Sorption Behavior of Copper(II) on Freshly Precipitated Aluminum Hydroxide

The isotherms of copper(II) sorption from aqueous solutions on freshly precipitated aluminum hydroxide obtained by hydrolysis of pentahydroxomonochlorodialuminum were studied. The sorption efficiency of copper(II) was studied as influenced by pH. Sorption of copper(II) by two different mechanisms is discussed.     

Recovery of heavy metal ions from aqueous solutions using modified organosilicas

Sorption of Cu(II), Pb(II), Cd(II), and Zn(II) from aqueous solutions on two-component organosilicas was studied as influenced by sorbent composition, contact time, ratio of solid and liquid phases, solution pH, nature and concentration of heavy metal ions, and content of modifying agent. The degrees of sorption of these metal ions from aqueous solutions using organosilicas modified with aluminum(III) added into the siloxane matrix or with copper(II) grafted to the sorbent surface layer were compared.     

The enthalpy of interaction between an aqueous solution of methionine and carboxyl cationites in the copper form

The influence of acidity of aqueous solutions of methionine on their interaction with carboxyl cationites in the copper form was studied by the calorimetric, sorption, and spectroscopic methods. The distribution of methionine between aqueous solutions and sorbents with the formation of Cu(II) cation complexes in both phases was observed over the pH range 5–12. The enthalpies of interaction between methionine and KB-2 and Kb-4 cationites in the copper form were determined at various pH.     

A study of the sorption properties of natural calcium clinoptilolite by using radioactive indicators

The sorption of monovalent ions (cesium, silver, thallium, mercury), bivalent ions (strontium, barium, lead, copper, cobalt, zinc) and polyvalent ions (cerium) on calcium clinoptilolite under dynamic conditions has been studied. Both the dynamic exchange capacities in the different break-through of the ions and the degree of the exchanging ions in sorption of different metal cations have been determined. The good selectivity of calcium clinoptilolite in relation to cesium and strontium is displayed in the presence of sodium. The influence of various factors on the sorption the thermal and radiation treatment of the sorbent, the pH and concentration of solutions, equilibration time, presence of alkali and alkali earth ions deactivating agents—EDTA, citric acid tartaric acid, and boric acid in solution has been studied. The optimum conditions of sorption have been determined. Experiments for the desorption of cesium and strontium have been carried out. The possibility to use calcium clinoptilolite for the purpose of deactivation of radioactive wastes is shown. The better sorption properties of that sorbent, compared to calcium clinoptilolite, can be explained by the higher aluminium content, as well as by a prevalence of calcium and magnesium in its ion exchange complex.     

Uranium adsorption characteristic and thermodynamic behavior of clinoptilolite zeolite

Summary Natural zeolite, clinoptilolite was tested for its ability to remove uranium from aqueous solutions. Influence parameters to the sorption process, such as initial uranium concentration, pH, contact time and temperature were investigated. Distribution coefficients of uranium on clinoptilolite were measured by batch technique. Experimental isotherms evaluated from the distribution coefficients were fit to Langmuir, Freundlich and Dubinin-Radushkevich (D-R) models. Values of ΔH and ΔS were found as 0.93 and 56.09 J/mole, respectively. It was observed that the adsorption process is endothermic. Kinetics of uranium sorption was investigated at different time intervals at 30 °C. The reaction rate and diffusion constant were calculated.     

Sorption behavior of Zn(II) ions on synthesized hydroxyapatites

Calcium hydroxyapatite (CaHAP) and barium hydroxyapatite (BaHAP) have been prepared by a wet method from aqueous solutions with cation/P molar ratio of 1.67. The prepared particles were characterized using XRD, IR, TG-DTA and BET-N(2) adsorption measurements. The potential of the synthesized hydroxyapatites to remove Zn(II) from aqueous solutions was investigated in batch reactor under different experimental conditions. Both hydroxyapatites remove Zn(II) from aqueous solutions with an efficiency higher than 98% at initial pH around 6-8. The data reveal that the initial uptake was rapid and equilibrium was established in 20 and 60 min for CaHAP and BaHAP. The sorption process follows the pseudo-first-order kinetic with a rate constant (k(ads)) equals to 1.06x10(-2) and 1.91x10(-2) min(-1) for CaHAP and BaHAP, respectively. Zn(II) removal was quantitatively evaluated using Langmuir isotherm model and the monolayer sorption capacity (Q(max)) shows the values 102.04 and 36.62 mg g(-1) for CaHAP and BaHAP clarifying the high affinity of these novel sorbents for Zn(II) ions. Kinetically, the prepared apatites are feasible sorbents retain Zn(II) ions through a favorable and spontaneous sorption process. The possibility of metal recovery and regeneration of hydroxyapatites were investigated using several eluting agents include hydrochloric acids, double distilled water, calcium chloride, barium hydroxide, and copper chloride. Different desorption levels were obtained with the different adsorbents and the maximum recovery yield was achieved with copper chloride.     

Solid phase extraction�Cinductively coupled plasma spectrometry for adsorption of Co(II) and Ni(II) from radioactive wastewaters by natural and modified zeolites

Natural and modified clinoptilolite as low-cost adsorbents have been used for adsorption of Co(II) and Ni(II) from nuclear wastewaters both in batch and continuous experiments. Zeolite X was also synthesized and its ability towards the selected cations was examined. Kinetic and thermodynamic behaviors for the process were investigated and adsorption equilibrium was interpreted in term of Langmuir and Freundlich equations. The effect of various parameters including the initial concentration, temperature, ionic strength and pH of solution were examined to achieve the optimized conditions. The clinoptilolite was shown good sorption potential for Co(II) and Ni(II) ions at pH values 4?C6. Based on desorption studies, nearly 74 and 85% of adsorbed Co(II) and Ni(II) were removed from clinoptilolite by HCl. The Na⁺ and NH₄ ⁺ forms of clinoptilolite were the best modified forms for the removal of investigated cations. It is concluded that the selectivity of clinoptilolite is higher for Co(II) than Ni(II). The synthesized zeolite showed more ability to remove cobalt and nickel ions from aqueous solution than the natural clinoptilolite. The microwave irradiation was found to be more rapid and effective for ion exchange compared to conventional ion exchange process.     

Sorption of cobalt by two Mexican clinoptilolite rich tuffs zeolitic rocks and kaolinite

Summary The sorption of cobalt from aqueous solutions was studied for two Mexican clinoptilolite rich tuffs zeolitic rocks and kaolinite clay. The effects of pH and contact time on the sorption were examined. Cobalt was determined by neutron activation analysis of the exchanged aluminosilicates. The sorption of cobalt by the aluminosilicates was similar in the pH range from 4 to 7. Kinetic studies showed a rapid sorption in the first 5 hours and equilibrium in about 24 hours. Sorption kinetics was best described by the second-order Ritchie modified model. The experimental results obtained at different concentrations and room temperature for both zeolites were fitted to Freundlich, Langmuir and Freundlich-Langmuir isotherms. The sorption pattern was found to follow the Freundlich model.     

Study of the selection mechanism of heavy metal (Pb2+, Cu2+, Ni2+, and Cd2+) adsorption on clinoptilolite

The study was carried out on the sorption of heavy metals (Ni2+, Cu2+, Pb2+, and Cd2+) under static conditions from single- and multicomponent aqueous solutions by raw and pretreated clinoptilolite. The sorption has an ion-exchange nature and consists of three stages, i.e., the adsorption on the surface of microcrystals, the inversion stage, and the moderate adsorption in the interior of the microcrystal. The finer clinoptilolite fractions sorb higher amounts of the metals due to relative enriching by the zeolite proper and higher cleavage. The slight difference between adsorption capacity of the clinoptilolite toward lead, copper, and cadmium from single- and multicomponent solutions may testify to individual sorption centers of the zeolite for each metal. The decrease of nickel adsorption from multicomponent solutions is probably caused by the propinquity of its sorption forms to the other metals and by competition. The maximum sorption capacity toward Cd2+ is determined as 4.22 mg/g at an initial concentration of 80 mg/L and toward Pb2+, Cu2+, and Ni2+ as 27.7, 25.76, and 13.03 mg/g at 800 mg/L. The sorption results fit well to the Langmuir and the Freundlich models. The second one is better for adsorption modeling at high metal concentrations.     

Sorption characteristics of uranium onto composite ion exchangers

The composite ion exchangers were tested for their ability to remove UO₂ ²⁺ from aqueous solutions. Polyacrylonitrile (PAN) composites having natural zeolite, clinoptilolite, and synthetic zeolite, zeolite X, were used as an adsorbents. The influences of pH, U(VI) concentration, temperature and contact time on the sorption behavior of U(VI) were investigated in order to gain a macroscopic understanding of the sorption mechanism. The optimum adsorption conditions were determined for two composites. The sorption behaviors of uranium on both composites from aqueous systems have been studied by batch technique. Parameters on desorption were also investigated to recover the adsorbed uranium.     

Study of <Superscript>63</Superscript>Ni(II) sorption on CMC-bound bentonite from aqueous solutions

Bentonite was investigated to remove Ni(II) from aqueous solutions because of its strong sorption ability. Herein, bentonite was modified with sodium carboxymethylcellulose (CMC) and used as an adsorbent to remove Ni(II) from aqueous solutions. The results indicated that CMC-bentonite had higher sorption capacity than bare bentonite in the sorption of Ni(II) from aqueous solutions. Sorption of Ni(II) on CMC-bentonite was mainly dominated by ion exchange or outer-sphere surface complexation at low pH values, but by inner-sphere surface complexation or surface precipitation at high pH values. The thermodynamic data calculated from temperature dependent sorption isotherms indicated that the sorption of Ni(II) to CMC-bentonite hybrids was an spontaneous process and enhanced with increasing temperature.     

Physicochemical and Sorption Properties of Silica Gel with Immobilized Xylenol Orange Surface Groups

Organomineral sorbents were prepared by sorption immobilization of Xylenol Orange on the surface of two different samples of silica gel from aqueous solutions with pH 1.68 under static conditions. The diffusion coefficients of Xylenol Organe in the near-surface layer of silica gel and the equilibrium sorption constants were determined. Wash-out of the dye from the sorbent was studied. Sorption of Cu(II), Zn(II), and Pb(II) on the sorbents from aqueous solutions with pH 5.8 was studied.__________Translated from Zhurnal Prikladnoi Khimii, Vol. 78, No. 1, 2005, pp. 73–78.Original Russian Text Copyright © 2005 by Korneev, Kholin.     

Removal of Co(II) from aqueous solution by using hydroxyapatite

Herein, hydroxyapatite (HAP) was prepared by aqueous precipitation technique and was characterized by using FT-IR and XRD to determine its chemical functional groups and micro-structure. The removal of cobalt from aqueous solution to HAP was studied by batch technique as a function of various environmental parameters such as contact time, pH, ionic strength, foreign ions, fulvic acid (FA), and temperature under ambient conditions. The results indicated that the sorption of Co(II) on HAP was strongly dependent on pH and ionic strength. The presence of FA enhanced the sorption of Co(II) on HAP at low pH, whereas reduced Co(II) sorption on HAP at high pH. The Langmuir, Freundlich and D-R models were used to simulate the sorption isotherms at three different temperatures of 303.15, 323.15 and 343.15 K. The thermodynamic parameters (ΔH°, ΔS° and ΔG°) calculated from the temperature dependent sorption isotherms indicated that the sorption process of Co(II) on HAP was spontaneous and endothermic. The sorption of Co(II) was dominated by outer-sphere surface complexation and ion exchange at low pH, whereas inner-sphere surface complexation or surface precipitation was the main sorption mechanism at high pH values. The results suggest that the HAP is a suitable material in the preconcentration and solidification of Co(II) from large volumes of aqueous solutions.     

Chelating ion-exchangers containing n-substituted hydroxylamine functional groups: Part V. Iron,copper, and uranium separations on Duolite CS-346 resin

The separation of iron(III), copper(II) and uranyl(II) ions from a series of salt solutions by chelating ion exchange on Duolite CS-346 resin by pH control is described. Recoveries of these ions from cobalt and nickel salt solutions were quantitative. Iron may also be separated from copper by selective sorption with pH control, and uranium from iron and copper by selective desorption with sodium carbonate solution as eluent.     

Impact of environmental conditions on the sorption behavior of Co(II) on Na-rectorite studied by batch experiments

The sorption of Co(II) from aqueous solution on Na-rectorite was investigated under ambient conditions. Experiments were carried out as a function of contact time, solid content, pH, ionic strength, foreign ions, fulvic acid and temperature. The results indicated that the sorption of Co(II) was strongly dependent on pH. At low pH the sorption was dominated by outer-sphere surface complexation or ion exchange, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models were used to simulate the sorption isotherms at three different temperatures. The thermodynamic data (∆G ⁰, ∆S ⁰, ∆H ⁰) were calculated from the temperature dependent sorption isotherms and the results suggested that the sorption process of Co(II) on Na-rectorite was spontaneous and endothermic. Experimental results indicate that Na-rectorite is a suitable adsorbent for preconcentration and solidification of Co(II) from large volumes of aqueous solutions.     

Sorption of radiocobalt(II) onto Ca-montmorillonite: effect of contact time, solid content, pH, ionic strength and temperature

In this paper, the sorption of Co(II) from aqueous solution to Ca-montmorillonite was studied under ambient conditions by using batch technique. The effects of contact time, solid content, pH, ionic strength and temperature on the sorption of Co(II) to Ca-montmorillonite was also investigated. The results indicated that the sorption of Co(II) was strongly dependent on pH values. The sorption was dependent on ionic strength at low pH values, but independent of ionic strength at high pH values. Outer-sphere surface complexes were formed on the surface of Ca-montmorillonite at low pH values, whereas inner-sphere surface complexes were formed at high pH values. The Langmuir, Freundlich and Dubinin–Radushkevich (D–R) models were used to simulate the sorption isotherms of Co(II) at three different temperatures. The thermodynamic parameters (ΔH ⁰, ΔS ⁰ and ΔG ⁰) were calculated from the temperature dependent sorption isotherms, and the results indicated that the sorption reaction of Co(II) to Ca-montmorillonite was an endothermic and spontaneous process. The high sorption capacity of Co(II) on Ca-montmorillonite suggests that the Ca-montmorillonite is a suitable material for the preconcentration and solidification of radiocobalt from aqueous solutions.     

Investigation of Co(II) sorption on GMZ bentonite from aqueous solutions by batch experiments

In this study, a local bentonite from Gaomiaozi county (Inner Mongolia, China) was converted to Na-bentonite and was characterized by FTIR and XRD to determine its chemical constituents and micro-structure. The removal of cobalt from aqueous solutions by Na-bentonite was investigated as a function of contact time, pH, ionic strength, foreign ions and temperature by batch technique under ambient conditions. The results indicated that the sorption of Co(II) was strongly dependent on pH. At low pH, the sorption of Co(II) was dominated by outer-sphere surface complexation or ion exchange whereas inner-sphere surface complexation was the main sorption mechanism at high pH. The Langmuir, Freundlich, and D-R models were used to simulate the sorption isotherms of Co(II) at the temperatures of 293.15, 313.15 and 333.15 K, respectively. The thermodynamic parameters (∆G°, ∆S°, ∆H°) of Co(II) sorption on GMZ bentonite calculated from the temperature-dependent sorption isotherms indicated that the sorption of Co(II) on GMZ bentonite was an exothermic and spontaneous process. The Na-bentonite is a suitable material for the preconcentration and solidification of Co(II) from aqueous solutions.     

Impact of environmental conditions on sorption of <Superscript>210</Superscript>Pb(II) to NKF-5 zeolite

The sorption of Pb(II) from aqueous solution using NKF-5 zeolite was investigated by batch technique under ambient conditions. The NKF-5 zeolite sample was characterized by using FTIR and X-ray powder diffraction in detail. The sorption of Pb(II) was investigated as a function of pH, ionic strength, foreign ions, and humic substances. The results indicated that the sorption of Pb(II) on NKF-5 zeolite was strongly dependent on pH. The sorption was dependent on ionic strength at low pH, but independent of ionic strength at high pH. At low pH, the sorption of Pb(II) was dominated by outer-sphere surface complexation and ion exchange with H⁺ on NKF-5 zeolite surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH. From the experimental results, one can conclude that NKF-5 zeolite has good potentialities for cost-effective preconcentration of Pb(II) from large volumes of aqueous solutions.     

Sorption/desorption of radionickel on/from Na-montmorillonite: kinetic and thermodynamic studies

In this work, Na-montmorillonite was used as a novel adsorbent for the sorption of Ni(II) from aqueous solutions. The sorption and desorption of Ni(II) on Na-montmorillonite was investigated as the function of pH, ionic strength, Ni(II) concentrations and temperature. The results indicated that the sorption of Ni(II) on Na-montmorillonite was strongly dependent on pH, ionic strength and temperature. The sorption of Ni(II) increases slowly from 22.1 to 51.4% at pH range 2–6.5, abruptly at pH 6.5–9, and at last maintains high level with increasing pH at pH > 9 in 0.1 mol/L NaNO₃ solutions. The Ni(II) kinetic sorption on Na-montmorillonite was fitted by the pseudo-second-order model better than by the pseudo-first-order model and the experimental data implies that Ni(II) sorption on montmorillonite were mainly controlled by the film diffusion mechanism. The Langmuir, Freundlich and D–R models were used to simulate the sorption data at three different temperatures (298.15, 318.15 and 338.15 K) and the results indicated that Langmuir model simulates the experimental data better than Freundlich and D–R models. The sorption–desorption isotherm of Ni(II) on montmorillonite suggested that the sorption is irreversible. The irreversible sorption of Ni(II) on montmorillonite indicates that montmorillonite can be used to pre-concentration and solidification of Ni(II) from large volumes of solution and to storage Ni(II) ions stably.     

Sorption of radiocobalt on acid-activated sepiolite: effects of pH, ionic strength, foreign ions, humic acid and temperature

The acid-activated sepiolite (ASEP) was prepared by physical purification and acid activation of natural sepiolite, and was characterized by XRD, FT-IR, SEM and N₂ adsorption–desorption. The prepared ASEP was applied for the sorption of ⁶⁰Co(II) from aqueous solutions. The sorption of ⁶⁰Co(II) from aqueous solutions by ASEP was investigated as a function of contact time, solid content, pH, ionic strength, foreign ions, humic acid (HA) and temperature. The results indicated that the sorption of ⁶⁰Co(II) on ASEP was strongly dependent on pH values. At low pH, the sorption of ⁶⁰Co(II) was dominated by outer-sphere surface complexation or ion exchange, whereas inner-sphere surface complexation or surface precipitation was the main sorption mechanism at high pH. The presence of HA increased the sorption of ⁶⁰Co(II) on ASEP at low pH values, and reduced the sorption at high pH values. The Langmuir and Freundlich models were applied to simulate the sorption of ⁶⁰Co(II) at three temperatures of 298, 318 and 338 K. The thermodynamic parameters ( $ \Updelta G^\circ ,\,\;\Updelta S^\circ $ and $ \Updelta H^\circ $ ) calculated from the temperature dependent sorption isotherms indicated that the sorption of ⁶⁰Co(II) on ASEP was an endothermic and spontaneous process. ASEP has a great application potential for cost-effective disposal of ⁶⁰Co(II) from large volumes of aqueous solutions.