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The presence of cobalt ions Co(II) in wastewater poses major threats to both humans and the environment. The effectiveness of the adsorption of modified quartz rock particles (MQRP) adsorbent with calcium hydroxide solution Ca(OH)2 for eliminating Co(II) from a water solution was examined. MQRP had a maximum ability to adsorb 47.112 mg g−1 for Co(II) at pH 6.0 and a contact time of 2 h. The HCl stripping agent offered the highest desorption efficiency to regenerate the adsorbent for use again for a new cycle of adsorption. The equilibrium isotherms of the adsorption characteristics were experimentally identified, and the results of adsorption aligned with the principles of the Langmuir model. Under the examined temperature conditions, thermodynamic evaluation proved that Co(II) adsorption on adsorbent vacancies was spontaneous and exothermic. The outcomes of the kinetic process demonstrated that the process closely conformed to a pseudo-secondorder pattern. Therefore, the high silica content of MQRP makes it an important adsorbent, and it could be applied as a cost-effective and efficient adsorbent to control the release of Co(II) ions in industrial wastewater. [ABSTRACT FROM AUTHOR]

Agricultural waste peanut shell was used as precursor for activated carbon production by chemical activation. The activated carbon was prepared by carbonization of nut shell in a conventional electric furnace by a two-stage carbonization process under optimized conditions. The prepared carbons were characterized for proximate and ultimate analysis and thermodynamic characteristics. It was used for the removal of Cr(VI) and Pb contained in metal plating effluent by adsorption process. Experiments were performed in batch mode to find the effects of pH, contact time, particle size, adsorbent dose, initial concentration of adsorbate, and temperature. Cr(VI) and Pb adsorption was strongly depended on solution pH, and the optimum adsorption was found at pH 3.5. The maximum Cr(VI) removal of 94.4% (initial Cr(VI) = 55.3 mg/L) and Pb removal of 96.1% (initial Pb = 3.5 mg/L) were achieved at operating condition pH = 3, T = 25°C and adsorbent dose = 5 g/L. The kinetic data were evaluated at different initial concentrations of Cr(VI) and Pb using pseudo-first-order, pseudo-second-order, and intraparticle diffusion models. Among these, the pseudo-second-order model fitted well. Langmuir, Freundlich, and Temkin isotherms were also tested for equilibrium studies, in which Langmuir adsorption isotherm model fitted the data better. The thermodynamic parameters, such as standard enthalpy change (ΔH°), Gibb's free energy change (ΔG°), and standard entropy change (ΔS°) were also evaluated. [ABSTRACT FROM AUTHOR]

Nanoparticles ofα-Fe2O3were synthesized by simple chemical precipitation method and characterized by X-ray diffraction study, scanning electron microscopy, and Fourier transform infrared spectroscopy. Feasibility of as-synthesized nanoparticles was investigated for adsorptive removal of methyl orange (MO) dye from aqueous solution. The effects of various experimental parameters such as solution pH, initial MO concentration, contact time, andα-Fe2O3nanoparticles dose were studied in batch mode. More than 90% removal was reported at pH 2.0 with 30 mg L−1initial MO concentration treated with 1.00 g L−1adsorbent dose. Isotherm study reveals that Langmuir isotherm model is the most efficient one in explaining the process and maximum adsorption capacity as much as 28.90 mg g−1is reported. Kinetic study shows that the adsorption process is best explained by second-order kinetic model confirming the dominancy of chemisorption in the process. Subsequently, the experimental data were modeled by artificial neural network to predict the removal efficiency of MO byα-Fe2O3nanoparticles following conduction of 95 experimental data points. A three-layer feed-forward back-propagation model with Levenberg–Marquardt algorithm was developed which show that the optimal network topology is 4–10–1. Model predicted data shows very good agreement with experimental data set with mean squared error and coefficient of determination (R2) as 0.00152 and 0.9916, respectively. [ABSTRACT FROM AUTHOR]

this study, adsorption of As(III) removal on iron oxide-coated quartz, iron oxide-coated lignite sand, and iron oxide-coated silica sand were investigated. Batch studies were performed to evaluate the influences of various parameters like initial pH, adsorbent dose, and initial concentration for the removal of As(III). Optimum conditions for As(III) removal on the three adsorbents were found to be pH 7, adsorbent dose 20 g/μ of solution, and equilibrium time 6 h. The kinetics study of As(III) removal have also been determined using a pseudo-first-order, pseudo-second-order, Weber and Morris, and Elovich model. Among the conventional models, the qe,exp and the qe,calc values from the pseudo-second-order kinetic model are very close to each other and followed by Weber-Morris and Elovich model for all adsorbents. In this system, the effective diffusion coefficient (De) value of As(III) is more than the order of 10-9cm2/s. This order shows in the literature that pore diffusion is the rate-limiting step for all the adsorbents. Equilibrium isotherms for the adsorption of As(III) on all the three adsorbents were analyzed by Langmuir, Freundlich, Redlich-Peterson (R-P), and Temkin isotherm models using nonlinear regression technique. R-P and Freundlich isotherm was found to be the best to represent the data for As(III) adsorption on all the adsorbents. The parameters obtained in this study for different kinetic and equilibrium models of all adsorbents are very comparable with other reported values for sand-based and other adsorbents. [ABSTRACT FROM AUTHOR]

In the present work, the abilities of chitosan-g-poly(acrylic acid)/vermiculite (CTS-g-PAA/VMT) hydrogel composites to remove Pb(II) and Cd(II) ions from aqueous solutions were compared. Batch adsorption studies were carried out to examine the influence of various parameters such as the VMT content, the initial pH value, the contact time, the initial metal ion concentration on adsorption capacities. Adsorption of Pb(II) and Cd(II) ions on the composite showed a pH-dependent profile. The maximum adsorption capacity for both metal ions was found to lie between 5.5 and 6.00. The adsorption processes were all relatively fast. Over 90% of the total adsorption was reached in around 3 min for both Pb(II) and Cd(II) adsorption at 303 K, and the equilibrium was reached after about 15 min of contact time. The adsorption data for the composite fitted well not only the Langmuir model but also the Freundlich model. The maximum Pb(II) adsorption capacity (3.0774 mol/g) of the composite is only a little more than that of Cd(II) (2.9817 mmol/g) at 303 K, however, the desorption efficiency of Pb(II) loaded sample (63.27%) is much lower than that of Cd(II) loaded sample (86.26%) when 0.1 mol/L HNO3 solution was used as the elutent. The adsorption of Pb(II) and Cd(II) ions by the composite seemed to involve ion exchange, chelation, electrostatic attraction or adsorption. -NH2, -COOH and -OH groups are all involved in the adsorption processes. Moreover, there are only few of -NH2 groups participating in the reaction with Pb(II) ions. [ABSTRACT FROM AUTHOR]

This study examined the efficacy of ProsopisJuliflora with surface changes as a bioadsorbent for the removal of Allura Red dye. The effects of adsorptive dosage, pH, and contact period with starting dye attentiveness on adsorption were examined in the batch adsorption study. The study demonstrated that the Allura Red dye may be absorbed by surfaces that had been treated with KOH compound.The percentages of Allura Red dye eliminated were 67.18 %, 75.88 %, and 94.37 %, respectively. UV-visible adsorption spectroscopy is used to quantify the extent of dye decolorization. The modified surface characteristics of the adsorbent produced by ProsopisJuliflora were reported using XRD, FTIR, and SEM. The Adams-Bohart mathematical models are employed in the computation and assessment of adsorption efficiency. The adsorption-derived R² values for the equilibrium isotherm data model were 94.63, 86.67, and 96.35. Diffusion and intraparticle regeneration were investigated to bolster the adsorption investigation. [ABSTRACT FROM AUTHOR]

Expanded graphite (EG) was prepared by microwave irradiation at 1000W for 60 s. EG is a novel adsorbent for Sn(II) adsorption and its ability to remove Sn(II) ions from wastewater was investigated. To characterize the adsorptive characteristics of the produced EG, the microstructures of the resultant EG were observed using scanning electron microscopy. Chemical characterization of the surface resultant EG was studied by Fourier transform infrared spectroscopy. The effects of pH, adsorbent dosage, initial concentration, temperature, and contact time on the adsorption surface were studied using the batch process technique. The data fitted with the Langmuir equilibrium isotherm and pseudo-second-order kinetics. The maximum adsorption capacity of Sn(II) on the resultant EG was 378.78mg g-1. [ABSTRACT FROM AUTHOR]

This study is aimed at using calcined Fe-Hydrotalcite (CFeHT) in removing arsenite (As(III)) from water. The arsenic concentration of solutions containing 1000 μg/L As(III) in adsorption studies was reduced below the permissible value (10 μg/L) with 2 g/L CFeHT for As(III). The effect of initial pH on adsorption was limited, and arsenic adsorption occurred relatively quickly under the pseudo-second-order kinetic model. In equilibrium isotherm studies, experimental data were consistent with Langmuir isotherm. Also, we clarified that CFeHT can be reused with proper treatments such as desorption and revivification. Competitive ions such as B(OH)4² did not significantly affect arsenic adsorption. It was determined that the adsorption process with CFeHT has high selectivity towards arsenic and is not affected by high amounts of borate anions in water. As a result of the regeneration tests, the arsenic removal efficiency from the solution containing As(III) was 62% at the end of the fourth cycle. This study reveals the great potential of CFeHT in removing arsenite contamination from groundwater originating from mines, especially from boron mines. [ABSTRACT FROM AUTHOR]

Batch adsorption of cephalexin (CFX) by walnut shell activated carbon is studied both experimentally and mathematically. Firstly, the adsorbent was prepared by chemical activation method in the presence of ZnCl2. Next, the values of adsorbent dosage and pH were optimized. Then, the effect of initial CFX concentration and contact time was studied to evaluate the kinetics and the equilibrium isotherm. It is found that the Freundlich and Toth models provided the best fit to the experimental data. Dynamic characteristics of this process are mathematically modeled. In the developed model, pore diffusivity is estimated according to the experimental results. The model reveals good agreement with experiment. The effective diffusivity of CFX in the walnut shell AC is estimated as 0.47 × 10−9 m2 s−1. [ABSTRACT FROM AUTHOR]

This study presents the synthesis of biosorbent by the immobilization of green algae (Chlorophyta) into calcium alginate as a supporting composite for the removal of heavy metals. The batch adsorption system was employed to investigate the effectiveness of the algae-alginate synthesized beads (AASB) in lead removal from an aqueous solution. Since pH 5 produced the greatest removal efficiency of Pb(II) ions, it reveals that the pH significantly affects the adsorption of Pb(II) ions using AASB as an adsorbent. Results showed that the ideal working conditions for AASB were: 5 g/L of AASB, 120 min of contact time, pH value of 5, and 200 rpm agitation speed, which achieved roughly 90.98% removal efficiency and a capacity of 9.0492 mg/g. Several analytical methods, such as Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS), were used to evaluate the adsorbent’s performance and investigate its adsorption mechanism. FTIR analysis showed the engagement of hydroxyl, amino, and carboxyl functional groups during Pb(II) ions adsorption, At the same time, the metal cations are adsorbed on the surface of the algal biomass, which is demonstrated by SEM to have an amorphous superficial structure, while EDS spectra showed the presence of elements that are favorable for Pb(II) adsorption. The equilibrium isotherm results were well suited to the Freundlich isothermal model, although the adsorption kinetic data is accurately articulated by the pseudo-first-order model. This suggests that heavy metals can be removed from wastewater using AASB which is considered a feasible and effective biosorbent. [ABSTRACT FROM AUTHOR]

The biosorption of Pb (II), Cd (II), and Hg (II) from simulated aqueous solutions using baker's yeast biomass was investigated. Batch type experiments were carried out to find the equilibrium isotherm data for each component (single, binary, and ternary), and the adsorption rate constants. Kinetics pseudo-first and second-order rate models applied to the adsorption data to estimate the rate constant for each solute, the results showed that the Cd (II), Pb (II), and Hg (II) uptake process followed the pseudo-second-order rate model with (R²) 0.963, 0.979, and 0.960, respectively. The equilibrium isotherm data were fitted with five theoretical models. Langmuir model provides the best fitting for the experimental results with (R²) 0.992, 0.9987, and 0.9995 for Cd (II), Pb (II), and Hg (II), respectively. The effect of various influent adsorbates concentration, and flow rate on the performance of fixed bed adsorber was found for the three heavy metals. A mathematical model was formulated to describe the breakthrough curves in the fixed bed adsorber for each component. The results show that the mathematical model provides a good description of the adsorption process for Cd (II), Pb (II), and Hg (II) onto fixed bed of baker's yeast biomass. [ABSTRACT FROM AUTHOR]

Because of the increasing use of vanadium in different industries, including alloys and steel man)ufacturing, catalysts, and electrochemical coating, the presence of vanadium as toxic metal in industrial effluents has become a worldwide environmental concern. In this study, the potential of natural bentonite as an available adsorbent for vanadium(IV) ions separation was investigated. The main properties of natural bentonite were characterized using analysis such as specific surface area measurement, scanning electron microscopy, and Fourier-transform infrared spectroscopy, X-ray diffraction, and X-ray fluorescence. The influence of main adsorption parameters such as initial vanadium(IV) concentration, solution pH and adsorbent dose were also investigated. The optimization of these parameters was performed by central composite design based on response surface methodology. Based on the results, the maximum vanadium(IV) adsorption obtained at optimum conditions was 43% for initial vanadium(IV) concentration (113 mg L–1), pH (2), adsorbent dosage (3.11 g L–1), and contact time (180 min). The vanadium adsorption on natural bentonite was firmly confirmed by the pseudo-second-order kinetic model. The equilibrium isotherm data was fitted with the Langmuir model with significant accuracy [ABSTRACT FROM AUTHOR]

This study aims to investigate the solid-phase extraction procedure of the most prescribed antibiotics in the world, ciprofloxacin, by using aluminosilicates grafted chitosan (Al2O3@SiO2-chitosan). The green adsorbent was synthesis via sol-gel process, and cross-linking with chitosan, in the presence of glutaraldehyde as chelating agent. The results show that the extraction yield of ciprofloxacin removal decreases in acidic medium, more than 52% of adsorption yield was obtained with an optimal pH solution of 5.77. The kinetic study shows also that ciprofloxacin adsorption was very fast at the initial stage of contact time up to 30 min when the equilibrium adsorption was established. The maximal adsorption capacity was found to be 31 mg g-1, under optimum conditions. Ciprofloxacin uptake process followed the pseudo-second-order rate expression. Equilibrium isotherm for ciprofloxacin has been modeled successfully using Langmuir isotherm model. Thermodynamics study leads to a spontaneous and exothermic process for ciprofloxacin adsorption by Al2O3@SiO2-chitosan (ΔH = -08.49 kJ mol-1). [ABSTRACT FROM AUTHOR]

The purpose of this investigation is to produce activated carbon from hazelnut shells by using chemical activation method of potassium carbonate. For the activation, the shells were milled and sieved in range of 50-150 mesh and then impregnation ratios were selected at the ranges of 1:1, 1:2 and 1:3. The carbonisation was carried out under the N2 gas pressure with flow rate of 100 mL min-1 at 873.15 K for 120 min. The characterization of carbonization of activated carbon were executed with the X-ray diffraction, Fourier-transform infrared spectroscopy and scanning electron microscopy after drying samples and also in order to determine the adsorption capacity, the iodine and Methylene blue numbers were used. In this research, the microporous character of series of activated carbons has been analyzed using of the Brunauer-Emmett-Teller (BET) equation. N2(BET) surface area was found to have the maximum BET area as 644 m² g-1, the absorbants of iodine and Methylene blue numbers were determined 1,974 mg/I2 and 489 mg g-1, respectively for 70 mesh in the impregnation ratio of 1:2. In the addition to that the kinetic of Methylene blue adsorption were determined by the pseudo-second-order kinetic model and also the thermodynamic parameters were calculated to see whether the adsorption was spontaneous or not. The experimental data indicated that the adsorption isotherms were well matched by the Langmuir equilibrium isotherm equation given as 454.5 mg g-1 at 293 K. [ABSTRACT FROM AUTHOR]

In this study, the use of chitosan-coated clinoptilolite zeolite as an adsorbents in the removal methyl violet from an aqueous solutions were investigated. Firstly, the structural and chemical characterization of the adsorbent was carried out using various analytical techniques such as X-ray diffraction, Brunauer–Emmett–Teller and scanning electron microscopy. Then, the effects of different batch parameters such as initial pH (2–9), adsorbent dosage (0.05-1.0 g/100 mL), temperature (298–318 K), initial dyestuff concentration (25-125 mg L-1) and mixing time (5-120 min) on the adsorption process were examined. The kinetic, thermodynamic and isotherm parameters of chitosan-coated clinoptilolite zeolite was investigated by batch adsorption experiments. The experimental data showed that the adsorption isotherms were well defined by the Langmuir equilibrium isotherm model equation. The maximum adsorption capacity was found 111.11 mg g-1 for chitosan-coated clinoptilolite zeolite adsorbent at 318 K. The methyl violet adsorption was determined to conform to the pseudo-second-order kinetic model. The thermodynamic calculations were made in the adsorption study of chitosan-coated clinoptilolite. As a result of calculations, it was determined that the ΔH° values were 34.53 kJ mol-1, and the fact that this value is positive indicates that the adsorption process is spontaneous and endothermic. The recovery test exhibited that the developed composite had significantly adsorption/desorption performance particularly until the seventh cycle. In the last step, considering the effects of some experimental parameters on methyl violet adsorption, an artificial neural network model was developed, and it was concluded that it could be used for dye removal from aqueous solutions. All experimental studies showed that found to be a natural, cost-efficient and eco-friendly of the developed chitosan coating on clinoptilolite zeolite composite make it economic easily applicable adsorbent in the removal of methyl violet from the aqueous solutions. [ABSTRACT FROM AUTHOR]

Residual biomass from the lactic acid production (fermented dairy industry) represents a viable and important source of valuable compounds (nutrient, material) and energy which can be used as raw material for the production of a wide range of new added-value products and in certain valorisation processes and sanitation services. The aim of this work is to use the prepared biosorbent from the residual biomass (a Lactobacillus plantarum and Lactobacillus casei bacteria consortium, separated after the biosynthesis process by centrifugation and dried at 80°C) immobilized in sodium alginate (by cell inclusion technology) (in form of spherical beads with 0.5 and 1.5 mm in diameter) into a specific biosorption treatment step applied for certain aqueous solutions containing the reactive Orange 16 dye (28.96–231.68 mg/L). The biosorption potential of this imobilized residual bacteria consortium for the reactive Orange 16 dye retention from aqueous solutions was studied in a batch system. The preparation and characterization of the obtained biosorbent (SEM and FTIR spectra), the analysis of different equilibrium isotherm (Langmuir, Freundlich and Dubinin–Radushkevich – D–R) to estimate the quantitative characteristic biosorption parameters, thermal effect and possible action mechanism were investigated, and the modeling of experimental data was satisfactorily achieved. Langmuir was found the most suitable isotherm model (L II) and the basic mechanism is found to be of physical type, being spontaneous (probably exothermic) after the calculated values of the free biosorption energy (E = 13 kJ/mol, from D–R equation), free Gibbs energy (ΔG° = –1.845 – –1.768 kJ/mol) and biosorption enthalpy (ΔH° = –6.512 kJ/mol). Analysis of SEM images and FTIR spectra suggests that Orange 16 reactive dye is retained on biosorbent granules by a physical adsorption mechanism. The obtained results conclude that this residual bacterial biomass immobilized in sodium alginate can be a good biosorbent in static operating system for reactive organic dye-containing effluents. [ABSTRACT FROM AUTHOR]

The aim of this work is to study the removal of Basic Blue 3 (BB3) and Methylene blue (MB) from aqueous solutions using raw and chemically treated cedar sawdust as eco-friendly and sustainable bioadsorbents. The raw and treated cedar sawdust (CS) samples were activated with NaOH (0.1 N) and HCl (0.1 N) solutions. The surface characteristics of the bioadsorbents were analyzed by diverse physico-chemical methods such as scanning electron microscopy with energy-dispersive X-ray analysis, Fourier transform infrared spectroscopy, point of zero charge (pHpzc), X-ray diffraction. The monitoring of the optimal experimental conditions of the different parameters such as dye concentration, contact time, adsorbent dose and solution pH were performed in a batch system. Experimental results show that the adsorption process is rapid and reaches equilibrium after 1 h of contact time. The adsorption capacities of the CS bioadsorbent depend on the pH of the solution and adsorbent dose. Consequently, the adsorption of BB3 and MB is favored at basic pH with the maximum adsorption percentage removal of 98% for BB3 and 99.8% for MB. Adsorption kinetics and equilibrium isotherm parameters were fit using two classic adsorption models (Langmuir and Freundlich). The adsorption kinetics of dyes onto CS followed could be described well with the pseudo-second-order model, whereas the equilibrium data fitted well to the Langmuir isotherm model with a correlating constant (R2) higher than 0.98. The maximum adsorption capacities (Qmax) onto of raw-CS, HCl-CS and NaOH-CS were estimated to be 47.62, 71.94 and 76.92 mg g-1 for MB and 33.67, 72.46 and 85.3 mg g-1 for BB3 respectively, showing that the NaOH-CS adsorbent is about 1.6-2.6 time more efficient that the natural-CS. As a result, chemically treated cedar sawdust has great potential as an inexpensive and readily available alternative bioadsorbent for the removal of cationic dyes from industrial wastewaters. [ABSTRACT FROM AUTHOR]

In the present study, the copolymerization of ethyl acrylate and guar gum was induced by microwave irradiation in the presence of catalytic amount of the initiator potassium persulfate (KPS). The maximum percentage conversion was found to be 107.1% under microwave power of 900 MW after 3 min exposure. The copolymerized guar gum-graft-poly-ethyl acrylate (GG-g-PEA) was characterized using FTIR spectroscopy and SEM analysis. The effect of pH on the capacity of the GG-g-PEA copolymers to reduce the hardness of the water was investigated, leading to the effective removal of Ca(II) and Mg(II) ions from solutions at pH 8. The calculated values of the coefficient of determination (0.914–0.9553) for Ca(II) and Mg(II), respectively, showed that the equilibrium isotherm data followed the Freundlich isotherm model. The pseudo-second-order model was suitable for the modelling of the kinetic data, predicting adsorption capacities of 0.2680 g/mg/min for Ca(II) and 0.3835 g/mg/min for Mg(II), respectively. The synthesized GG-g-PEA adsorbent could therefore be recommended for the reduction in the water’s hardness. [ABSTRACT FROM PUBLISHER]

Batch biosorption experiments were carried out for the removal of malachite green (MG) from its aqueous solution using rawSargassum swartziibiomass (RSSB) as biosorbent. The effect of various operating parameters was optimized for enhancing biosorption capacity. The biosorption capacity was found to increase with contact time and initial malachite green concentration. The biosorption of the dye was pH dependent and maximum uptake was observed at a pH of 10. The experimental data were analyzed using Langmuir, Freundlich, and Temkin equilibrium isotherm models. Langmuir isotherm (R2 = 0.98) was found to fit the experimental data well. The biosorption kinetics of MG was found to follow pseudo-second-order kinetic model (R2 = 0.967). The mechanistic study revealed that the biosorption of malachite onto RSSB was controlled by film diffusion. The characteristics of the RSSB biosorbent were studied using Fourier transform-infrared spectroscopy and scanning electron microscopy. [ABSTRACT FROM PUBLISHER]

The capacity of a strong cation-exchange resin for removal of nickel from aqueous solutions was investigated under different conditions such as contact time, initial nickel ion concentration, stirring speeds, solution pH, and resin dose. The equilibrium isotherm data were analyzed using Langmuir, Freundlich, Temkin, Elovich, Fowler–Guggenheim, Kiselev, Hill–de Boer, Jovanovic, Hill, and Koble–Corrigan isotherms. Correlation coefficients indicated the following order to fit isotherms: Langmuir > Koble–Corrigan > Freundlich > Hill > Jovanovic > Temkin > Hill–de Boer > Fowler–Guggenheim > Kiselev > Elovich. On the basis of the lowest values of the four error functions studied, Hill model provided the best correlation for the experimental data. The kinetic data were analyzed using pseudo-first-order, pseudo-second-order, and Elovich model. Intra-particle diffusion model and the liquid film diffusion model were used to investigate the adsorption mechanism. Kinetic studies showed that the adsorption of Ni2+ions onto ion-exchange resin followed Elovich kinetic model, and indicates that the intra-particle diffusion controls the rate of adsorption. Furthermore, separation factors and distribution coefficients of nickel were calculated. [ABSTRACT FROM PUBLISHER]

Resin adsorbent for gold recovery have the characteristics of simple preparation, good reusability and low consumption performance, but their shortcomings of low adsorption efficiency and poor adsorption capacity cannot be ignored. Based on this, a novel adsorbent with high adsorption performance towards Au(III) was prepared by functionalizing D301 resin with 1-vinylimidazole using the surface-initiated graft-polymerization method. The physicochemical characteristics of D301-g-PVIM (PVIM -- polyvinylimidazole) were characterized by Fourier-transform infrared spectroscopy, scanning electron microscopy, Brunauer--Emmett--Teller and elemental analysis. The adsorption capacity of Au(III) was studied by a static adsorption experiment. The maximum adsorption capacity of D301-g-PVIM for Au(III) was 543.9 mg g--1. The kinetic study shows that the adsorption data can well described by the pseudo-second-order kinetic model. The equilibrium isotherm for the adsorption of Au(III) on D301-g-PVIM has a good correlation with the Freundlich model, and the adsorption is a multilayer sorption. The adsorption thermodynamics study indicated that the adsorption process is spontaneously endothermic. Repeated use experiments showed that D301-g-PVIM has high efficiency and good regeneration performance. [ABSTRACT FROM AUTHOR]

One of the efficient techniques for the removal of heavy metals from wastewater is adsorption. In this paper, the adsorption of Ni on a new porous carbonaceous adsorbent, pre-treated rice husk particles, was investigated in both batch and column experiments. The equilibrium isotherm was described well by both the Langmuir and Freundlich isotherm. The Langmuir constants,qmandb, were estimated to be 8.0 and 0.15 l/mg, respectively. Different conditions of flow rate, bed heights, and initial nickel concentrations were considered in the column experiments. It was observed that the adsorption capacity of the packed-bed column and the breakthrough time were increased with an increase in the bed height and a decrease in the flow rate and the influent Ni concentration. The traditional Bohart–Adams, Thomas, and Yoon–Nelson models in accompany with the mass transport model were used to describe the adsorption process in the columns. The experimental breakthrough curves were described satisfactorily by all the aforementioned continuous models. However, the predicted maximum adsorption capacity using Bohart–Adams and Thomas models was less than the one obtained from batch equilibrium experiments. Whereas, there was a good agreement between the batch equilibrium results and the continuous mass transport model regarding the maximum adsorption capacity, indicating the prediction of column performance using batch experiments. [ABSTRACT FROM PUBLISHER]

The magnetite-impregnated almond shell (MIAS) and untreated almond shell (UAS) were used as adsorbents for the removal of methyl violet 2B from aqueous solution. The adsorption of MV2B from water onto adsorbent surface was investigated in batch adsorption experiments to evaluate the effect of pH, contact time, adsorbent dose, initial dye concentration, and temperature, after being analyzed the surface morphology and elemental composition of the adsorbents. The adsorptions of MV2B onto both adsorbents were favorable in basic medium. The pseudo-second order represents the kinetic adsorption of MV2B on to both adsorbents. Equilibrium isotherm data were analyzed by Langmuir and Freundlich adsorption isotherms, which were best fitted to Langmuir adsorption isotherm model. The monolayer Langmuir adsorption capacities of UAS and MIAS were 29.4 and 33 mg/g, respectively. The thermodynamic parameters including entropy (ΔS), enthalpy (ΔH), and Gibbs free energy (ΔG) indicated that the adsorption of MV2B on to both adsorbents was spontaneous, feasible, and endothermic. [ABSTRACT FROM AUTHOR]

In this work, TiO2nanopowder (TIP600) was prepared by a sol–gel method and titanium isopropoxide, glacial acetic acid, and deionized water were used as the starting materials. Adsorption of congo red (CR) on Degussa-P25 (P25), commercial TiO2(C-TiO2), and TIP600 was investigated. But, photochemical and photocatalytic event were not used for this adsorption process. Adsorption of CR onto the adsorbents was studied at different temperatures (25.0, 40.0, and 50.0°C) and various adsorbent doses (0.1, 0.05, and 0.025 g). The kinetics of dye adsorption has been investigated in terms of pseudo-first order, pseudo-second order, and intra-particle diffusion rate. The results indicate that pseudo-second order plays a significant role in the adsorption mechanism. The adsorptive capacity of TIP600 is much higher than that of other adsorbents. The value of ∆H#was obtained as positive, therefore the nature of adsorption was found endothermic. Equilibrium isotherm of CR was fitted to the Freundlich and Langmuir models. The equilibrium data of adsorbate were found to best fit the Langmuir model. For CR, TIP-600 was demonstrated as the best adsorption capacity (qmax112 mg g−1). [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the removal of As(V) from aqueous solutions using functionalized activated carbon fiber (ACF) as an adsorbent. The functionalized ACF was prepared through the impregnation of iron oxides on the surfaces of ACF. The X-ray fluorescence spectrometer analysis showed that carbon (C, 70.1%) and iron (Fe, 28.5%) were the major constituents of functionalized ACF. The N2adsorption–desorption analysis showed that the Brunauer–Emmett–Teller surface area of functionalized ACF was determined to be 418.2 m2/g, which was 2.7 times smaller than that of raw ACF (1,123.0 m2/g) due to the impregnation of iron oxide. From the batch experiments, the maximum adsorption capacity of As(V) in functionalized ACF was determined to be 1.208 mg/g. The adsorption of As(V) to functionalized ACF was sensitive to solution pH changes, decreasing from 0.045 to 0.029 mg/g with increasing pH from 2.6 to 8.9. Kinetic model analysis showed that the pseudo-second-order model was most suitable at describing the kinetic data. Equilibrium isotherm model analysis illustrated that the Redlich–Peterson model fitted well with the equilibrium data. Thermodynamic tests demonstrated that As(V) sorption to functionalized ACF increased with increasing temperature from 20 to 40°C, indicating the endothermic and spontaneous nature of sorption process (ΔH° = 38.02 kJ/mol, ΔS° = 149.15 J/K/mol, and ΔG° = –5.70 and –8.69 kJ/mol). This study demonstrated that the removal of As(V) by ACF could be enhanced via iron oxide impregnation. [ABSTRACT FROM PUBLISHER]

Pistia stratiotesL.(water lettuce or WL) was investigated for its potential as an effective low-cost biosorbent for the removal of methyl violet 2B (MV). Equilibrium isotherm for the adsorption of MV, fitted using six different isotherm models followed by error analyses, indicates that the maximum biosorption capacity (qmax) is 0.68 mmol g−1(267.6 mg g−1) and that both the Langmuir and Sips isotherm models lead to good correlation with experimental data. Investigation on effects of pH, ionic strengths, and pre-treatment of the biosorbent on the extent of biosorption indicates the effect of these parameters on MV–biosorbent interaction. Kinetics of the interaction of MV and the biosorbent is fast with more than 50% dye being removed and follows the pseudo-second-order model. [ABSTRACT FROM PUBLISHER]

This study investigates the removal of ammonium from aqueous using zeolite synthesized from red mud. The zeolite was characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), the specific surface area, and the cation exchange capacity (CEC). SEM and XRD indicated that most of the synthetic zeolite was crystalline, with zeolite P and Analcime as the major components. The CEC increased from 81.9 to 111 mmol/100 g during the synthesis process. The effects of adsorbent dosage, shaking time, initial pH, initial ammonium ion concentration, and competitive cations were investigated by batch experiments. The result shows that the parameters mentioned above have great influence on the ammonium removal by using the synthesized zeolite, and the effect of cations follows the order Na+ > K+ > Ca2+ > Mg2+. To understand the exchange process of ammonium by the synthesized zeolite, the adsorption dynamics was described by Ho’s pseudo-second-order kinetic model. The Ho’s pseudo-second-order kinetic model was found to provide excellent kinetic data fitting. Five models including Langmuir, Freundlich, Koble–Corrigan, Tempkin and D–R were used in this experiment to fit with the equilibrium isotherm data, and the Koble–Corrigan model gave the best fit. The maximum ammonium adosorption capacity obtained is 17.5 mg/g. The results implies that the zeolites synthesized from red mud is an efficient adsorbent for the removal of ammonium ion. [ABSTRACT FROM PUBLISHER]

Cu-BTC, one of the metal–organic frameworks (MOFs), has been applied to remove the cationic dye methylene blue (MB) and anionic dye methyl orange (CR) from contaminated water. Liquid phase adsorption experiments were conducted and the maximum adsorptive capacity was determined. Various conditions were evaluated, including initial dye concentration, contact time, solution pH, and temperature. The Langmuir and Freundlich adsorption models were used to describe the equilibrium isotherm and isotherm constant calculation. It was found that the Cu-BTC adsorption capacities of MB and CR are much higher than those of the other types of MOFs and adsorbents. Maximum equilibrium adsorption capacities of 143.27 and 877.19 mg/g for MB and CR were achieved. Three simplified kinetic models including pseudo-first-order, pseudo-second-order, and intra-particle diffusion equations were used to investigate the adsorption process. The pseudo-second-order equation was followed for adsorption of MB and CR on Cu-BTC. Temperature-dependent adsorption behaviors of MB and CR show that the adsorption is a spontaneous and endothermic process accompanying an entropy increase. This work indicates that Cu-BTC could be employed as an effective adsorbent in the removal of the textile dyes from effluents. [ABSTRACT FROM PUBLISHER]

Adsorption is one of the important methods used to remove dyestuff (methylene blue) from industrial wastewaters with suitable adsorbents. In this study, magnetic wild chestnut shell coated Fe3O4 was used as the adsorbent. The magnetic wild chestnut shell coated Fe3O4 nanoparticles were synthesized using the chemical precipitation method. The surface properties of the adsorbents were characterized by using spectroscopic techniques such as scanning electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller, and Fourier transform infrared spectroscopy. The effect of adsorption parameters such as initial pH (2-9) value, adsorbent dosage (0.1-0.5 g), temperature (298-318 K), contact time (0-240 min), and initial concentration (25-150 mg L-1) were researched. The experimental data indicated that the adsorption isotherms were well described by the Langmuir equilibrium isotherm equation and the calculated adsorption capacities of the magnetic wild chestnut shell coated with Fe3O4 were 140.84 mg g-1. The adsorption of methylene blue was determined as in compliance with the pseudo-second-order kinetic model. The thermodynamic parameters calculated to estimate the nature of adsorption indicated spontaneous and endothermic adsorption (H° = 69.00 kJ mol-1). The adsorption/desorption circulation test showed good reusability performance up to the fourth cycle. Furthermore, considering all the results, the advantage of being produced from a cheap source, high adsorption capacity, and rapid procurement feasibility has led to a great promise for the removal of methylene blue from aqueous solutions. [ABSTRACT FROM AUTHOR]

At present study, multi-walled carbon nanotubes were used as an adsorbent for Reactive Black 5 (RB5) removal from aqueous solutions. The influence of important parameters including initial pH, concentration of dye, contact time, adsorbent dosage, and temperature has been investigated in order to find the optimum adsorption conditions. The results show that all the parameters have a strong effect on the adsorption of RB5 onto adsorbent. Adsorption kinetics was best described by the pseudo-second-order model. In addition, equilibrium data were better represented by Freundlich isotherm among Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich equilibrium isotherm models. The negative values of free-energy change confirmed the feasibility of the process and the spontaneous nature of adsorption. Furthermore, from the magnitude of ΔH, the process was found to be endothermic physisorption. [ABSTRACT FROM PUBLISHER]