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Removal of Methylene Blue by Carbons Derived from Peach Stones by H3PO4 Activation: Batch and Column Studies
Abstract
Several activated carbons were obtained by H3PO4 at 500 °C, under increasing acid concentrations of 30–70%. Products were characterized by N2 at 77 K, and proved to be highly microporous with high surface area and pore volume that increased with impregnation ratio. Two modified carbons were prepared by concurrently passing N2 during pyrolysis of impregnated precursor with 50% H3PO4 at 500 °C, and post-heat treatment at 800 °C for one carbon. A low reduction in porosity accompanied this treatment. Equilibrium adsorption of methylene blue (MB) proved good uptake of the bulky dye, which improved considerably with impregnant concentration that was related to enhanced porosity. Dynamic removal of MB was carried out by running solutions of influent concentrations, of 100–200 mg/L, through a mini-column. Many column performance parameters were estimated at different stages on the typical S-shaped breakthrough curves: volume treated, amounts uptaken, bed service time, height of mass transfer zone, and column exhaustion characteristics. Increased impregnation ratio improved column performance, as well as forcing N2 pyrolysis or extra heat-treatment. Activated carbon impregnated with 70% H3PO4 and carbonized at 500 °C exhibited the best properties which prevailed upon raising treated dye concentration to 150 and 200 mg/L, although degraded its capacity due to the limited mass of adsorbent and to the short contact time.
... Discharging of some dyes shush as MB into natural water bodies prior to treatment could contribute to water pollution because of their persistence and non-biodegradable characteristics [4]. Highly concentration can cause some specific harmful effects in humans such as vomiting, heartbeat increase, cyanosis, shocks, jaundice and tissue necrosis as well as it can affect aquatic life found in natural water bodies by reducing sunlight penetration and/or even causing direct poisoning to living organisms [5,6]. In order to avoid these problems, effluents containing dyes must be treated for their removal before disposal. ...
... This model is often used for the study of the biosorption behaviour of heterogeneous surface energy systems [14] and is expressed as = 1⁄ , (6) A linear form log = log + 1 log , (7) Where ( / ) represents the amount of dye adsorbed; ( / ) is the dye concentration at equilibrium; ...
... This treatment process was repeated three times to obtain triplicate data. Similarly, the treatment process was repeated with variations in contact time (10,20,30,40,45, and 50 minutes) [21], adsorbent dose (30,35,40,45,50, and 55 mg) [22], initial concentration (22,24,26,28,30, and 32 ppm) [22], and pH levels (3,4,6,8,10, and 12) [22]. Adsorption capacity and efficiency can be calculated using the formula: ...
In this study, the adsorption of Remazol Blue and Indigosol Yellow using Bidara Arab leaves (Ziziphus spina-christi) as adsorbents was investigated through batch adsorption. The experimental parameters included contact time, adsorbent mass, initial concentrations, and pH. UV-Vis spectrophotometer was employed to measure the adsorption results at the maximum wavelength of each dye. The research was conducted in triplicate, and a t-test, "Paired Two Sample for Means", with a standard deviation <2% was employed for statistical analysis. Optimal adsorption conditions were achieved at a contact time of 45 minutes, an adsorbent mass of 45 mg, an initial concentration of 30 ppm, and a pH of 3. The results indicated that Bidara Arab leaves effectively reduced the concentration of the mixed dyes with %decoloration up to 99,79% on Remazol Blue and 99,50% on Indigosol Yellow.
... The RS values were found to be 0.049 and 0.075 for the adsorption of glyphosate onto KAC and ZnAC, respectively. This means that the adsorption process of herbicide onto prepared activated carbons is very favourable isotherm (0< RS <1) and the type of adsorption is physisorption (Attia et al., 2008). ...
In this study, glyphosate removal from aqueous solution was compared using activated carbon prepared from rice husk and activated with KCl or ZnCl2. The Min Run Res IV design was used to select the main effect factors of adsorption, and the 3D response surface design was applied to evaluate the interactive effects of the three most important variables. Two adsorption isotherms (Langmuir and Freundlich) and two models of kinetics (pseudo first and second order reaction) were used. The Min Run Res IV design considered five variables, including pH, temperature, time, dose of adsorbents, and type of metals. The three significant factors were further examined using 3D response surface plots, and the optimal conditions were found to be pH 5.8, dose 265 mg, and KAC more effective than ZnAC. The results showed that the adsorption data fitted the Langmuir isotherm model better than the Freundlich model. The rate of glyphosate adsorption followed a pseudo-second-order model.
... Activated carbon (powdered or granular) is the most efficient adsorbent used for dye removal (Anshar et al., 2016;Nandiyanto et al., 2017;Nandiyanto et al., 2018). However, commercially available activated carbons are still considered as expensive materials for many countries due to the use of nonrenewable and relatively expensive starting material such as coal, which is unjustified in pollution control applications (Attia et al., 2008). Therefore, in recent years, this has prompted a growing research interest in the production of activated carbons from renewable and cheaper precursors which are mainly industrial and agricultural byproducts, such as apricot shell (Karagozuglu et al., 2007), male flower of coconut tree (Senthilkumaar et al., 2006), jute fiber (Senthilkumaar et al., 2005), rubber wood sawdust (Kalavathy et al., 2005), corncob (Tseng et al., 2006), bamboo and oil palm fibre (Tan et al., 2007). ...
This research has been conducted on process of production activated carbon from coconut shells, which are activated both physics and chemistry to improve the adsorption of methylene blue. The process of physical activation was done by burning the coconut shell using a furnace at a temperature of 700°C. The chemical activation was done using H3PO4 activator. The result of activated carbon physical activation (CAP) has a greater absorbency than activated carbon chemical activation (CAC) with each of the absorption of methylene blue at 99.42 and 98.64%. Analysis of surface morphology on the adsorbent was performed using a Scanning Electron Microscope (SEM). SEM results indicated that (CAP) has a surface morphology that is relatively similar to commercial activated carbon (CACm). Adsorption test was conducted on the determination of the optimum pH, adsorption rate, and isotherm adsorption of methylene blue. The results of the optimum pH on CAC, CAP, and CACm respectively obtained at pH 8 and the optimum contact time is obtained respectively at 40, 60, and 80 minutes. Adsorption kinetics data of methylene blue on CACm, CAP, and CAC tend to follow the pseudo second order kinetics with a correlation coefficient (R 2) is 0.937; 0.950; and 0.999, respectively. Adsorption isotherm of methylene blue on CACm, CAP, and CAC tend to follow the model of Freundlich isotherms.
... Our rosemary powder was impregnated in a 1:1 ratio with H 3 PO 4 (1 g powder:1 ml H 3 PO 4 ) [15,16]. After that, the mixture was parafilm and left for 24 h. ...
... The design of the RB adsorption system can constitute the most optimal correlation for the equilibrium curves 11 . Here, the Langmuir [equation (8)] and Freundlich [equation (9)] equations, which are common isotherm equations, have been used to determine the equilibrium data of the RB adsorption onto non-chemically modi ed adsorbents at the abovementioned various temperatures. As shown in Table 1 and Fig. 9, the Langmuir isotherm is well tted (R 2 ∼ 0.99) in the entire adsorption period at different temperatures, thereby indicating the homogeneous nature of the surface of non-chemically modi ed adsorbents. ...
Bamboo and coffee, which are abundant and inexpensive, have been used as green adsorbents for the adsorption of industrial dye rhodamine B (RB). Bamboo and coffee are natural sources of cellulose, hemicellulose, and lignin, making them promising green materials for industrial dye removal. The effects of various adsorption conditions, such as contact time, temperature, dose of bamboo powder (BP), coffee ground (CG), initial concentration of RB, and pH values of RB solution, were measured. Consequently, the kinetics of RB adsorption onto bamboo and coffee was in accordance with the pseudo-second-order model, with an activation energy of 29.51 kJ·mol − 1 for bamboo and 27.46 kJ·mol − 1 for coffee. The Langmuir model is well fitted to the whole adsorption period at different temperatures, indicating maximum adsorption capacities of 6.76, 6.96, and 7.64 mg⋅g − 1 (BP) as well as 6.53, 6.80, and 7.51 mg⋅g − 1 (CG) at 30°C, 40°C, and 50°C, respectively. Moreover, the spontaneous nature of the adsorption was based on the negative Gibbs free energy values obtained ( i.e. , from − 11.09 to − 14.30 kJ⋅mol − 1 [BP] and from − 10.34 to − 13.07 kJ⋅mol − 1 [CG]), revealing that RB adsorption occurred at physical and chemical adsorption states. In addition, the recycling capability of adsorbents was determined in five cycles. Therefore, these materials are promising candidates for low-cost adsorbents.
... wood, and rice husk have also been reported for dye adsorption [23][24][25][26]. These described adsorbent's sluggish kinetics make them undesirable. ...
One of the main issues confronting researchers is the removal of hazardous organic dyes from industrial effluent. In this work, a biodegradable starch-based polymer (starch-PMA) and silver blend (Ag@starch-PMA) nanocomposite were developed by a free radical process and employed as adsorbents for efficiently removing the hazardous dyes from industrial wastewater. The synthesized polymer adsorbent’s ability to bind to the methylene blue dye in water was tested under optimal conditions. The techniques, including FTIR, indicate the functional groups, TGA/DTG provide the thermal degradation of Ag@starch-PMA (76%) and starch-PMA (90%) at 520 °C and 500 °C, respectively. The surface morphology of the composites was investigated using SEM, and their biodegradation was examined using the soil burial technique. Further, in the adsorption process, parameters like adsorbent dose (0.15 g), pH range (2–12), and dye solution concentration (10 ppm) are optimized. The experimental data indicate the adsorption efficiency of Ag@starch-PMA (95%) and starch-PMA (92%) under the basic pH (8.4–10.4) and further remains constant. The qmax of starch-PMA (522.7834 mg/g) and Ag@starch-PMA (541.2563 mg/g) were assessed by Freundlich adsorption isotherm. In addition, linear fitting kinetic data of starch-PMA (R² = 0.8619) and Ag@starch-PMA (R² = 0.9898) showed that the adsorbents follow the pseudo-first order and pseudo-second order of reaction, respectively. A unique adsorbent for the removal of MB dye from an aqueous solution may therefore be found in the resultant nanocomposite.
... Today, azo dyes (with one or more R1-N = N-R bonds) are the most widely used synthetic dyes in industry, including the dyeing of jeans, cotton and polyester, accounting for at least 50% of the synthetic dyes used worldwide (Khli et al. 2010;Paquini et al. 2023). This also results in their abundance in wastewater (Yeow et al. 2021), as approximately 10-25% of the amount of dye used in the dyeing process is not bound to the textile bres and can enter the wastewater of these industries (Afroze and Sen 2018; Attia et al. 2008; Konicki et al. 2017). ...
The aim of the study was to determine the feasibility of using compost as a 'green adsorbent' for the removal of five anionic azo dyes belonging to the monoazo, disazo and trisazo classes: Direct Red 81 (DR-81), Direct Blue 74 (DB-74), Reactive Blue 81 (RB-81), Reactive Red 198 (RR-198) and Acid Black 194 (ABk-194) from aqueous solutions. The adsorption capacity of the compost was determined using a batch method with initial dye concentrations ranging from 1 to 1000 mg/L. The kinetics of dye removal followed a pseudo-second-order model, indicating chemisorption as the rate-limiting step. The monoazo dyes RB-81, RR-198 and ABk-194 with the smaller molecule size were adsorbed the fastest. The Langmuir and Sips models best fit the adsorption system with maximum adsorption capacities in the range of 12.64 mg/g (RR-198) − 20.92 mg/g (ABk-194) and 12.57 mg/g (RR-198) − 25.43 mg/g (ABk-194), respectively. The adsorption depended on the dye structure, especially on the ratio of the numbers of proton donor to proton acceptor locations in functional groups. The differences in adsorption mechanism could be explained by thermodynamic properties such as dipole moments, HOMO-LUMO energy gap, polarisability, electron affinity, ionisation potential, electronegativity and chemical hardness obtained by Density Functional Theory.
... Among these, adsorption is one of the most effective methods to remove heavy metals using a suitable adsorbent (Singh et al., 2017). Although, activated carbon is a quite expensive adsorbent depending on its high-cost sources such as wood, coal, and coconut shell (Attia et al., 2008) but cheap sources of plant parts for preparing activated carbon can minimize the cost of preparation. Singh et al. (2017) used low-cost adsorbent for preparing activated for the removal of cadmium from aqueous solutions using water hyacinth (Eichhornia crassipes). ...
Aim: Methodology: Results: Interpretation: To assess the phytoaccumulation efficiency of arsenic in different parts of Typha tripholia (cattail) grown in the natural habitat of a pond located in Rada village of Bijua block, district Lakhimpur Kheri (U.P.) and to develop an adsorbent based removal technology by activated carbon prepared from Typha tripholia (ACTT) using physical activation. Phytoaccumulation of arsenic was studied in cattail plants. Rhizomes and leaves of plants were used to prepare activated carbon. The morphological characterization and surface structure were studied by using different modern techniques like Scanning electron microscopy (SEM), Energy-dispersive X-ray (EDX), and Brunauer-Emmett-Teller (BET). The adsorption efficiency and removal of arsenic were studied by using different-1 doses of ACTT, i.e., 0.5, 1.0, 1.5, 2.0, 2.5 g 100 m l in the known solution of arsenate (30 ppb).-1 The arsenic concentration in pond water was 19 µg l , which was-1 higher than the permissible limit (10 µg l) of WHO, while in the soil it was 123-1-1 µg kg. The maximum As concentration in the root was 360 µg kg , while in-1-1 the stem and leaf, it was 20 µg kg and 26 µg kg , respectively. Characteristics properties of ACTT showed amorphous nature and it contained 81.71 % carbon while other elements like oxygen (10.65 %), chloride (2.12 %) and potassium (5.52%) were also detected. The porosity of-1-1 ACTT was 1.271 × 10-3 cc g with pore volume 3.7 × 10-3 cc g , while the pore size, pore width, and pore diameter were 4.498 nm, 2.0208 nm and 4.498 nm, respectively. Removal of arsenic increased on increasing the dose of activated carbon, and the maximum adsorption (99.6%) was observed at-1 1.5 g 100 ml further it decreased. Thus, Typha tripholia may be used as phytoremediation, a plant-based green technology for the removal of As from contaminated water while ACTT acts as a good adsorbent for As, due to its large surface area and pore space and a high degree of surface reactivity.
... Linear plot of C e /q e against C e (Fig 3.2 , 3.3) for the adsorption of crude oil onto activated carbon suggests the applicability of the Langmuir isotherm of the present system, and demonstrates monolayer coverage of the adsorbate at the outer surface of the adsorbent [66]. the maximum adsorption capacity (q max ) of the crude oil it is found that the q max values are 100 mg.g -1 . ...
One of the major sources of water pollution is oil spills or oily waste waters
... Discharging of some dyes shush as MB into natural water bodies prior to treatment could contribute to water pollution because of their persistence and non-biodegradable characteristics [4]. Highly concentration can cause some specific harmful effects in humans such as vomiting, heartbeat increase, cyanosis, shocks, jaundice and tissue necrosis as well as it can affect aquatic life found in natural water bodies by reducing sunlight penetration and/or even causing direct poisoning to living organisms [5,6]. In order to avoid these problems, effluents containing dyes must be treated for their removal before disposal. ...
Separation of several organic dyes and trace elements from aqueous effluents have a great importance in many areas of research today. Therefore, the main objective of this work was to remove methylene blue (MB) dye from effluents by using cost effective and environmentally method like adsorption. To achieve this work, batch experiments were carried out with an artificial effluent comprising of MB dye in deionised water. The effects of the initial dye concentration, volume, PH value, stability and removal kinetics were studied. An adsorbent dosage of 0.5 g/L was effective in height removal percent of the dye ion, at pH 12.6, and equilibrium time 20-25 minutes. Also, the kinetic process of MB adsorption onto polyurethane foam (PUF) was investigated by applying Lagergen pseudo-first-order and Morris-Weber models to correlate the experimental data and to estimate the kinetic parameters. The adsorption isotherm data were correlated by the Langmuir and Freundlich models. A maximum monolayer adsorption capacity of 0.0929 mg/g was calculated using the Langmuir adsorption isotherm, suggesting a functional group limited adsorption process. The results confirmed that foam are effective sorbent for the removal of dye from effluent
... In sum, RHA possesses superior adsorptive properties for pollutant elimination from aqueous effluents and has previously been applied for metallic pollutant and dye effluent removal [21,22]. The application of such "low cost" material in adsorption was previously investigated for RH in its natural form as an effective methodology for water decontamination [23,24]. However, it has rarely been applied in its modified form especially using a green activation technique such as γ-irradiation [25,26]. ...
Nowadays, the use of natural materials and especially “waste” valorization has evolved and attracted the wide attention of scientists and academia. In this regard, the use of rice husk (RH) powder as a naturally abundant and cheap byproduct material is gaining superior attention. However, improving the physicochemical properties of such RH is still under research. In the current investigation, the modification of rice husk (RH) via γ-irradiation has shown to be a promising green tool to meet such a need. Clean, prepared, powdered RH samples were subjected to various γ-radiation doses, namely 5, 10, 15 and 25 kGy, and the corresponding samples were named as RH-0, RH-5, RH-10, RH-15, RH-15 and RH-25. Then, the samples were characterized via scanning electron microscopy (SEM). After irradiation, the samples showed an increase in their surface roughness upon increasing the γ-radiation up to 15 kGy. Furthermore, the sorption capacity of the irradiated RH samples was investigated for eliminating Urolene Blue (UB) dye as a model pharmaceutical effluent stream. The highest dye uptake was recorded as 14.7 mg/g, which corresponded to the RH-15. The adsorption operating parameters were also investigated for all of the studied systems and all adsorbents showed the same trend, of a superior adsorption capacity at pH 6.6 and high temperatures. Langmuir and Freundlich isotherm models were also applied for UB adsorption and an adequate fitted isotherm model was linked with Langmuir fitting. Moreover, the pseudo-second-order kinetic model provided the best fit for the adsorption data. Experimental assays confirmed that the UB dye could be successfully eradicated feasibly from the aqueous stream via a sustainable green methodology.
... The data epitomized in Table 3 show no considerable differences between pure and pharmaceuticals. 29,30 ...
A simple, fast, sensitive and selective spectrophotometric method has been developed based on the oxidative coupling reaction process, which depends on the determination of clonazepam (CZP) drug using an oxidizing agent sodium periodate (NaIO4) in the presence of a reagent, phenylephrine hydrochloride (PH-HCL), that uses the pink color of CZP at a wavelength of 495 nm. Where several factors aff ecting the color intensity and absorbance were studied, including the eff ect of color stability time, eff ect of the volume of the reagent, the eff ect of the volume of the oxidizing agent, order of addition and temperature. The calibration curve found to obey Lambert beer at range concentration (2–20 mg/L), while the limit of detection (LoD) (8. 9*10-2), limit of quantitation (LoQ) (2.6*10-2) and molar absorbance is 1.4 × 102 liters mol-1cm-1. The method was applied to pharmaceutical preparations (Tablet) and was found to characterize the best precision and accuracy. The standard methods not need any control of temperature and also not aff ected by interferences and henceforth successfully utilized to determine CZP in pharmaceutical preparations
... Thus, a lower activation temperature is required when using this chemical agent. For the carbon materials derived from precursors of a different nature, there are also reports on the S BET and pore volume decreasing as the agent ratio and temperature increase (Attia et al., 2008;Benadjemia et al., 2011, Kang et al., 2018Khamkeaw et al., 2019. Zinc chloride is another chemical agent used for inducing porosity in the plastic-based carbons. ...
In circular economy, useful plastic materials are kept in circulation as opposed to being landfilled, incinerated, or leaked into the natural environment. Pyrolysis is a chemical recycling technique useful for unrecyclable plastic wastes that produce gas, liquid (oil), and solid (char) products. Although the pyrolysis technique has been extensively studied and there are several installations applying it on the industrial scale, no commercial applications for the solid product have been found yet. In this scenario, the use of plastic-based char for the biogas upgrading may be a sustainable way to transform the solid product of pyrolysis into a particularly beneficial material. This paper reviews the preparation and main parameters of the processes affecting the final textural properties of the plastic-based activated carbons. Moreover, the application of those materials for the CO2 capture in the processes of biogas upgrading is largely discussed.
... q e. exp − q e.cal 2 q e.cal (12) where q e.cal and q e.exp are the calculated and experimental adsorption capacities, respectively (mg/g). ...
In the context of the circular economy, used coffee grounds were transformed into powdered activated carbon by chemical activation using potassium hydroxide. Its characterisation was conducted in comparison with that of a commercial activated carbon by scanning electron microscopy (SEM) coupled with energy dispersive X-ray microanalysis (EDX), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Boehm titration, and point zero charge (pHPZC) and by determination of the methylene blue number (MBN) and the iodine number (IN). Performance of the prepared activated carbon was tested in the adsorption of the cationic dye crystal violet (CV) and hexavalent chromium. Batch adsorption tests were carried out and the effects of operating parameters were studied. The results collected on the adsorption kinetics show that the adsorption followed pseudo-second order kinetics and that the Langmuir isotherm best fits the equilibrium data for crystal violet and hexavalent chromium. The thermodynamic study showed that the adsorption of both adsorbates is spontaneous and exothermic and leads to a decrease in disorder at the solid–liquid interfaces. These results indicate that this activated carbon can be used as an alternative adsorbent to remove cationic dyes and heavy metals from aqueous solutions.
... Discharging of some dyes shush as MB into natural water bodies prior to treatment could contribute to water pollution because of their persistence and non-biodegradable characteristics [4]. Highly concentration can cause some specific harmful effects in humans such as vomiting, heartbeat increase, cyanosis, shocks, jaundice and tissue necrosis as well as it can affect aquatic life found in natural water bodies by reducing sunlight penetration and/or even causing direct poisoning to living organisms [5,6]. In order to avoid these problems, effluents containing dyes must be treated for their removal before disposal. ...
... Methylene blue dye (MB) is one of the most recognized probe molecules and frequently mentioned in the technical specifications of activated carbons (Attia et al. 2008;Girgis et al. 2011). The fitting parameters of Langmuir and Freundlich models are given in Table 3, and the applicability was evaluated by using the correlation coefficients (R 2 ). Figure 7A depicts the adsorption isotherms for MB dye onto D and DCGr samples as an example with their analyzed data by Freundlich isotherm (Fig. 7B). ...
The main purpose of this work was to boost the surface and adsorption characteristics of diatomite (D) through chemical modifications with chitosan (DC), chitosan/titanium isopropoxide (DCTi), or chitosan/ graphene oxide (DCGr), respectively. Physicochemical characteristics of the prepared samples were investigated using SEM, TEM, XRD, FTIR, TGA, and porosity measurements. The impact of such modifiers into the D surface on the removal efficiency of chromium (VI) ions and methylene blue dye was studied in an equilibrium mode. Langmuir and Freundlich isotherms were used to analyze the adsorption data. Modifiers considerably enhanced the surface and textural properties of D through insertion of the main surface functional groups of chitosan and graphene oxide together compared to chitosan and titanium isopropoxide
together or chitosan alone. In addition, the total surface area and total pore volume parameters of the unmodified D sample were improved greatly from 16.5 m2/g, 0.036 cm3/g to 39.8 m2/g and 0.174 cm3/g for DCGr, while they were 17.7 m2/g and 0.132 cm3/g for DC. The best adsorption results were well-defined with the Langmuir isotherm equilibrium model. Accordingly, the DCGr sample exhibited the highest uptake of Cr(VI) (about 167 mg/g) and methylene blue (66.7 mg/g). Hence, the chemical modification strategy of diatomite performed by using chitosan and graphene oxide significantly boosted the
surface active sites and porosity properties and thus gave rise to the high adsorption capacity of Cr(VI) and methylene blue dye from wastewater. Hence, these findings affirmed the validity of the current strategy for surface modification of diatomite with chitosan and graphene oxide.
... Activated carbon is widely used for the treatment of wastewater due to internal surface which makes them ideal for the removal of soluble substances from water [13]. The agricultural solid waste as an abundant and cheap material widely used as raw adsorbent or converted into activated carbon by a physical activation process such as pistachio shells [14], almond shells [15], rattan sawdust [16], cotton stalk [17], orange peel and oil-palm shell [18], powdered peanut hull [19], bagasse [20], Sugarcane [21], Peach stones [22]. Glucose, cellulose and hazelnut shells [23]. ...
The date stones were obtained from the market place and the feasibility of utilizing low-cost carbonized datestones for the removal of erythrosine dye from an aqueous media was carefully conducted under laboratory restrictedconditions. Experimental parameters such as temperature, pH, dosage, and concentration were painstakingly maintained.Outcomes show the efficient removal of the contaminant by the substrate CDS (Carbonized date stones), Kinetics models“pseudo-first and pseudo second order was applied. Afterwards, the Langmuir and Freundlich adsorption isotherms wereutilized to identify the adsorption mechanisms. The mechanism of this adsorption process displayed Langmuir adsorptionisotherm which is a monolayer with R2 value of 0.9780 which is higher than that of Freundlich with R2 value of 0.8933. Also,the research work showed that the adhered and suitable kinetic model for the removal of erythrosine dye using carbonized datestones was pseudo second order due to the adsorption capacity of the dye at equilibrium qe was high at the value of 1.8900 to8.3689 in pseudo second order compared to pseudo-first order with 7.4567
... Activated carbon is widely used for the treatment of wastewater due to internal surface which makes them ideal for the removal of soluble substances from water [13]. The agricultural solid waste as an abundant and cheap material widely used as raw adsorbent or converted into activated carbon by a physical activation process such as pistachio shells [14], almond shells [15], rattan sawdust [16], cotton stalk [17], orange peel and oil-palm shell [18], powdered peanut hull [19], bagasse [20], Sugarcane [21], Peach stones [22]. Glucose, cellulose and hazelnut shells [23]. ...
The date stones were obtained from the market place and the feasibility of utilizing low-cost carbonized date stones for the removal of erythrosine dye from an aqueous media was carefully conducted under laboratory restricted conditions. Experimental parameters such as temperature, pH, dosage, and concentration were painstakingly maintained. Outcomes show the efficient removal of the contaminant by the substrate CDS (Carbonized date stones), Kinetics models “pseudo-first and pseudo second order was applied. Afterwards, the Langmuir and Freundlich adsorption isotherms were utilized to identify the adsorption mechanisms. The mechanism of this adsorption process displayed Langmuir adsorption isotherm which is a monolayer with R2 value of 0.9780 which is higher than that of Freundlich with R2 value of 0.8933. Also, the research work showed that the adhered and suitable kinetic model for the removal of erythrosine dye using carbonized date stones was pseudo second order due to the adsorption capacity of the dye at equilibrium qe was high at the value of 1.8900 to 8.3689 in pseudo second order compared to pseudo-first order with 7.4567.
... When an acidic chemical activator is used, it is better to have a temperature in the range of 400-500 °C [49]. The temperature of 500°C in other cases producing activated carbon by phosphoric acid as an activation agent was obtained as the best temperature [50][51][52][53][54][55][56]. The activation temperature of H 3 PO 4 , ZnCl 2 , K 2 CO 3 , NaOH, and KOH ranges from 450 to 600, 500 to 900, 700 to 1000, 550 to 850, and 700 to 850 °C, respectively, the minimum of which is related to H 3 PO 4 . ...
Activated nanocarbons are suitable adsorbents for the removal of metal cations from aqueous solutions, and surface modification is an essential technique for developing this efficiency. In this study, activated carbon was first synthesized by the chemical activation method from bitter orange wood and Amygdalus scoparia Spach, which are used as inexpensive raw materials for activated carbon synthesis. Parameters affecting synthesis include the type of chemical activator (potassium hydroxide, phosphoric acid, and nitric acid), activation time (30 to 90 min), activation temperature (400 to 600 °C), and initial particle size (200 to 400 microns) that optimized based on the Taguchi method. Then, the process of synthesis and surface modification of activated carbon was investigated using detection analyses. The results of FT-IR spectroscopy with elemental analysis indicated that the surface modification was successful at each stage, and the presence of epoxide, carbonyl, amino, and thiol functional groups on the activated carbon surface was confirmed. According to FESEM images, the synthesized particles were three-dimensional with an average thickness of 400–300 nm. Nitrogen uptake and desorption tests followed type I isotherms before surface modification and type II isotherms after surface modification.
... AC is cited preferentially among the many materials considered to be the most promising for the elimination of organic and mineral micropollutants [4]. Various studies have been devoted to the production of activated charcoals from lignocellulosic biomass: grape seeds [4], almond shell [5], coconut shell [6], date pits [7], peach stones [8], woods [9], pods of Flamboyant delonixregia [10]. AC is obtained either by chemical activation or by physical activation. ...
The objective of this work is to prepare an Activated Carbon (AC) from eucalyptus sawdust, having an important pore structure and the best chemical properties for the removal of Methyl Orange (MO) and chromium (Cr-VI) in an aqueous medium. The materials were activated with zinc chloride (ZnCl2). The latter were characterized by thermogravimetric analysis, differential thermal and differential scanning calorimetry (TG-DTG-DSC), Fourier transforms infrared (FT-IR), pH at zero charge point (pHPZC), iodine number (II2), and methylene blue number (IMB). The evaluation of adsorption capacity consisted of discussing the effects of contact time, solution pH, and the effect of temperature using a batch adsorption technique. In addition, different kinetic models (first-order, second-order, and Intra-particle diffusion) and adsorption isotherms (Langmuir, Freundlich) were applied. Analysis of the TG curve illustrates the presence of hemicellulose, cellulose, and lignin, thus confirming the lignocellulosic structure of Eucalyptus Sawdust. Samples AC1/1, AC1/2, and AC1/3 prove to be the best absorbents. The measurement of their iodine numbers gave, respectively II2 (1269.000, 1395.900, and 1395.900 mg/g) indicating a better microporosity and the specific surface area by iodine adsorption (SI2, 1282.900, 1411. 200, and 1411.200 m²/g) justifies the development of porosity. The pseudo-second-order kinetic model better describes the adsorption of MO and chromium (VI) on AC with R 2 = 1 for MO and R² ≥ 0.9996 for chromium (VI). The thermodynamic study gave negative values of free energy which justify the feasibility and spontaneity of the adsorption process of MO and chromium (VI) on AC, the positive values of free enthalpy and entropy reflect that the process is endothermic and reflect the good affinity of chromium (VI) on AC due to pore swelling, whereas, negative values indicate that the process is exothermic and indicate an increase in order at the solid/liquid interface. The heat of adsorption value (ΔH°> 42 kJ mol-1) indicates that the chromium (VI) adsorption process on AC is chemical. On the other hand, the adsorption of MO on AC (ΔH° < 42 kJ mol-1) is of the physical type.
Addressing the complex issue of plastic waste disposal requires a nuanced approach, as no single solution proves universally effective. This review advocates for a comprehensive strategy, combining mechanical recycling and chemical methods to manage plastic waste while emphasizing the transformative potential of carbonization and activation processes specifically. With a focus on chemical activation, this review explores the synthesis of high surface area activated carbon (AC) from diverse plastic sources including polyesters (e.g., polyethylene terephthalate), polyolefins (e.g., polyethylene, polypropylene), and non-recyclable thermoset resins (e.g., epoxy, phenolics). The resulting AC products exhibit notable potential, with high surface areas exceeding 2000 m² g⁻¹ in some cases. Furthermore, the adsorptive behavior of the plastic derived ACs are discussed with respect to common pollutants such as dyes and CO2 in addition to emerging pollutants, such as micro/nano-plastics. Overall, this work highlights carbonization and chemical activation as important upcycling methods for plastic wastes that may otherwise end up in landfills or spills into the environment. Given the urgency of plastic waste disposal, it is recommended that the feasibility and scalability of plastic-derived AC production is explored in future work for the potential replacement of conventional AC feedstocks derived from coal or biomass.
Photocatalysis emerges as a potential remedy for the issue of an unreliable light source. Recognized as the most dependable and potent energy source sustaining life on Earth, sunlight offers a promising solution. Sunlight is abundant and free, operational costs associated with running photocatalytic system using nanoparticles are often lower compared to system relying on artificial light source. The escalating problem of water pollution, particularly in highly industrialized nations, necessitates effective wastewater treatment methods. These methods aim to combat elevated pollution levels, encompassing pharmaceuticals, dyes, flame retardants, and pesticide components. Advanced oxidation processes within photocatalytic wastewater treatment exhibit substantial promise for removing complex organic pollutants. Doped nanomaterials, with their enhanced properties, enable efficient utilization of light. Coupled nanomaterials present significant potential in addressing both water and energy challenges by proficiently eliminating persistent pollutants from environment. Photocatalysis when exposed to sunlight can absorb photons and generate e- h + pairs. This discussion briefly outlines the wastewater treatment facilitated by interconnected nanomaterials, emphasizing their role in water-energy nexus. In exploring the capabilities of components within a functional photocatalyst, a comprehensive analysis of both simple photocatalysts and integrated photocatalytic systems is undertaken. Review aims to provide detailed explanation of the impact of light source on photon generation and significance of solar light on reaction kinetics, considering various parameters such as catalyst dosage, pH, temperature, and types of oxidants. By shedding light on these aspects, this review seeks to enhance our understanding of intricate processes involved in photocatalysis and its potential applications in addressing contemporary environmental challenges.
دراسة اتزان وحركية وثرموداينميكية لامتزاز عدد من المبيدات على سطح الفحم المنشط المحضر والتجاري
Bamboo and coffee, which are abundant and inexpensive, have been used as green adsorbents for the adsorption of industrial dye rhodamine B (RB). Bamboo and coffee are natural sources of cellulose, hemicellulose, and lignin, making them promising green materials for industrial dye removal. The effects of various adsorption conditions, such as contact time, temperature, dose of bamboo powder (BP), coffee ground (CG), initial concentration of RB, and pH values of RB solution, were measured. Consequently, the kinetics of RB adsorption onto bamboo and coffee was in accordance with the pseudo-second-order model, with an activation energy of 29.51 kJ mol⁻¹ for bamboo and 27.46 kJ mol⁻¹ for coffee. The Langmuir model is well fitted to the whole adsorption period at different temperatures, in which the increase in the tested temperature has improved the adsorption capacity (i.e., BP: 6.76 mg g⁻¹/30 °C, 6.96 mg g⁻¹/40 °C, 7.64 mg g⁻¹/50 °C and CG: 6.53 mg g⁻¹/30 °C, 6.80 mg g⁻¹/40 °C, 7.51 mg g⁻¹/50 °C). Moreover, the spontaneous nature of the adsorption was based on the negative Gibbs free energy values obtained (i.e., from − 11.09 to − 14.30 kJ mol⁻¹ [BP] and from − 10.34 to − 13.07 kJ mol⁻¹ [CG]). These revealed that RB adsorption occurred at physical and chemical adsorption states. In addition, the recycling capability of adsorbents was determined in five cycles. Therefore, these materials are promising candidates for low-cost adsorbents.
Ensuring access to affordable water treatment systems is paramount, given the dire situation where millions are deprived of clean drinking water. Industrial wastewater discharge, tainted with hazardous substances, including dyes like methylene blue (MB) from the textile sector, further emphasizes the need for water treatment to produce safe drinking water. This study explores the potential of Olive Mill Solid Waste (OMSW), an abundant and cost-effective agricultural waste in Mediterranean regions, to yield high-quality activated carbon (AC) with zinc chloride (ZnCl 2 ) activation for MB adsorption. The activation process, carried out at a modest temperature of 500°C without the need for an inert atmosphere, resulted in AC with remarkable characteristics, boasting a substantial surface area of 1,184 cm ² .g − 1 and a total pore volume of 0.824 cm ³ .g − 1 . Extensive characterization of the AC was carried out through diverse techniques; Fourier Transform Infrared Spectroscopy (FT-IR), X-Ray Diffractometry (XRD), Brunauer, Emmett and Teller (BET) analysis, Zeta potential, Scanning Electron Microscopy (SEM), and Energy Dispersive X-ray (EDX) spectroscopy. The adsorption performance of the prepared AC was thoroughly evaluated through a comprehensive examination of various factors, including initial dye concentration, contact time, adsorbent dosage, and solution pH. The pH of the solution had minimal influence on MB adsorption, the maximum removal was 95% which was under slightly acidic pH conditions (5.8) and with an adsorbent dose of 0.4 g.L − 1 for a 50 mg.L − 1 MB concentration. Equilibrium data pertaining to MB adsorption were subjected to fitting with different models, namely Langmuir, Freundlich, and Temkin. Notably, the Langmuir model exhibited the best fit, revealing a maximum monolayer adsorption capacity of 500 mg.g − 1 at 25°C, and the adsorption kinetics closely followed a pseudo-second order model. These experimental results underscore the promising potential of Olive Mill Solid Waste (OMSW) as an affordable adsorbent for MB, hinting at its applicability for a diverse array of pollutant removal scenarios.
Activated plant charcoal plays major role in adsorption chemistry and finds a huge application in industry, pharmaceuticals, cosmetics and water treatment. Present work planned to utilize waste sweet corn cop and areca nut husk to prepare charcoal by chemical method. The charcoal was carbonized at 8000C using muffle furnace. The adsorption efficiency of the experimental activated carbon adsorbents towards the model organic compounds methylene blue and salicylic acid were assessed by UV-Vis spectrophotometric method. Experimental results clearly indicates that sweet corn cop charcoal recorded maximum absorption for salicylic acid 640ppm/g in compare to areca nut shell husk charcoal 480ppm/g. Sweet corn cop charcoal recorded optimum absorption for methylene blue 240 ppm/g in compare to areca nut shell husk charcoal 240ppm/g. The experimental charcoal projects noticeable results in scavenging salicylic acid and methylene blue from polluted samples. This experimental results and affordable cost the raw material made the sweet corn cop and areca nut husk activated carbon a powerful alternative for the adsorption of carcinogenic organic compounds salicylic acid and methylene blue.
Industrial effluents produce vast amounts of pollutants and account for 20% of industrial wastewater annually. Methylene blue (MB) is one of the most widely used dyes in the medical, pharmaceutical, and textile industries. However, it is toxic to living organisms, and even a short-time exposure to it can be potentially harmful. Therefore, the purpose of this study was to investigate the efficiency of zinc oxide nanoparticles in removing MB from aqueous solutions in the presence of hydrogen peroxide. The effects of various parameters such as pH (3-10), ZnO nanoparticle dose (0.01-0.08 g/L), reaction time (5-50 minutes), initial concentration of MB (20-200 mg/L), and the hydrogen peroxide concentration (0.5-5 mg/L) were studied. The wavelength of maximum absorption (λmax) was 665 nm. The optimal pH value was 5, zinc oxide nanoparticle dose was 0.05 g/L, the initial concentration of MB was 40 mg/L, the concentration of hydrogen peroxide was 2 mg/L, and the contact time was 20 minutes. The efficiency of MB removal was 97.99%. The results showed that zinc oxide nanoparticles in the presence of hydrogen peroxide could remove the MB from aqueous solutions with high efficiency.
In this study, based on the free radical polymerization, a high-efficiency sodium carboxymethyl cellulose-grafted-Poly (acryl acid-acrylic amide) (SCC-g-Poly (AAc-AAm) hydrogel was prepared using initiators for the generation of free radicals (KPs) and a cross-linking agent, N,N’-Methylene-bis-acrylamide (MBA) as well as loading silver nanoparticles onto SCC-g-poly (AAc-AAm) hydrogel cross-linked by silver nitrate was added at the concentration (1000 mg/L) for about one day to load silver ions on the surface. utilized this AgNP/SCC-g-poly (AAc-AAm) hydrogel to drug release of metformin hydrochloride (MH) was studied at different acid mediums (pH = 7.4 and 1.2) and temperatures of 37℃. This study then studied the ability of the surface to release silver controlled. Field emission scanning electron microscopy (FESEM), Fourier-transform infrared (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), atomic force microscopy (AFM) as well as Brunauer–Emmett–Teller (BET), were among the techniques used to examine the prepared surface’s properties. The highest reported drug release rates occurred at (pH = 7.4) when the rate of drug release was 97.19% after 500 minutes. This is caused by the hydrogel containing COOH, C=O, and OH groups that ionize in the neutral medium (pH = 7.4), forming negative ions, which electrostatically repel each other with the unshared electron pair of the NH group. On the contrary to in an acidic medium (pH = 1.2), the hydrophilic groups included in the hydrogel composition are saturated, making them bond with hydrogen bonds with each other and the percentage of swelling of hydrogel is very small. Two different bacteria species (Gram-negative and Gram-positive bacteria) were used to study the AgNP/SCC-g-poly (AAc-AAm) hydrogel and the ability of the surface to inhibit the two types of bacteria.
REMOVAL OF SELECTED HEAVY METALS FROM WATER BY ADSORBENTS
Granular metallic iron (gFe0) materials have been widely used for eliminating a wide range of pollutants from aqueous solutions over the past three decades. However, the intrinsic reactivity of gFe0 is rarely evaluated and existing methods for such evaluations have not been standardized. The aim of the present study was to develop a simple spectrophotometric method to characterize the intrinsic reactivity of gFe0 based on the extent of iron dissolution in an ascorbic acid (AA-0.002 M or 2 mM) solution. A modification of the ethylenediaminetetraacetic acid method (EDTA method) is suggested for this purpose. Being an excellent chelating agent for FeII and a reducing agent for Fe III , AA induces the oxidative dissolution of Fe0 and the reductive dissolution of FeIII oxides from gFe0 specimens. In other words, Fe0 dissolution to FeII ions is promoted while the further oxidation to FeIII ions is blocked. Thus, unlike the EDTA method that promotes Fe0 oxidation to FeIII ions, the AA method promotes only the formation of FeII species, despite the presence of dissolved O2. The AA test is more accurate than the EDTA test and is considerably less expensive. Eight selected gFe0 specimens (ZVI1 through ZVI8) with established diversity in intrinsic reactivity were tested in parallel batch experiments (for 6 days) and three of these specimens (ZVI1, ZVI3, ZVI5) were further tested for iron leaching in column experiments (for 150 days). Results confirmed the better suitability (e.g. accuracy in assessing Fe0 dissolution) of the AA test relative to the EDTA test as a powerful screening tool to select materials for various field applications. Thus, the AA test should be routinely used to characterize and rationalize the selection of gFe0 in individual studies.
Activated carbon (palm leaf): low-cost sorbents, successfully used for dye adsorption from wastewater preparation of palm leaf, obtained from the grower in Iraq and dry in sunlight and im-pregnated to 3% HNO3 and then dried for 24 hours at 90°C. The adsorption was proved via way of utilizing the (FTIR) and (FE-SEM) analysis, it was observed that there is no change in the beam before and after adsorption only shifts in intensity, evidence of physical adsorption, and FESEM appear image before adsorption contains many smaller granules that are not clustered together and spread on the surface, but after the adsorption we notice the swelling of these particles and they form irregular clusters, evidence of loading the dye inside these granules, which led to swelling. The kinetic model experimental result was carried out via two models fi rst and second order, utilized to describe the adsorption process. Second model kinetic by greater than R2= 0.9864. The study discusses the thermodynamic Factors having changes in enthalpy, entropy, and Gibbs free energy. Through the results, it was found that the adsorption process is an endothermic and spontaneous reaction.
The concept that metallic iron (Fe0) is a reducing agent under environmental conditions has urged the large-scale application of Fe0 filters for environmental remediation and water treatment. During the past two decades, some 3,000 scientific articles have widely discussed the importance of processes yielding water treatment in Fe0/H2O systems. The current state-of-the-art knowledge is that Fe0 is the generator of (i) contaminant scavengers (iron hydroxides/oxides), and (ii) reducing agents (e.g. H/H2, FeII, green rusts, Fe3O4). In other words, contaminant reductive transformation in the presence of Fe0 is not mediated by electrons from the metal body (direct reduction).
The realization that Fe0 is not the reducing agent in Fe0/H2O systems has redirected fundamental researches on the operating mode of Fe0 filters. In this effort, a cationic azo dye (methylene blue, MB) has been presented as reactivity indicator to characterize changes in Fe0/H2O systems. The present study investigates the impact of contact time on the efficiency of Fe0/H2O systems. The research questions are "is there any direct relationship between experimental duration and system's efficiency?" If yes, how is the efficiency modified in the presence of natural additives such as manganese oxides (MnO2) and sand? Both research questions are justified by the evidence that the Fe0 surface is constantly shielded by an oxide scale which has been reported to mediate a 'reactivity loss' of Fe0 materials.
The methodology consists of (i) varying the experimental duration, and (ii) modifying the Fe0/H2O system by amending it with various amounts of MnO2 and sand. The efficiency of Fe0/sand/MnO2 systems for water treatment is characterized using methylene blue (MB) as reactivity indicator. Batch experiments using various weight ratios of Fe0 and the two additives were performed for up to six weeks (47 days). The impact of the intrinsic reactivity of MnO2 was characterized by using different types of MnO2. The MB discoloration process was investigated both under shaking and non-disturbed conditions.
The results clearly demonstrate the impact of increased contact time on the extent of MB discoloration in all tested systems (Fe0, Fe0/sand, Fe0/MnO2 and Fe0/sand/MnO2). As a rule, MB discoloration was improved by increased experimental duration. It was noted that the extent of MB discoloration is influenced by the diffusive (or advective) transport of MB from the solution to the reactive materials at the bottom of the test tubes. Without shaking, more time is needed for the transport of MB to the particles of tested materials. For experiments lasting for longer times, sand addition prevented Fe0 particles from compaction (cementation) at the bottom of the test-tubes. This enabled the long-term generation of iron hydroxides (new iron corrosion products) for the discoloration of MB by adsorption and co-precipitation. The same observation was made for Fe0/MnO2 systems. In other words, the addition of non-expansive materials (e.g. MnO2, sand) is necessary to sustain the efficiency of Fe0 filters. Shaking the test tubes increased the extent of MB discoloration by two different mechanisms: (i) speeding up the mass transport of MB solution towards the adsorptive materials, and (ii) speeding up the kinetics of Fe0 corrosion, creating new corrosion products. Discoloration processes occur due to MB diffusion and advection which are accelerated during the shaking operation. The results clearly delineate the complexity of the Fe0/MnO2/sand system and suggest that varying the experimental conditions will give more opportunities to discuss the efficiency of Fe0/H2O systems.
The high demand for supercapacitors has led to the importance of developing low-cost and eco-friendly materials. Instead of powders, nanofibers were widely developed as a carbon source to increase their durability and ease of handling. Herein, we report the effect of dispersed activated carbon derived from coconut shell charcoal on the supercapacitor performance of activated carbon nanofibers (ACNFs) by electrospinning. The solution was formed by blending coconut shell charcoal (CSC)-based activated carbon and polyvinyl alcohol (PVA) as a spinning polymer agent. This synthesis was conducted using various concentrations of activated carbon and introducing a surfactant during the process. The electrospinning was held at a 10 kV DC voltage, followed by iodine treatment, thermal stabilization, and carbonization at 800 °C. The highest surface area of 250.46 m2/g was obtained from the ACNFs 25S, consisting of PVA 15 w/v %, CSC 25 wt%, and an anionic surfactant. The electrochemical measurement was conducted using Cyclic voltammetry (CV) and possessed a specific capacitance of 186.50 F/g. Moreover, the ACNFs with dispersed activated carbon are promising to be a high capacitance, low cost, and renewable, thereby representing material toward high-power, environmentally friendly, and renewable energy storage devices through further exploration.
This study aimed to investigate the effect of different activations on the properties of bio-based activated carbons (BACs) for water treatment. BACs were produced via pyrolysis by the carbonization stage and were followed by four different activation procedures. Chemical activation included the introduction of metal oxides or alkali on the structure of the sawdust-derived BACs, resulting in iron-activated carbon (BAC-Fe), copper-activated carbon (BAC-Cu), and sodium-activated carbon (BAC-Na). The physical activation was conducted in a CO2 environment with the usage of two types of locally available biomasses, resulting in husk-activated carbon (HAC) and wood-activated carbon (WAC). Depending on the activation, BACs can be developed with high porosity, active sites, and different additional functionalities such as antimicrobial and magnetic. The adsorption of natural organic matter (NOM) with chemically activated BACs yielded high removal percentages (97, 87, and 80% for BAC-Fe, BAC-Cu, and BAC-Na, respectively). The physically activated BACs demonstrated high adsorption capacities for dye – 278 mg/g for WAC and 213 mg/g for HAC. This outlines a wide range of BAC production possibilities with advanced functionalities.
HIGHLIGHTS
Various production parameters and methods allow the modification of final properties of bio-based activated carbons.;
Physical activation provides sufficient surface area for pollutants such as dye; it is cheap and environmental friendly.;
Chemical activation allows the implementation of functional groups on carbon surfaces to improve adsorbent selectivity and reach specific properties.;
N, S co-doped graphene (NSG) has been synthesized by using graphene oxide, cyanamide and sodium sulphide as a source of C, N and S respectively. Due to its excellent electronic properties and stability, NSG has been used as an adsorbent for methylene blue (MB) removal from aqueous solution. Adsorption efficiencies of Graphene, N-doped graphene, S-doped graphene and NSG were compared during the study and it was found that NSG was the most efficient material for the adsorption of MB. The study was carried out in the UV-visible region by observing the changes in absorbance. NSG has excellent properties to adsorb the MB dye with a removal efficiency of 93.76±0.2 %. Additionally, desorption studies were also carried out using 0.1M cetylpyridinium chloride as cationic surfactant and the desorption % was found to be 50.28±0.1 %, signifying its reusability as an adsorbent. This indicates that NSG opens a new window for the design of heteroatom-doped carbon material as well as its application in the adsorption studies. Accordingly, the synthesized material will be employed for wastewater treatment as a reusable adsorbent of MB in the near future with high efficiency and appreciable stability. In addition, the material has several other future applications such as electrode material for supercapacitor battery, sensor, adsorbent for metal ions and biomolecules, etc.
To address the increasing accumulation of water bottle waste and lack of effective recycling processes, water bottle waste was upcycled into a high value activated carbon product. This growing waste feedstock has proved to be a promising precursor for activated carbon, but it has not been investigated for use in the treatment of dye-contaminated effluent which is a very high-volume source of waste from textile industries. In this work, the production of activated carbon from water bottle waste by chemical activation using KOH was optimized and validated for the application as an adsorbent of textile dyes. The activation conditions of 800 °C for 1 h proved to be most optimal based on conversion efficiency, surface area, surface charge, and yield measurement. It was found that the product’s negative zeta potential (−40 mV) and high surface area (1124 m²/g), provided excellent adsorption capacity for the cationic methylene blue dye (335 mg/g). The adsorption of this representative dye was studied in detail and compared with cationic brilliant green dye and a mixture containing anionic methyl orange dye. Although the adsorption was found to depend on dye charge characteristics, there is potential for adsorption enhancement through pH adjustments. Additionally, the AC demonstrated the ability to treat mixed dye wastes containing anionic dyes despite its selective adsorption towards cationic dyes of over twice the amount. Overall, the product showed potential to be extended to a variety of textile dyes to provide excellent value for the textile industry while also helping to divert a significant amount of waste from landfills.
In this article, the technical feasibility of raw and activated carbonActivated carbonhazelnut shellsHazelnut shells for the removal of heavy metalsHeavy metals and dyes from wastewaters has been reviewed. Adsorption has been proved to be an excellent way to treat industrial waste effluents, offering significant advantages like the low-cost, availability, profitability, convenience in operation and efficiency. There is a great potential of hazelnut shells to be used in adsorption applications. Nanotechnology is an advanced field of science having the ability to solve the variety of environmental challenges by controlling the size and shape of the materials at a nanoscale. Carbon nanomaterialsCarbon nanomaterials are unique because of their nontoxic nature, high surface area, easier biodegradation and particularly useful environmental remediation. TextileTextile dyes industry effluents and heavy metal contamination in water are major problems and pose a great risk to human health. Carbon nanomaterials namely carbon nanotubes, fullerenes, graphene, graphene oxide and activated carbon have great potential for removal of heavy metals and dyes from water because of their large surface area, nanoscale size and availability of different functionalities and they are easier to be chemically modified and recycled. Activated carbon was also prepared using agricultural by-products such as palm-tree cobs, grape seeds, several nutshells (almond shell, hazelnut shell, walnut shell and apricot stone), olive-waste cakes and corn cob due to the fact that activated carbon made from conventional raw materials are expensive. This review reports the removal of heavy metalsHeavy metals and dyes from wastewaters using raw and activated carbon hazelnut shells in order to provide useful information on various aspects of utilization of the agricultural waste materials and carbon nanomaterialsCarbon nanomaterials. The adsorption capacities of raw and activated carbonActivated carbonhazelnut shellsHazelnut shells under different experimental conditions are also reported and compared with other agro-based adsorbents.
Animal models form the foundation for preclinical biomedical research and will certainly do so, seeing as their life span, albeit, brief, unmistakably mimics that of humans – and further affirms the universality of the aging process. When it comes to animal models for aging research it is important to note that some organisms, such as mice, age diametrically than humans. It is also paramount to note that no single animal model is perfect; therefore, it is prudent to utilise data from both conventional and non-conventional model systems, provided the results are not skewed. The best approach to picking animal models for aging and age-related research is the multifaceted approach, which involves the use of different models. The use of model animals in aging research is risky in light of the fact that our capacity to extrapolate across the tree of life is not clear. On one hand, there are moderated pathways that direct life expectancy in creatures, including yeast, nematodes, natural product flies, and mice. On the other hand, many
middle taxa across the tree of life seem not to age by any means, and there is considerable variety in aging mechanisms and patterns – once in a while, even between firmly related species. There are multitude of evidence that show that active behaviours performed by animals daily may have short-term and, sometimes, long-term physiological cost, causing an increase in oxidative stress, DNA damage, and, in some instances, reducing survivability. Quantification of physical activity (such as reproductive events, migration) and measurement of its resulting physiological costs (such as immune-compromisation, production of reactive oxygen species, DNA damage, and distortion of physiological homeostasis) is important in studying the physiology of aging. Understanding the peculiarities of very slow-aging and long-lived creatures, as well as broad comparison trends, will be critical. Aging appears to be significantly influenced by evolutionary history, ecological context, and the habitat in which an organism lives, therefore findings must be evaluated with caution and always in a comparative context.
Only by continuing to apply a multi-pronged strategy that includes standard lab models,
uncommon lab models, wild animals, and comparative physiological and demographic data will the mysteries of aging be unraveled.
الماء المتوفر للاستخدام في العادة يكون فاقداْ لكثير من خواصه بسبب عمليات التصنيع أو التلوث التي يتعرض لها. ويتطلب الأمر إلى عمليات المعالجة أو التحلية للحصول على ماء ذو خواص حيوية مناسبة للاستخدام. توجد العديد من عمليات معالجة الماء وتنقيته من الشوائب من أهمها عملية معالجة الماء مغناطيسياً، التي تعمل على إعادة احيائه وتغذيته وإظهار خواصه. تمتاز عملية معالجة الماء باستخدام المجال المغناطيسي برخص التكلفة وسهولة الاستخدام والاستدامة .إن معالجة الماء مغناطيسياً تمنع تشكل الترسبات الكلسية على السطوح الداخلية والخارجية للأجهزة والمعدات التي تتدفق من خلالها الماء، وتمنع تكون القشور والترسبات على الأسطح الداخلية للأنابيب والتي تؤدي بدورها إلى عدم انسدادها. كما يسبب المجال المغناطيسي في انخفـــاض كتلة جزئيــات الماء بحيث ينخفض عدد الجزيئـــات في الكتلة المــــائية الي النصف تقريبا، وهذا يؤدي الي زيادة مشاركة جزيئات الماء في ترطيب أو تذويب المواد مثل الخلطات الإسمنتية. في هذا البحث تم اجراء التجارب المعملية لدراسة تأثير المياه المعالجة بالتقنية المغناطيسية على الخلطات الاسمنتية. حيث أثبتت التجارب أن الماء الممغنط يزيد من قوة الانضغاط الخرسانة، أي أن قوة الانضغاط للخرسانة المخلوطة بالماء الممغنط أعلى من قيمة قوة الانضغاط للخرسانة العادية.
Mixing iron ore tailings with clay for manufacturing bricks was investigated
with the objective of converting the hazardous solid waste into useful
products. Blocks were prepared using different compositions of iron ore tailings and
clay in 70.6 mm cubic moulds. They were sundried and then placed in a furnace at
110 °C for 24 h to remove water. The dry blocks were fired at temperatures ranging
from 900 to 1050 °C for 3 h. Characterization of tailings, clay, and sintered blocks
was done. Mechanical properties such as compressive strength, water absorption
rates, loss on ignition, and bulk density were measured. The maximum compressive
strength of 25.40 MPa was recorded for tailing and clay ratio of 40:60 sintered at
950 °C. This compares very well with the best quality bricks in India. The results
also indicate that the percentage of tailings in the blocks influences their mechanical
properties. The water absorption rates of the sample blocks are low compared to
clay and fly ash bricks, and the same varies with process parameters. The low
porosity may deter the formation of efflorescence. The process, with standardized
parameters, may be commercially adapted, and large quantities of iron ore tailings
may be put to use in making bricks. Thus, the process technology delineated in this
paper can potentially convert the huge amount of environmentally harmful useless
waste into wealth. Iron ore tailing may emerge as a sustainable supplement to clay,
use of which in brick making is increasingly being restricted. The work also paves
the way for a new strand of research.
Ba0.77Sr0.23TiO3 (BST)/kaolinite 5, 10, and 20% w/w nanocomposites were synthesized by the modified wet chemistry sol-gel method. FTIR (Fourier transform infrared) spectrum represented the formation of barium strontium titanate at 950-970 cm⁻¹ which was corresponding to the Ti-O-Si bridge. Two distinct bands at 600 and 760 cm⁻¹ confirmed the appearance of kaolinite in nanocomposite structures. The crystallite structure and lattice parameters of samples was studied by X-ray diffraction. Adding kaolinite to BST nanoparticles resulted in increasing the intensity of metakaolinite peaks. FESEM (field emission scanning electron microscope) pictures illustrated the cracks on the layer of kaolinite as well as the tetragonal shape of BST nanoparticles. Photocatalytic studies confirmed that by kaolinite insertion, the decolorization efficiency decreased dramatically. Barium strontium titanate by generating electron-hole mechanisms could decompose methylene blue (MB) dye, conveniently, and the sample with the formula of Ba0.77Sr0.23TiO3/kaolinite 5%w/w represented the highest photodegradation properties. The kinetics and mechanism of photodegradation were studied for all samples.
The equilibrium and dynamic adsorption of methylene blue from aqueous solutions by activated carbons have been studied. The equilibrium studies have been carried out on two samples of activated carbon fibres and two samples of granulated activated carbons. These activated carbons have different BET surface areas and are associated with varying amounts of carbon oxygen surface groups. The amounts of these surface groups was enhanced by oxidation with and gas at and decreased by degassing at increasing temperatures of , and . The adsorption increases on oxidation of the carbon surface and decreases on degassing. The increase in adsorption has been attributed to the formation of acidic carbon-oxygen surface groups and the decrease in adsorption on degassing to their elimination. The dynamic adsorption studies have been carried out on the two granulated activated carbons using two 50 mm diameter glass columns at a feed concentration of 300 mg/L and at different hydraulic loading rates (HLR) and bed heights. The minimum achievable concentrations are comparatively lower while the adsorption capacities are higher for GAC-S under the same operating conditions. The adsorption capacity of a carbon increases with increase in HLR but the rate of increase decreases at higher HLR values.
A series of activated carbons was prepared from coconut shell impregnated with phosphoric acid using a one-step carbonization procedure and varying conditions in order to optimize preparation parameters. The mode and nature of gaseous flow during carbonization were found to affect the surface area and yield, suggesting that oxygen derived from the gas phase may play an important role in activation, and that coking of volatiles could be contributing to the building of the porous structure. The optimum activation temperature for a higher surface area was 450°C. Higher surface area and mesoporosity were favored by increasing the acid concentration of the impregnating solution. Infrared spectra showed bands corresponding to surface oxygen complexes and a band assigned to P-O groups. Temperature-programmed reduction and desorption spectra showed two signals ascribed also to surface oxygen complexes, and other higher-temperature signals corresponding to hydrogen desorption. These were all significantly more intense in the carbons prepared with phosphoric acid as compared with a standard prepared using high-temperature activation.
The use of activated charcoal (M-76) prepared from low cost wood of Brausonitia paypyrifera. (Paper Mulberry), for the removal of dye Basic blue3 (BB3) from aqueous solution was investigated. The linear applicability of Langergren equation points towards pseudo-first order rate expression. Activation energy of adsorption were also determined. The results indicate that Brausonitia papyripera could be employed as low cost alternative to commercial activated carbon in wastewater treatment for the removal of basic dyes.
Dyes are used in various sectors like textile, paper and dyeing industries which discharge hazardous coloured dye effluents. The ability of heterogeneous mixture of alumina and clay (1:2) to remove the colour of dyes has been investigated. It was found that low adsorbate concentration, small particle size of adsorbent, temperature 25°C and pH 7.2 of the medium favour the removal of dye from aqueous solution. The dynamics of adsorbate transport from bulk to the solid phase has been studied at different temperatures. The applicability of Langmuir isotherm suggests the formation of monolayer coverage of dye molecules on the outer interface of the adsorbent. The thermodynamic studies of dye-alumina clay system indicates spontaneous and exothermic nature of the process.
Activated carbons (ACs) were prepared from apricot stone shells impregnated with H3PO4, followed by carbonization at 400-500°C. Fixed-bed removal of two dyestuffs, i.e. Direct Red 99 (DR) and Reactive Orange 11 (RO) was followed at constant bed height and flow rate. Several column characteristics were evaluated from the breakthrough curves obtained including: the volume and loading at breakpoint, the height of the mass transfer zone, the bed service time, the time and loading at exhaustion, and the factional bed loadings at various stages. The bed performance with RO was better than for DR, which was ascribed to a screening effect towards the larger DR molecules and to enhanced adsorption arising from the polyhalogenated nature of the RO molecule. The removal of colour was favoured as the porosity of the AC developed, being particularly related to its mesoporosity and total pore volume.
The application of the n and α methods to two different groups of N2 adsorption isotherms of activated carbons has been studied. The chemical nature of the adsorbent and the adsorbate and the adsorbent-adsorbate interactions have been established as two different means of assessing the standard N2 adsorption isotherms of non-porous carbon. The application of both criteria to N2 adsorption isotherms of activated carbons gave deviations at low and high relative pressures; these deviations were not significant in the evaluation of the micropore volumes and non-microporous surface areas of the carbons. Alternatively, the comparison between micropore volumes obtained by applying the Dubinin–Raduskevich (DR) equation and those from the n and α plots showed different results relating to the pore-size distributions of the carbons. Some α plots showed two straight portions, that located at lower α values being the most appropriate for evaluating the micropore volumes. In general, α and n plots have been shown to be more useful than the DR equation for analysing the N2 adsorption isotherms of highly activated carbons.
Locally discarded olive oil waste was tested as a potential raw material for the preparation of activated carbons. Chemical activation by impregnation with H3PO4 was employed using acid solutions of varying concentration in the range 30-70% followed by thermal treatment at 500-700°C. The development of porosity was followed from an analysis of the nitrogen adsorption isotherms obtained at 77 K by applying standard BET and t-plot methods. Carbons with low to moderate surface areas (273-827 m2/g) and total pore volumes (0.27-0.69 ml/g), containing essentially micropores with diameters of 8.2 Å up to 12.4 Å were obtained. Increasing the concentration of impregnant led to the development of porosity with the optimum being attained at 60% H3PO4. Phosphoric acid is visualized as acting both as an acid catalyst promoting bond-cleavage reactions and the formation of new crosslinks and also as a reactant which combines with organic species to form phosphate and polyphosphate bridges which connect and crosslink biopolymer fragments. The present study suggests many applications for environmental pollution control, firstly by utilizing accumulating low-cost agricultural by-products and secondly by producing a multi-purpose high-capacity adsorbent useful in the remediation of micropollutants in various water courses.
Activated carbons, prepared from low-cost mahogany sawdust and rice husk have been utilized as the adsorbents for the removal of acid dyes from aqueous solution. An acid dye, Acid Yellow 36 has been used as the adsorbate. Results show that a pH value of 3 is favourable for the adsorption of acid dye. The isothermal data could be well described by the Langmuir and Freundlich equations. Kinetic parameters of adsorption such as the Langergren pseudo-first-order constant and the intraparticle diffusion rate constant were determined. For the present adsorption process, intraparticle diffusion of dye molecule within the particle has been identified to be rate limiting. The adsorption capacities of sawdust carbon (SDC) and rice husk carbon (RHC) were found to be 183.8 mg and 86.9 mg per g of the adsorbent respectively. The results indicate that SDC and RHC could be employed as low-cost alternatives to commercial activated carbon in wastewater treatment for the removal of acid dyes.
Guava seeds have been used as a raw material to produce activated carbon. Dried, milled, guava seeds were activated by pyrolysis at temperature up to 700 o C, and by using zinc chloride as chemical activation agent. The adsorption capacity was demonstrated by the isotherms of methylene blue from aqueous solution. Pyrolysis alone yields a poor adsorbing carbon with adsorbing capability of only ~ 55 % due to the blockage of pores by decomposition products of lignocellulosic materials. Optimum absorption capacity was obtained when the samples were subjected to chemical activation, followed by pyrolysis at 700 oC. Abstrak : Biji jambu batu telah digunakan sebagai bahan mentah untuk menghasilkan karbon teraktif. Biji jambu yang dikering dan dikisar telah diaktifkan secara pirolisis pada suhu sehingga 700 o C dengan menggunakan zink klorida sebagai agen pengaktifan. Muatan penjerapan ditentukan dengan menggunakan larutan akueus metilena biru. Pirolisis hanya menghasilkan karbon dengan muatan penjerapan ~ 55% sahaja kerana penutupan liang oleh hasil-hasil penguraian bahan lignoselulosa. Muatan penjerapan optimum diperoleh apabila pengaktifan kimia dilakukan kepada sampel, dan diikuti pirolisis pada 700 oC.
Studies about the removal of lead from aqueous solutions by activated carbons are described. These activated carbons were prepared from almond shells, olive stones, and peach stones. A commercial one was also used in this study. The adsorption isotherms of lead on those activated carbons at 298 K have been obtained. From these isotherms some adsorption parameters have been calculated. The lead removal process in dynamic regimen has also been studied by using different columns of activated carbon. In order to know the operational parameters for optimum removal, the breakthrough curves of column tests carried out at different experimental conditions were obtained. From these curves the characteristics of each column were determined.
Rice husk, an agricultural waste, was studied as a potential scavenger of lead from various aqueous solutions. Physicochemical parameters such as selection of appropriate electrolyte, shaking time, and the concentrations of adsorbent and adsorbate were studied to optimize the conditions to be utilized on a commercial scale for the decontamination of effluents using a batch technique. Maximum adsorption was observed with 0.01 mol/dm{sup 3} acid solutions (HNO{sub 3}, HCl, H{sub 2}SO{sub 4} and HClO{sub 4}) using 1000 mg of adsorbent for a 4.82 {times} 10{sup {minus}5} mol/dm{sup 3} lead concentration in less than 10 minutes equilibration time. Studies show that the adsorption decreases with an increase in the concentrations of all the acids. The adsorption data follows the Freundlich isotherm over the 9.65 {times} 10{sup {minus}5} to 4.83 {times} 10{sup {minus}3} mol/dm{sup 3} range of lead concentration. The characteristic Freundlich constants, i.e., l/n = 0.93 {+-} 0.04 and A = 19.86 {+-} 0.82 m{center_dot}mol/g, have been computed for the sorption system. Thermodynamic parameters, i.e., {Delta}G{degree}, {Delta}S{degree}, and {Delta}H{degree}, have also been calculated for the system.
The use of low-cost adsorbent has been investigated as a replacement for the current expensive methods of removing dyes from wastewater. As such, fly ash generated in National Thermal Power plant was collected and converted into a low-cost adsorbent. The prepared adsorbent was characterized and used for the removal of dyes from wastewater. Adsorption studies were carried out for different temperatures, particle sizes, pH's, and adsorbent doses. The adsorption of each dye was found to increase with increasing temperature, thereby indicating that the process is endothermic in nature. The removal of each dye was found to be inversely proportional to the size of the fly ash particles, as expected. Both the linear and nonlinear forms of the Langmuir and Freundlich models fitted the adsorption data. The results indicate that the Freundlich adsorption isotherm fitted the data better than the Langmuir adsorption isotherm. Further, the data were better correlated with the nonlinear than the linear form of this equation. Thermodynamic parameters such as the free energies, enthalpies, and entropies of adsorption of the dye−fly ash systems were also evaluated. The negative values of free energy indicate the feasibility and spontaneous nature of the process, and the positive heats of enthalpy suggest the endothermic nature of the process. The adsorptions of crystal violet and basic fuschin follow first-order rate kinetics. In comparison to other low-cost adsorbents, the sorption capacity of the material under investigation is found to be comparable to that of other commercially available adsorbents used for the removal of cationic dyes from wastewater.
Crushed apricot stone shells were impregnated with varying H3PO4 acid concentrations (20–50 wt%), followed by carbonisation at 573–773 K. The products were characterised by nitrogen gas adsorption. Analysis of the nitrogen isotherms by the DR and s methods proved that most of the obtained carbons are highly microporous, with high surface areas (⩾1000 m2 g-1) and very low mesoporosity. Increasing acid concentration, at 573 and 673 K, increases surface area and pore volume, whereas at 733 K a small decrease in both parameters appears at higher H3PO4 concentrations. Whole apricot stones produce activated carbon of inferior porous characteristics. Development of the extensive pore structure was described in light of the effect of H3PO4 on the lignocellulosic mataerial during carbonisation.
Two activated carbons were obtained from pistachio shells by impregnation with H3PO4 under standard conditions of acid concentration (50 wt%) and heat treatment at 773 K for 2 h. The soaking time was 24 and 72 h for the two samples before thermal pyrolysis. Analysis of the N2/77 K adsorption isotherms proved that both were highly adsorbing carbons with considerable microporosity, and that the prolonged contact with activant enhanced total porosity (surface area and pore volume) and increased the amount of mesoporosity. Adsorption isotherms of probe molecules, viz methylene blue (MB), rhodamine B (RB), phenol (P) and p-nitrophenol (PNP), were determined at room temperature, from aqueous solutions. Both the Langmuir and Freundlich model adsorption equations show satisfactory fit to experimental data. Both carbons exhibit similar adsorption parameters irrespective of their porosity characteristics. The sequence of uptake per unit weight was: PNP > MB > RB > P. Low affinity towards phenol may be associated with its competition with water molecules which are more favourably attracted to the acid surface which has a high oxygen functionality. Preferred adsorption in the order PNP > MB > RB is proposed to be a function of carbon porosity, related to the increased molecular dimensions of the solutes. Adsorption from a binary mixture of equal concentrations of MB and RB showed reduced uptake for both sorbates in comparison to the single component experiments. RB removal surpasses that of MB in the binary test and may be attributed to lower water solubility and higher molecular dimensions. Copyright © 2003 Society of Chemical Industry
The physico-chemical characteristics of activated carbons obtained from different agricultural by-products by pyrolysis in a stream of water vapor have been investigated. It was established that under the same conditions of treatment the physico-chemical and adsorption characteristics of activated carbons depend on the composition of the initial raw materials. Activated carbon obtained from apricot stones has the best properties. It is characterized by a large specific surface area and micropores volume and high iodine and methylene blue adsorption activity. The activated carbons produced from cherry stones and grape seeds are characterized by predominating meso- and macropores structure. It can be supposed this is related to the larger content of lignin in those materials.
Physical properties of activated carbons prepared from pinewood at different activation times (0.5, 1.5, 2.7, and 4.0 h) in steam at 900 °C were studied. The adsorption equilibria and kinetics of three dyes and three phenols (phenol, 3-chlorophenol, and o-cresol) from aqueous solutions on such carbons were then examined at 30 °C. The adsorption isotherms of phenols could be well fitted by the Freundlich equation, and those of dyes were adequately described by the Langmuir–Freundlich equation. The effect of microporosity of the carbons on adsorption capacity was explored. Four simplified kinetic models including pseudo-first-order equation, pseudo-second-order equation, intraparticle diffusion model, and the Elovich equation were selected to follow the adsorption processes. The adsorption of all six adsorbates could be best described by the Elovich equation. The kinetic parameters of this best-fit model were calculated and discussed.
The impact of pore size on the competition mechanism between natural organic matter (NOM) in Illinois groundwater and the micropollutant atrazine was assessed using activated carbon fibers (ACFs). Two microporous ACFs with narrow and broad pore size distributions, designated ACF-10 and ACF-25, respectively, were used. The average pore sizes of ACF-10 and ACF-25 were 6 and 13.4 Å. Single solute adsorption, simultaneous adsorption and preloading experiments were performed. On ACF-10 it was found that the adsorption of atrazine was reduced significantly in the presence of NOM, even though the NOM loading was very small as a result of pore exclusion. The uptake of atrazine by ACF-10 in the presence of NOM (simultaneous adsorption) was comparable to the NOM-preloaded capacity. In addition, preloaded atrazine was not displaced by subsequently adsorbed NOM. The results support a pore blockage mechanism by which NOM molecules block access to, but do not penetrate into the primary micropores. Atrazine capacity on ACF-25 which has primary micropores as well as a large volume of secondary micropores, was reduced in the presence of NOM; however, the reduction in capacity was much less than that observed with ACF-10. Preloading with NOM showed further capacity reduction compared with simultaneous adsorption. These results combined with the result that preloaded atrazine exposed to NOM showed displacement of atrazine support a direct site competition mechanism in the secondary micropore region. Attempts to regenerate NOM preloaded ACF-10 and ACF-25 using a strong alkali solution failed to recover atrazine capacity, suggesting that NOM was strongly adsorbed at the fiber surface as well as within micropores.
According to iodine number, amount of methylene blue adsorption, the BET specific surface area, and the yield, the conditions for preparing activated carbons as adsorbents from plum kernels were optimized. The activation temperature and time tested were in the ranges 750–900°C and 1–4 h, respectively. Adsorption isotherms of two commercial dyes and phenol from water on such activated carbons were measured at 30°C. It was shown that the optimal activation temperature and time depended on the molar mass of the solutes, and all equilibrium isotherms could be fitted by the Langmuir equation. The experimental results indicated that the prepared activated carbons were economically promising for adsorption removal of dyes and phenol, in contrast to other commercial adsorbents.
Date pits, a low-cost agricultural by-product, was tested as a precursor for the production of porous carbons in a chemical scheme using phosphoric acid. The raw material was impregnated with increasing concentrations of H3PO4 (30–70 vol.%) followed by pyrolysis at 300, 500 or 700 °C. Texture characteristics of the products were determined by adsorption of N2 at 77 K, as well as iodine, phenol, and methylene blue values. Carbons obtained at 300 °C were very poorly porous, although with anomalously high capacity for the uptake of probe molecules from solution. This was attributed to the contribution of unsaturated chemical bonds initiated in the partially decomposed material. Carbons obtained at 500 and 700 °C are good to excellent adsorbents and attain best developed porosity at 700 °C, contrary to the earlier well-established temperature of 500 °C recommended for treatment of agricultural precursors. Thermogravimetric/differential thermogravimetric tracings of the H3PO4-impregnated date pits indicated a delayed-decomposition effect shifted to higher temperature as compared to the raw material. Phosphoric acid is suggested to inflict physical and chemical modifications on the botanical structure by penetration, particle swelling, partial dissolution of the biomass, bond cleavage and reformation of new polymeric structures resistant to thermal decomposition. In addition, raw date pits are proposed to be composed of a low-porosity and compact cellular structure that needs higher acid concentrations and/or temperatures to attain the optimum effect normally reached at lower temperature in case of other feedstocks of botanical origin.
Powdered dried peanut hulls were treated by one-step procedures to get activated carbon using chemical activation by H3PO4, ZnCl2, KOH and thermal activation by steam pyrolysis. Products were characterized by adsorption of N2 at 77 K and methylene blue (MB) from aqueous solution. Simple carbonization at 700–900 °C yields low adsorbing microporous carbons. Steam pyrolysis at 600 °C generates porosity in the mesopore range. KOH activation results in carbons of low surface area similar to steam pyrolysis, but with much developed mesoporosity, whereas ZnCl2 activation yields a moderate adsorbing carbon, essentially microporous. Treatment with H3PO4 at increasing impregnation ratios creates abundant microporosity with extended surface area attaining a maximum at a ratio of 1.0. Considerable loss in porosity accompanies additional activating acid indicating the governing action of the amount of activant. A 50% diluted H3PO4 acid results in a carbon with considerable reduction in the internal porosity. Highest removal capacity of MB appears with H3PO4-activated carbons, whereas KOH-activated carbons show the weakest uptake for the dye.
The purpose of this study is to suggest an efficient process, which does not require a big investment for the removal of pyridine from wastewater. Activated carbons developed from agricultural waste materials were characterized and utilized for the removal of pyridine from wastewater. Systematic studies on pyridine adsorption equilibrium and kinetics by low cost activated carbons were carried out. Adsorption studies were carried out at different temperatures, particle size, pH and adsorbent doses. Both Langmuir and Freundlich models fitted the adsorption data quite reasonably. The results indicate that the Langmuir adsorption isotherm model fits the data better as compared to the Freundlich adsorption isotherm model. Various mechanisms were established for pyridine adsorption on developed adsorbents. Further, the data are better correlated with non-linear form as compared to the linear one. The kinetic studies were conducted to delineate the effect of temperature, initial adsorbate concentration, particle size of the adsorbent and solid to liquid ratio. The adsorption of pyridine follows the first order rate kinetics. On the basis of these studies, various parameters such as effective diffusion coefficient, activation energy and entropy of activation were evaluated to establish the mechanisms. It is concluded that the adsorption occurs through a particle diffusion mechanism at temperatures 10 and 25 °C while at 40 °C it occurs through film diffusion mechanism. Similarly at concentrations 25 and 50 mg/l the adsorption is particle diffusion controlled while at⩽50 mg/l it is film diffusion controlled.
The seed husks of the multipurpose tree Moringa oleifera are potentially a waste product that may be available in large quantities, and previous work has demonstrated that a microporous activated carbon can be produced from them by carbonisation under nitrogen followed by activation in steam. This research examines the efficacy of a simpler and cheaper activation process, single-step steam pyrolysis activation, with a view to promoting the production of low-cost activated carbon in the developing world.Husks were heated in a steam atmosphere to 750°C for 30 or 120 min, or 800°C for 30 min, then the resulting carbons were tested to determine their iodine numbers and adsorption isotherms for phenol, 4-nitrophenol and methylene blue. Phenol and 4-nitrophenol were adsorbed rapidly by all three carbons, with 80–90% w/w adsorbed in the first 30 min, whereas methylene blue adsorption was slower. Pyrolysis at 800°C for 30 min produced a carbon (yield 12.2% w/w) with an iodine number of 703 mg g−1, a phenol specific surface area (SSA) of 629 m2 g−1, a 4-nitrophenol SSA of 664 m2 g−1 and a methylene blue SSA of 211 m2 g−1. The carbon produced at 750°C for 120 min (yield 11.9% w/w) had similar properties, but the one produced at 750°C for 30 min (yield 16.6% w/w) had a less developed porosity. The adsorbance characteristics of the two best carbons were superior to those produced previously by the conventional two-stage carbonisation-activation, and were competitive with commercial carbons. These results demonstrate that steam pyrolysis activation of M. oleifera husks could provide a low-cost, local source of high quality activated carbon in the developing world.
The adsorption of Congo Red by coir pith carbon was carried out by varying the parameters such as agitation time, dye concentration, adsorbent dose, pH and temperature. Equilibrium adsorption data followed both Langmuir and Freundlich isotherms. Adsorption followed second-order rate kinetics. The adsorption capacity was found to be 6.7 mg dye per g of the adsorbent. Acidic pH was favourable for the adsorption of Congo Red. Desorption studies suggest that chemisorption might be the major mode of adsorption.
The bioadsorption of Pb(II), Cd(II), and Cr(VI) using bacteria and activated carbon has been studied. Preliminary studies yielded the chemical and textural characterization of the carbons. The adsorption of bacteria on the activated carbons modified their surface characteristics, reducing the volume of pores and the pH of the point of zero charge, with a resulting increase in the density of the negative charge of their surface. The adsorption of the above metals was studied in both static and dynamic conditions and in the absence and presence of bacteria (Escherichia coli). The presence of bacteria in aqueous solution enhances the adsorption of Pb(II) and Cd(II) and reduces the adsorption of Cr(VI). These results can be explained by changes in the surface charge density of the carbons when bacteria are adsorbed, and by considering the structural and chemical characteristics of the bacterial cell walls. Investigation of the effect of electrolytes on the bioadsorption of these metals showed, in general, a resulting reduction in the amount of metal adsorbed, mainly in the presence of divalent cations. According to the divalent cation bridging theory, these results derive from competition between the Pb(II) or Cd(II) cations and the electrolyte cations for the negatively charged functional groups of extracellular polymeric substances.
Experimental studies were carried out to determine the effects of influent pH, ionic strength, metal concentration, and empty-bed contact time (EBCT) on copper sorption in the activated carbon fixed-bed columns. As the influent pH was increased, the column performance significantly improved. An overshoot of the effluent concentration was observed at pH 3.0 due to desorption of copper from the surface–metal complexes. The uptake enhanced as the ionic strength was increased; however, this role was much weaker than that of pH. An increase in metal concentration resulted in a decrease in the bed volumes at the breakthrough. In the beginning of all the experiments, the effluent pH increased dramatically and then dropped and approached lower values. Less sorption was observed when prewashed columns were used, in which the pH in the columns was kept constant. Modelling of the metal sorption in the prewashed columns was performed using a metal ion transport model hydrogeochem and a fixed-bed model.
Experimental research into the bench-scale production of activated carbon from waste-activated sludge from water purification, sawdust, peat, and their mixtures, by carbonisation and activation was undertaken. The research work was carried out to determine possible methods of production of cheap activated carbon from local raw materials and to use it in water purification technology. Along with the samples produced, several commercial activated carbons (namely RB-1, F 100, CA (adsorbent from military gas masks), BAY (product of the USSR)) were tested to compare adsorption properties in the adsorption of phenols, xylidines, amines, methylene blue and molasses. It has been found that the activated carbon produced from waste biosludge was of higher quality than that produced from either sawdust or peat, and performed similarly to RB-1 and F100 in adsorption tests. It was also determined that the activated carbon produced from biosludge could possibly be used in the post-treatment of wastewater. Residual sludge from the biological treatment of the wastewater from the purification of oil-shale in the chemical processing industry could cover up to 80% of the need for activated carbon. Some of this activated carbon could be used in the post-treatment of the same water, adsorbing polyalcaline phenols from the initial content of 4 mg l-1 to the demanded level of 1 mg l-1.
The effect of different methods for fly ash treatment using conventional chemical, sonochemical and microwave method on dye adsorption in aqueous solution was investigated. Three basic dyes, methylene blue, crystal violet and rhodamine B, are employed for adsorption testing. It is found that fly ash shows different adsorption capacity depending on type of dyes. Chemical treatment using HCl will increase the adsorption capacity. The adsorption capacity of HCl treated fly ash varies with the preparation conditions. Microwave treatment is a fast and efficient method while producing the sample with the highest adsorption capacity. Solution pH and inorganic salts in dye solution can significantly influence the adsorption. The adsorption data have been analysed using Langmuir, Freundlich and Redlich-Peterson isotherms. The results indicate that the Freundlich and Redlich-Peterson models provide the better correlations with the experimental data.
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