecules through a variety of mechanisms (Bhatnagar et al., 2015). In this regard, many review articles have addressed the utilization of various biomasses such as coconut Khan et al., 2023;Ighalo et al., 2023), oil palm (Ayob et al., 2021), date seeds (Nouri, 2023;Al-Zahrani et al., 2022), luffa cylindrica (Anastopoulos and Pashalidis, 2020), apple wood (Mahajan et al., 2023), plant bark (Ighalo and Adeniyi, 2020), bamboo (Kalderis et al., 2023), eucalyptus (Anastopoulos et al., 2022), corn (Ahmed et al., 2023), rice waste (Foong et al., 2022;Goodman, 2020), agricultural shell (Nayagam and Prasanna, 2022), and coffee husk (Castillo et al., 2021) as raw materials to prepare effective adsorbents for different aquatic contaminants. ...
Tobacco (Nicotiana tabacum L.) is a significant crop widely planted worldwide. Its leaves have a special economical value as raw materials for the cigarette industry. During tobacco harvesting and cigarette production, a large amount of wastes that could not be used in the cigarette industry are generated such as tobacco stems, stalks, and low-grade leaves. The utilization of such agro-industrial wastes in raw or carbonaceous form as adsorbents for wastewater treatment is an economic and eco-friendly step for elimination of such waste. Tobacco waste can be directly applied as adsorbents for aquatic pollutants owing to its favorable lignocellulosic composition and functional groups enriched structure. Moreover, this waste has high volatile matters and thus can be an efficient precursor for high surface area carbonaceous adsorbents including biochar and activated carbon with high removal performance. This article is a recent and comprehensive review about the preparation of adsorbents (raw, biochar and activated carbon) from different tobacco wastes (stems, stalks, leaves, etc.) along with its characterization and regeneration. The adsorption behavior of different aquatic adsorbates on these adsorbents under specific conditions along with the isotherm, kinetic, thermodynamic, and mechanism studies is also considered. The highest uptakes for most tested pollutants were 399.0, 195.2, and 173.0 mg/g for lead, chromium, and cadmium, 517.5 mg/g for methylene blue, and 210.66 and 1.602 mg/g for phosphate and chlorpyrifos. Significant findings and future ideas for the studied adsorbate/adsorbent systems are finally given.
... These materials should be ample, non-toxic, derived from renewable sources, and possess the potential for reuse. Noteworthy is eucalyptus, a prevalent hardwood tree that holds substantial economic value, robust survival rates, and extensive cultivation, making it a cost-effective, renewable, and environmentally benign biomass source and in line with the goals of sustainable development with regard to environmental protection and pollution reduction (Anastopoulos et al., 2022). Yusuff et al. (2022) used eucalyptus bark as a precursor, transforming it into activated biochar through pyrolysis-chemical activation. ...
... Eucalyptus residues, like sawdust, bark, leaves, and seeds, have shown to be a promising alternative for the development of low-cost, sustainable, eco-friendly, and excellent efficiency adsorbents [27]. Notoriously, eucalyptus sawdust, which is a by-product that is difficult to management and dispose in the wood industry, especially because a large volume is generated, making it an environmental liability. ...
In the present study, a new application was proposed for the eucalyptus sawdust waste, which is an environmental passive. Three adsorbent materials composed of chitosan (CS), sawdust (CSW), and magnetic beads (CSWF) were developed and used for the Direct Violet-51 remediation. The adsorption testes were optimized based on the variation of the adsorption parameters: (i) pH (2−12), (ii) contact time (5–60 min), (iii) initial dye concentration (10–60 mg L−1), (iv) adsorbent mass (10–100 mg) in 10 mL. The optimized conditions of the adsorption essays showed that the three synthesized adsorbents completely removed the dye from the aqueous medium, but under different experimental conditions. As the main findings in this study, we can highlight the excellent performance of CSW adsorbent material, which promoted maximum removal efficiency of Direct Violet-51 at neutral pH, which is of great importance for the industrial processes. On the other hand, CS and CSWF adsorbent materials exhibited a maximum adsorption efficiency at pH 2. Furthermore, the adsorbent materials were applied in the dye remediation in environmental water samples from the tap water, Marcela dam, and Poxim River, they did not suffer any major matrix interference, whose removal efficiency values varied between 99.8 and 100, 70.7–100, and 98.8–99.5 % for the CS, CSW, and CSWF, respectively. Finally, besides being materials produced from the waste, they can be reused more times, fitting into the concept of circular economy.
... Plant leaves are one of the inexpensive tree biomass materials widely used to remove pollutants from aquatic environments. The reviews [8][9][10][11] provide information on the use of tree leaves as adsorbents of various pollutants from aqueous environments. One of the most widespread tree species in the world are Acacia trees. ...
Isotherms of Zn²⁺ ions adsorption by native and 3% H2SO4 solution-treated leaves of Acacia auriculiformis were plotted. The resulting adsorption isotherms were processed using the Langmuir, Freundlich, Dubinin-Radushkevich and Temkin models. It was found that the isotherms of these Zn²⁺ ions adsorption with native leaves of earleaf acacia are most accurately described by the Temkin model and with modified leaves by the Langmuir model. It was found that the modification of acacia leaves with a 3% H2SO4 solution contributes to an increase in the maximum sorption capacity for Zn²⁺ ions from 9.5 mg/g to 30.5 mg/g. It was found that the kinetics of Zn²⁺ ions adsorption by native and modified Acacia auriculiformis leaves is most accurately described by a pseudo-second order model. The calculated values of the Biot's coefficient are in the range of 1 < Bi < 20, which indicates mixed diffusion in all cases. Thermodynamic parameters of the process of Zn²⁺ ions adsorption by native and acid-modified Acacia auriculiformis leaves were determined. The calculated adsorption (E) and Gibbs (∆G⁰) energies, as well as enthalpy and entropy indicate spontaneous, self-induced endothermic physical adsorption process in both cases.
... There is cause for concern regarding the release of toxic metals into water bodies. Metal ions, for example, Pb(II), Cr(III), Hg(II), Cd(II), Zn(II), Co(II), and Ni(II) are known to be poisonous when they discharged into the environment in amounts that pose significant human health risks [4][5][6]. These metals frequently accumulate in various organs and tissues of living things, causing a variety of impairments and diseases. ...
In the water purification field, heavy metal pollution is a problem that causes severe risk aversion. This study aimed to examine the disposal of cadmium and copper ions from aqueous solutions by a novel Fe 3 O 4 /analcime nanocomposite. A field emission scanning electron microscope (FE-SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction were used to characterize the synthesized products. The FE-SEM images showed that the analcime and Fe 3 O 4 samples consist of polyhedral and quasi-spherical shapes with average diameters of 923.28 and 28.57 nm, respectively. Besides, the Fe 3 O 4 /analcime nanocomposite consists of polyhedral and quasi-spherical shapes with average diameters of 1100.00 nm. The greatest uptake capability of the Fe 3 O 4 /analcime nanocomposite toward the copper and cadmium ions is 176.68 and 203.67 mg/g, respectively. The pseudo-second-order kinetic model and Langmuir equilibrium isotherm best describe the uptake of copper and cadmium ions using the Fe 3 O 4 /analcime nanocomposite. The uptake of copper and cadmium ions using the Fe 3 O 4 /analcime nanocomposite is exothermic and chemical in nature.
... [2] Approximately 7 million tons of dyes are released worldwide each year from the textile, paper, tanning and paint industries, which are toxic and may also lead to the death of aquatic organism and cause many severe diseases such as cancer. [3] A large amount of wastewater is discharged from battery, electroplating, circuit board, metallurgy, and other industries. These heavy metals are not biodegradable, they can accumulate in human body through the food chain even at low concentrations, thus threatening human health. ...
An emerging “one stone, three birds” strategy was proposed to realize the value‐added disposal of solid waste coal gangue (CG), the synthesis of superb adsorbent and the efficient decontamination of pollutants (i. e., dyes, heavy metals). In this process, the metal ions extrated from calcined coal gangue (CCG) was reconstituted by a one‐step hydrothermal process to yield porous polymetallic silicate adsorbent (named HECCGA8h). The adsorbent has a high adsorption capacity of 270.27 and 185.53 mg/g for methylene blue (MB) and Cd(II), respectively. In the actual waters, the removal rate of MB by this adsorbent reaches 99.8% (in Yangtze River water) and 99.42% (in Seawater), and the removal rate of Cd(II) reaches 99.11% (in Yangtze River water) and 92.52% (in Seawater), respectively. Thermokinetic analysis showed that the adsorption of MB by HECCGA8h is spontaneous and endothermic with increased entropy, and the adsorption of Cd(II) is spontaneous and exothermic. The adsorption of MB is mainly driven by synergism of hydrogen bond, electrostatic attraction and ion exchange, and the adsorption of Cd(II) is mainly driven by the complexation and ion exchange between the surface group of the adsorbent and Cd(II). This research provides a new way for the realization of “treating waste with waste”.
... Many of them have extremely high adsorption capacities, some even exceeding 1000 mg⋅g − 1 [22]. However, due to the complex preparation process and high cost, the application of these advanced adsorbents is severely limited [23]. Solid wastes such as waste plastics/rubbers, waste ore, sludge, biowastes (various peels, wood, straw, waste paper, etc.) and so on, are cheap and can be found everywhere in our daily life [24][25][26][27]. ...
Remediation of wastewater with solid waste-based adsorbents is of great environmental significance, but most current waste-based adsorbents suffer from low efficiency. In this work, aminated waste paper (WP-NH2) membrane is successfully prepared by oxidation of various types of waste paper followed by grafting and crosslinking polyethyleneimine (PEI). WP-NH2 shows extremely high adsorption for various anionic dyes and antibiotics. Specifically, the adsorption amount for methyl orange (MO) and tetracycline (Tc) are 2156.2 mg·g⁻¹ and 253.7 mg·g⁻¹, respectively. WP-NH2 is stable enough to be regenerated several times and still maintains high adsorption efficiency. Mechanistic studies show that the adsorption toward anionic MO is mainly through electrostatic interaction and hydrogen bonding, and the adsorption of antibiotic Tc relies on hydrogen bonding and Lewis acid-base reaction. Grafting PEI on the fiber surface enables efficient exposure of adsorption sites. Therefore, WP-NH2 membrane can quickly, continuously and efficiently filter out MO and Tc from water. After 5800 L·m⁻² MO and 3150 L·m⁻² Tc filtration, the interception rate of the two contaminants is still higher than 90%. Moreover, WP-NH2 shows high selectivity and can be used for efficient separation of dye mixture. These results reveal that this advanced adsorbent made from waste paper has great potential application in industrial dye and antibiotic wastewater remediation.
... A solution's pH has a significant bearing on the amount of material that can be adsorbed from that solution. When the pH of a solution increases, cation adsorption goes up while anion adsorption goes down [77]. It is possible, for instance, for the physicochemical characteristics of an adsorbent, such as the surface area of the adsorbent, the particle size of the adsorbent, and the pore volume of the adsorbent, to have a considerable impact on the adsorption capacity of the adsorbent [78]. ...
Environmental pollution has been determined to be the root cause of a large number of deaths and illnesses around the world. Heavy metals in wastewater have been a major problem in recent years due to their hazardous effects. Human health, living resources, and ecological systems are all at risk because of the increasing levels of hazardous metals that are being released into the environment as industrial wastes. Heavy metals in wastewater are strictly regulated by environmental organizations and authorities due to their harmful health impacts and toxicological properties. As a result, adequate safeguards must be taken, and technologies for detecting, quantifying, and removing heavy metals from effluent waterways must be developed. The most prevalent method for removing heavy metals from wastewater is adsorption. As a result of recent advances in adsorption technology, it's a potential wastewater treatment method. In recent years, the utilization of agricultural waste materials has grown in popularity. Due to their physicochemical and nontoxic properties, agricultural wastes have the potential to be employed as adsorbents. A low-cost adsorbent made from agricultural waste is one of the most common applications for agricultural waste products. This review provides an overview of applications for various agricultural waste materials added to their ability to absorb heavy metals. The different properties of agricultural waste materials are also summarized. The review article also covered the treatment procedure’s effectiveness, difficulties, effects on the environment and public health, and other elements. The process parameters, the adsorption isotherm, and the adsorption kinetics are all thoroughly discussed. In this review, it has been shown that several heavy metals can be effectively removed from wastewater using inexpensive adsorbents.
... For example, Mandal and Singh [12] prepared biochar with rice straw to remove atrazine and imidacloprid; Sbizzaro and co-workers [1] studied the removal of atrazine using biochar prepared from bamboo stems; Tchikuala et al., [13] used natural Fibers from African baobab wastes to produce activated charcoal to remove the herbicide diuron; Tongur and Ayranci [14], studied the adsorption of the herbicides paraquat, diquat and difenzoquat using activated carbon; finally, Salomón and co-workers [15] obtained a high performance of removal from the herbicide 2,4-dichlorophenoxyacetic acid in water using activated carbon derived from the endocarp of the Queen palm (Syagrus romanzoffiana). Anastopoulos et al. [16], used eucalyptus residues to remove organic compounds from the water, while Usman et al. [17], used fly ash to remove dyes; Anastopoulos et al. [18], applied sunflower residues to remove metal ions and finally, Philippou et al. [19], developed pine-based adsorbents to remove different contaminants from water. ...
The species Hovenia dulcis has become a major issue for the Brazilian biome due to its high adaptation and accelerated propagation, putting the local biodiversity at risk. In this sense, this study sought to generate a new purpose for the fruits of this peculiar species. They were carbonized with ZnCl2 to produce porous activated carbon, which was used to remove the herbicide atrazine from aqueous solutions. The Hovenia dulcis activated carbon (Hd-AC) presented a surface area of 898.4 m² g⁻¹, with narrow pores with an average diameter of 1.24 nm and a pore volume of 0.296 cm³ g⁻¹. Hd-AC for atrazine adsorption was efficient at a pH of 6.0 for an adsorbent dosage of 0.5 g L⁻¹, where the adsorption capacity was 58 mg g⁻¹ at 328 K. The isothermal curves showed a good adjustment to the Freundlich isotherm. The thermodynamic results indicated that herbicide adsorption was spontaneous, favorable, and endothermic (ΔH⁰ = 8.21 kJ mol⁻¹). Besides, the linear driving force model (LDF) was used satisfactorily to describe the kinetic behavior of atrazine. Also, in treating a sample of river water contaminated with atrazine, Hd-AC showed high performance, reaching the removal of 70% of the emerging pollutant. Therefore, using the residual fruits of the Hovenia Dulcis as biomass to prepare a highly porous adsorbent reveals a promising alternative.
Oily wastewater is one of the most hazardous contaminants that can hurt the ecosystem. There is an urgent need to adopt an efficient, eco-friendly, and low-cost material to replace the old traditional treatment methods of oily wastewater that were very expensive in addition to their relatively low efficiency. Eucalyptus bark is considered one of the materials that are rarely used in this field, although it has the characteristics that qualify it to be a distinguished and promising one. The optimum conditions of using Eucalyptus globulus Labill. (Blue gum) bark in the removal of oil from prepared aqueous solutions were concluded before applying in the treatment of real oily industrial wastewater from New Borg El-Arab City, Egypt. The sequential optimization adsorption results were as follows: initial oil concentration, 500 mg/l; adsorbent dosage, 0.5 g/l; pH, 3; exposure time, 45 min; temperature, 20 °C; and shaking rate, 300 rpm. The pretreatment of biomass with H3PO4 proved it to be superior in the oil removal process where the efficacy reached 450.69 mg/g, while the unmodified form came second where the adsorption efficacy reached 395.86 mg/g, after that the NaOH-modified form came third by efficacy reached 315.85 mg/g. The results of SEM elucidated this order of efficacy according to the porosity of the bark surface. FTIR analysis indicated that OH, carboxylic C = O, and carboxylic C-O groups are the contributing groups in the oil adsorption process for the three forms of Eucalyptus bark. The reusability of Eucalyptus bark using n-hexane for one cycle reached 96.34, 97.13, and 95.83% for unmodified, H-modified, and OH-modified forms, respectively, and for five cycles reached 56.29, 58.01, and 55.81% for unmodified, H-modified, and OH-modified forms, respectively. The application of Eucalyptus bark in the H-form in the treatment of real oily wastewater was achieved by efficacy ranging between 91.46 and 96.23% which proves the excellence of Eucalyptus bark in the treatment of oily wastewater.
Adsorption is an effective and promising technology for removing a variety of pollutants from (waste)water. Many adsorbents are capable of removing pollutants. Among them, clays and clay minerals, nanomaterials, Metal Organic Frameworks (MOFs), Layered Double Hydroxides, Aerogels, Cryogels, Xerogels, etc. Based on the principles of the Circular Economy and Green Chemistry, agriculture biomass/waste, as renewable, non-toxic, and eco–friendly materials, has attracted the interest to produce adsorbents (raw and/or modified) to decontaminate (waste)water. This chapter contains information about the applicability of pineapples, pomegranate- and mango–based adsorbents to remove cationic and anionic dyes. Various adsorption parameters (solution pH, initial concentration, adsorbent dose, temperature, etc.) were explored in detail. Isotherm and kinetic modeling and thermodynamic aspects are also discussed. Maximum adsorption was determined to be 2.98–708.15, 5.42–288.34, and 17.75–1029.11 mg/g for mango, pineapple, and pomegranate-based adsorbents, respectively. The chapter's conclusions confirm that the investigated materials can successfully remove dye pollutants, and they also suggest a management strategy considering sustainability aspects for dealing with this kind of biomass/waste.
With the development of economy and increasing environmental awareness, how to effectively remove organic pollutants in wastewater is a research hotspot. Adsorption is one of the effective methods, and the adsorption material is the key factor to determine the efficiency. In this review, biomass‐derived carbon materials as adsorbents of organic pollutants and the adsorption mechanism are discussed in depth. The effects of carbonization and activation on the morphology and structure of carbon materials; the modification strategies of carbon adsorbents, the adsorption performance of biomass‐derived carbon materials for organic pollutants are described and illustrated; the future work of the biomass‐derived carbon materials is proposed.
The reuse of biomass waste has been gaining attention in adsorption processes to remove pollutants of emerging concern from water and wastewater. In this work, the potential of alginate-extracted macro-algae waste to uptake synthetic dyes and metal cations was evaluated in comparison with raw algae. In affinity assays, both materials were able to remove metal cations and cationic dyes up to maximum rates, and no significant removal was observed for an anionic dye in an acidic medium. Competition was observed in multi-component systems of metal cations and dyes. For binary samples containing organic and inorganic contaminants, kinetic modeling evidenced the distinct nature of both types of adsorbates. Pb(II) biosorption was best described as a first-order process, while second-order and Elovich models better fitted methyl blue (MB) uptake data. For equimolar binary samples, the Sips isothermal model fitted the experimental data more satisfactorily at room temperature. Isotherms for 20, 30, 40, and 60 °C exhibited favorable adsorption profiles with spontaneous ΔG values for both raw macro-algae and waste from alginate extraction. Maximum adsorption capacities were competitive with previous reports in the literature for a wide range of biomaterials, pointing to the slightly higher efficiency with algae waste in batch experiments. In elution tests, HNO3 (0.5 M) showed the best recovery rates of metal cations. Continuous biosorption operation revealed the performance of the brown algae waste was considerably more efficient than raw algae with breakthrough biosorption capacities up to 3.96 and 0.97 mmol.g⁻¹ for the removal of Pb(II) and MB, respectively. A total of 3.0 g of algae and algae waste were able to deliver 1.20 and 1.62 L of contaminant-free water, respectively. XPS analyses corroborate previous assays that pointed to the prevalence of physisorption with evidence of complexation, ionic exchange, and hydrogen displacement mechanisms.
It is essential to remove rhodamine 6G and acid orange 10 dyes from contaminated water because they can induce cancer and irritate the lungs, skin, mucous, membranes, and eyes. Hence, in the current work, the Pechini sol–gel method was used for the facile synthesis of ZrO2/CdMn2O4/CdO as novel nanocomposites at 600 and 800 °C. The synthesized nanocomposites were used as novel adsorbents for the efficient removal of rhodamine 6G and acid orange 10 dyes from aqueous media. The nanocomposites, which were synthesized at 600 and 800 °C, were abbreviated as EK600 and EK800, respectively. The synthesized nanocomposites were characterized by EDS, XRD, N2 adsorption/desorption analyzer, and FE-SEM. The patterns of XRD showed that the average crystal size of the EK600 and EK800 nanocomposites is 68.25 and 85.32 nm, respectively. Additionally, the images of FE-SEM showed that the surface of the EK600 nanocomposite consists of spherical, polyhedral, and rod shapes with an average grain size of 99.36 nm. Additionally, the surface of the EK800 nanocomposite consists of polyhedral and spherical shapes with an average grain size of 143.23 nm. In addition, the BET surface area of the EK600 and EK800 nanocomposites is 46.33 and 38.49 m2/g, respectively. The optimal conditions to achieve the highest removal of rhodamine 6G and acid orange 10 dyes are pH = 8, contact time = 24 min, and temperature = 298 kelvin. The greatest removal capacity of the EK600 and EK800 adsorbents towards rhodamine 6G dye is 311.53 and 250.63 mg/g, respectively. Additionally, the greatest removal capacity of the EK600 and EK800 adsorbents towards acid orange 10 dye is 335.57 and 270.27 mg/g, respectively. The removal of rhodamine 6G and acid orange 10 dyes using the EK600 and EK800 adsorbents is spontaneous, exothermic, follows the Langmuir adsorption isotherm, and fits well with the pseudo-first-order kinetic model.
In this study, for the first time, a selenium-doped mesoporous biochar was prepared and efficiently employed for sodium diclofenac and reactive orange 16 dye adsorption. The characterization results indicated that selenium doping had a remarkable impact on Biochar-Se morphological and physicochemical structures. The efficacy of developed biochar samples on reactive orange 16 (RO-16) and diclofenac (DCF) removals was fully investigated. For both molecules (DCF and RO-16), Liu's equilibrium model offered the best fitness with maximum adsorption capacity values of 355 mg g-1 for DCF and 538 mg g-1 for RO-16 for Biochar-Se. Multiple mechanisms including pore filling, π-π interaction, and hydrogen bonding between the Biochar-Se and DCF/RO-16 molecules were involved in the adsorption process. Se-nanoparticles formed metal-oxygen bonds, which boosted the adsorption of DCF and RO-16 molecules. The current work offered a feasible approach for the development of Se-doped biochar adsorbent that is incredibly effective in treating wastewater.
This study presents the use of H3PO4 surface-modified coco peat biochar (PSMCB), as an effective adsorbent to remove Cr (VI) from aqueous and real systems. Microstructure and adsorption mechanisms were analysed via pre- and post-adsorption characterization techniques, with experimental results demonstrating PSMCB capacities of 122.5 mg/g and 149.25 mg/g in batch and column studies, respectively. XPS analysis revealed the significant
contribution of P–O, C–P, and C–O bonds to the adsorption of Cr (VI), with reduction, complexation, and electrostatic interaction influencing the adsorption process. The removal efficiency of PSMCB in binary, ternary, and real systems exceeded 90 %. PSMCB was found stable up to 4 cycles, with a maximum desorption of 97.4 %. Spent biochar was successfully demonstrated as an effective bio-fertilizer. Cost analysis revealed that PSMCB is highly cost-effective (Rs 164.7 INR/kg or 2.03 USD/kg) indicating that it has a great promise for industrial applications.
The conversion of agricultural waste into high-value carbon products has been an attractive area in waste management strategy. This study highlighted the synthesis and effectiveness of green pea peels (GPP), green pea biochar (GPBC), and nano-ferromagnetic green pea biochar (NFGPBC) by the ferrous/ferric co-precipitation synthesis method for eliminating cationic dyes molecules from solutions. The morphological, physicochemical, and structural properties of GPP, GPBC, and NFGPBC were approved by Scanning Electron Microscopy (SEM), Transmission Emission Microscopy (TEM), Energy Dispersive X-ray (EDX), Bruneau Emmett Teller (BET), Fourier Transform Infrared spectroscopy (FTIR), and X-ray Diffraction (XRD) techniques. Vibrating Sample Magnetometry (VSM) analysis confirmed the NFGPBC magnetization performance. The capacity of each adsorbent for methylene blue removal was evaluated at various parameters of material dosage (50-250 mg/150 mL), pH (2-12), initial concentration (50-250 mg/L), contact time (0-90 min) and temperature (20-60 °C). The three developed adsorbent materials GPP, GPBC, and NFGPBC, possessed reasonable BET surface areas of 0.6836, 372.54, and 147.88 m2g-1, and the corresponding monolayer adsorption capacities of 163.93, 217.40, and 175.44 mg/g, respectively. The superior performances of GPBC and NFGPBC were due to their increased surface area compared with the parent green pea peels (GPP). The results from adsorption kinetics studies of all prepared materials were pseudo-second-order and Elovich kinetics models. The thermodynamic parameters exhibited MB sorption's favorability, spontaneity, and endothermic nature. The NFGPBC material experienced Vander Waal forces, electrostatic interaction, hydrogen bonding, and hydrophobic interactions as predominant modes of the solid-liquid interaction. The regeneration, recycling, and reusability of the synthesized GPP, GPBC, and NFGPBC performed at five adsorption cycles revealed that NFGPBC demonstrated excellent cyclical performances attaining a minimum 8.9% loss in capacity due to paramagnetic properties. Thus, NFGPBC is a green, efficient, and eco-friendly material recommended for large-scale production and application in wastewater.
Agricultural-based adsorbents have received an upsurge of interest in the water treatment industry especially in the area of adsorption. They have been widely investigated as the next generation adsorbents due to their unique physio-chemical properties and high affinity towards a wide variety of constituents ranging from organic compounds to heavy metal ions. In addition, agricultural-based adsorbents are now a cheaper and sustainable option as opposed to non-renewable and expensive adsorbents originating from coal, polymers, and petroleum residues. Among different agriculture wastes available, walnut shells exhibit great potential as activated carbon precursor. They have outstanding chemical stability, high surface area and low ash content. In this review, walnut shell-based adsorbents have been assessed in terms of their activation methods and preparation. Furthermore, adsorbents' resulting characteristics and factors influencing the adsorption capacity have been summarized and thoroughly analyzed. It has been determined that the adsorption efficiency is heavily associated with the characteristics of the adsorbent including pore diameter, surface area, surface functional groups and the nature of the background solution including pH, temperature and ionic strength. This review identifies different activation methods reported in the literature including chemical and physical activation and chemical impregnation and functionalization. The literature survey also entails a comprehensive discussion involving types of mechanisms and factors controlling adsorption behaviors towards targeted contaminants. Moreover, a detailed analysis of adsorption isotherms and kinetics involved in the adsorption process is also included. Finally, this review mentions future research needs and challenges of adsorption by walnut shell-based adsorbents.
The by-product from pistachio (Pistachia vera) has been valorised over the years as an adsorbent material for water treatment. The aim of this review was to synthesise the empirical findings on the uptake of different pollutants using adsorbents developed from pistachio waste. This was done to evaluate the progress of research on the subject matter, identify knowledge gaps and propose interesting areas for future work. Iran was observed to be a major source country (31%) of pistachio feedstock for adsorbent preparation. The highest reported specific surface area for pistachio adsorbent was 1884 m 2 /g for a carbon activated by NH 4 NO 3 + NaOH and carbonised at 800 °C. Pistachio adsorbents showed very good removal efficiencies (> 90% in most cases) for both dyes, heavy metals, pharmaceuticals and other compounds. Isotherm and kinetics modelling was always best-fit to the classical Langmuir and Freundlich models and the pseudo-second-order kinetics model, respectively. HCl was the regularly used eluent for heavy metals desorption, while alkalis and organic acids were more regularly used for dyes. Interesting areas for future work include adsorbent preparation by physical activation, research interest in emerging contaminants, improvement of adsorbent desorption, utilisation of statistical physics modelling tools and the investigation of spent adsorbent disposal.
Mesoporous composite activated carbon (AC) prepared from cocoa (Theobroma cacao) pod and sunflower (Tithonia diver-sifolia) stalk were evaluated for the sorption of Pb(II) and Fe(II) from wastewater. The different biomasses were acid activated by wet impregnation with phosphoric acid and carbonised at 500 °C. Adsorbents studied were AC from Theobroma cacao (TC-AC) and Theobroma-Tithonia blend (TT-AC) in a mass ratio of 75-25 wt%. The adsorbent was characterised by FTIR, BET and SEM-EDS. The specific surface areas were 237.445 and 392.508 m 2 /g for TC-AC and TT-AC respectively. Parametric studies revealed that adsorbate uptake reduced with increased initial concentration and increased with increasing dosage and contact time. The monolayer adsorption capacities for Pb(II) sorption onto TC-AC and TT-AC were 47.17 and 46.95 mg/g and for Fe(II) sorption onto TC-AC and TT-AC was 37.45 and 37.04 mg/g respectively. Langmuir isotherm and pseudo-second-order kinetic models were the best fits for the adsorption process. From the study, it has been observed that high-quality mesoporous adsorbent can be obtained from the carbonisation of the cocoa pod and sunflower stalk for water treatment applications.
Wastewater contains many organic and inorganic pollutants and discharging them into received waters leads to serious environmental problems. The wastewater that is produced from various industries contains a noticeable amount of dyes; heavy metals and metalloids this has remained one of the major environmental problems facing public health. Unfortunately, the conventional wastewater remediation process is unable to remove dyes and heavy metals completely. One of the widely used water treatment technologies is biosorption, biosorbents are considered to be an emerging green, cost-effective, and efficient alternative. Therefore, the search for locally or regionally available biomasses for heavy metals/metalloids and dyes removal gained rapid attention. Methylene blue, Crystal violet, Reactive black 5, and Congo red; Cd, Cr, Cu, Pb, Hg, Ni, and Zn; and As were selected as examples for dyes, heavy metals, and metalloids, respectively, In this regard, a comprehensive understanding of the biosorption capability of different biosorbents is necessary to know how they can remove inorganic and organic contaminants in wastewater. Biosorption is an ion exchange, complexation, and coordination process. Besides, the recent advances in various biomaterials-based biosorbents and different approaches of pollutants removal from wastewater with several examples to provide a backdrop for future research have been reviewed. This can be beneficial for developing more effective technologies to eliminate contaminants, thus bridging the gap between laboratory results and industrial use. crustacean shells, algae, chitosan are the most effective biosorbents. These biosorbents can serve as good alternatives to synthetic materials for pollutants removal from wastewater.
The rapid increase in toxic dye wastewater generated from various industries remains a severe public health issue and prime environmental protection concern, posing a major challenge to existing conventional water treatment systems. Consequently, various physicochemical and biological treatment processes have been studied, which exhibit varying removal abilities depending on their experimental constraints. Among them, adsorption is considered to be the most efficient due to its high removal efficiency, easy operation, cost-effectiveness, and recyclability of the adsorbents. Considering this, the present review article focused on presenting a comprehensive summary of the various types of adsorbents such as commercial activated carbon, metal oxide-based, carbon-based, metal–organic framework, and polymer-based adsorbents used in dye remediation of contaminated water. The effects of several critical factors such as initial dye concentration, solution pH, temperature, and adsorbent dose on the dye adsorption performance are also described. In addition, the adsorption mechanisms responsible for dye removal are explained based on electrostatic attraction, ion exchange, surface complexation, and π–π interactions. Finally, critiques, future perspectives, and a summary of the present article are given. Various adsorbents such as carbon-based materials, metal oxides, bio-adsorbents, and polymer-based materials, have been shown to be efficient for the removal of dye pollutants from wastewater. Thus, it is anticipated that dye removal by adsorption can provide a feasible solution for the treatment of dye-laden water.
The raw sawdust of Eucalyptusglobulus Labill was studied as an alternative of residual biomaterial for the adsorption of lead (II) in wastewater, evaluating the effect of pH (3, 4, 5, and 6) in a batch system. From the characterization of the biomaterial, it was found that the biomass has a low ash content, and from the scanning electron microscopy (SEM) microphotographs that it presents a porous morphology with diverse texture and presence of fiber fragments, which describe the heterogeneity of the material. The Fourier transform infrared (FTIR) spectrum showed the presence of functional groups of NHR, OH, COOH, and hydrocarbons, which are part of the structure of lignin, cellulose, hemicellulose, and pectin. From the adsorption experiments, it was obtained that the optimal value of pH 6, reaching a removal percentage of 96% and an adsorption capacity of 4.80 mg/g. The model that better adjusted the kinetics results was the pseudo-second-order model and the Langmuir and Freundlich isothermal models described the adsorption equilibrium; it was found that in the system prevails chemisorption, supported in ion exchange by Pb (II) and the biomass’ functional groups. From the results, eucalyptus sawdust is suggested as a low-cost adsorbent for Pb (II) bioadsorption present in solution.
Eucalyptus camdulensis biochar (Ec-bio) was used to adsorb crystal violet (CV) and methylene blue (MB) dyes, which was optimized and further evaluated using different isotherm and kinetic models. Microscopy and spectroscopy techniques showed the interactions of the dyes with the surface functional groups of the Ec-bio, resulting in the removal of the dyes from aqueous solution. Both dyes were immediately uptaken, with equilibrium reached in 60 min, with a higher sorption efficiency of CV compared to MB. Thermodynamic parameters showed endothermic adsorption and the nonspontaneous adsorption of both dyes onto the Ec-bio. Both the adsorption capacity and percentage removal increased with the increasing solution pH from 2.0 to 4.0 and to 10 for CV and MB. An increase in adsorption capacity was observed upon increasing the initial concentrations, with a corresponding decrease in the percentage removal. The pseudo-second-order (PSO) and Elovich kinetic models (nonlinear approach) were a good fit to the data of both dyes, confirming a chemisorptive adsorption process. The Langmuir isotherm fitted well to the CV data, supporting its monolayer adsorption onto the Ec-bio, while the Freundlich isotherm was a good fit to the MB dye data, suggesting the surface heterogeneity of the Ec-bio. The Dubinin–Radushkevich isotherm was a good fit to the adsorption CV data compared with the MB dye, suggesting the physisorption of both dyes onto the Ec-bio due to its mean free energy of adsorption of <8 kJ mol−1.
In this study, a comparison between charcoal produced from Eucalyptus urograndis modified and unmodified with HNO3 on the adsorption capacity of metals (Cu(II), Cd(II), and Ni(II)) in aqueous solutions was performed. The modification was performed using charcoal from the wood of a hybrid of Eucalyptus urophylla x Eucalyptus grandis (commonly referred to in Brazil as Eucalyptus urograndis). The charcoal was produced at a final temperature of 450 °C. Nitric acid was the oxidizing agent, employed at a concentration of 12.5% (v/v) and a reaction time of 3 h. The materials were characterized and compared using thermogravimetric analysis, thermogravimetric index, specific surface area analysis, scanning electron microscopy, elemental analysis, and point of zero charge. Studies of the process factors (contact time, mass, ideal pH), adsorption isotherms (Langmuir and Freundlich), and the thermodynamics of the process were also carried out. Treatment with nitric acid altered the elemental composition of charcoal, and functional groups, like carbonyl groups, were added to the surface, which caused a significant increase in total adsorption capacity (from 114.27 to 310.53 mg g⁻¹ in a solution with a mix of metals). The model that best fit the data was Langmuir, and the maximum removal of Cu(II) ions was 96%, and occurred at pH 5, at 318 K, with a dose of biosorbent equal to 0.4 g 50 mL⁻¹ of solution and equilibrium contact time of 30 min. Thermodynamic parameters suggested that adsorption occurred spontaneously and occurred through the ion exchange and electrostatic interaction mechanisms. In systems with the presence of more than one metal ion, the total adsorption capacity increased.
Graphical abstract
Textile wastewater heavy metal pollution has become a severe environmental problem worldwide. Metal ion inclusion in a dye molecule exhibits a bathochromic shift producing deeper but duller shades, which provides excellent colouration. The ejection of a massive volume of wastewater containing heavy metal ions such as Cr (VI), Pb (II), Cd (II) and Zn (II) and metal-containing dyes are an unavoidable consequence because the textile industry consumes large quantities of water and all these chemicals cannot be combined entirely with fibres during the dyeing process. These high concentrations of chemicals in effluents interfere with the natural water resources, cause severe toxicological implications on the environment with a dramatic impact on human health. This article reviewed the various metal-containing dye types and their heavy metal ions pollution from entryway to the wastewater, which then briefly explored the effects on human health and the environment. Graphene-based absorbers, specially graphene oxide (GO) benefits from an ordered structured, high specific surface area, and flexible surface functionalization options, which are indispensable to realize a high performance of heavy metal ion removal. These exceptional adsorption properties of graphene-based materials support a position of ubiquity in our everyday lives. The collective representation of the textile wastewater's effective remediation methods is discussed and focused on the GO-based adsorption methods. Understanding the critical impact regarding the GO-based materials established adsorption portfolio for heavy metal ions removal are also discussed. Various heavy-metal ions and their pollutant effect, ways to remove such heavy metal ions and role of graphene-based adsorbent including their demand, perspective, limitation, and relative scopes are discussed elaborately in the review.
A review of adsorption mechanisms for heavy metal removal using low cost adsorbent has been carried out in this article. Some metal ion sequestration techniques used over the years have some demerits, ranging from generation of sludge to high operational cost. Adsorption process using low cost adsorbents has been found cost effective and environmentally nuisance-free. In this review, various low cost adsorbents for heavy metal sequestration have been studied. The application of some adsorption models such as single and multi-component isotherms, adsorption thermodynamics, and kinetics as well as the effect of process parameters on heavy metal sequestration using low cost adsorbents has also been reviewed so as to better understand the adsorption process. From the literature reviewed, the percentage removal of chromium, copper and zinc was favoured by an increase in contact time, temperature, initial concentration, adsorbent dosage as well as a decrease in pH.
Sustainable wastewater treatment is one of the foremost challenges of twenty first century. With the ever in- creasing levels of industrial toxic sludge disposal to water bodies, finding environment friendly and affordable treatment options will remain a priority, especially for developing countries. Adsorption is one of the most re- searched and used wastewater treatment methods for removing dyes and heavy metals. Adsorption using living and non-living biomass, termed as biosorption has gained attention in the last two decades due to some promising results. Agricultural waste materials e.g. fruit wastes has been widely used for dye and heavy metal sequestration from wastewater. Various researchers have analyzed the potential of watermelon rind (WMR) as a biosorbent for wastewater treatment and have found encouraging results. Functional groups such as carboxyl and hydroxyl are primarily responsible for sorption of dyes and metals into watermelon rind. The most important parameters af- fecting the biosorption of contaminants using watermelon rind were found to be pH and co-solute concentration. Kinetic and isotherm studies performed by numerous authors revealed that pseudo second order kinetic model and Langmuir isotherm model were best suited for describing WMR based biosorption of dyes and heavy metals. The feasibility of WMR as a reusable biosorbent has been further proved by the results of desorption studies per- formed by several researchers. This paper reviews the various important aspects of utilization of watermelon rind as a biosorbent for removing dyes and heavy metals from contaminated water. The effects of several factors such as pH, initial solute concentration, biosorbent dose, co-solute concentration, activation etc. has been reviewed in this paper.
The use of functional material can help mitigate the pollution by heavy metals, which presents an array of risks to human production and life. This work provides a comprehensive review of the current knowledge on functionalized layered double hydroxide (LDH) as a heavy metal absorption material, by synthesizing the information from a total of 141 relevant publications published since 2005. LDH provides a potentially highly efficient method to adsorb heavy metal ions, which is simple to prepare and of low cost. The lack of functional groups and structural components of pristine LDH, however, limits the absorption capacity and widespread applications of LDH. Through intercalation, surface modification, or loading on substrates, functional groups or structural components are introduced into the pristine LDH to prepare functionalized LDH. In this process, the hydroxyl group and the valence state of [Mg (OH) 6 ] octahedrons play a crucial role. Functionalized LDH can be endowed with selective absorption capacity and enhanced stability and recyclability. After adsorbing heavy metal ions, functionalized LDH can be readily separated from the liquid phase. These aspects are discussed, along with the structure and composition, shape and size, and synthesis methods and research tools of LDH. This work concludes with the discussion of preparation and utilization and a look to the future in terms of identified research needs regarding the preparation, use, and recycling (or upcycling) of economical and environmental-friendly LDH.
Adsorption is one of the oldest and extensively studied techniques for water and wastewater treatment. As a surface phenomenon, adsorption efficiency relies heavily on the surface chemistry of the natural and modified material. The mode of surface modification and the nature of the precursor have significant impacts on surface functionalities. Chemical method of surface treatment is a technique that alters the structure and the surface properties of the precursor to enhance adsorption process. The present work intends to deliver precise knowledge on the choice and impacts of chemical modification on some known adsorbing materials.
Magnetic fluids (ferrofluids) have found many important applications in various areas of bio-sciences, biotechnology, medicine, and environmental technology. In this review, we have summarized the relevant information dealing with a magnetic modification of diamagnetic materials using different types of ferrofluids. Special attention is focused on a magnetic modification of plant-derived biomaterials, microbial and microalgal cells, eukaryotic cells, biopolymers, inorganic materials, and organic polymers. Derivatization is usually caused by the presence of magnetic iron oxide nanoparticles within the pores of treated materials, on the materials surface or within the polymer gels. The obtained smart materials exhibit several types of responses to an external magnetic field, especially the possibility of the selective magnetic separation from difficult-to-handle environments by means of a magnetic separator. The ferrofluid-modified materials have been especially used as adsorbents, carriers, composite nanozymes or whole-cell biocatalysts.
Industrial solid waste (ISW) is the waste obtained from the industrials activities which include any solid materials that are rendered useless during a manufacturing process. The ISW considers a global environmental problem and serious solutions must be taken to face this problem and decrease its environmental load and impact. Adsorption of heavy metal from industrial effluents using ISW is considered as a promising, potential and inexpensive alternative concept for ISW management. The ISW offering potential advantages as the zero cost, availability, high efficiency, and green alternative source. Heavy metals adsorption onto ISW is a complex process that affected by several factors including initial metal ions concentration, contact time, pH of the solution, temperature and adsorbent dose. In this paper, we review the factors that affect heavy metal adsorption onto ISW, such as contact time, temperature, pH, and adsorbent dose. The chief findings of the present review are: (1) The heavy metal ions removal% is high at the initial stage of the adsorption process then it decreases till it reaches equilibrium. (2) Temperature greatly affects the heavy metal adsorption process. (3) There is a definite pH value for each metal ion, at which the extreme adsorption of those metal ions occurs. (4) Increasing adsorbent dose generally increases catalytic activity due to the increase in the total surface area and the number of active places on the surface of the adsorbent. Knowing the factors that affect heavy metal adsorption onto ISW will help in optimizing the condition for heavy metal adsorption onto ISW.
Chitosan and chitin are categorized as low cost, renewable and eco-friendly biopolymers. However, they have low mechanical properties and unfavorable pore properties in terms of low surface area and total pore volume that limit their adsorption application. Many studies have shown that such weaknesses can be avoided by preparation of composites with carbonaceous materials from these biopolymers. This article provides a systematic review on the preparation of chitosan/chitin-carbonaceous material composites. Commonly used carbonaceous materials such as activated carbon, biochar, carbon nanotubes, graphene oxide and graphene to prepare composites are discussed. The application of chitosan/chitin-carbonaceous material composites for the adsorption of various water pollutants, and the regeneration and reusability of adsorbents are also included. Finally, the challenges and future prospects for the adsorbents applied for the adsorption of water pollutants are summarized.
The aim of this study is more towards environmental friendly solutions by transforming the lignocellulosic waste into valuable material which improves and upgrades technology for waste management and minimization. Therefore, the recent advances are based on improvements in the removal of hazardous materials by efficient and low-cost bio-sorbents. Agricultural waste contains a high concentration of cellulose which is a low cost, biodegradable, non-toxic, thermally and mechanically stable which explores the study towards clean and sustainable development. Different types of biomass are taken as adsorbent like leaves, fibers, husk, stem, seeds etc. The present study emphasis a clean and sustainable treatment for the elimination of metal ions from the environment by the management of waste i.e. sugarcane bagasse, rice husk, coconut husk etc. Various adsorption parameters have been examined at optimized conditions such as temperature, the dosage of adsorbent, contact/agitation time, pH, flow rate, bed height and concentration of dye or metal ions. Spectrophotometric techniques are used for the evaluation of the concentration of metal ions before and after sorption. This review summarizes many modifying agents and grafting techniques for the elimination of metal ions which improves the adsorption capacity. The present study compiles the grafting on the backbone of cellulose. This review recapitulates the different routes of extraction and modification of cellulose. The properties of biosorbent will be enhanced by several modification techniques but out of all these grafting is considered as the most effective one is shown in this study. This review also summarizes the various grafting methods with free radical grafting mechanism. This review also compiles the studies based on modified and unmodified biosorbents for the comparison of sorption capacities with and without modification. The chemically modified cellulosic biomass is mostly preferred than unmodified one due to more adsorption efficiency favored by a maximum number of reactive binding sites, enhanced ion-exchange properties and availability of more functional groups after modification.
In this paper, the adsorption properties of wheat straw (WS) and corn straw (CS) for Cr(VI) and Cr(III) in solution were studied. The effects of adsorption time, pH of the solution, temperature, and initial concentration of metal ions on adsorption capacity were investigated. The adsorption mechanism was discussed. The results showed that the adsorption isotherms of WS and CS for Cr(VI) and Cr(III) satisfied the Langmuir equation. By fitting the Langmuir equation, the saturated adsorption capacity of WS for Cr(VI) and Cr(III) can reach 125.6 and 68.9 mg g–1, and that of CS for Cr(VI) and Cr(III) can reach 87.4 and 62.3 mg g–1 , respectively. The adsorption kinetics conformed to the pseudo-second-order kinetic equation. The effect of temperature on the adsorption capacity was not significant. Physical diffusion and chemical adsorption coexist in the process of adsorption of metal ions by straws, and chemical adsorption is dominant, and the effect of physical diffusion on the chemical adsorption rate can be neglected. It can be seen from the experimental results that the treatment of chromium-containing wastewater by using cheap and easily available wheat straw and corn straw had a remarkable effect. The adsorbed straw could be completely desorbed and had excellent recyclability, indicating that the straws are ideal adsorbents.
Plant barks are among the most widely applied low-cost biomass materials in the study of pollutant removal from aqueous media. This paper extensively reviews the experimental findings presented in open literature with much focus on the last 15 years. This study classified plant bark adsorbents into 5 broad groups (based on their preparation technique): unmodified biosorbent, pre-modified biosorbent, chemically modified biosorbent, physically modified biosorbent and bio-based activated carbon. It was observed that eucalyptus, pine, neem, acacia and mango are the most explored source species in tree bark adsorption studies. About two-third of target impurities reported on the subject in open literature have been on heavy metals. The review elucidated the excellent adsorption capacities of plant bark based adsorbents and biosorbents for the uptake of heavy metals, dyes, pesticides and other pollutants. Adsorption was majorly best-fit to either the Langmuir or Freundlich isotherm models and the pseudo-second order kinetic model. The thermodynamics findings revealed that the adsorption is highly spontaneous and is by a physical mechanism in most cases. It was also observed that plant barks have high reusability potential thereby underlying their usefulness for industrial application. Knowledge gaps in the research area were also discussed in line with future perspectives.
Water pollution is a grave concern in the 21st century. The challenge is to devise techniques to treat water that are facile, does not involve toxic resources or by-products, and are not energy-intensive. Adsorption using agricultural wastes seems to be a promising approach. Parts of coconut palm such as shell, husk, coir etc in their native or modified form can be used for wastewater treatment. Several studies suggest that pollutants such as heavy metals, industrial dyes, pharmaceuticals, organic contaminants can be successfully adsorbed on to coconut biomass. The abundance in availability, renewability and high adsorption are the useful advantages conferred by coconut by-products. This review has focused on all the valuable studies reported on the facile valorization of various coconut palm wastes such as shell, husk, coir etc. for remediation of pollutants from waste water since the year 2010. The chemical modifications of the adsorbents and their capacities for removal of various contaminants have been mentioned. Various computer software modelling studies and reuse of the bioadsorbents have been included. Most of the data has been given in tabulated form for ease of understanding. The important advancements, challenges and future prospective have also been discussed along with compilation of all the relevant scientific reports of the last decade on the potential of coconut refuse for waste water treatment. The main aim of this review is to highlight the importance of utilization of biomass, particularly those that lie waste, for remediation of environmental pollution in a sustainable manner.
The last years adsorption is assumed to be one of the most prosperous and efficient, user-friendly, and low-cost wastewater purification technique to remove a wide range of pollutants. For that scope, commercial activated carbons, are commonly used as traditional adsorbents. However, due to some crucial disadvantages (e.g. high cost and incomplete regeneration) their use is limited. Agricultural waste/biomass/residues have attracted interest as alternative and efficient adsorbents because they can be utilized without any or after chemical treatment, or can be used as precursors to fabricate activated carbon or biochar. Moreover, agricultural wastes are renewable, inexpensive and abundantly available, essentially non-toxic, and environmentally friendly, thus satisfying the concept of Green or Sustainable Chemistry. This review article emphasizes on the utilization of sunflower-derived adsorbents to remove potentially toxic elements (PTEs) from aqueous media. The effect of crucial adsorption parameters (effect of initial pH, contact time etc.) is discussed in detail. Data obtained from adsorption experiments, thermodynamic and kinetic modeling, and desorption studies are presented and analyzed. The maximum adsorption capacity values obtained for sunflower adsorbents vary between 3.28 and 252.52 mg/g for PTEs, indicating that these materials could be satisfactorily used as alternative adsorbents.
The world has been facing a severe problem concerning water quality deterioration due to anthropogenic activities. Among many water treatment techniques, adsorption is one of the most promising methods owing to advantages such as relatively low cost, versatility, effectiveness and simplicity. The most widely used adsorbents are based on activated carbon, however such are expensive and their production is burdened with big environmental footprint. Consequently, there is a need of finding new, more sustainable solutions for abatement of water pollutants. Low-cost, alternative materials-based adsorbents such as bark, feather, husks, leaves, peels, rinds, seeds, stones and spent coffee or tea, derived from waste generated by various industries, may find application in the field. Nonetheless, there is still a substantial amount of issues connected with the materials' stability and the logistics that impede their wide application and still require investigation.
Nickel nanoparticles (NiNPs) supported on activated multi walled carbon nanotubes (MWCNTs) were used as an adsorbent applied towards Pb(II), As(V) and Cd(II) remediation from industrial wastewater. The result revealed the hydrophilic surface of MWCNTs-KOH was enhanced with the incorporation of NiNPs enabling higher surface area, functional groups and pores distribution. Comparatively, the removal of Pb(II), As(V) and Cd(II) on the various adsorbents was reported as NiNPs (58.6±4.1, 46.8±3.7 and 40.5±2.5%), MWCNTs-KOH (68.4±5.0, 65.5±4.2 and 50.7±3.4%) and [email protected] (91.2±8.7, 88.5±6.5 and 80.6±5.8%). Using [email protected], the maximum adsorption capacities of 481.0, 440.9 and 415.8 mg/g were obtained for Pb(II), As(V) and Cd(II), respectively. The experimental data were best suited to the Langmuir isotherm and pseudo-second order kinetic model. The fitness of experimental data to the kinetic models in fixed-bed showed better fitness to Thomas model. The mechanism of metal ions adsorption onto [email protected] show a proposed electrostatic attraction, surface adsorption, ion exchange and pore diffusion due to the incorporated NiNPs. The nanocomposite was highly efficient for 8 adsorption cycle. The result of this study indicate that the synthesized nanocomposite is highly active with capacity for extended use in wastewater treatment.
The adsorption technique has been observed to be very effective for the sequestration of pollutants in wastewater remediation processes with the material used as the adsorbent playing a crucial role. In this regard, the use of agricultural waste residues has been widely explored owing to their unique properties which enable them to be applied as adsorbents. However, their use in pristine forms leaves much to be desired. Several modification agents have been applied for the treatment of agricultural waste residues with the view of enhancing their adsorption capacity and ameliorating the disadvantages accompanying their use in the pristine state. Due to the abundance of peanut husk generated globally and its cellulosic nature, it has been extensively applied as an adsorbent for the removal of a broad-spectrum of pollutants in wastewater. This makes it a useful model for the design of efficient adsorbents based on agricultural biomass. In this review, the application of functionalized adsorbents, based on peanut husk (an agricultural waste material) for the sequestration of pollutants in aqueous solution, is presented. In a bid to understand the suitability of these functionalized adsorbents, a brief overview on the surface properties of the modified adsorbent, mechanism of adsorption process as well as advantages associated with the modified agents are presented. This review presents cost-effective and efficient adsorbents based on peanut husk for the sequestration of wastewater which can aid in the design of novel adsorbents hinged on agricultural waste materials for environmental remediation processes.
Mineral acid post treatment is a common value-addition method for biochar (BC). However, it can cause digestion of the product, thus reducing the yield. Acid treatment on raw feedstock is anticipated to enhance adsorption properties of produced BC while avoiding such digestive effects. Hence, the presented study has focused on pre-modification of Lasia spinosa (Kohila) BC by using nitric acid, to improve its sorption capacity towards removal of methylene blue (MB). Raw and pre-modified BC (abbreviated as RBC and PMBC respectively) were produced at three different temperatures (300, 500 and 700 °C). Highest capacities were obtained for 300 °C produced BC (abbreviated as R300 and PM300 respectively). The experimental data was best fitted to Sips isotherm model, with a maximum Sips capacity of 9.58 mg/g and 81.35 mg/g at 30 °C for R300 and PM300 respectively. The enhanced capacity of PM300 could be attributed to the increased surface functionality and the reduced pore size which resulted in a feasible adsorptive removal of MB. XPS results showed a slight increase in nitrogen containing groups upon modification. The adsorption kinetics accurately described the pseudo-first order (PFO) behavior of PM300 and pseudo-second order (PSO) behavior of R300. The MB uptake of PMBC was governed by a pore filling mechanism whereas electrostatic attractions were predominant in the sorption process of RBC. Both BCs showed a spontaneous endothermic adsorption and the overall rate of the adsorption process was a combination of liquid film diffusion and intra particle diffusion. After four cycles of regeneration, the dynamic capacity of PMBC remained more than 50% of its initial value, which was approximately twice of RBC. Pre-modification caused an eight-fold increase in MB adsorption capacity, qualifying it to be a simple, economically feasible and energetically effective technique for the value-addition of BC.
Hazardous contamination of water is a major hurdle in the provision of usable and drinkable water to the world. Innovative, economic, renewable and environment friendly technologies are need of the hour for wastewater treatment. Several technologies such as ion-exchange, co-precipitation, adsorption, membrane separation, oxidation, biochemical processes etc. are being researched to encourage the wastewater treatment. Among these technologies, the adsorption is being considered as a promising approach owing to its short route. To adsorb the pollutants, different types of adsorbents are synthesized and utilized for wastewater treatment. The bio-adsorbents (BAs) from waste biomass sources are renewable, sustainable, economical, and ecofriendly for wastewater treatment. Among other biomass waste sources, fruit-based biomass wastes are on rise due to global food and fruit demand. The utilization of fruit wastes for the development of BAs have received high attention due to their low cost, rich in bio cellulose and abundance. Herein, we report a comprehensive review on the fruit waste derived bio-adsorbents for wastewater treatment. The manuscript includes synthesis, characterizations, and utilization of fruit waste derived bio-adsorbents for removal of various water contaminants. Characteristics, adsorption capacities, isotherms and adsorption kinetics of various bio-adsorbents and influence of parameters on adsorption is provided and critically analyzed.
As a green adsorbent, biochar has attained progressive attention due to its advantages such as high carbon content, high surface area, stable structure, and heavy metals removal through cation exchange capacity. Biochar can be synthesized from the feedstock, agricultural, and organic waste. In this study, the activated biochar (AC) and ammonia modified biochar (NAC) were prepared from Eucalyptus waste by acid activation. The adsorption properties of pure AC and NAC were compared for aqueous Cr(VI) removal. Advanced characterization techniques such as scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR) were used to examine the morphology, elemental composition, and functional groups. Several influencing factors on adsorption processes such as solution pH, adsorption dosage, contact time, and initial concentration were investigated. The ammonia modified biochar (NAC) could remove 85.67% of Cr (VI), whereas 76.73% removal rate was observed for the activated biochar (AC) at an initial concentration of 300 mg/L at pH 2.0 and 25 °C with a dosage of 0.025 g/25 mL. The pseudo-second-order kinetic and Freundlich isotherm adsorption models showed close-fitting for the activated biochar (AC) and the ammonia modified biochar (NAC) adsorption in Cr(VI) equilibrium state. Cr (VI) oxidizes nitrogen and oxygen functional groups on NAC following the conversion into Cr (III). The removal and adsorption mechanism was the coexistence of physical adsorption and chemical reduction examined by FTIR and XPS illustrating Cr(VI) removal.
The physicochemical properties of biochars derived from rice straw, eucalyptus leaves, and vetiver grass pyrolyzed at 400 ℃ were investigated. It was found that rice straw biochar (RSB) may possess more acidic functional groups than eucalyptus leaves biochar (ELB) and vetiver grass biochar (VGB) while the specific surface area of VGB was the largest. Cd²⁺ adsorption characteristics by the three biochars were established under the effects of time, initial pH and concentration of solution. Maximum adsorption capacities of RSB, ELB, and VGB calculated by Langmuir model were 57.87 mg/g, 50.21 mg/g, and 44.09 mg/g, respectively, reflecting adsorption mechanisms may be dominated by chemical reaction than physical interaction. SEM-EDS, XRD, FTIR and XPS were employed before and after adsorption to qualitatively explore possible adsorption mechanisms of the three biochar. It was found that precipitation, ion exchange, complexation and cation π interaction occurred in all the biochars. The relative contribution of the four main mechanisms to total adsorption capacity was quantitatively determined, suggesting precipitation, ion exchange, and cation π interaction were dominated for the three biochar, while complexation accounted for an insignificant part. This study clearly demonstrated mineral constituents of biochar had significant effects on Cd²⁺ adsorption by plant-based biochars, shedding some light on their future application.
Crop straws represent the major part of lignocellulosic wastes that mainly consist of three polymeric components, namely cellulose, hemicellulose, and lignin. These straws gain great attention owing to their low cost, abundance, renewability and functional groups enriched structure. However, the low adsorption capacity and the tendency to release soluble organic components into water limit the application of crop straws as adsorbents. Chemical modification has been efficiently adopted to avoid these drawbacks and improve the adsorption performance of raw straws. This article presents a review on the chemical modification of crop straws such as wheat, rice, corn, barley, and other straws. Commonly used modifications such as acid or alkali, esterification, etherification, surfactant, magnetic, etc. as well as their combination are discussed. The application of chemically modified crop straws as adsorbents for a variety of water contaminants, and their reuse after regeneration by different eluents are considered. The competitive adsorption behavior of multi-contaminant systems on these adsorbents was also included. The findings and future perspectives for the modification of crop straws and their utilization as adsorbents for water contaminants are finally summarized.
The aim of this investigation concerns the elimination by batch adsorption method of a primary (cationic) textile dye (Crystal Violet) from the synthetic medium, using raw and acid-modified eucalyptus leaves. Parametric studies, such as pH (2–10), unmodified and acid-modified eucalyptus leaves dose (1–10 g L⁻¹), time (5–300 min), and initial strength of CV (10–300 mg L⁻¹) are performed on the elimination of Crystal Violet from the Synthetic Medium. The R–P model gives the maximum coefficient of correlation (R² = 0.99), which denotes the best fitting isotherms with the investigational data from the other isotherms. The maximal capacity of adsorption is 141 mg g⁻¹ for Crystal Violet (CV) on PEUL at 25 °C and pH7. The kinetics study of the CV elimination signifies the pseudo 2nd order kinetics model gives the acceptable fitting rate equation (R² = 0.99) with the investigational data. Intraparticle diffusion model, IPD implies it's not only the rate-limiting step. The overall outcome recommends eucalyptus leaves probably utilized as a low-cost environment-friendly adsorbent for the de-pollution of effluents laden with basic (cationic) textile dye (CV). MPR and GA application on experimental data correctly predicted the removal percentage.
This review provides an important insight on using Sugarcane Bagasse (SB) biosorbent in raw and modified form for removal of dyes from wastewater. Various methods of activation and modification of SB like physical, chemical, biological, composite formation and grafting were explored. Beside this, effect of different optimization conditions like adsorbent dosage, initial dye concentration, pH, temperature and contact time on the adsorption process were studied. Also, regeneration of dye loaded SB, the challenges and perspectives for future researches on waste-derived adsorbents were studied.
Biochar, due to its ability to remediate heavy metals and organic contaminants from polluted water is considered as an economic adsorption material. This work involved pyrolysis driven eucalyptus carbon (EC) to produce eucalyptus activated carbon (AC) through a novel mechanism of using phosphoric acid (H 3 PO 4) and its subsequent testing for efficient adsorption of Cr (VI) from aqueous environments. Advanced characterization techniques like XRD, SEM, BET, FTIR, and XPS were employed to characterize the structure and composition of EC and AC. The AC could remove 99.76% of Cr(VI), which was higher than EC removal rate of 25.24%. The surface area of AC increased by almost 5 times 1265.56 m 2 /g compared to EC (253.25 m 2 /g). The removal rate of Cr(VI) was highly influenced by adsorption capacity, pH, adsorption time, temperature, kinetics, and isotherm. Reaction rate kinetics, isothermal, and ther-modynamic analysis revealed that the adsorption curve of AC fits well with the quasi-second-order kinetic model. AC adsorption process was a spontaneous endothermic reaction limited by intraparticle diffusion and a combination of chemical and physical adsorption.
To meet the demands for screening out the optimal utilization channel for biomass from wheat straw, a number of researches have been reported in the comprehensive utilization about wheat straw including cellulose, hemicellulose and lignin. By reviewing the research status, processing method and comprehensive application of wheat straw, this paper summarizes the application fields, main pretreatment processing methods and bio-products of wheat straw. The paper also detailed novel pretreatment methods and bio-products during the comprehensive utilization of wheat straw. The assessment of more effective pretreatment methods has enabled the examination of wheat straw materials’ potential in the field of lignocellulose that, today, is little exploited. Bioconversion of lignocellulose to bioproducts e.g. bioethanol, biohydrogen and bio-composites has made achievements, however, several limitations such as pretreatment methods remain to be solved.
Straw bale constructions are considered as a promising solution towards the goal of decarbonisation of building sector. In particular, its use as an alternative thermal insulation and load-bearing material has been promoted. This study provide a thorough review of material properties of straw bale including mechanical, thermophysical and hygric. Furthermore, mechanical, hygrothermal, energy and acoustical performance as well as life cycle assessment of straw bale constructions are reviewed and discussed. The critical evaluation of the recent research confirms that straw bales can provide satisfactory results as thermal insulation material compared to conventional materials, while in parallel reflects a high potential for constructions with low embodied emissions. The potential of straw bale is tackled by the lack of consistent representation of material properties, which is controversial to the significant amount of the relevant scientific results that have been reported during the last years. This review provides a systematic framework that can function as basis for future research on straw bales as building material.
Adsorption is considered to be a simple, low cost, and effective technique to decontaminate polluted (waste)water. A lot of research has been done on the application of commercial activated carbon, a traditional adsorbent, that gives satisfactory results but its application is restricted due to high cost. For this purpose, researchers, based also on the concept of green chemistry and circular economy, turn their efforts to finding other adsorbents that are economical, eco-friendly, and abundant. Luffa cylindrica has many applications in medicinal, industrial, and cosmetic sectors. This review article focuses on the alternative use of Luffa biomass (prior and after chemical modification) in the (waste)water treatment process. Specific emphasis is given in the effect of adsorption parameters (such as initial concentration, solution pH, contact time, that affected the adsorption process and on the thermodynamic of the adsorption. Adsorption isotherms and kinetic modeling are also presented and discussed. The adsorption capacities estimated to lie between 2.335 mg/g and 714 mg/g for toxic metals, 9.63 mg/g and 210.97 mg/g for dyes, and 9.25 mg/g and 278 mg/g for emerging pollutants.
The main aim of this work was the development of the chemical activated carbon (AC) method from specific wood biomass, i.e., Eucalyptus camaldulensis sawdust (ECS), and this AC is proposed as a promising alternative treatment for hazardous Cr(VI) from aqueous solution. ECS waste sawdust was carbonized in two stages, i.e. 170 °C for 60 min, followed by 500 °C for 120 min under the continuous steam of nitrogen gas, and rated as an efficient method with H3PO4 activation (>80% Cr(VI) removal). Finally, activated carbon-Eucalyptus camaldulensis sawdust (AC-ECS) was selected for batch and column reactor studies and different influencing parameters, such as contact time, pH, temperature, initial Cr(VI) metal concentration, particle size, and bed height were optimized. AC-ECS was characterized through analysis by SEM, EDX, FTIR, and BET. Cr(VI) adsorption was found to be highly pH-dependent, i.e., 87% at pH 3.0. AC-ECS adsorption mechanism for Cr(VI) with experimental and maximum predicted adsorption capacities of 104 and 125 mg g−1, respectively, was best described by the Langmuir isotherm (R2 = 0.999) and pseudo-second-order kinetics (R2 = 0.999). The column study showed an improvement in the breakthrough curve time from 5595 to 12,270 min, with the respective increase of bed height from 5 to 15 cm, respectively. Column breakthrough data was found to be well fitted to the bed depth service time model. Current batch and column studies indicate that freshwater contamination with Cr(VI) can be managed by upscaling the AC-ECS as an efficient treatment solution.
Rice straw is a potential green resource due to its low cost and high renewability. From the perspective of waste reutilization and green chemistry, an alkali-cooking modified rice straw fiber (AMSF) was prepared as a biosorbent to remove ciprofloxacin (CPFX) from water. To gain the ability of self-generation, a TiO2 hydrogel layer was coated on the surface of AMSF. The adsorption equilibrium was reached at approximately 35 min for AMSF, and the maximum adsorption capacity was 93.5 mg/g. The CPFX removal ability was enhanced by the TiO2-gel layer, especially under ultraviolet, and the CPFX removal quantity by TiO2@AMSF can be 153, 112, and 60 mg/g under ultraviolet, natural light and dark, respectively. The whole adsorption-degradation reaction lasted up to 450 min, and the pseudo-second-order model showed better linearity compared to the Langmuir-Hinshelwood. The CPFX removal ability of TiO2@AMSF in fluoroquinolone antibiotics system was also evaluated, and the adsorption and photodegradation effects were the removal mechanism. Providing more TiO2-gel layers or adding a UV irradiation can be an effective way to regenerate saturated TiO2@AMSF.
Cadmium (Cd) and lead (Pb) have been remained the topic of investigation for various research studies because of their adverse effects on human health, furthermore, they have toxic and non‒biodegradable properties. In this study, vermiculite (VER) was functionalized with octylamine (OCT) to obtain a novel organoclay (OCT-VER) for enhanced simultaneous adsorption of Cd(II) and Pb(II) from aqueous solution. Adsorbents were characterized and parameters influencing on adsorption were also investigated. The adsorption of Cd(II) and Pb(II) by OCT-VER was monolayer and homogenous which was described well by Langmuir isotherm model. After modification, the affinities of OCT-VER towards both metal ions were enhanced. In single system, maximum adsorption capacities for Cd(II) and Pb(II) were improved from 45.245 and 102.289 mg.g⁻¹ to 69.595 and 184.603 mg.g⁻¹, while in binary system from 37.539 and 78.265 mg.g⁻¹ to 61.630 and 121.986 mg.g⁻¹, respectively. In adsorbent regeneration experiment of OCT-VER, the removal ratio was found ≈90% even after 5 consecutive cycles, exhibiting good stability and easy regeneration potential. After studying thoroughly, ion-exchange and complexation properties were the main reaction mechanism. These findings suggested that the proposed low cost adsorbent was suitable and promising material for Cd(II) and Pb(II) adsorption in water.
Water pollution with heavy metals poses many global challenges, especially concerning environmental sustainability, which raises more attention to the field of increasing the performance of the adsorbent materials for toxic heavy metals. This study presents the synthesis of silica nanocomposite from rice straw residues with a high surface area and activating its surface with (3-aminopropyl)triethoxysilane and 3-(trimethoxysilyl)propyl methacrylate (VNH2–SiO2), and the exploitation of acrylates group to link vinylpyrrolidone monomer to produce nontoxic polyvinylpyrrolidone-propylmethacrylate-silica nanocomposite (PVP-SiO2). FTIR and low/high angle-XRD, surface-area profiles are used to identify the properties of these materials. The BET-surface area of silica and activated silica, VNH2–SiO2, and PVP-SiO2 materials were of 985, 603, and 388 m² g⁻¹, with a pore diameter of 4.1, 2.8 and 2.1, respectively. The obtained PVP-SiO2 showed fast adsorption rates and good adsorption capacity of 142.8, 111, 46.08 mg/g, toward lead, copper, and nickel cations, respectively, compared to VNH2–SiO2. Strengthening the structure of silica pores with the groups of carbonyl, amine, and pyrrolidone rings has helped to enhance the adsorption of metal cations on the PVP-SiO2 nanocomposite. By applying the polymer to a sample that mimics a contaminated industrial wastewater sample, the adsorption efficiency was estimated at 99% and decreased to 96% after reuse for four times. Adsorption kinetics are well-matched with the model of pseudo-first-order, whereas the adsorption equilibrium coincided well with the Langmuir model. The calculated thermodynamic parameters (Δ G°, Δ H°, and Δ S°) indicate that the adsorption of lead, copper, and nickel ions on PVP-SiO2 was endothermic and spontaneous. The study of the possibility of material reuses demonstrated that the proposed PVP-SiO2 can be used multiple cycles without a significant reduction in the original adsorption performance.
Efficacy of Eucalyptus camaldulensis seeds in raw (ECS) and phosphoric acid activated form (PECS) in the remediation of Cr(VI) from simulated and electroplating waste has been checked in this study. Structural and physico-chemical characterization of the biosorbents have been elucidated using CHNS, Mercury intrusion porosimetry, FTIR and SEM-EDAX analyses. Batch parameters like dose of biosorbent, pH, contact time, speed of contact, temperature were optimized for a maximum removal of 91.44% for ECS and 98.27% for PECS. Monolayer adsorption capacity for ECS and PECs were found to be 35.3 ± 4.84 mg/g and 51.93 ± 8.11mg/g respectively, elucidated from the nonlinear isotherm analysis. Freundlich Model fitted well for both the biosorbents in removing Cr(VI) at optimum conditions. Interaction of Cr(VI) with ECS and PCES was explained more suitably by kinetics. Pseudo second order model fitting for ECS and PECS revealed that the process followed multilayered chemisorption. Thermodynamic studies confirmed the adsorption of Cr(VI) by ECS and PECS are energetically favorable, stable and exothermic. Continuous column operations for maximum removal of Cr(VI) were optimized for Column bed-height, Initial Cr(VI) concentration and Initial flow rate. Column performances were checked with Adams-Bohart, Thomas, Yoon-Nelson and Bed Depth Service Time (BDST) models. Efficacy of PECS in removing Cr(VI) from real effluent was checked using electroplating effluent containing 190 mg/L of Cr(VI) and resulted with 45.35% removal. Thorough experimental findings showed that PECS is a feasible biosorbent that can remediate Cr(VI) from aqueous solutions effectively.
The presence of toxic pollutants such as dyes and metal ions at higher concentrations in water is very harmful to the environment. Removal of these pollutants using diatomaceous earth or diatomite (DE) and surface-modified DE has been extensively explored due to their excellent physio-chemical properties and low cost. Therefore, naturally available DE being inexpensive, their surface modified adsorbents could be one of the potential candidates for the wastewater treatment in the future. In this context, the current review has been summarized for the removal of both pollutants i.e., dyes and metal ions by surface-modified DE using the facile adsorption process. In addition, this review is prominently focused on the various modification process of DE, their cost-effectiveness; the physio-chemical characteristics and their maximum adsorption capacity. Further, real-time scenarios of reported adsorbents were tabulated based on the cost of the process along with the adsorption capacity of these adsorbents.
Cotton-based adsorbents (CBAs) are promising materials for combating the problem of heavy metal pollution of environmental waters. This is ascribed to the low cost, abundance, biodegradability and efficiency of CBAs. Herein we review the adsorption of heavy metals (HMs) onto CBAs. We found that several surface modifications were employed to improve the efficiency of the CBAs. These modifications were effected via thermal, physical and chemical means to obtain activated carbons, biochars, ionic liquids, aerogels, hydrogels, chitosans and nanoparticle-derived CBAs. The CBAs exhibited maximum HMs uptake as low as 0.002 mg/g to as high as 505.6 mg/g. Although, the cotton-derived activated carbons and biochars exhibited enhanced HM uptake from that of the unmodified CBAs, they were less efficient than CBAs modified by other methods. Recent chemical, ionic liquid, chitosan and nano-derived CBAs were the most efficient, with high uptake and fast kinetic removal. However, the nanoparticle-based adsorbents are preferred to the chemically modified forms, due to the possibility of secondary pollution and the noxious effect of the latter to the environment. Findings showed that chemical treatment produced CBAs most efficient for As(V), Pb(II) and Fe(III), while ionic liquid CBA was more efficient for Cu(II) and Ni(II). Nano-based treatment was suitable for the uptake of Co(II), Zn(II), Pb(II) and Cd(II), while the chitosan based adsorbent was viable for Hg(II). Isotherm and kinetic evaluation of CBAs mostly conformed to the Langmuir and pseudo-second order models, respectively. Spontaneous adsorption of HMs onto CBAs was deduced from thermodynamic analysis, with endothermic and exothermic characteristics. Over 88% desorption of HMs was obtained from the CBAs studied with good average reusability from 3 to 20 cycles. We also discussed the directions for future research.
Straw as an agricultural byproduct has been recognized as a potential resource. However, open-field straw burning is still the main mean in many regions of the world, which causes the wasting of resource and air pollution. Recently, many technologies have been developed for energy and resource recovery from straw, of which the biological approach has attracted growing interests because of its economically viable and eco-friendly nature. However, pretreatment of straw prior to biological processes is essential, and largely determines the process feasibility, economic viability and environmental sustainability. Thus, this review attempts to offer a critical and holistic analysis of current straw pretreatment technologies and management practices. Specifically, an integrated biological process coupled with microbial degradation and enzymatic hydrolysis was proposed, and its potential benefits, limitations and challenges associated with future large-scale straw treatment were also elaborated, together with the perspectives and directions forward.
The development of lignocellulose-based adsorbents for the removal of heavy metals from wastewater has attracted much recent attention. In this work, a high-yield cellulose bacterial strain Comamonas testosteroni FJ17 was evaluated for its capacity to modify rice straw towards increased Cu(II) removal. For optimum modification time (45.5 h), inoculum concentration (1.25%), and rice straw dose (12.6 g L⁻¹) the optimized adsorption capacity was 28.4 mg g⁻¹. After strain FJ17 modification the equilibrium adsorption percentage of rice straw for Cu(II) increased from 6.6 to 27.4% at an initial concentration of 100 mg L⁻¹. This increase was attributed to an increase in rice straw surface modification, leading to improved adsorption ability. SEM-EDS indicated that, following strain FJ17 treatment, the surface of the rice straw became more disintegrated and the specific surface area consequentially increased from 1.9 to 3.7 m² g⁻¹. FTIR analysis also showed new functional groups (carbonyl) appearing, and CC and CH3CR functionality being enhanced after biomodification. Functional groups associated with the benzene ring, silicified polymer and carbohydrates were all involved in the adsorption process. Adsorption of Cu was well described by the Freundlich isotherm model (R² > 0.98) where adsorption was endothermic with potential for both chemical and physical interactions to coexist. Reusability experiments showed that the removal efficiency of Cu(II) decreased from 96.9 to 73.2% after five cycles. Overall C.testosteroni-treated rice straw had significant potential as a heavy metal biosorbent.
Solid state anaerobic digestion (SSAD) with leachate recirculation is an appropriate method for the valorization of agriculture residues. Rape straw is a massively produced residue with considerable biochemical methane potential, but its degradation in SSAD remains poorly understood. A thorough study was conducted to understand the performance of rape straw as feedstock for laboratory solid state anaerobic digesters. We investigated the methane production kinetics of rape straw in relation to cellulose accessibility to cellulase and the microbial community. Improving cellulose accessibility through milling had a positive influence on both the methane production rate and methane yield. The SSAD of rape straw reached 60% of its BMP in a 40-day pilot-scale test. Distinct bacterial communities were observed in digested rape straw and leachate, with Bacteroidales and Sphingobacteriales as the most abundant orders, respectively. Archaeal populations showed no phase preference and increased chronologically. © 2016 Elsevier Ltd
Surfactants have been used often in environmental remediation strategies due to their special amphiphilic nature which alters surface and water interfacial properties. When the aqueous concentration of a cationic surfactant far exceeds the critical micelle concentration (CMC), a large concentration of cationic micelles will form in water. These micelles each consist of tens to hundreds of surfactant monomers, and collectively can be utilized as nano-sized ion exchangers to assist with ultrafiltration separation (i.e., removal) of anionic pollutants from natural waters or wastewaters. Target anionic pollutants include nitrate, phosphate, arsenate and chromate. However, most polluted waters contain a complex mixture of anions, with these different anions competing for the micellar pseudo-phase, thus potentially reducing the overall removal efficiency of the target anions. Further, loss of surfactant monomers through the membrane also reduces process efficiency as replenishment of surfactant over time is required. In this review, the existing research on inorganic anion removal by micellar enhanced ultrafiltration (MEUF) and similar processes are summarized. Operating condition factors are discussed, including pressure, membrane pore size, surfactant-contaminant concentration ratios, and water chemistry conditions (i.e., pH, salinity). Because most micellar surfactant – anion interactions are through outer-sphere electrostatic association, emphases in this review are given to the measurement of selectivity coefficients used for identifying the affinity of anions to the micelles, which generally decreases in the order of: Fe(CN)6³⁻ > CrO4²⁻ > SO4²⁻ > HAsO4²⁻ > HPO4²⁻ > NO3⁻ > Cl⁻ > HCO3⁻ > H2AsO4⁻ > H2PO4⁻ > F⁻ > IO3⁻; and to the development of a speciation model, based on these selectivity coefficients, for predicting anion distribution in micellar solutions. Ways to address improved process efficiency, as well as future challenges and opportunities, are also discussed.
Landfill leachate is a significant environmental threat due to the complexity and variety of its pollutants. There are various physical, chemical, and biological treatment methods proposed for leachate treatment. Adsorption with conventional adsorbents such as activated carbon is a process which has been widely employed with relative success. Magnetic adsorbents are a special type of adsorbents with favorable stability, high adsorption capacities, and excellent recycling and reuse capabilities when compared to conventional sorbents. Research regarding the synthesis and use of magnetic adsorbents has been growing at a rapid pace, exhibiting >8-fold increase in publications in the decade of 2010 to 2020. In the current study, both conventional and magnetic adsorbents for landfill leachate treatment have been comprehensively reviewed and discussed. The application of magnetic adsorbents for landfill leachate treatment is relatively new, with numerous avenues of research open to study. Although the production of magnetic adsorbents is significantly more expensive than conventional adsorbents, when taking into consideration all life cycle costs, they are much more competitive than it initially appears. If environmental impacts are of concern, research should shift towards the use of greener chemicals and processes for magnetic adsorbent synthesis, because preliminary analysis of the current synthesis processes shows a much higher environmental impact compared to conventional adsorbents, in particular in terms of global warming potential and energy use.
The present study investigated the possibility of valorizing rape straw through anaerobic digestion and the possibility of improving biomethane yield by pretreatment with H2SO4, combined H2SO4 with steam explosion (SE) and SE combined with superfine grinding (SFG). To evaluate the pretreatment method efficiency, several analytical techniques were applied. Additionally, the performance of co-digesting of cattle manure (CM) with pretreated rape straw (PRS) at different ratios was evaluated. The results showed that combined pretreatment could dissolve the lignocellulosic fiber structure, which positively stimulated methane yield. The highest cumulative CH4 yield (CMY) of 305.7 mLg⁻¹VS was achieved by combined SE at 180 ˚C for 5 min with SFG, which was 77.84% higher than the untreated. The CMY was further improved by 11.4-59% higher than the control (CM) using co-digestion. This study confirmed that, under optimal parameters of AD, pretreatment with SEG180 could significantly boost the CMY from co-digestion of CM and PRS.
Soybean straw cannot be efficiently degraded and utilized by ruminants due to the complex cross-linked structure among cellulose, hemicellulose, and lignin in its cell wall. Xylanase can degrade the xylan component of hemicellulose, destroy the xylan-lignin matrix and, consequently, would theoretically improve the hydrolysis effectiveness of cellulose. Therefore, this study was performed to investigate the effects of recombinant Lentinula edodes xylanase (rLeXyn11A) on fiber structure, hydrolysis, and in vitro ruminal fermentation of soybean straw. Treatment with rLeXyn11A enhanced the hydrolysis of soybean straw with an evident increase in productions of ribose, rhamnose, and xylose. Soybean straw treated by rLeXyn11A had lower hemicellulose content and greater cellulose and lignin contents. The rLeXyn11A could remove xylan, loosen unordered fibrous networks, enhance substrate porosity, and rearrange lignin, consequently increasing the exposure of cellulose and improving the cellulase hydrolysis of soybean straw. Supplemental rLeXyn11A stimulated the dry matter digestion, volatile fatty acids production, and microbial protein synthesis during in vitro ruminal incubation. This paper demonstrated that rLeXyn11A could strengthen the cellulase hydrolysis and in vitro ruminal fermentation of soybean straw by degrading xylan and changing fiber structure, showing its potential for improving the utilization of soybean straw in ruminants.
Activated carbon with large specific surface area (1545 m²·g⁻¹) and total acid density (2.47 mmol·g⁻¹) was prepared by thermal activation of phosphoric acid treated eucalyptus residue, and was successfully used for simulated dye wastewater treatment where it showed high methylene blue (MB) adsorption capacity (977 mg·g⁻¹). The textural properties and acidic functional groups of the activated carbon could be adjusted and controlled by phosphoric acid/eucalyptus residue mass ratios and activation temperature. Moreover, acidic functional groups could enhance MB adsorption by converting the adsorption pattern from planar to side adsorption with a decrease in activation temperature. The adsorption process was well described by the pseudo-second order kinetics and the Langmuir isotherm model, and it was demonstrated that intra-particle diffusion involved multi-linear stages. These findings provide important insights for the efficient treatment of dye wastewater on an industrial scale using waste eucalyptus residue.