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Batch sorption experiments were performed to investigate the potential of Bauhinia variagata fruit (BVf) and nano-magnetic Bauhinia variagata fruit (nM-BVf) to remove methylene blue (MB) and malachite green (MG). Equilibrium studies have been carried out using various experimental parameters such as the amount of biosorbent, initial solution concentration, contact time, pH, and temperature. The Langmuir, Freundlich, Scatchard, D-R and Temkin adsorption models were applied for the experimental information of MB and MG. The Freundlich model fits better than the Langmuir model. Freundlich model confirmed the magnificent dye sorption ability; 19.3 mg/g for BVf/MB, 21.2 mg/g for nM-BVf/MB, 19.7 mg/g for BVf/MG, and 30.1 mg/g for nM-BVf/MG. The pseudo-second-order kinetic model displayed a more suitable behavior to the experimental result for the removal of MG and MB. Thermodynamic parameters such as changes in Gibbs free energy (Delta G(o)), enthalpy (Delta H-o), and entropy (Delta S-o) were investigated and the fine details in the adsorption system were completed. The conclusion from this study is that the prepared nano biosorbent can be efficient for the removal of cationic dyes from wastewater.

This study evaluates the application of Cr(VI) adsorption from the prepared synthetic solution by black sesame (Sesamum indicum L.) seed pulp (BSSP) and chitosan (Cts)-coated black sesame seed pulp beads (Cts-BSSP). BSSP and Cts-BSSP were used as an adsorbent without any chemical or physical treatment to remove Cr(VI) from an aqueous medium. The results indicated that the Cr(VI) removal was pH-dependent and reached an optimum at pH 2.0. It has been observed that the percentage of adsorption increased from 62% to 95% when the amount of Cts-BSSP increased from 0.0125 g to 0.0250 g. The required adsorbent amount for the maximum removal was 0.05 g and 0.1 g for Cst-BSSP and BSSP, respectively. The contact time for the adsorption was 120 min and 90 min for BSSP and Cst-BSSP, respectively. Scanning electron microscopy and Fourier transform infrared spectroscopy were used to explore the possible adsorption mechanism for Cr(VI). The equilibrium data for the BSSP and Cts-BSSP were used with the Langmuir and Freundlich adsorption isotherm models to assess the adsorption capacity and relevant mechanism. The adsorption capacity of the Cts-BSSP for Cr(VI) is relatively high compared to BSSP. The monolayer maximum adsorption capacities for Cr(VI) ions were 31.44 and 18.32 mg/g for Cts-BSSP and BSSP, respectively.

International Congress on Semiconductor Materials and Devices (ICSMD) -- AUG 17-19, 2017 -- Selcuk Univ, Konya, TURKEY, WOS: 000495858400025, This work investigates the adsorption of chromium ions on chitosan doped with multiwalled carbon nanotubes (Cht-MWCNT). The effects of initial pH, amount of Cht-MWCNT, temperature, contact time, and the initial concentration of Cr (VI) were investigated during the equilibrium and kinetic studies. The equilibrium time was found to be 60 min. Adsorption isotherms of Cr (VI) on Cht-MWCNT was determined and correlated with Langmuir, Freundlich, Scatchard and D-R isotherm equations. The adsorption data showed that adsorption of Cr (VI) was fitted by Langmuir isotherm model and pseudo-second-order kinetics model. Under optimum conditions, maximum adsorption capacity of Cr (VI) determined by Langmuir model were enhanced 26.14 mg/g. Thermodynamic parameters such as Delta G degrees, Delta H degrees, Delta S degrees were calculated and the interaction of Cr (VI) with Cht-MWCNT was found to be endothermic and spontaneous in nature. (C) 2019 Elsevier Ltd. All rights reserved.

This study investigates the adsorption of Cu(II) and Pb(II) ions onto magnetic-plum stone activated carbon (m-PSAC). Plum stone-activated carbon (PSAC) was produced by chemical activation of plum stone (PS) with phosphoric acid (H3PO4) in N2 inert atmosphere. The effects of activator ratio, activation temperature, and impregnation temperature were examined. m-PSAC was prepared by co-precipitation method which is a combination of PSAC with Fe2 +:Fe3 + salts. The prepared m-PSAC was characterized by scanning electron microscopy (SEM) and Fourier Transform infrared spectrophotometer (FT-IR). Then m-PSAC was used for the removal of Cu(II) and Pb(II) ions from aqueous solutions. The effects of initial pH, the amount of m-PSAC, temperature, contact time, and the initial concentration of Cu(II) and Pb(II) were investigated during the equilibrium and kinetics studies. Adsorption isotherms for the Cu(II) and Pb(II) on m-PSAC was determined and correlated with Langmuir, Freundlich, Scatchard and D-R isotherm equations. The adsorption data showed that adsorption of Cu(II) and Pb(II) was fitted by Langmuir isotherm model and pseudo-second-order kinetics model. Under the optimized conditions, maximum adsorption capacities of Cu(II) and Pb(II) ions determined by Langmuir model were enhanced 48.31 and 80.65 mg/g, respectively. Thermodynamic parameters such as ΔG°, ΔH°, ΔS°, Ea were calculated and the interaction of metals with m-PSAC was found to be exothermic and spontaneous in nature.

This study was performed to evaluate Cr(VI) removal performance of three anion-exchange resins with different quaternary amine functional groups by varying the conditions of the solution phase. The effects of process variables on the sorption, such as solution pH, temperature, adsorbent dose, phases contact time, and initial Cr(VI), concentration were performed at laboratory condition. The suitability of Freundlich, Langmuir, and Scatchard isotherm models was investigated for Cr(VI)-resin equilibrium. According to the results, calculated maximum ion-exchange capacities were 280.25 mg/g, 147.67 mg/g, and 163.67 mg/g of Cr(VI)/g, for Eichrom 1-X4, Lewatit M+ M800, and Lewatit A8071, respectively. The sorption kinetics and thermodynamic parameters for the equilibrium were studied for all three resins.

Copper ion (Cu 2 + ) removal from aqueous solutions was performed with two different chelating resins (bis-picolylamine, iminodiacetate). In order to compare the results obtained from the chelating resins, strong acid cation exchangers were used with sulfonic acid functionally. The effects of the following parameters such as the amount of resin, the duration, pH levels and concentration were noted for the ion-exchange. The Langmuir, Freundlich, D-R and Scatchard isotherm models were used to evaluate the data. The Langmuir isotherm model was found to be the best model. The chelating resins which retained some of their functional groups showed good properties for the removal of Cu 2 + from aqueous solutions. The sorption capacity of the resins increased with the rising Cu 2 + concentration in the aqueous medium. FT-IR analysis results show clearly that the ion-exchange and chelating took place as mechanisms which rule during the sorption of Cu 2 + from aqueous phase.

WOS: 000360793100010, PubMed: 26322758, Because of the recognition that arsenic (As) at low concentrations in drinking water causes severe health effects, the technologies of As removal have become increasingly important. In this study, a simplified and effective method was used to immobilize iron oxyhydroxide onto a pretreated naturally occurring rice straw (RS). The modified RS adsorbent was characterized, using scanning electron microscope, Fourier transform infrared spectroscopy, thermogravimetric analyzer, and surface area analyzer. Experimental batch data of As(V) adsorption were modeled by the isotherms and kinetics models. Although all isotherms, the Langmuir model fitted the equilibrium data better than Freundlich and Dubinin-Radushkevich models and confirmed the surface homogeneity of adsorbent. The iron oxyhydroxide-coated rice straw (IOC-RS) was found to be effective for the removal of As(V) with 98.5% sorption efficiency at a concentration of, German Federal Ministry for Economic Cooperation and Development (BMZ); German Academic Exchange Service (DAAD)Deutscher Akademischer Austausch Dienst (DAAD), This investigation was performed at the Guest Chair within the project 'Exceed - Excellence Center for Development Cooperation - Sustainable Water Management in Developing Countries' at the Technische Universitaet Braunschweig, Prof. Pehlivan being the visiting professor, and Ms Tran and Dr Ouedraogo being the international exchange staff members. The Exceed Project is granted by the German Federal Ministry for Economic Cooperation and Development (BMZ) and German Academic Exchange Service (DAAD), and their financial support we gratefully acknowledge.

The removal of Cr(III) ions from aqueous solution by two commercially available resins (Amberlite IRN77 and Purolite C160) was investigated. Batch adsorption processes were carried out as a function of time, adsorbent dosage, pH, concentration and temperature to evaluate the performance of the resins. It was found that more than 90% removal was achieved under optimal conditions. The optimum pH for Cr(III) adsorption was found as 4.0 for these resins. The suitability of Freundlich, Langmuir, Scatchard and Dubinin–Radushkevich adsorption models was also investigated for Cr(III)-resin system. A pseudo-second-order kinetic model has been proposed to correlate the experimental data. The equilibrium adsorption level for Amberlite IRN77 slightly decreased with increasing temperature, while it was nearly the same for Purolite C160.

A lignocellulosic material extracted from rice husk (Oryza sativa), Vietnam, was modified as a new adsorbent for the removal of As(V) ions from aqueous solution. Iron was coated onto this adsorbent by hydrolization of ferric nitrate while adding an alkaline solution drop wise into the batch type reactor. The adsorption of As(V) ions from aqueous solution on coated rice husk was then studied at varying pH, As(V) concentrations, contact times, ionic strength, and adsorbent amounts. The minimum contact time to reach equilibrium is about 6 h. The adsorption of As(V) anions on the coated rice husk was found to be highly pH dependent due to Coulomb interactions between As(V) species in solution and positively charged surface groups RH-FeOOH, as well as formation of chelate complexes with naturally occurring carboxyl and carbonyl functional groups in the matrix. As(V) adsorption on Fe(III)-coated rice husk (RH-FeOOH) from aqueous solution was studied in the pH range 2–10. The main effects of pH on adsorption are estimated by considering both the behavior of As(V) ions (hydrolysis and hydroxide precipitation) and the effect of pH on coordination. A strong effect of pH was demonstrated at pH 4.0 with a maximum percentage for removal of As(V) ions 94%. Although both Langmuir and Freundlich isotherms have been used to characterize the adsorption of As(V), the Langmuir model fitted the equilibrium data better than Freundlich model and confirmed the surface homogeneity of adsorbent. The maximum adsorption capacity is determined as 2.5 mg/g of adsorbent at pH 4.0 for the Fe(III)-coated rice husk. It is concluded that initial As(V) concentration has an effect on the removal efficiency of RH-FeOOH. Higher adsorption of As(V) was observed at lower initial concentrations. RH-FeOOH as a low cost material is effective for the removal of As(V) ions and may become a valuable adsorbent to improve the ground water quality in Vietnam.

Barley straw (BS), a very low-cost material, has been utilized as a biosorbent material for the removal of copper (Cu 2+ ) ions from aqueous solutions after treatment with citric acid. Barley straw was thermochemically modified with citric acid (CA–BS) for the purpose of improving the Cu 2+ ion sorption capacity of the straw. Biosorption studies have been carried out to determine the effect of pH, adsorbent concentration, contact time, extent of modification, and adsorbate concentration on the biosorption capacity of Cu 2+ ions by the esterified straw. The equilibrium sorption capacities of Cu 2+ were 4.64 mg/g and 31.71 mg/g for BS and CA–BS, respectively. The optimum pH for the removal of Cu 2+ ions by CA–BS was around pH 7.0 and the removal of Cu 2+ ions was 88.1%. Langmuir, Freundlich, Scatchard and D–R (Dubinin–Radushkevich) isotherms have been used to characterize the observed biosorption phenomena of Cu 2+ ions on CA–BS. The carboxyl groups on the surface of the modified barley straw were primarily responsible for the sorption of Cu 2+ ions.

Walnut shell (WNS) ( Juglans regia ) has been utilised as an adsorbent for the removal of Cr(VI) ions from aqueous solutions after treatment with citric acid. The modification reaction variables, such as citric acid level (5–10 g), reaction time (0–24 h), and temperature (110–130 °C) were studied in batch experiments. The rate of adsorption was studied under a variety of conditions, including initial Cr(VI) concentration (0.1–1.0 mM), amount of adsorbent (0.02–0.20 g), pH (2–9), temperature and contact time (10–240 min). Adsorption of Cr(VI) is in all cases pH-dependent showing a maximum at equilibrium pH values between 2.0 and 3.0 for citric acid modified walnut shell (CA-WNS). The applicability of the Langmuir, Freundlich and D–R adsorption isotherms has been tested for the equilibrium. Maximum adsorption capacities of CA-WNS and untreated WNS under experimental conditions were 0.596 and 0.154 mmol/g for Cr(VI) ions, respectively.

The removal of Cr(VI) from aqueous solution by two commercially available resins (Amberlite IRA96 and Dowex 1×8) was investigated. Batch adsorption processes were carried out as a function of time, adsorbent dosage, pH and temperature to evaluate the performance of the resins. The optimum pH for Cr(VI) adsorption was found as 3.0 for these resins. It was found that more than 93% removal was achieved under optimal conditions. The maximum adsorption capacities are 0.46 and 0.54 mmol/g of Amberlite IRA96 and Dowex 1×8 resin for Cr(VI) ion, respectively. The suitability of Freundlich and Langmuir adsorption models were investigated for Cr(VI)-resin equilibrium. A pseudo-second order kinetic model has been proposed to correlate the experimental data. The equilibrium adsorption level for Dowex 1×8 decreased with increasing temperature, while it increased for Amberlite IRA96.

The aim of this study is to demonstrate the potential of humic acids (HAs) as a low-cost reactive barrier material for environmental protection applications of toxic Cr(VI). Sorption of Cr(VI) on the HAs obtained from Ilgin, Beysehir and Ermenek lignites in Turkey were investigated and their sorption properties were compared with the activated carbon (AC) from Merck. The adsorption was carried out using a batch method. The sorption of Cr(VI) on the surface of HAs depends strongly on the pH and Cr(VI) sorption increased with a decreasing pH and increase in the concentration of this metal. The Freundlich adsorption isotherm was used to describe observed sorption phenomena. It was observed that the maximum adsorption capacity of 0.55 mmol Cr(VI)/g for Ilgin, 0.64 mmol Cr(VI)/g for Beysehir and 0.40 mmol Cr(VI)/g for Ermenek was achieved at pH of 3.2. The rise in temperature caused a slight decrease in the value of the equilibrium constant ( K c ) for the sorption of Cr(VI). The Cr(VI) sorption capacities of Beysehir and Ilgin HAs were nearly as same as that of AC (0.58 mmol Cr(VI)/g). Therefore, HAs are used for the adsorption of Cr(VI) in wastewater treatment applications.

The main objective of this study was to remove Cu2+ and Ni2+ ions from aqueous solution by using fly ash, an industrial solid waste of the sugar industry and commercial activated carbon at equilibrium, which follows Langmuir and Freundlich adsorption isotherms. In order to identify influential parameters and to evaluate their interactions, effects of time, pH, initial metal concentration, and amount of adsorbent were studied, and the results were compared with those of activated carbon under the same experimental conditions. Adsorption studies were performed in a time interval (1–240 min), at various pH values (2.0–8.0) at 25°C and at metal concentrations of 1–10 × 1−4 M using different amounts of adsorbent (1–12 g/L). The equilibrium time was fixed at 60 min in the case of Cu2+ and Ni2+, and 8 g/L of fly ash and 6 g/L activated carbon was sufficient for the optimum removal of both the metal ions. The sorption of metal ions increased with an increase of pH, and maximum removal was obtained at 5.0...

In this article, the adsorption of Cu 2+ and Cr 3+ onto pumice (Pmc) and polyacrylonitrile/pumice (PAn/Pmc) composite has been investigated by using a batch method at room temperature and their adsorption properties were compared. To highlight their application, selected information on pH, initial metal concentration and adsorption capacity of the adsorbents is presented. Depending on the characteristics of the individual adsorbents viz. surface modification, initial concentration of adsorbates, and pH, their adsorption capacities were found to vary. The time required for the removal of metal ions (100–500 mg/g) from aqueous solutions was about 6 h. The experimental data have been analyzed using the Langmuir and Freundlich isotherm models. The results of adsorption were fitted to the Langmuir models and coefficients indicated favorable adsorption of Cu 2+ and Cr 3+ on the adsorbents. Adsorption of Cu 2+ and Cr 3+ in the solutions was in following order: (PAn/(Pmc) composite > Pmc). The adsorption capacity of the adsorbents Pmc and (PAn/Pmc) were determined from the isotherms equations and were found to be 0.055 and 0.065 mmol/g for Cu 2+ and 0.031 and 0.268 mmol/g for Cr 3+ , respectively. More than 80% of studied cations were removed by Pmc and 87% (PAn/Pmc), respectively, from aqueous solutions in single step. Effective removal of metal ions was demonstrated at pH values of 8.0. The mechanism for cations removal by the Pmc and (PAn/Pmc) composite includes complexation and sorption. The process is very efficient especially in case of low concentrations of pollutants in aqueous solutions, where common methods are either economically unfavorable or technically complicated. © 2007 Elsevier B.V. All rights reserved.

The adsorption of Cr(VI) from aqueous solutions on sawdust (SD), base extracted sawdust (BESD) and tartaric acid modified sawdust (TASD) of Turkish red pine tree (Pinus nigra), a timber industry waste, was studied at varying Cr(VI) concentrations, adsorbent dose, modifier concentration and pH. Batch adsorption studies have been carried out. Sawdust was collected from waste timber industry and modified with various amount of tartaric acid (TA) (0.1-1.5M). The batch sorption kinetics has been tested and the applicability of the Langmuir and Freundlich adsorption isotherms for the present system has been tested at 25+/-2 degrees C. Under observed test conditions, the equilibrium adsorption data fits the linear Freundlich isotherms. An initial pH of 3.0 was most favorable for Cr(VI) removal by all adsorbents. Maximum Cr(VI) was sequestered from the solution within 120 min after the beginning for every experiment. The experimental result inferred that chelation and ion exchange is one of the major adsorption mechanisms for binding metal ions to the SD. Percentage removal of Cr(VI) was maximum at the initial pH of 3.0 (87.7, 70.6 and 55.2% by TASD, BESD, and SD, respectively). Adsorption capacities range from 8.3 to 22.6 mg/g for SD samples.

The batch removal of Cu(II) ions from aqueous solution using low-cost adsorbents such as walnut (WNS) (Juglans regia), hazelnut (HNS) (Corylus avellana), and almond (AS) (Prunus dulcis) shell under different experimental conditions was investigated in this study. The main parameters influencing Cu(II) ion sorption on WNS, HNS, and AS were: initial metal ion concentration, amount of adsorbent, contact time, and the pH value of the solution. The influences of initial Cu(II) ion concentration (0.005-0.05 mmol/mL), pH (2-9), contact time (10-240 min), and adsorbent amount (0.1-1.0 g) have been reported. WNS presented the highest adsorption capacities for the Cu(II) ion. Each of WNS, HNS, and AS as sorbents for the removal of Cu(II) ions showed that the sorption process was pH dependent. The greatest increase in the rate of adsorption of metal ion on the shells was observed for pH changes from 5.5-7.0. For WNS, HNS, and AS, the optimum pH value was 6 and the equilibrium time was 120 min. The metal ion sorption obeyed both the Langmuir and Freundlich isotherms. The sorption process conformed to the Langmuir isotherm with maximum Cu(II) ion sorption capacities of 6.74, 6.65, and 3.62 mg/g for WNS, HNS, and AS, respectively. The experimental results demonstrated that chelation and ion exchange is one of the major adsorption mechanisms for binding metal ions to the sorbents. The percentage removal Cu(II) ion was maximum at 10 -3 mol/L solution concentration and initial pH of 6.0 (80.3, 75.6, and 75.0% by WNS, HNS, and AS, respectively).

The ability of using low-rank Turkish brown coals (Ilgin: BC1, Beysehir: BC2, and Ermenek: BC3) to remove Cr(VI) from aqueous solutions was studied as a function of contact time, solution pH, temperature, concentration of metal solutions and amount of adsorbent. Their sorption properties were compared with the activated carbon from Chemviron (AQ-30). Adsorption of Cr(VI) uptake is in all cases pH-dependent showing a maximum at equilibrium pH values between 2.0 and 3.2, depending on the biomaterial, that correspond to initial pH values of 2.3 units for BC1, 3.0 units for BC2 and 3.2 units for BC3 and AQ-30. Batch equilibrium tests showed that the Cr(VI) removal was fitted with Freundlich isotherm and the adsorption reached equilibrium in 80 min. It was proceeding effectively into a short acid pH interval (2.0–3.2) where processes of Cr(VI) sorption are maximized. It was observed that the maximum adsorption capacity of 11.2 mM of Cr(VI)/g for Ilgin (BC1), 12.4 mM of Cr(VI)/g for Beysehir (BC2), 7.4 mM of Cr(VI)/g for Ermenek (BC3) and 6.8 mM of Cr(VI)/g for activated carbon (AQ-30) was achieved at pH of 3.0. The rise in temperature caused a slight decrease in the value of the equilibrium constant (Kc) for the sorption of Cr(VI) ion. The Cr(VI) sorption capacities of Beysehir and Ilgin brown coals were the same. Ermenek brown coals and activated carbon (AQ-30) showed a similar sorption capacity.

The biosorption of Cr(VI) by the garlic stem (GS)-Allium sativum L. and horse chesnut shell (HCS)-Aesculus hippocastanum plant residues in a batch type reactor was studied in detail for the purpose of wastewater treatment. The influence of initial Cr(VI) concentration, time, and pH was investigated to optimize Cr(VI) removal from aqueous solutions and equilibrium isotherms and kinetic data. This influence was evaluated. The adsorption capacity of the GS and the HCS for Cr(VI) was determined with the Langmuir and Freundlich isotherm models, and the data was fitted to the Langmuir. The adsorption capacity of the GS and the HCS was found to be 103.09 and 142.85 mg/g of adsorbent from a solution containing 3000 ppm of Cr(VI), respectively. The GS's capacity was considerably lower than that of the HCS in its natural form. Gibbs free energy was spontaneous for all interactions, and the adsorption process exhibited exothermic enthalpy values. The HCS was shown to be a promising biosorbent for Cr(VI) removal from aqueous solutions.

In the present work, the abilities of native sugar beet pulp (SBP) and fly ash (FA) to remove copper (Cu(2+)) and zinc (Zn(2+)) ions from aqueous solutions were compared. The SBP and FA, an industrial by-product and solid waste of sugar industry, were used for the removal of copper and zinc from aqueous water. Batch adsorption experiments were performed in order to evaluate the removal efficiency of SBP and lignite-based FA. The effect of various operating variables, i.e. initial pH, adsorbent dose, initial metal ion concentration, and time on adsorption of copper and zinc onto the SBP and FA, has been studied. The sorption process was relatively fast and equilibrium was reached after about 60 min of contact. As much as 60-97% removal of copper and zinc for SBP and FA are possible in about 60 min, respectively, under the batch test conditions. Uptake showed a pH-dependent profile. The overall uptake for the SBP is at a maximum at pH 5.5 and gives up to 30.9 mg g(-1) for copper and at pH 6.0 and gives 35.6 mg g(-1) for zinc for SBP, which seems to be removed exclusively by ion exchange and physical sorption. Maximum adsorption of copper and zinc occurred 7.0 and 7.84 mg g(-1) at a pH value of 5.0 and 4.0 for FA, respectively. A dose of 8 g l(-1) of SBP and 8 g l(-1) FA were sufficient for the optimum removal of both the metal ions. The sorption data were represented by the Freundlich for SBP and the Langmuir and Freundlich for FA. The sorption data were better represented by the Langmuir isotherm than by the Freundlich one for FA in the adsorption of zinc ion, suggesting that the monolayer sorption, mainly due to ion exchange. The presence of low ionic strength or low concentration of Na and Cl ions does not have a significant effect on the adsorption of these metals by SBP and FA. The SBP and FA are shown to be effective metal adsorbents for these two metals.

Novel adsorbents, wheat bran (WB) and modified wheat bran (M-WB) with tartaric acid were developed and Cr(VI) adsorption was investigated by changing various parameters. The adsorption increased with contact time and become optimum at 180 min for WB and 200 min for M-WB. When the pH of the solution phase increased, some of toxic Cr(VI) reduced into less toxic Cr(III) on the WB surface. The maximum removal of Cr(VI) from the solution having an initial Cr(VI) concentration of 200 mg L-1 was obtained at pH 2.0 as 51.0% and 90.0% for WB and M-WB, respectively. Isotherm data of Cr(VI) adsorption on WB and M-WB was described by the Freundlich adsorption model. The adsorption capacity of 4.53 mg of Cr(VI)/g for WB and 5.28 mg of Cr(VI)/g for M-WB was obtained at pH 2 and 2.2 respectively. (C) 2014 Elsevier Ltd. All rights reserved.

Natural Turkish dolomite was shown to be effective for removing Cu(2+) and Pb(2+) from aqueous solution. Selected information on pH, dose required, initial metal concentration, adsorption capacity of the raw dolomite powder was evaluated for its efficiency in adsorbing metal ions. Dolomite exhibited good Cu(2+) and Pb(2+) removal levels at all initial metal amount tested (0.04-0.32 mmol, 20 mL). It is important to note that the adsorption capacities of the materials in equilibrium vary, depending on the characteristics of the individual adsorbent, the initial concentration of the adsorbate and pH of the solution. One hour was enough for the removal of metal ions from (0.2 mmol in 20 mL) aqueous solution. Effective removal of metal ions was demonstrated at pH values of 5.0. The adsorptive behavior of dolomite was described by fitting data generated from the study of the Langmuir and Freundlich isotherm models. The adsorption capacity of dolomite was found as 8.26 mg for Cu(2+) and 21.74 mg for Pb(2+), respectively, from the calculation of adsorption isotherm equation. More than 85% of studied cations were removed by dolomite from aqueous solution in single step. The mechanism for cations removal by dolomite includes surface complexation and ion exchange.

The sorption of Cr(VI) from aqueous solutions with macroporous resins which contain quarternary amine groups (Lewatit MP 64 and Lewatit MP 500) was studied at varying Cr(VI) concentration, adsorbent dose, pH, contact time and temperature. Batch shaking sorption experiments were carried out to evaluate the performance of Lewatit MP 64 and Lewatit MP 500 anion exchange resins in the removal of Cr(VI) from aqueous solutions. The concentration of Cr(VI) in aqueous solution was determined by UV–visible spectrophotometer. The ion exchange process, which is dependent on pH, showed maximum removal of Cr(VI) in the pH range 3–7 for an initial Cr(VI) concentration of 1 × 10 −3 M. The optimum pH for Cr(VI) adsorption was found as 5.0 for Lewatit MP 64 and 6.0 for Lewatit MP 500. The maximum Cr(VI) adsorption at pH 5.0 is 0.40 and 0.41 mmol/g resin for Lewatit MP 64 and Lewatit MP 500 anion exchangers, respectively. The maximum chromium sorption occurred at approximately 60 min for Lewatit MP 64 and 75 min for Lewatit MP 500. The suitability of the Freundlich and Langmuir adsorption models was also investigated for each chromium–sorbent system. The uptake of Cr(VI) by the anion exchange resins was reversible and so it has good potential for the removal of Cr(VI) from aqueous solutions. Both ion exchangers had high bonding constants but Lewatit MP 500 showed stronger binding. The rise in the temperature caused a slight decrease in the value of the equilibrium constant ( K c ) for the sorption of Cr(VI) ion.

The adsorption of Cd2+ and Pb2+ on sugar beet pulp (SBP), a low-cost material, has been studied. In the present work, the abilities of native (SBP) to remove cadmium (Cd2+) and lead (Pb2+) ions from aqueous solutions were compared. The (SBP) an industrial by product and solid waste of sugar industry were used for the removal of Cd2+ and Pb2+ ions from aqueous water. Batch adsorption studies were carried out to examine the influence of various parameters such as initial pH, adsorbent dose, initial metal ion concentration, and time on uptake. The sorption process was relatively fast and equilibrium was reached after about 70 min of contact. As much as 70–75% removal of Cd2+ and Pb2+ ions for (SBP) are possible in about 70 min, respectively, under the batch test conditions. Uptake of Cd2+ and Pb2+ ions on (SBP) showed a pH-dependent profile. The overall uptake for the (SBP) is at a maximum at pH 5.3 and gives up to 46.1 mg g−1 for Cd2+ and at pH 5.0 and gives 43.5 mg g−1 for Pb2+ for (SBP), which seems to be removed exclusively by ion exchange, physical sorption and chelation. A dose of 8 g L−1 was sufficient for the optimum removal of both the metal ions. The Freundlich represented the sorption data for (SBP). In the presence of 0.1 M NaNO3 the level of metal ion uptake was found to reach its maximum value very rapidly with the speed increasing both with the (SPB) concentration and with increasing initial pH of the suspension. The reversibility of the process was investigated. The desorption of Cd2+ and Pb2+ ions which were previously deposited on the (SBP) back into the deionised water was observed only in acidic pH values during one day study period and was generally rather low. The extent of adsorption for both metals increased along with an increase of the (SBP) dosage. (SBP), which is cheap and highly selective, therefore seems to be a promising substrate to entrap heavy metals in aqueous solutions.

A gel resin containing sulfonate groups (Dowex 50W) was investigated for its sorption properties towards copper, zinc, nickel, cadmium and lead metal ions. The use of selective ion exchange to recover metals from aqueous solution has been studied. The ion exchange behavior of five metals on Dowex 50W, depending on pH, temperature, and contact time and adsorbate amount was studied. Experimental measurements have been made on the batch sorption of toxic metals from aqueous solutions using cation exchanger Dowex 50W. The maximum recoveries (about 97%) Cu(2+), Zn(2+), Ni(2+), Cd(2+) and (about 80%) Pb(2+) were found at pH ranges 8-9. The amount of sorbed metal ion was calculated as 4.1, 4.6, 4.7, 4.8, and 4.7mequiv./gram dry resin for Pb(2+), Cu(2+), Zn(2+), Cd(2+), and Ni(2+), respectively. The precision of the method was examined at under optimum conditions. Selectivity increased in the series: Pb>Cd>Cu>Zn>Ni. It has been observed that, selectivity of the -SO(3)H group of the resin increases with atomic number, valance, degree of ionization of the exchanged metals. The equilibrium ion exchange capacity of resin for metal ions was measured and explored by using Freundlich and Langmuir isotherms. Langmuir type sorption isotherm was suitable for equilibrium studies.

The adsorption of copper(II), zinc(II), nickel(II), lead(II), and cadmium(II) on Amberlite IR-120 synthetic sulfonated resin has been studied at different pH and temperatures by batch process. The effects of parameters such as amount of resin, resin contact time, pH, and temperature on the ion exchange separation have been investigated. For the determination of the adsorption behavior of the resin, the adsorption isotherms of metal ions have also been studied. The concentrations of metal ions have been measured by batch techniques and with AAS analysis. Adsorption analysis results obtained at various concentrations showed that the adsorption pattern on the resin followed Freundlich isotherms. Here we report the method that is applied for the sorption/separation of some toxic metals from their solutions. (C) 2004 Elsevier Inc. All rights reserved.

WOS: 000219332000003, The powdered activated carbon (AC) supported by carbonaceous nano-adsorbents were examined to remove hexavalent chromium [Cr(VI)] from aqueous solution The adsorption behaviour of micro-level concentration of Cr(VI) on those nano-adsorbents was investigated as a function of the experimental conditions such as the contact time, the pH, the dosage of adsorbent, and the initial concentration of Cr(VI). The structural characterization of the adsorbents was accomplished by Fourier transform infrared spectroscopy and scanning electron microscopy. Adsorption isotherms including Freundlich and Langmuir have been applied to study the equilibrium of the adsorption behaviour and identify the adsorption capacity of the activated carbon-functionalized multiwalled carbon nanotubes (AC/f-MWCNTs) and activated carbon-functionalized carbon nanospheres (AC/f-CNSs). Langmuir isotherm model showed that the adsorption process was monolayer type under working with an adsorption capacity of 113.29 and 105.48 mg/g, respectively, for AC/f-MWCNTs and (AC/f-CNSs)., TUBA (Turkish Academia of Sciences); Selcuk University, BAPSelcuk University [14101008], The authors thank TUBA (Turkish Academia of Sciences) and Selcuk University, BAP (Project number-14101008) for the financial support.