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Adsorptive properties of the pesticides 2,4-D, mecoprop, and dicamba on a pinus-based biochar: Conventional and statistical physics evaluation
Abstract
The adsorptive properties of the pesticides 2,4-D, mecoprop, and dicamba on a pinus-based biochar were scrutinized from conventional and statistical physics approaches.
Firstly, the pinus-based biochar was prepared from Pinus elliottii and extensively
characterized. Then, the conventional adsorption studies were made using kinetic
equilibrium and thermodynamics. Subsequently, the statistical physics model of Hill
was used to interpret the data. Finally, the pinus-biochar was used to uptake the
pesticides from a real river water sample. The results revealed that the pinus-biochar is a rich-carbon material (carbon content higher than 99%) with high thermal stability,
interesting textural features, and proper characteristics to effectively uptake small and
polar organic molecules. At a pH of 7.0 and using 1.0 g L-1, the biochar reduced the
concentration of pesticide solutions from 50 μg L-1 to less than 4.0 μg L-1 in 2 h of
operation. The conventional evaluation revealed that the General order model properly
represented the kinetic profile of the pesticides adsorption, while the Langmuir model
better represented the isotherms. The maximum uptakes of 2,4-D, mecoprop, and
dicamba at 298 K were 100.9 μg g-1, 122.5 μg g-1, and 95.9 μg g-1. The statistical
physics model of Hill could explain the adsorption of all pesticides, and new insights
were proposed for the adsorption mechanism. The pinus-based biochar was also
efficient in decontaminating river waters containing the pesticides, using 5.0 g L-1.
Finally, it can be concluded that pinus-based biochar is a rich-carbon material able to
efficiently uptake the pesticides 2,4-D, mecoprop, and dicamba from synthetic and
natural waters. The efficiency, even in a concentration range of μg L-1, was attributed
to the intrinsic features of the new material
... As a result, these parameters allow for a more comprehensive theoretical depiction of adsorption process across a broad range of adsorbates and adsorbents. Lately, the significance of SPMs has become evident due to the growing number of recently published papers, particularly in contexts such as the adsorption of dyes (Li et al., 2020), (Xue et al., 2022), metals (Pinheiro et al., 2023), and emergent contaminants like naproxen (Franco et al., 2022), acetaminophen (Sellaoui et al., 2023a) and 2,4-D (Sellaoui et al., 2023b). ...
... Additionally, distinct initial 2,4-D concentration (between 10 and 100 mg/L) was tested in adsorption isotherm experiments. Langmuir, Hill (a statistical physics model) and Freundlich models (Sellaoui et al., 2023b) helped in adsorption isotherm analysis. These experiments were performed under optimal pH, dosage, and time determined from earlier experimental sets. ...
... However, these bands are attributed to residual interactions of S with the solvents used [58]. The pattern for AC shows a subtle band with valleys around 2800 cm − 1, representing the asymmetric stretching between C-H and -CH bonds in -CH 2 [59]. The bands between 1500 and 1300 cm − 1 are attributed to C = O and C = C aromatic structures, and their low signal is attributed to the lower oxidation of the kind of substrate employed for producing the AC sample. ...
... The k value obtained for KTP in this study was found to be approximately 5 times higher than the k values reported using other heterostructures and composite catalysts, being equal to 0.0168 min − 1 for CuO-doped TiO 2 supported on graphitic carbon nitride [64] and 0.0182 min − 1 for Ag deposited onto mono-aminated highly porous TiO 2 and CdS heterojunction [12]. Both studies used the same initial KTP concentration of 10 mg L -1 that was also employed in this work, but while total KTP removal was reached by ACFS composite after only 30 min (Fig. 3b2), Mofokeng et al. [59] and Zheng et al. [13] reported the need of 180 min for reaching approximately 95 % of KTP removal. ...
... Therefore, the application of a statistical physics model can be used to describe this orientation at different temperatures by the analysis of the amount of CFN and ACT that was adsorbed by the AC adsorption sites. This model is defined by (Sellaoui et al., 2023): ...
The removal of caffeine (CFN) and acetaminophen (ACT) from water using low-cost activated carbons prepared from artichoke leaves (AAC) and pomegranate peels (PAC) was reported in this paper. These activated carbons were characterized using various analytical techniques. The results showed that AAC and PAC had surface areas of 1203 and 1095 m2 g−1, respectively. The prepared adsorbents were tested for the adsorption of these pharmaceuticals in single and binary solutions. These experiments were performed under different operating conditions to evaluate the adsorption properties of these adsorbents to remove CFN and ACT. AAC and PAC showed maximum adsorption capacities of 290.86 and 258.98 mg g−1 for CFN removal, 281.18 and 154.99 mg g−1 for the ACT removal over a wide pH range. The experimental equilibrium adsorption data fitted to the Langmuir model and the kinetic data were correlated with the pseudo-second order model. AAC showed the best adsorption capacities for the removal of these pharmaceuticals in single systems and, consequently, it was tested for the simultaneous removal of these pollutants in binary solutions. The simultaneous adsorption of these compounds on AAC was improved using the central composite design and response surface methodology. The results indicated an antagonistic effect of CFN on the ACT adsorption. AAC regeneration was also analyzed and discussed. A statistical physics model was applied to describe the adsorption orientation of the tested pollutants on both activated carbon samples. It was concluded that AAC is a promising adsorbent for the removal of emerging pollutants due to its low cost and reusability properties.
... An adsorption energy that characterizes the interactions of the Hg ions with the adsorbent surface can be considered. The mathematical formulation of this model can be summarized as follows [35]: ...
Using organic waste and residue streams to be turned into valuable and greener materials for various applications has proven an efficient and suitable strategy. In this work, two green materials (nanosponges and a polymer) were synthesized using potato peels and applied for the first time to adsorb and recover Neodymium (Nd3+) from aqueous solutions. The recovery of Nd3+ that belongs to the rare earth elements has attracted important interest due to its/their importance in several industrial and technological applications. The fine potato peel waste (FPPW) polymer presented an irregular shape and porous surface. At the same time, the β-cyclodextrin (β-CD) nanosponges had uniform distribution with regular and smooth shapes. β-CD nanosponges exhibited a much higher total carboxyl content (4.02 mmol g-1) than FPPW (2.50 mmol g-1), which could impact the Nd3+ adsorption performance because carboxyl groups can interact with cations. The adsorption capacity increased with the increase of the pH, reaching its maximum at pHs 6-7 for β-CD nanosponges and 4-7 for FPPW polymer. The kinetic and equilibrium data were well-fitted by General order and Liu models. β-CD nanosponges attained adsorption capacity near 100 mg Nd per gram of adsorbent. Thermodynamic and statistical physical results corroborated that the adsorption mechanism was due to electrostatic interaction/complexation and that the carboxyl groups were important in the interactions. β-CD nanosponges (3 cycles of use) were more effective than FPPW (1 cycle of use) in the regeneration. Finally, β-CD nanosponges could be considered an eco-friendly adsorbent to recover Nd3+ from aqueous matrices.
The consumption of açaí fruit (Euterpe oleracea) has largely increased worldwide, resulting in a significant increase in the demand for its pulp. As a result, the small producing communities end up with large amounts of açaí endocarp residues, creating local environmental pollution problems. Therefore, chemical and physical routes were investigated for producing açaí endocarp adsorbents to propose a locally viable solution for this problem. The adsorption properties of the produced biochars were tested for clonazepam (CZM) removal, and the toxicity of the final solutions was evaluated. The results revealed that the chemical route generated biochar with about twice the surface area and pore volume (762 m² g⁻¹ and 0.098 cm³ g⁻¹) than the physical route (498 m² g⁻¹ and 0.048 cm³ g⁻¹). Furthermore, the Sips isotherm better described the CZM adsorption equilibrium for both biochars, with qs values of 26.94 and 61.86 mg g⁻¹ for the physical- and chemical-activated adsorbents. Moreover, recycling studies were performed, and the chemical-activated biochar was stable for up to three cycles, reaching removal rates superior to 80%. Besides, the final toxicity decreased after the adsorptive treatment. Therefore, chemical activation can be used as a simple and effective method for producing stable and compelling adsorbents as an elegant way of adding value to the residues from açaí production, helping solve local environmental problems.
Atrazine and diuron are two pesticide compounds with very low surface interaction capacity, whose adsorption efficiency remains a challenge in environmental remediation applications. In this work, statistical physics (sta-phy) modelling and density functional theory (DFT) calculations have explored several still unveiled mechanisms involved. A model activated carbon (AC) sample was produced with Hovenia dulcis fruit residues, a local invasive tree species. The adsorption process was spontaneous and endothermic, and the adsorption capacities (Qm) increased as the temperature increased. The number of adsorbate molecules per site (n) decreased as the density of the receptor site (Nm) increased, revealing that the temperature influences the geometry of the molecules during the surface interaction. According to the electrostatic mapping provided by the DFT calculations, it was possible to infer that the obtained Qm values for atrazine, between 42.54 to 73.20 mg g⁻¹, can be a response caused by its own self-repulsion. For diuron, due to its increased neutrality, the potential balance of the electrostatic charges between adsorbate-adsorbent tends to be more effective, resulting in higher Qm values, ranging from 97.91 to 119.7 mg g⁻¹. Therefore, the combination of sta-phy modelling with quantum mechanics calculations is a powerful tool for mechanism interpretation, capable of providing complementary insights into the adsorption process from both adsorbent and adsorbate perspectives.
Removal of Reactive Black 5 (RB5) dye from an aqueous solution was studied by its adsorption on banana peel biochars (BPBs). The factors affecting RB5 dye adsorption such as pH, exposure time, RB5 dye concentration, adsorbent dose, particle size and temperature were investigated. Maximum 97% RB5 dye removal was obtained at pH 3 with 75 mg/L adsorbate concentration by banana peel biochars. Fourier transform infrared (FTIR) and scanning electron microscopy (SEM) were used to characterize the adsorbent material. The data of equilibrium were analyzed by Langmuir and Freundlich isotherm models. The experimental results were best reflected by Langmuir isotherm with maximum 7.58 mg/g adsorption capacity. Kinetic parameters were explored and pseudo-second order was found suitable which reflected that rate of adsorption was controlled by physisorption. Thermodynamic variables exhibited that the sorption process was feasible, spontaneous, and exothermic in nature. Banana peel biochar showed excellent regeneration efficiency up to five cycles of successive adsorption-desorption. Banana peel biochar maintained >38% sorption potential of RB5 dye even after five cycles of adsorption-desorption. The phytotoxic study exhibited the benign nature of BPB-treated RB5 dye on tomato seeds.
Bark residues of the forest species Cedrela fissilis were physically and chemically modified with zinc chloride (ZnCl2) as an activating agent. The two modified materials were analyzed as adsorbents in removing atrazine and 2,4-D herbicides from effluents. Firstly, the precursor material and the modified ones were characterized by different techniques to identify the structural changes that occurred in the surfaces. Through TGA, it was observed that both modified materials have thermal stability close to each other and are highly superior to the precursor. X-ray diffractions proved that the amorphous structure was not altered, the three materials being highly heterogeneous and irregular. The micrographs showed that the treatments brought new spaces and cavities on the surface, especially for the material carbonized with ZnCl2. The pHPZC of the modified materials was close to 7.5. The physically modified material had a surface area of 47.31 m2 g−1 and pore volume of 0.0095 cm3 g−1, whereas the carbonized material had a surface area of 98.12 m2 g−1 and pore volume of 0.0099 cm3 g−1. Initial tests indicated that none of the adsorbents were efficient in removing 2,4-D. However, they showed good potential for removing atrazine. The Koble-Corrigan isothermal model best fits the experimental data, with a maximum capacity of 3.44 mg g−1 and 2.70 mg g−1 for physically modified and with ZnCl2, respectively. The kinetic studies showed that the system tends to enter into equilibrium after 120 min, presenting good statistical indicators to the linear driving force model (LDF). The surface diffusion coefficients were 2.18×10−9 and 2.37×10−9 cm2 s−1 for atrazine adsorption on the physically and chemically modified materials. These results showed that the application of residues from the processing of cedar bark is promising. However, new future studies must be carried out to improve the porous development of the material and obtain greater adsorption capacities.
In this work, a novel and effective hydrochar was prepared by hydrothermal treatment of Prunus serrulata bark to remove the pesticide atrazine in river waters. The hydrothermal treatment has generated hydrochar with a rough surface and small cavities, favoring the atrazine adsorption. The adsorption equilibrium time was not influenced by different atrazine concentrations used, being reached after 240 min. The Elovich adsorption kinetic model presented the best adjustment to the kinetic data. The Langmuir model presented the greatest compliance to the isotherm data and indicated a higher affinity between atrazine and hydrochar, reaching a maximum adsorption capacity of 63.35 mg g-1. Thermodynamic parameters showed that the adsorption process was highly spontaneous, endothermic, and favorable, with a predominance of physical attraction forces. In treating three real river samples containing atrazine, the adsorbent showed high removal efficiency, being above 70 %. The hydrochar from Prunus serrulata bark waste proved highly viable to remove atrazine from river waters due to its high efficiency and low precursor material cost.
Background
Environmental contamination by microbes is a major public health concern. A damp environment is one of the potential sources for microbe proliferation. Smart synthesis nanocatalytic coatings on surfaces, food, and material from different pathogen bacteria can inhibit using the Fe 3 O 4 /CNTs as anti-microbial growth can effectively curb this growing threat. In this present work, the anti-microbial efficacy of synthesis of a compound nanoparticle-containing iron oxide-multi-walled carbon nanotube was combined by laser ablation PLAL and explored the anti-bacterial action of colloidal solution of Fe 3 O 4 /CNTs NPs that was evaluated against bacteria which is classified as gram-negative ( Escherichia coli ( E. coli ), Klebsiella pneumonia (K. pneumonia ), and also that is identified as gram-positive ( Streptococcus pyogenes ( S .pyogenes ) and Staphylococcus aureus ( S. aureus ) under visible light irradiation.
Results
Doping of a minute fraction of iron(III) salt (0.5 mol%) in a volatile solvent (ethanol) was carried out via the sol-gel technique. Fe 3 O 4 was further calcined at various temperatures (in the range of 500–700 °C) to evaluate the thermal stability of the Fe 3 O 4 nanoporous oxidizer nanoparticles. The physicochemical properties of the samples were characterized through X-ray diffraction (XRD), atomic force microscopy (AFM), attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), and UV–Visible spectroscopy techniques. XRD results revealed that the nanoparticles framework of Fe 3 O 4 was maintained well up to 650 °C by the Fe dopant. UV–Vis results suggested that absorption property of combination Fe 3 O 4 /CNTs nanopowder by PLAL was enhanced and the band gap is reduced into 2.0 eV.
Conclusions
Density functional theory (DFT) studies emphasize the introduction of Fe+ and Fe2+ ions by replacing other ions in the CNT lattice, therefore creating oxygen vacancies. These further promoted anti-microbial efficiency. A significantly high bacterial inactivation that indicates results was evaluated and that the mean estimations of restraint were determined from triple assessment in every appraisal at 400 ml which represent the best anti-bacterial action against gram-positive and gram-negative microbes.
The high demand for food consequently increases the entry of agricultural residues into water resources, and this phenomenon can affect non-target organisms in different ways. Environmentally relevant pesticide effects (per se or in combinations) are scarce in the scientific literature. Therefore, the aim of this study was to investigate: (1) the presence of pesticide residues in an important Brazilian source of water supply and power generation (Jacuí river), during 1 year of monitoring. (2) in a laboratory study verify the effects of the most frequently, herbicide, fungicide, and insecticide found in Jacuí river (individualized or in a mixture) on biochemical parameters in different tissues of Oreochromis niloticus. Twenty pesticide residues were detected in superficial water samples, and two of them are banned in Brazilian territory. Atrazine (0.56 µg L−1), azoxystrobin (0.024 µg L−1), and imidacloprid (0.11 µg L−1) were the most frequently herbicide, fungicide, and insecticide, respectively, found in the river and were used in the laboratory assay. O. niloticus exposed to the pesticide mixture exhibited more biochemical effects than individualized exposure groups. This response can be a result of the combined pesticide effects, culminating in an additive or synergistic effect, depending on the biomarker. In individual exposure groups, atrazine presented the most pronounced alterations, followed by azoxystrobin and imidacloprid. Overall, pesticide exposure increased levels of oxidative stress parameters, reduced antioxidant enzyme activities, and induced acetylcholinesterase activity. These findings highlight the threat to aquatic organisms which may be exposed to a miscellaneous of toxic compounds in the environment.
The global usage of pesticides has increased by more than 1.5 times over the last three decades. As a consequence, waters are increasingly contaminated by pesticides and their degradation products. For example, organochlorine pesticides are considered most hazardous due to their long half-lives in the environment, up to 5–15 years, and because they bioaccumulate. This is a major health issue requiring advanced methods for water cleaning such as adsorption with activated carbon, yet actual methods are limited by the cost, poor recyclability and disposal of current adsorbents. Here, we review pesticide adsorbents made of materials. Biochars derived from plant materials show maximal adsorption capacities up to around 900 mg/g due to high carbon content in the range of 38 to 80%. Strategies for field applications and post-treatment of spent adsorbents are discussed.
The objective of this study was to evaluate the adsorption capacity of atrazine and the effects of different environmental conditions such as temperature, pH, Ca²⁺ and biochar on the adsorption characteristics of atrazine in different types of soil using the intermittent adsorption method. The kinetic experiment showed that the adsorption of atrazine in albic, black and saline–alkaline soils reached equilibrium within 24 h. In the thermodynamics experiment, the Freundlich model effectively described the adsorption characteristics of atrazine in all three types of soil, indicating that the adsorption process forms multi-molecular layers. Lower soil pH conditions were more favorable for the absorption of atrazine. The addition of appropriate concentrations of Ca²⁺ or biochar could promote the adsorption of atrazine by the soil. Biochar could promote the fixation of atrazine in soils.
Health concerns have been raised over the excessive occurrences of antibiotics such as tetracycline in aquatic environments. Adsorption is a simple and cheap technique for the removal of pharmaceuticals from industrial wastewater. To date, limited information exists on the fate, economical treatment and safe disposal of spent adsorbents in the environment, and this is often considered as the main drawback of adsorption. In this article, an alternative strategy to dispose and reuse spent inorganic adsorbents is proposed. We synthesized CoO/CuFe2O4 mixed metal oxide from layered double hydroxides by a modifed co-precipitation and calcination method at 500 °C for 5 h. CoO/CuFe2O4 has a 348.5 m2/g surface area, pH point zero charge
of 5.8 and an average pore diameter of 5.8 nm. Results show that the tetracycline removal efciency at pH 6 reached 96.6% and 84–87.3% in the absence and in the presence of 4 g/L competing ions (Cl− and NO3−), respectively. Moreover, CoO/CuFe2O4 retained stable activities, of about 90%, over five consecutive recycling runs. Spent CoO/CuFe2O4 was reused as a catalyst in the presence of sunlight for degradation of azo dye, and this is the first report of achieving ~ 77% discolouration of eriochrome black T dye using a recycled adsorbent.
Glyphosate has emerged as the most widespread herbicide to control annual and perennial weeds. Massive use of glyphosate for decades has resulted in its ubiquitous presence in the environment, and poses a threat to humans and ecosystem. Different approaches such as adsorption, photocatalytic degradation, and microbial degradation have been studied to break down glyphosate in the environment. Among these, microbial degradation is the most effective and eco-friendly method. During its degradation, various microorganisms can use glyphosate as a sole source of phosphorus, carbon, and nitrogen. Major glyphosate degradation pathways and its metabolites have been frequently investigated, but the related enzymes and genes have been rarely studied. There are many reviews about the toxicity and fate of glyphosate and its major metabolite, aminomethylphosphonic acid. However, there is lack of reviews on biodegradation and bioremediation of glyphosate. The aims of this review are to summarize the microbial degradation of glyphosate and discuss the potential of glyphosate-degrading microorganisms to bioremediate glyphosate-contaminated environments. This review will provide an instructive direction to apply glyphosate-degrading microorganisms in the environment for bioremediation.
Pesticides and herbicides gained popularity due to a strong need to curb the starvation of billions of humans. Glyphosate is the most commonly used herbicide and was considered to be non-toxic. But its use in excess in agricultural lands has polluted soils and waters. Nowadays, glyphosate residues are found in soil, water and food. As a result glyphosate causes severe acute and chronic toxicological effects. We review toxicological effects of glyphosate and metabolites on organisms of the kingdom animalia, both unicellular and multicellular organisms. Adverse effects on unicellular organisms have been established in many experiments. For instance, glyphosate has reduced the rate of photosynthesis in Euglena, has decreased the radial growth of mycorrhizal fungal species and is also reducing the profusion of certain bacteria present in rhizospheric microbial communities. Glyphosate poses serious threat to multicellular organisms as well. Its toxicological effects have been traced from lower invertebrates to higher vertebrates. Effects have been observed in annelids (earthworms), arthropods (crustaceans and insects), mollusks, echinoderms, fish, reptiles, amphibians and birds. Toxicological effects like genotoxicity, cytotoxicity, nuclear aberration, hormonal disruption, chromosomal aberrations and DNA damage have also been observed in higher vertebrates like humans.
The effectiveness of chemical and thermal pretreatments on Moringa oleifera pods for the atrazine removal from water was investigated. The untreated pods (MOPun), the chemically treated pods (MOPC), and the chemically treated pods followed by the thermally treated pods (MOPT) were physico-chemically and morphologically characterized by elemental, pHZPC, N2 physisorption, FTIR and SEM analysis. The effect of modified pods was significant in increasing surface porosity, favouring the surface chemistry and improving the atrazine biosorption capacity. Kinetics data were best explained by pseudo-second order model for all biosorbents. The equilibrium data for biosorption were analysed by using Langmuir, Freundlich, Sips, and Polanyi-Manes (PMM) isotherm models to define the best correlation for atrazine biosorption capacity. Among the four isotherm models, both Sips and PMM were the models best fitted with the equilibrium isotherm for atrazine. The maximum atrazine adsorption capacities were 0.629, 1.580, and 7.47 mg.g−1 to MOPun, MOPC and MOPT respectively with a maximum removal percentage of 65%, 82%, and 99%. The thermodynamic studies showed that atrazine biosorption is favourable. The biosorption experiments demonstrated that Moringa oleifera pods have great potential for removing atrazine and other organic contaminants from water. This article is protected by copyright. All rights reserved
Gas adsorption is an important tool for the characterisation of porous solids and fine powders. Major advances in recent years have made it necessary to update the 1985 IUPAC manual on Reporting Physisorption Data for Gas/Solid Systems. The aims of the present document are to clarify and standardise the presentation, nomenclature and methodology associated with the application of physisorption for surface area assessment and pore size analysis and to draw attention to remaining problems in the interpretation of physisorption data.
The present work synthesized two new materials of functionalized multi-walled carbon nanotubes (MWCNT-OH and MWCNT-COOH) impregnated with magnetite (Fe3O4) using solution precipitation methodology. The resulting MWCNT-OH-Mag and MWCNT-COOH-Mag materials were characterized by scanning electron microscopy coupled with energy dispersion X-ray spectroscopy, Fourier transform infrared, X-ray diffraction, atomic force microscopy, and electrical force microscopy. The characterization results indicate that the -OH functional groups in the MWCNT interact effectively with magnetite iron favoring impregnation and indicating the regular distribution of nanoparticles on the surface of the synthesized materials. The adsorption efficiency of the MWCNT-OH-Mag and MWCNT-COOH-Mag materials was tested using the pollutants 2,4-D and Atrazine. Over batch studies carried out under different pH ranges, it was found that the optimal condition for 2,4-D adsorption was at pH 2, while for Atrazine, it was found at pH 6. The rapid adsorption kinetics of 2,4-D and Atrazine reaches equilibrium within 30 min. The pseudo-first-order model described 2,4-D adsorption well. The General-order model described better atrazine adsorption. The magnetically doped adsorbent functionalized with -OH surface groups (MWCNT-OH-Mag) demonstrated superior adsorption performance and increased Fe-doped sites. The Sips model described the adsorption isotherms accurately. MWCNT-OH-Mag presented the greatest adsorption capacity at 51.4 and 47.7 mg g-1 for 2,4-D and Atrazine, respectively. Besides, electrostatic forces and complexation rule the molecular interactions between metals and pesticides. The leaching and regeneration tests of the synthesized materials indicate high stability in an aqueous solution. Furthermore, experiments with wastewater samples contaminated with the model pollutants indicate that the novel adsorbents are highly promising for enhancing water purification by adsorptive separation.
In this study, six statistical physics (sta-phy) models were used to further describe and enlighten the mechanisms behind the adsorption of a low interaction model molecule through the interpretations of the real and ideal gas. Density functional theory (DFT) was employed for the simulation of electronic structure and reactivity parameters (Eg, η, μ, and ω). Experimental assays were carried out with a representative activated carbon sample and 2,4-dichlorophenoxyacetic acid (2,4-D) pesticide as a base for the modeling and simulation. According to the classical interpretations, the adsorption was a monolayer exothermic process dependent on temperature. From the sta-phy perspective, the Hill model for monolayer adsorption with two energies best described the process. According to the estimations, the number of molecules adsorbed increases with increasing temperature, yet the number of primary adsorption sites (n) decreases with increasing temperature. The concentrations at a half-saturation (Ci), in turn, increase with the increase in temperature. At last, by combining the sta-phy estimations with the DFT interpretations, it was possible to infer that, in addition to the thermal effects, electrostatic repulsion is a possible contribution that increases as the primary receptor sites are occupied. Therefore, the combination of simulations can provide answers to unclear mechanistic steps and help predict the contribution of the adsorbate to the estimated sta-phy parameters, with a very high degree of precision as statistically validated.
A potential biochar from pepper stems (PS-biochar) was developed via a one-stage pyrolysis process of precursor at 700 °C and employed to adsorb ibuprofen (IBP) in water media. Results showed that PS-biochar was a carbonaceous mesoporous adsorbent with well-developed porosity (SBET= 727.5 m²/g and VTotal= 0.36 cm³/g) and rich surface functional groups. Mechanism of IBP adsorption consisted mainly of π- π interaction, pore filling, and H-bonding. The Langmuir monolayer capacity (569.6 mg/g) was very high compared to values reported in similar studies. The successful PS-biochar regeneration after four cycles in the batch system confirmed the high performance of the NaOH (0.1 M) as a desorbing agent. Therefore, the prepared biochar can be considered as a cost-effective and high-performance material for water decontamination.
Wheat husks (Fagopyrum esculentum) were modified by treatment with sulfuric acid. The precursor material (FEWS) and the modified material (TFEWS) were characterized by different techniques to identify the structural changes promoted by the chemical treatment. Subsequently, TFEWS was applied as an adsorbent to remove the 2,4-dichlorophenoxyacetic acid (2,4-D) pesticide from aqueous solutions. Adsorption studies considered the pH effects and adsorbent dosage on the sorption capacity. Also, it evaluated the kinetics, equilibrium, and thermodynamic behavior. Also, the TFEWS was used to treat spiked-pesticide river waters to check its applicability in actual situations. It was found that the pH of the solution had a strong influence on the adsorption process, selecting pH 2 for the subsequent experiments. Regarding the adsorbent dosage, the best relationship between the percentage of herbicide removal (45%) and the material’s adsorption capacity (24 mg g⁻¹) occurred at 0.95 g L⁻¹. The Avrami-fractional order (also known as Bangham) kinetic model better represented the experimental data. In contrast, the Liu model showed the best adjustment of the equilibrium isotherms of the system, reaching a Qmax of 161.1 mg g⁻¹ at 298 K. The thermodynamic behavior pointed to be spontaneous, favorable, and exothermic, consistent with a mechanism involving electrostatic interactions. The material application in situations close to the actual ones presented 76.00 and 76.30% removals for the simulated effluent of the “Conceição” and “Jacuí” rivers, respectively.
In this work, Diospyros kaki fruit waste was employed as a precursor material to develop a high surface area activated carbon, which efficiently removed the toxic herbicide atrazine (ATZ) from synthetic water solutions and river waters. The alternative activated carbon presented excellent characteristics and structure, including high values of specific surface area (1067 m² g⁻¹) and pore volume (0.530 cm³ g⁻¹) and some important functional groups on the surface. The temperature positively influenced the adsorption capacity, from 194.20 to 211.51 mg g- 1. The Freundlich model was the proper one to represent the equilibrium data. Thermodynamic parameters confirmed the endothermic nature of the adsorption process. Kinetic studies confirmed that equilibrium was reached until 240 min, regardless of ATZ initial concentration. The LDF model adjusted well to the kinetic data, resulting in a diffusion coefficient ranging from 0.89x10⁻⁹ to 1.63x10⁻⁹ cm² s⁻¹ as the ATZ concentration increased. The activated carbon also decreased 85% of the ATZ concentration in a river water sample. Overall, the activated carbon developed from Diospyros kaki fruit waste presented an efficient ATZ removal from aqueous matrices.
The pyrolysis of excess sludge derived from wastewater treatment plants to prepare biochar can achieve the mass-reduction and harmlessness of solid waste, but it is also necessary to further explore the application prospect of these biochars as a resource for wastewater treatment. In this study, Fe-modified biochar (BC–Fe) was prepared by pyrolysis of excess sludge modified by FeCl3 solution. The molecular structure, elemental valence state, and composition of biochars were comprehensively investigated. The results showed that, compared with the biochar prepared from sludge without modification (BC-blank), the O/C ratio of BC-Fe increased from 0.07 to 0.12, and the (N + O)/C ratio increased from 0.21 to 0.27, indicating increased polarity and weakened aromaticity. The ratio of integrated intensity of the D band and G band in the Raman spectrum increased from 1.34 to 2.40, showing the increased defect structure of the biochar obtained by Fe modification. In the reaction between BC-Fe and dicamba, the removal rate of dicamba reached 92.1% within 180 min, which was far higher than the 17.8% of BC-blank. It was confirmed the adsorption removal dominated and accounted for 70.6% of the dicamba removal by BC-Fe, and the adsorption capacity of biochar could be significantly enhanced by Fe-modification by 5.3 times. Moreover, the persistent free radicals (PFRs) on the surface of biochar was detected by an electron paramagnetic resonance analyzer, and the decline of PFRs signals after the reaction revealed that PFRs participated in the degradation process of dicamba. Through Q-TOF analysis, it could be concluded that dicamba was first converted to 3,6-dichlorosalicylic acid (DCSA) by PFRs reduction and then further transformed to 3,6-dichlorogentisic acid (DCGA). This study provided a reference for the understanding of the removal mechanism of dicamba by Fe-modified biochar and offered an application potential of biochar derived from Fe-containing sludge for the pollution control of dicamba pesticide pollutants.
In this work, the adsorption capacity of the biochar obtained from Pinus patula biomass micro-gasification was studied using malachite green (MG) as the probe pollutant. For this purpose, the biomass type (wood pellets and chips) was selected to produce two kinds of biochar (BC). Afterwards, the effects of the adsorbent dose (6, 9 and 12 g/L), the solution pH (4, 7 and 10) and the BC particle size distribution (150-300, 300-450 and 450-600 μm) for the maximization of the MG retention by the selected BC were evaluated using a faced-centered central composite design, as response surface methodology. The results indicated that the BC derived from wood chips (BWC) exhibited a higher MG dye adsorption capacity than the BC obtained from the wood pellets (BWP) gasification under the same operating conditions after having reached the equilibrium. A second-order regression model was built for describing the MG adsorption behaviour by BWC under the considered experimental domain. The model, which was validated, resulted to be statistically significant and suitable to represent the MG adsorption by the studied BC with a p-value of 0.00 and a correlation coefficient (R²) of 95.59%. Additionally, a three-dimensional response surface graph and a contour plot were utilized to analyze the interaction effects between the factors influencing the adsorption system and to discern the optimal operating conditions for the use of BWC. The maximal MG dye retention (99.70%) was found to be at an adsorbent dose, pH solution and a particle size distribution of 9.80 g/L, 10 and from 150 to 300 μm, respectively. Therefore, the BWC tested can be utilized for the treatment of water polluted with dyes, contributing to the establishment of a circular economy.
Anthropogenic activities have severely affected biogeochemical cycles on a global scale, resulting in a drastic increase in environmental problems, intensified by wastewater generation containing high levels of pollutants. As it is known that water is precious yet limited, viable wastewater treatments must be developed. Adsorption is an environmentally friendly option, and it offers the possibility of resolving two problems simultaneously. Besides removing pollutants from water, many adsorbents can be produced using wooden forestry residues. Such materials are generally considered as waste, which leads to their direct disposal. In addition, there are types of wooden forestry waste that have little or no use for humankind, such as fallen leaves or rotten fruits. Therefore, the utilization of wooden forestry residues for preparing low-cost adsorbents is promising. In this review, we briefly approach adsorption advantages to wastewater treatment. Later on, we focus on several types of wooden forestry residues as alternative low-cost adsorbents.
In the present work, multi-walled carbon nanotubes (MWCNTs) were used as support material for the impregnation of metallic nanoparticles (MNPs) produced by green synthesis. The influences of the plant extracts (pomegranate (Punica Granatum), Eucalyptus, and pecan (Carya illinoinensis, leaves), metal species (copper and iron), metallic concentrations, and type of functionalization (OH and COOH) on the characteristics of the obtained materials were studied. The precursor and impregnated MWCNTs were characterized through X-ray diffraction, Fourier transformed infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, point of charge, N2 adsorption/desorption isotherms and, X-ray photoelectron spectroscopy. All the synthesized materials were tested as adsorbents to remove glyphosate (GLY) in an aqueous medium. The MWCNTs were resistant to withstand the synthesis process, preserving its structure and morphological characteristics. The copper and iron on the surface of MWCNTS confirm the successful synthesis and impregnation of the MNPs. The MWCNTs impregnated with high metallic concentrations showed favorable adsorption of GLY. The adsorption capacity and percentage of removal were 21.17 mg g⁻¹ and 84.08%, respectively, for the MWCNTs impregnated with iron MNPs using the pecan leaves as a reducing agent. The results indicated that an advanced adsorbent for GLY could be obtained by green synthesis, using MWCNTs as precursors and pecan leaves as a reducing agent.
A novel green composite catalyst was prepared by doping CuFe2O4 nanoparticles in the malt bagasse biochar. Composites with different ratios of malt biochar and CuFe2O4 were produced and characterized by XRD, FE-SEM, EDS, HR-TEM, UV-Vis, and Zeta potential. The results revealed that CuFe2O4 was successfully supported on the malt biochar surface. The prepared composites showed the band gap energies were narrower than of CuFe2O4, increasing the photocatalytic activity. At 60 minutes of heterogeneous photo-Fenton, tests under visible light indicated CuFe2O4 removed 39% of the rhodamine B color, while composites CFO1B3, CFO1B1, and CFO3B1 removed 88%, 81%, and 44% of the dye, respectively. The recycling of the CFO1B3 composite indicated that it can be used in eight cycles without major losses in efficiency. In sunlight, the CFO1B3 composite achieved efficiencies of 100% for 10 mg L⁻¹ and 50 mg L⁻¹ of rhodamine B at 10 and 20 minutes of reaction, respectively. In the proposed mechanism, it was verified that the radical •OH, O2•− and h⁺ were the predominant reactive species involved in the degradation to intermediates of low m/z. Results showed that the novel composite formed is a promising photocatalyst for removing organic pollutants in water.
The preparation, characterization and adsorption properties of an avocado seed hydrochar for heavy metal removal are reported in this paper. Equilibrium adsorption of Ni²⁺, Pb²⁺ and Cu²⁺ ions on this hydrochar was experimentally quantified at pH 5 and 298 – 313 K and results were used to interpret the role of surface functionalities via statistical physics calculations. A heterogeneous monolayer model that assumed the presence of both phenolic and carboxylic functional groups on hydrochar surface was utilized to estimate the steric and energy parameters of the heavy metal adsorption mechanism. Overall, the maximum heavy metal adsorption capacities of this hydrochar ranged from 0.12 to 0.35 mmol/g at tested operating conditions where the highest adsorption was obtained for Ni²⁺. Statistical physics calculations indicated a multi-ionic adsorption process of these heavy metals where the carboxylic functional groups played a relevant role despite they represented only ∼ 37% of total acidic functional groups available on the hydrochar surface. In fact, the adsorption capacities of carboxylic groups outperformed those of phenolic functional groups where this behavior could be associated to polar character and dissociation degree of these oxygenated surface functionalities. Calculated adsorption energies indicated an endothermic adsorption of these metals where electrostatic interactions and van der Waals forces were involved. This paper contributes with new findings to characterize and understand the adsorption of heavy metal ions on surfaces of adsorbents prepared from hydrothermal carbonization of lignocellulosic biomasses.
Carbon nanotubes with multiple walls (MWCNTs) were modified via green synthesis methodology, with metal nanoparticles (MPNs-Fe). The prepared material (MWCNT/MPNs-Fe) was characterized and used to remove the herbicide glyphosate (GLY) from an aqueous matrix through the adsorption process. The characterization results indicated the presence of MPNs-Fe incorporated between the tangled wires of the MWCNTs, thus confirming the green synthesis success. The kinetic studies showed a percentage of GLY removal of up to 86.23% (for C0 = 35 mg L⁻¹), with the process equilibrium being reached in 120 min. The pseudo-first-order model demonstrated a greater prediction capacity for the system. The Sips isotherm model was best suited to the equilibrium data, providing a maximum adsorption capacity of 43.66 mg g⁻¹ (298 K). The thermodynamic behavior showed that the process is spontaneous and favorable, with exothermic nature. The material's application in close to real circumstances presented the removals of 68.38 and 40.33% for two simulated effluents with different compositions. The adsorption regeneration tests found that the adsorption kept similar adsorption capacities after six cycles. Therefore, it can be concluded that the MWCNT/MPNs-Fe synthesized in the present work is a promising alternative as an adsorbent in the treatment of effluents and waters containing GLY.
A heterogeneous physical model with two bindings sites (HPMTBS) was successfully used to explain the adsorption of Cd²⁺, Ni²⁺, Zn²⁺, and Cu²⁺ ions on flamboyant pods functionalized with citric acid. Experimental results and statistical physics modeling showed that carboxylic and phenolic functionalities of this adsorbent played a relevant role for the adsorption of Cd²⁺, Ni²⁺, Zn²⁺, and Cu²⁺ ions. Calculations performed with HPMTBS suggested that the removal of these cations was a multi-ionic adsorption process at tested operating conditions. This adsorbent was more effective to remove Cd²⁺, Ni²⁺, Zn²⁺ and Cu²⁺ ions at high solution temperatures thus indicating an endothermic process with adsorption energies ranging from 20.3 to 29.5 kJ/mol, which were associated to physisorption. The total adsorption capacities varied from 0.10 to 0.32, 0.28 to 0.39, 0.19 to 0.25 and 0.20 to 0.31 mmol/g for Cd²⁺, Ni²⁺, Zn²⁺ and Cu²⁺, respectively. This difference in adsorption capacities could be attributed to the ionic radius of tested adsorbates. This functionalized biomass can be considered as an alternative adsorbent for facing water pollution by heavy metal ions.
Glyphosate is an herbicide used to control weeds and optimize agricultural production. However, since glyphosate is an emerging pollutant claimed to be potentially carcinogenic, glyphosate pollution of soils and water is a health issue. There is therefore a need for advanced techniques to remove glyphosate from the environment. Here, we review glyphosate properties and materials for glyphosate adsorption such as biochar and graphene, which display high glyphosate adsorption capacities.
The presence of emerging contaminants such as pharmaceuticals in aquatic means presents as a serious threat, since their real consequences for the environment and human health are not well known. Therefore, this work consisted of preparing and characterize sludge-derived activated carbons (beverage sludge activated carbon - BSAC and acid-treated beverage sludge activated carbon - ABSAC) to investigate their use in the pharmaceuticals adsorption in aqueous media. The morphology study has demonstrated that ABSAC, unlike BSAC, exhibited an abundant porous structure, with smaller particles and bigger roughness. Adsorption results indicated that the ABSAC was more effective that BSAC, since it presented superior surface area (642 m2 g-1) and total pore volume (0.485 cm3 g-1) values. Pseudo-second-order kinetic model was more suitable to predict experimental data. Sips model best described the equilibrium data, with maximum adsorption capacities of 145, 105, and 57 mg g-1 for paracetamol, ibuprofen, and ketoprofen, respectively. Besides, the sludge-derived adsorbent was highly efficient in the treatment of a simulated drug effluent, removing 85.16% of the pharmaceutical compounds. Therefore, the material prepared in this work possesses intrinsic characteristics that make it a remarkable adsorbent to be applied in the treatment of pharmaceutical contaminants contained in industrial wastewater.
In this opinion paper, the current scenario and the main challenges in adsorption for water treatment are presented shortly. It is expected that this discussion paper will serve as a fast literature directive to support new ideas and novel investigations in the field. A general background about the topic is first presented. Subsequently, some important aspects that are well developed in literature are discussed, including adsorbent materials, adsorption operation mode, modeling, regeneration, and process operation with real samples. In the last section, it has been pointed out what should likely be the next steps required to advance in this knowledge.
In this study, we developed innovative biochars with high porosity and excellent paracetamol (PRC) adsorption capacity. The optimal pyrolysis temperatures of spherical biochar (derived from pure glucose) and non-spherical biochar (from pomelo peel wastes) were obtained at 900 °C and 700 °C, respectively. Various advanced techniques were applied to characterize the prepared biochars. Spherical and non-spherical biochars exhibited large specific surface area (1292 and 1033 m2/g) and high total pore volume (0.704 and 1.074 cm3/g), respectively. The adsorption behavior of PRC onto two biochars was conducted utilizing batch experiments. Results demonstrated that the adsorption process was slightly affected by the change of solution pH (2–11) and addition of NaCl (0.05–1.0 M) and was able to achieve fast equilibrium (~120 min). The maximum adsorption capacity of spherical biochar (286 mg/g) for PRC was approximately double that of non-spherical biochar (147 mg/g). The signal of thermodynamic parameters was negative ∆G° and ∆H° values, but positive ∆S° value. The adsorption mechanism consisted of pore-filling, hydrogen bonding formations, n-π and π-π interactions, and van der Waals force. The adsorption capacities of two biochar were insignificantly dependent on different real water samples containing PRC. Consequently, the biochars can serve as a green and promising material for efficiently removing PRC from water.
Sulfur-modified pine-needle biochar (BC-S) was produced for the removal of Hg(II) in aqueous media via post-pyrolysis S stream exposure. Fourier-transform infrared spectroscopy, elemental analysis, and X-ray photoelectron spectroscopy confirmed the addition of S(0) groups on the surface of BC-S. Hg(II) adsorption on BC-S was best described by the Freundlich isotherm with a KF of 21.0 mg L g-1 and a pseudo-second-order adsorption kinetics model with a rate of 0.35 g mg-1 min-1. Hg(II) removal on BC-S was found to be an endothermic process that relied on C-Hg and S-Hg interactions rather than reduction by S(0) groups. The adsorption increased with increasing solution pH and decreased with increasing dissolved organic matter concentration, but was unaffected by increasing salt concentrations. BC-S showed a maximum of 3 % S leaching in aqueous media after 28-d exposure time, and exposure to aqueous media did not convert Hg(II) to elemental Hg. Overall, BC-S exhibited superior Hg(II) removal performance over unmodified BC, thus having potential applications in natural water and wastewater treatment with no significant threat of secondary pollution.
A novel Fe3O4-graphene-biochar composite (GBC-Fe3O4) was prepared to enhance the adsorption capacity and recollection efficiency of graphene-biochar composites (GBCs). The adsorption characteristics were tested to remove crystal violet (CV), which is a refractory compound in industrial wastewater. Structural and morphological analysis exhibited that a larger surface area, greater thermal stability, and more functional groups were present after Fe3O4 nanoparticles coated the GBC surface. This improved the CV adsorption versus uncoated GBC. The introduction of G and Fe3O4 nanoparticles collectively reduced the zeta potentials of GBC-Fe3O4 to -38.1 ± 1.1 mV versus -24.3 ± 2.2 mV for GBC and -20.7 ± 1.2 mV for BC. The maximum Qmax values were obtained 436.68 mg/g at 40 °C. Fourier transform infrared analysis suggested that the interactions of functional groups, such as aromatic C = C and C = O, -OH, C-C, and π-π played an important role in CV adsorption. The thermodynamic analysis of Langmuir and Freundlich isotherms indicated that the adsorption improved as a spontaneous endothermic process. The saturation magnetization of GBC-Fe3O4 reached 61.48 emu/g, allowing efficient recollection of the material with a magnet. The CV adsorbability of the re-collected GBC-Fe3O4 was 157.31 mg/g, which was slightly lower than freshly prepared GBC-Fe3O4 (199 mg/g). These findings demonstrated that GBC-Fe3O4 was an efficient and reusable multifunctional biochar.
Biochar is increasingly gaining attention for their potential environmental benefits. In addition to carbon (C), silicon (Si) is a major elemental component in biochar with abundant precursor sources and remarkable properties. Due to the abundance and utilization of silicon-rich biochar (Sichar), as well as the significant function of Si in agricultural production and environmental remediation, it is indispensable to understand the environmental effects of Si within Sichar. Therefore, this review focused on carbon-silicon coupling in Sichar and summarized the advanced studies on Si within Sichar regarding characterization, soil improvement, pollution remediation, and C-Si coupling interactions. After an understanding of Si content, morphology, species and releasing behaviors, the environmental effects on soil Si balance, the plant uptake of Si and remediation potentials of inorganic pollutants (Al, As, Cd, and Cr) were summarized. The C-Si coupling interactions were highlighted in the processes of Sichar preparation, pollution remediation, and soil C sequestration. The coupling relationship of C and Si from biomass under natural, pyrolysis and geological processes for the biogeochemical cycling of C and Si can obtain four “F” benefits of farm, food, fuel, and finance. To better understand the environmental effects and maximize the benefits of the designed utilization of Sichar, more investigations are required with an extension to microbes and more interactions with different ions via quantitative modeling.
In this study, chicken manure biochar (CBC) was prepared and applied as adsorbent for the removal of phenolic pollutants including phenol (Ph) and 2,4-Dinitrophenol (DNP) from wastewaters. The feasibility analysis was focused on the adsorption effects of various factors, such as initial concentration, adsorbent dosage and reaction time. The results showed that BC could efficiently remove the Ph and DNP within 90 min of reaction time. Increasing of CBC dosage up to 0.3 g results in the maximum removal efficiency of Ph and DNP and lowers initial concentration which is beneficial for the adsorption of phenolic compounds. The second-order kinetic model and the Langmuir isotherm provided the best correlation with the adsorption data. Based on the Langmuir isotherm, maximum adsorption capacities (qmax) of Ph and DNP were found at 106.2 and 148.1 mg g⁻¹, respectively. The obtained qmax values for CB were higher than those reported in literature on the adsorption of Ph and DNP using different biochar. Analyzing the regeneration characteristics, BC displayed high reusability with less than 20% loss in adsorption capacities of Ph and DNP, even after five repeated cycles. Investigation of the adsorption equilibrium under various conditions suggested several possible interaction mechanisms, including hydrogen bonding, electrostatic interaction and π- π bonding, which were attributed to the binding affinity of the adsorbent-adsorbate interaction.
In the field application, the CBC showed an excellent removal efficiencies of Ph and DNP from industrial wastewaters (around 80% phenolic pollutants were removed). These findings support the potential use of CBC as effective adsorbent for treatment of wastewater containing Ph and DNP.
Activated carbons from Brazil nutshells were produced by ZnCl2-activation at different biomass: ZnCl2 ratios of 1.0:1.0 and 1.0:1.5 at 600°C and the samples were denominated as BNS1.0 and BNS1.5, respectively. The obtained activated carbons were used in the adsorption of acetaminophen (paracetamol) and for the treatment of synthetic hospital effluents. Several analytical techniques were used to characterize the activated carbons. The N2 isotherms presented the SBET values of the BNS1.0 and BNS1.5 are very high, 1457 and 1640 m2 g-1, respectively. The FTIR and Boehm titration analysis demonstrated the presence of several surface functional groups on both ACs surfaces, which can influence the acetaminophen adsorption. The adsorption studies revealed that the maximum adsorption capacities (Qmax) are very high for both ACs; however, the BNS1.5 capacity is higher (411.0 mg g-1) than that of BNS1.0 (309.7 mg g-1). The thermodynamic assessments revealed that the process of acetaminophen adsorption is spontaneous, energetically favorable, and exothermic, and the magnitude of enthalpy is compatible
with physisorption . Besides, it suggests that the acetaminophen adsorption on both ACs is dominated by van der Walls forces and microporous filling mechanism. The use of activated carbons for treatment of synthetic hospital effluents, containing different pharmaceuticals as well as organics and inorganic salts, presented a high percentage of
removal (up to 98.83%). The adsorbent was magnificently regenerated up to 74% with a mixture of 0.1 mol L-1 NaOH + 20% EtOH solution and can be reused up to four cycles ensuring sustainable use of proposed adsorbent for acetaminophen removal from aqueous media. In the light of these results, it is possible to say that Brazil nutshell is an excellent raw material to prepare efficient ACs which can be successfully used in the
treatment of real hospital effluents.
Sisal fibers were employed as cost-effective adsorbent material to remove methylene blue (MB) and reactive black 5 (RB5) dyes from aqueous solutions. The fibers were characterized and the effects of adsorbent dosage and pH were investigated. Kinetic, equilibrium, and thermodynamics were analyzed. Desorption studies were performed and simulated textile effluents were treated with the fibers. The results revealed that the homogeneous surface diffusion model (HSDM) for cylindrical geometry was able to explain the adsorption kinetics, being the diffusion coefficients (DS) of 3.45 and 1.94 × 10⁻¹⁴ cm² s⁻¹ for MB and RB5, respectively. The BET model was adequate to represent the equilibrium data for MB and RB5. Adsorption capacities reached 553.4 and 310.2 mg g⁻¹ for MB and RB5, respectively. Adsorption was spontaneous and favorable. Chemisorption was involved in the MB adsorption, while, physisorption was dominant for RB5 adsorption. Sisal fibers were efficient to decolorize a simulated effluent, reaching color removal percentage of 85%. It can be concluded that sisal fibers are a promising adsorbent to treat colored effluents, since has low cost, require little processing and possess high adsorption capacity for anionic and cationic dyes.
Purpose:
Degradation or decomposition of the chemical herbicides by natural reagents after using can lead to produce various types of harmful intermediates. Ultrafiltration by the mixed matrix membranes blended with the graphene oxide/TiO2 can remove the residual herbicides from aqueous solution.
Methods:
Graphene oxide/TiO2x% (x = 10, 30, 50%) was prepared by solvothermal method and blended by polysulfone to prepare GO/TiO2/PSf membranes for dynamic rejection of aqueous solutions of glyphosate, 2,4-D, butachlor, and trifluralin in a dead-end flow system. The blended membranes were also applied for the adsorption of herbicides in batch experiments.
Results:
Addition of GO/TiO2 nanocomposite increased water flux from 7.3 for pure membrane to 211-326 kg/m2 h for mixed matrix samples in order to increase of the membrane porosity and surface hydrophilicity. The herbicides rejections were found in the range of 50-70% related to GO/TiO2 content. It was found that the membrane blended with 0.5 wt.% of GO/TiO2(10%) demonstrated the most efficiency.
Conclusions:
Details of dynamic filtration showed that the blended membrane acted based on the size exclusion mechanism. Adsorption experiments indicated that the strong attractions between H-bond donor sites of the herbicide and GO/TiO2 nanoparticles in membranes played a key role in the increase of adsorption of herbicides on the membrane.
In the adsorption literature, the Van't Hoff equation is used in different manners without any criteria about the concepts of physical-chemistry of equilibrium for calculation of thermodynamic parameters of adsorption. Indeed, the equilibrium constant (K) should be dimensionless for being used in the Van't Hoff equation. However, this is not a simple adjustment of units, as being spread in the literature, to become K dimensionless. In this paper, it will be calculated the equilibrium constants using numeric examples and show the flaws of the thermodynamics calculations, when the value of K is wrongly calculated, and what are the expected results of the changes in enthalpy (ΔH°) and changes in the entropy (ΔS°) that are spread in the literature.
Glyphosate (PMG) has been demonstrated to be strongly adsorbed on iron oxides, but few studies have been made on the subsequent degradation process. As the mechanism and process of PMG degradation plays a crucial role on its existence in the environment, this study aims to investigate the comparative adsorption and photo-degradation of PMG on goethite and magnetite. The results show that the Langmuir adsorption capacity of goethite (7.9 mg/g) was higher than that of magnetite (6.7 mg/g) at pH = 7. Further clarifying of Zeta potential and attenuated total reflectance Fourier-transform infrared spectroscopy measurements revealed that PMG was absorbed through the coordination of phosphonate moiety. In contrast, PMG degradation due to the photo-catalysis effectiveness of magnetite (kapp = 1.2 h⁻¹) was significantly higher than that of goethite (kapp = 0.4 h⁻¹) at pH = 7. This phenomenon was primarily due to the greater release of the dissolved iron in magnetite which led to the promotion of reactive oxygen species generation in the magnetite/UV system. DFT results show that the formation of Fe–O–P bonds in the presence of iron oxide would change the electron density distribution around the phosphorus center of PMG, and potentially made the C–P bond more assailable to ROS. Furthermore, electron spin resonance results identified the existence of [rad]OH and O2[rad]−, and further tests by adding radical captures proved the domination of [rad]OH in degrading PMG. In addition, intermediate identification of PMG revealed that amino acid, carboxyl acid and other inorganic ions were the main products in the process of photo-degradation. Therefore, it is concluded that the comparative exploration of goethite and magnetite on PMG degradation provides an integrated insight into the similar fate of PMG heterogeneous photo-degradation in the environment.
The widespread use of glyphosate and the resulting environmental residues pose a serious threat to both crops and human health. The aim of this study was to investigate the adsorption process and removal mechanism of glyphosate by modified biochar (BC). Nano-zero-valent iron (NZVI) was loaded on the palm BC through liquid-phase chemical reduction. The composite material ((BC-NZVI)) was characterized using scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy, revealing that it had a high specific surface area, rich oxygen-containing functional groups and complex ligands. Adsorption experiments were conducted with modified BC to study the effects of contact time (0–3750 min), initial concentration (5–40 mg/L), pH (2.00–7.00) and coexisting pollutants (0–20 mg/L). The adsorption data could be fitted well with the pseudo second-order kinetic model and Langmuir isotherm, indicating that the adsorption of glyphosate on the BC supported NZVI was a chemical and surface process. The maximum adsorption capacity was 80 mg/g at pH = 4, twice that of the original BC. At low concentrations, there was no influence on the adsorption of coexisting pollutants, sulfamethazine, cadmium ions, or phosphate; however, it had antagonistic effect (Rq < 1) when the initial concentration of H2PO4⁺ was higher than 10 mg/L. The adsorption mechanisms involved pore-filling, hydrogen-bond, electrostatic interactions and complexation. Such strong absorbability, along with being easy to obtain and inexpensive, makes (BC-NZVI) potentially suitable for the treatment of agricultural wastewater and acidic farmland soils contaminated with organic pollutants.
This present research work investigates the adsorption of hazardous 2-(2-methyl-4-chlorophenoxy) propionic acid (MCPP) from water using electrochemically synthesized zinc hydroxide material. In order to compute the conditions of higher adsorption efficiency, the various parameters such as pH, temperature, current density and the concentration of the contaminant, and inter-electrode distance were studied. The obtained results were analysed by modeling studies viz. Langmuir, Freundlich, D-R isotherm, and Temkin isotherms. The Langmuir isotherm confirms that the monolayer adsorption of 2-(2-methyl-4-chlorophenoxy) propionic acid molecule on the surface of zinc hydroxide. The adsorption mechanism was studied by pseudo-first order, second-order, Elovich model Weber and Morris intraparticle diffusion models. The adsorption of MCPP on zinc hydroxide follows the second-order kinetic model. Based on the heat effect of adsorption, the thermodynamic parameter via enthalpy, entropy, and free energy was evaluated. The calculated thermodynamic parameters endorse that the adsorption was endothermic, spontaneous and thermodynamically feasible.
A new biochar derived from pecan nutshell was prepared, characterized, and applied as an alternative and low–cost adsorbent for removing Reactive Red 141 (RR141) from aqueous solutions. The yield from raw pecan nutshell to biochar was approx. 30%. The biochar presented a micro/mesoporous structure with a surface area of 93 m² g⁻¹, which is considered high for biomass derived materials. For both, raw pecan nutshell and its biochar, the RR141 adsorption was favored under acid conditions (pH of 2 and 3, respectively). The dye removal percentage was 85% using the biochar as an adsorbent, and was only 23% when raw pecan nutshell was used. The adsorption kinetics of RR141 on the biochar followed the pseudo–second order model. The equilibrium isotherms were well represented by the Freundlich model. The maximum adsorption capacity was approx. 130 mg g⁻¹. The adsorption was spontaneous, favorable, and exothermic (ΔH⁰ = −56.42 kJ mol⁻¹). These findings indicated that the new biochar prepared in this work is an alternative, low–cost, and eco–friendly adsorbent that can be used to remove dyes from colored effluents.
Biochar microparticles were prepared from three different types of biochar, derived from waste materials, such as pine wood (BC-PW), pig manure (BC-PM) and cardboard (BC-PD) under various pyrolysis conditions. The microparticles were prepared by dry grinding and sequential sieving through various ASTM sieves. Particle size and specific surface area were analyzed using laser particle size analyzer. The particles were further characterized using scanning electron microscope (SEM). The adsorption capacity of each class of adsorbent was determined by methylene blue adsorption tests in comparison with commercially available activated carbon. Experimental results showed that dye adsorption increased with initial concentration of the adsorbate and biochar dosage. Biochar microparticles prepared from different sources exhibited improvement in adsorption capacity (7.8 ± 0.5 mg g−1 to 25 ± 1.3 mg g−1) in comparison with raw biochar and commercially available activated carbon. The adsorption capacity varied with source material and method of production of biochar. The maximum adsorption capacity was 25 mg g−1 for BC-PM microparticles at 25 °C for an adsorbate concentration of 500 mg L−1 in comparison with 48.30 ± 3.6 mg g−1 for activated carbon. The equilibrium adsorption data were best described by Langmuir model for BC-PM and BC-PD and Freundlich model for BC-PW.
Biochar microparticles were prepared from three different types
of biochar, derived from waste materials, such as pine wood (BC-PW), pig
manure (BC-PM) and cardboard (BC-PD) under various pyrolysis conditions.
The microparticles were prepared by dry grinding and sequential sieving
through various ASTM sieves. Particle size and specific surface area were
analyzed using laser particle size analyzer. The particles were further
characterized using scanning electron microscope (SEM). The adsorption
capacity of each class of adsorbent was determined by methylene blue
adsorption tests in comparison with commercially available activated
carbon. Experimental results showed that dye adsorption increased with
initial concentration of the adsorbate and biochar dosage. Biochar
microparticles prepared from different sources exhibited improvement in
adsorption capacity (7.8±0.5 mg g-1 to 25±1.3 mg g-1) in comparison
with raw biochar and commercially available activated carbon. . The
adsorption capacity varied with source material and method of production
of biochar. The maximum adsorption capacity was 25 mg g-1 for BC-PM
microparticles at 25 °C for an adsorbate concentration of 500 mg L-1 in
comparison with 48.30±3.6 mg g-1 for activated carbon. The equilibrium
adsorption data were best described by Langmuir model for BC-PM and BC-PD
and Freundlich model for BC-PW
The primary aim of this review on the phenoxyalkanoic acid herbicides (2,4-D, MCPA, dichlorprop-P, mecoprop-P, 2,4-DB and MCPB) was to compare the extent of their adsorption in soils and degradation rates to assess their potential for groundwater contamination. We found that adsorption decreased in the sequence 2,4-DB > 2,4-D > MCPA > dichlorprop-P > mecoprop-P. Herbicides are predominantly adsorbed as anions - on organic matter and through a water-bridging mechanism with adsorbed Fe cations, and their neutral forms are adsorbed mainly on organic matter. Adsorption of anions of 2,4-D, MCPA, dichlorprop-P and mecoprop-P is inversely correlated with their Log D values, and modeling of adsorption of the compounds based on this relationship is possible. The predominant dissipation mechanism of herbicides in soils is bacterial degradation. The contribution of other mechanisms, such as degradation by fungi, photodegradation or volatilization from soils is much smaller. The rate of bacterial degradation decreased in the following order: 2,4-D > MCPA > mecoprop-P > dichlorprop-P. It was found that 2,4-D and MCPA have the lowest potential for leaching into groundwater, and mecoprop-P and dichlorprop-P have slightly higher potential. Because of limited data on adsorption and degradation of 2,4-DB and MCPB, estimation of their leaching potential was not possible. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
The main objective of this work was to find optimal production parameters for the preparation of activated hemp fibers (ACh) with good adsorption properties toward pesticides. In order to examine the role of manufacturing parameters on ACh surface characteristics, activation process of carbonized hemp fibers was investigated by temperature programmed reaction and evolved gaseous products of activation were monitored by mass spectrometry. ACh samples were characterized by BET surface area, scanning electron microscopy and temperature-programmed desorption. KOH activation induces the reduction of oxygen groups existing on the carbonized hemp fiber surface and the formation of the more stable, predominantly anhydride groups, while porosity development correlates with both H2 and CO, evolved during the activation, and increases with carbonization and activation temperature. Finally, the highest efficiency in pesticides removal was achieved by carbonization of waste hemp fibers and activation at 900 °C with KOH/carbonized material ratio of 2/1. High efficiency in pesticides removal indicates that activated hemp fibers could be successfully used as a sorbent in water purification.