Chelating Sorbent Research Articles

Chromatofocusing of metal ions on chelating sorbent Tetren-SiO2 with simple eluents

Simple eluents consisting of tri- or tetrabasic acids solutions (citric and pyromellytic acids and a number of complexon acids-nitriltriacetic (NTA), ethylenediaminetetraacetic (EDTA), cyclohexane-1,2-diamine-N,N,N,N-tetraacetic (CDTA)) or their two-component mixtures were applied for the first time in the chromatofocusing of metal ions on chelating sorbent Tetren-SiO2 (Silochrom S-120 with bonded tetraethylene pentamine groups). Smoother, quasi-linear pH gradients were formed for eluents; they consisted of citric acid and an EDTA mixture. The separation of Mn2+, Cr3+, Co2+, and Ni2+ were achieved with s simple two-component eluent.

Preconcentration and Determination of Traces of Heavy Metals with Polymer Chelating Sorbents in the Analysis of Natural and Waste Water

Monitoring the concentrations of heavy metals in natural and waste water at and below the level of their maximum permissible concentrations is an urgent environmental problem. Hence, new procedures for the preconcentration of heavy metals with their subsequent determination by different methods are required. Along with other sorbents, significant attention is attracted to polymer chelating sorbents, which provide individual or group extraction of trace elements, eliminate matrix effects, and provide high concentration factors. The effect of the various parameters such as electrochemically and chemically synthesis methods, physical oxidation state of the polymer, polymer thickness, solution pH and metal ion concentration on the adsorption, kinetics and efficiency were investigated. The results showed a vary broad concentration range of the heavy metals from (0.05 to 10 mg/L) can be adsorbed on different kinds of polymers at different pH values and different efficiently. The adsorption capacity of the polymer to different concentrations of heavy metals was evaluated as the milligram of metal ions by one gram of various forms of the polymer. The DC conductivity measurements were also employed on the solid polymer before and after adsorption of metal ions. The experimental adsorption date was fitted to different mathematical isotherms to estimate the binding constant of heavy metals with the polymer in both single and mixed ion solutions. The method provides the extraction of analytes from natural water of complex composition containing high concentrations of alkali, alkaline-earth and other elements and is characterized by rapidly, selectivity, low detection limits, and a high reproducibility of the results. The relative standard deviation is 2-4%. The technique was test with real waste water samples.

Synthesis of 1-(furan-2-yl) imine Functionalized Silica as a Chelating Sorbent and its Preliminary Use in Metal Ion Adsorption

A new silica gel material covalently bonded with 1-(furan-2-yl) imine (SiNFn) was synthesized and well characterized by elemental analysis, FT-IR, 13C NMR of the solid state, nitrogen adsorption-desorption isotherm, BET surface area, B.J.H. pore sizes, thermogravimetry analyzer (TGA) curves, and scanning electron microscope (SEM). The new chelating surface exhibits good chemical and thermal stability. The synthesized SiNFn was investigated as an adsorbent for the removal of Cu(II), Zn(II), Cd(II), and Pb(II) from aqueous solution. The determination of metal ions was carried out on FAAS using batch method. The adsorption capacity was investigated using kinetics and pH effects. The preliminary results show that the new material presents high adsorption toward copper compared to other described sorbents.

Removal of the Malachite Green (MG) Dye From Textile Industrial Wastewater Using the Polyurethane Foam Functionalized with Salicylate

Polyurethane foam was chemically functionalized with salicylate through the –N˭N– group generating a stable chelating sorbent PUFSalicylate (PUFS) for being used as a low cost, available, and renewable adsorbent for the removal of Malachite Green (MG) textile dye from aqueous solutions. Batch experiments were carried out for sorption kinetics and isotherms. The synthesized adsorbent was characterized by Fourier Transform Infrared Spectroscopy (FTIR), scanning electron microcopy (SEM), and X-ray diffraction. The present study is related to the removal of colorants. Adsorption of MG dye on PUFS was studied as a function of different experimental parameters such as temperature, contact time, amount of adsorbent, and pH. A spectrophotometer technique was used for measuring the extent of adsorption. The data were fitted with Langmuir and Freundlich isotherm equations and their corresponding constants were calculated from the slopes and intercepts of their respective lines. From the measured adsorption isotherms at different temperatures 298, 308, and 318 K, it was found that adsorption increases as the temperature increases within this range. The measured adsorption amount of MG dye increases with increased pH.

Efficient sorption of Cu(2+) by composite chelating sorbents based on potato starch-graft-polyamidoxime embedded in chitosan beads.

Ionic composites based on cross-linked chitosan (CS) as matrix and poly(amidoxime) grafted on potato starch (AOX) as entrapped chelating resin were prepared as beads, for the first time in this work, by two strategies: (1) thorough mixing of previously prepared AOX in the CS solution followed by the bead formation and (2) thorough mixing of the potato starch-g-poly(acrylonitrile) (PS-g-PAN) copolymer in the initial CS solution, followed by bead formation, the amidoximation of the nitrile groups taking place inside the beads. Ionotropic gelation in tripolyphosphate was used to obtain the composite beads, and in situ covalent cross-linking by epichlorohydrin was carried out to stabilize the beads in the acidic pH range. Fourier transform infrared spectroscopy and the swelling ratio values in the acidic pH range confirmed the influence of the synthesis strategy on the structure of the CS/AOX composites. Scanning electron microscopy was employed to reveal the morphology of the novel composites, both before and after their loading with Cu(2+). The binding capacity of Cu(2+) ions as a function of sorbent composition, synthesis strategy, pH, sorbent dose, contact time, initial concentration of Cu(2+), and temperature was examined in batch mode. The main difference between the composites prepared with the two strategies consisted of the higher sorption capacity and the much faster settlement of the equilibrium sorption for the composite prepared by the in situ amidoximation of PS-g-PAN. The Langmuir, Freundlich, Temkin, Dubinin-Radushkevich, and Sips isotherms were applied to fit the sorption equilibrium data. The maximum equilibrium sorption capacity, qm, evaluated by the Langmuir model at 25 °C was 133.15 mg Cu(2+)/g for the CS/AOX composite beads prepared with the first strategy and 238.14 mg Cu(2+)/g for the CS/AOX composite beads prepared with the second strategy, at the same AOX content. The pseudo-second order kinetic model well fitted the sorption kinetics data, supporting chemisorption as the mechanism of interaction between the chelating composites and the Cu(2+) ions. The CS/AOX composite sorbents could be reused up to five sorption/desorption cycles with no significant decrease in Cu(2+) sorption capacity.

Using amino acids for the chromatofocusing of metal ions on silica with bonded tetraethylenepentamine groups

Amino acid-based eluents are used for the chromatofocusing of metal ions on Tetren-SiO2 chelating sorbent (silica with bonded tetraethylenepentamine groups) for the first time. The smoothest quasilinear pH gradients form for eluents based on glutamic and aspartic acids. The separation of Mn2+, Cr3+, Co2+, Ni2+, and Cu2+ is achieved.

Removal of aluminum (III) from environmental samples by siliceous support grafted with poly[1‐(N,N‐bis‐carboxymethyl)amino‐3‐allylglycerol‐co‐dimethylacrylamide] brushes

Silica gel was grafted with polymer containing a functional monomer for metal chelating, poly[1‐(N,N‐bis‐carboxymethyl)amino‐3‐allylglycerol‐co‐dimethylacrylamide] (poly(AGE/IDA‐co‐DMAA)). A system for preconcentration and measurement of aluminum as complexed with iminodiacetic acid was developed. The effects of the analytical parameters, such as sample pH, contact time on sorption capacity of the chelating sorbent and matrix ions, were investigated. The optimum pH value for sorption of the aluminum ions was 6. A recovery of 91.6 % was obtained for the metal ion with 0.5 mol L−1 sulphuric acid as eluting agent. The chelating resin can be reused for five cycles without any significant changes in sorption capacity. The sorption capacity of functionalised sorbent was 25.3 mg g−1. The developed method was utilized for preconcentration and determination of aluminum in environmental water samples by flame atomic absorption spectrometry with satisfactory results. The equilibrium adsorption data of Al(III) on modified sorbent were analysed by Langmuir, Freundlich and Temkin. Based on equilibrium adsorption data the Langmuir, Freundlich, Temkin and Redlich–Peterson constants were determined to be 0.076, 3.21, and 3.46, respectively, at pH 6 and 20 °C.

Novel Oral Detoxification of Mercury, Cadmium, And Lead with Thiol-Modified Nanoporous Silica

We have developed a thiol-modified nanoporous silica material (SH-SAMMS) as an oral therapy for the prevention and treatment of heavy metal poisoning. SH-SAMMS has been reported to be highly efficient at capturing heavy metals in biological fluids and water. Herein, SH-SAMMS was examined for efficacy and safety in both in vitro and in vivo animal models for the oral detoxification of heavy metals. In simulated gastrointestinal fluids, SH-SAMMS had a very high affinity (Kd) for methyl mercury (MeHg(I)), inorganic mercury (Hg(II)), lead (Pb(II)), and cadmium (Cd(II)) and was superior to other SAMMS with carboxylic acid or phosphonic acid ligands or commercially available metal chelating sorbents. SH-SAMMS also effectively removed Hg from biologically digested fish tissue with no effect on most nutritional minerals found in fish. SH-SAMMS could hold Hg(II) and MeHg(I) tightly inside the nanosize pores, thus preventing bacteria from converting them to more absorbable forms. Rats fed a diet containing MeHg(I), Cd(II), and Pb(II) and SH-SAMMS for 2 weeks had blood Hg levels significantly lower than rats fed the metal-rich diet only. Upon cessation of the metal-rich diet, continued administration of SH-SAMMS for 2 weeks facilitated faster and more extensive clearance of Hg than in animals not continued on oral SH-SAMMS. Rats receiving SH-SAMMS also suffered less weight loss as a result of the metal exposure. Retention of Hg and Cd in major organs was lowest in rats fed with SH-SAMMS throughout the entire four weeks. The reduction of blood Pb by SH-SAMMS was significant. SH-SAMMS was safe to intestinal epithelium model (Caco-2) and common intestinal bacteria (Escherichia coli). Altogether, it has great potential as a new oral drug for the treatment of heavy metal poisoning. This new application is enabled by the installation of tailored interfacial chemistry upon nontoxic nanoporous materials.

Synthesis, characterization of carbon polyurethane powder and its application for separation and spectrophotometric determination of platinum in pharmaceutical and ore samples

A new chelating sorbent was synthesized by covalently linking carbon nano-fiber with ion exchange polyurethane foam (CNF-PUFIX). CNF-PUFIX was characterized using different tools e.g. elemental analysis, IR spectrum and SEM. The functional groups of PUF have disappeared. The phenolic, carboxylic, quaternary ammonium salt and tertiary amine groups are detected in the CNF-PUFIX. The sorption properties of platinum (IV) onto CNF-PUFIX were investigated, the maximum sorption of platinum ions (~100%) was at the pH ranges 4-5, shaking for 18 min and sample flow rate 1.3 mL min(-1). The experimental data was fitted by kinetic models, the pseudo-second order is predominant (R(2)=0.998), the values of h and k2 are 4.4 mmol g(-1)min(-1) and 0.15 g mmol(-1)min(-1), respectively. The sorption capacity of CNF-PUFIX and the recovery percentage of Pt (IV) were 0.19 mmol g(-1) and 99-103%, respectively (RSD=1.72%, n=5). The CNF-PUFIX could be used many times without decreasing their capacities significantly. The equilibrium process is well described by the Langmuir isotherm model (R(2)=0.857), which is attributed to the homogeneous surface structure of the CNF-PUFIX. The values of ΔG and ΔH were -3.5 and -26.1 kJ mol(-1), respectively, which indicate that the sorption of platinum onto CNF-PUFIX is spontaneous and exothermic. The lower detection limit of platinum using spectrophotometric method is 2.4 µg L(-1) (RSD~3.8%, n=6). The accuracy of the procedure was verified by the analysis of standard reference materials of pharmaceutical and granite samples.

Extraction of uranium from nuclear industrial effluent using polyacrylhydroxamic acid sorbent

Solid-phase extraction process using chelating sorbent is a novel technique due to its high separation efficiency and simplicity. A designed three-dimensional cross-linked hydrophilic chelating polymeric sorbent, polyacrylhydroxamic acid, was developed for enhanced uptake of uranium from waste solution (pH 6–9) by complexation between the sorbent’s active functional group and uranium. The sorbent was synthesized by polymerization of acrylamide with cross-linking agent, followed by conversion and functionalization with hydroxylamine hydrochloride. In this paper, removal and recovery of uranium from effluent of uranium material processing plant in the presence of competitive ions such as sodium, calcium and magnesium were studied using the sorbent. Uranium uptake property of the developed sorbent was also investigated with respect to sorbent’s physical characteristics such as bead size distribution and bead swelling, in batch experiments. Distribution coefficient of uranium in the sorbent was substantially high (1,250 mL of effluent/g of sorbent), and immobilization factor was 0.028. The results showed that more than 90 % recovery of uranium is viable from nuclear effluent without preconditioning. Breakthrough profiles of column operation were successfully described for effective removal of uranium in continuous mode. The novel sorbent has been used for polishing the nuclear wastewater and hence to mitigate the environmental issues.

Preparation of a chelating sorbent based on pyridylethylated polyethylenimine for recovering transition metal ions

A method was developed for preparing a chelating amino polymer, pyridylethylpolyethylenimine with maximal degree of substitution, by polymer-analogous transformations of branched polyethylenimine in reaction with 2-vinylpyridine. The ability of cross-linked pyridylethylpolyethylenimine with the degree of substitution of 0.32 to sorb Cu2+, Ni2+, Co2+, Zn2+, Cd2+, Mn2+, and Pb2+ ions present simultaneously in solution was evaluated. In an ammonium acetate sorption system (pH 3.5–4.0), the sorbent selectively interacts with Cu(II) ions.

Poly[1-(N,N-bis-carboxymethyl)amino-3-allylglycerol-co-dimethylacrylamide] brushes grafted onto siliceous support for preconcentration and determination of cobalt (II) in human plasma and environmental samples

A chelating matrix prepared by surface grafting of polymer containing a functional monomer, poly[1-(N,N-bis-carboxymethyl)amino-3-allylglycerol-co-methylacrylamide] (poly(AGE/IDA-co-DMAA) onto a modified silica. The silica surface was modified by silylation with 3-mercaptopropyltrimethoxysilane followed by graft polymerization. Monomer of allyl glycidyl ether-iminodiacetic acid was synthesized by reaction of allyl glycidyl ether with iminodiacetic acid. The chelating sorbent can be reused for 15 cycles of sorption-desorption without any significant change in sorption capacity. The profile of cobalt uptake on the sorbent reflects good accessibility of chelating sites in poly(AGE/IDA-co-DMAA)-grafted silica gel. The equilibrium adsorption data of Co(II) on modified sorbent were analyzed by Langmuir, Freundlich, Temkin and Redlich-Peterson models. The method was applied for cobalt ions determination in human plasma and sea water sample with satisfactory results.

An ICP-MS procedure to determine Cd, Co, Cu, Ni, Pb and Zn in oceanic waters using in-line flow-injection with solid-phase extraction for preconcentration

An automated procedure including both in-line preconcentration and multi-element determination by an inductively coupled plasma mass spectrometer (ICP-MS) has been developed for the determination of Cd, Co, Cu, Ni, Pb and Zn in open-ocean samples. The method relies on flow injection of the sample through a minicolumn of chelating (iminodiacetate) sorbent to preconcentrate the trace metals, while simultaneously eliminating the major cations and anions of seawater. The effectiveness of this step is tested and reliability in results are secured with a rigorous process of quality assurance comprising 36 calibration and reference samples in a run for analysis of 24 oceanic seawaters in a 6-h program. The in-line configuration and procedures presented minimise analyst operations and exposure to contamination. Seawater samples are used for calibration providing a true matrix match. The continuous automated pH measurement registers that chelation occurs within a selected narrow pH range and monitors the consistency of the entire analytical sequence. The eluent (0.8M HNO3) is sufficiently strong to elute the six metals in 39s at a flow rate of 2.0mL/min, while being compatible for prolonged use with the mass spectrometer. Throughput is one sample of 7mL every 6min. Detection limits were Co 3.2pM, Ni 23pM, Cu 46pM, Zn 71pM, Cd 2.7pM and Pb 1.5pM with coefficients of variation ranging from 3.4% to 8.6% (n=14) and linearity of calibration established beyond the observed concentration range of each trace metal in ocean waters. Recoveries were Co 96.7%, Ni 102%, Cu 102%, Zn 98.1%, Cd 92.2% and Pb 97.6%. The method has been used to analyse ~800 samples from three voyages in the Southern Ocean and Tasman Sea. It has the potential to be extended to other trace elements in ocean waters.

Pressure-driven mesofluidic platform integrating automated on-chip renewable micro-solid-phase extraction for ultrasensitive determination of waterborne inorganic mercury

A dedicated pressure-driven mesofluidic platform incorporating on-chip sample clean-up and analyte preconcentration is herein reported for expedient determination of trace level concentrations of waterborne inorganic mercury. Capitalizing upon the Lab-on-a-Valve (LOV) concept, the mesofluidic device integrates on-chip micro-solid phase extraction (μSPE) in automatic disposable mode followed by chemical vapor generation and gas–liquid separation prior to in-line atomic fluorescence spectrometric detection. In contrast to prevailing chelating sorbents for Hg(II), bare poly(divinylbenzene-N-vinylpyrrolidone) copolymer sorptive beads were resorted to efficient uptake of Hg(II) in hydrochloric acid milieu (pH=2.3) without the need for metal derivatization nor pH adjustment of prior acidified water samples for preservation to near-neutral conditions. Experimental variables influencing the sorptive uptake and retrieval of target species and the evolvement of elemental mercury within the miniaturized integrated reaction chamber/gas–liquid separator were investigated in detail.Using merely <10mg of sorbent, the limits of detection and quantification at the 3sblank and 10sblank levels, respectively, for a sample volume of 3mL were 12 and 42ngL−1 Hg(II) with a dynamic range extending up to 5.0μgL−1. The proposed mesofluidic platform copes with the requirements of regulatory bodies (US-EPA, WHO, EU-Commission) for drinking water quality and surface waters that endorse maximum allowed concentrations of mercury spanning from 0.07 to 6.0μgL−1. Demonstrated with the analysis of aqueous samples of varying matrix complexity, the LOV approach afforded reliable results with relative recoveries of 86–107% and intermediate precision down to 9% in the renewable μSPE format.

Facile preparation of polyphenolic hydroxyl functionalized uranium-selective chelating sorbent: simple oxidation of styrene–divinylbenzene copolymer microparticles by Hummers method

Hummers method, a classical approach for preparation of graphitic oxide, was employed for the first time to prepare polymer-based uranium selective chelating sorbent by directly oxidizing styrene–divinylbenzene copolymer microparticles synthesized through the mix-solvothermal method in a mild binary solvent system. The resulting material was found rich in phenolic hydroxyl groups (17mmol/g) using techniques such as FT-IR and XPS. Batch adsorption experiments proved that the chelating sorbent exhibited excellent uranium selectivity from multi-ion solution containing 12 coexisting ions with 0.45mmol/g of uranium adsorption capacity accounting for up to 52% of the total adsorption capacity, while 373mg/g of the maximum adsorption capacity for the sorbent was obtained in the “pure” U(VI) ion solution. The proposed method has the advantages of simpleness, cheapness, and high yield of phenolic hydroxyl groups, which could provide a new and generally applicable approach for facile preparation of polyphenolic materials based on phenyl-rich polymer.

Концентрирование и определение меди, цинка и кадмия хелатообразующим модифицированным сорбентом

A modified sorbent by immobilization of antipyrine-2COOH on highly basic anion exchanger was ыynthesized. The sorption, complexation and kinetic characteristics of the modified chelating sorbent to ions of copper, zinc and cadmium are studied. Thermogravimetric analysis of the modified sorbent is carried out. Selective adsorption of various ions to ions of copper, zinc and cadmium was investigated. The technique of group concentration and determination of heavy metals in sea water was developed. Keywords : modified sorbent, copper, zinc, cadmium, complexation, sorption, kinetics. (Russian) DOI: http://dx.doi.org/10.15826/analitika.2013.17.1.012 R . Z . Zeynalov , S . D . Tatayeva , N . I . Atayeva Dagestan State University, Russian Federation , the Republic of Dagestan, Makhachkala

Synthesis of pyridin-3-yl-functionalized silica as a chelating sorbent for solid-phase adsorption of Hg(II), Pb(II), Zn(II), and Cd(II) from water

Silica gel modified with 3-aminopropyltrimethoxysilane was anchored with nicotinaldehyde to prepare a new chelating surface (or matrix). It was synthesized and characterized by elemental analysis, cross-polarization magic-angle spinning 13C nuclear magnetic resonance (NMR) spectroscopy, diffuse reflectance infrared Fourier-transform spectroscopy, nitrogen adsorption–desorption isotherm, Brunauer–Emmett–Teller surface area, and Barrett–Joyner–Halenda pore sizes. The new surface exhibits good chemical and thermal stability as determined by thermogravimetry curves. This new organic–inorganic material was used for preconcentration of Hg(II), Pb(II), Zn(II), and Cd(II) from water prior to their determination by inductively coupled plasma atomic emission spectrometry. The optimum pH for quantitative sorption of these metal ions is in the range of 6–8, and the sorption capacity is in range of 486–1,449 μmol/g. By batch method, 95 % extraction takes ≤30 min. All the metals could be desorbed with a solution of hydrochloric acid (6 N) without loss of the expensive ligand. Solutions of the metal ions were prepared by dissolution of the nitrate solution.

Removal of cobalt from human serum and environmental samples by adsorption using Amberlite XAD-2–salicylic acid–iminodiacetic acid

A new chelating resin was prepared by coupling Amberlite XAD-2 with salicylic acid (SAL) through an azo spacer. Then the polymer support was coupled with iminodiacetic acid (IDA). The resulting sorbent has been characterized by FT-IR, elemental analysis, thermogravimetric analysis, and scanning electron microscopy, and studied for the preconcentration and determination of trace Co(II) ion from human biological fluid and environmental water samples. The optimum pH value for sorption of the metal ion was 7.5. The sorption capacity of functionalized resin was 87.4 mg g-1. The chelating sorbent can be reused for 20 cycles of sorption–desorption without any significant change in sorption capacity. A recovery of 95.3% was obtained for the metal ion with 0.5M nitric acid as the eluting agent. The profile of cobalt uptake on this sorbent reflects good accessibility of the chelating sites in the Amberlite XAD-2–SAL/IDA. Scatchard analysis revealed that the homogeneous binding sites were formed in the polymers. The equilibrium adsorption data of Co(II) on modified resin were analyzed by Langmuir, Freundlich, Temkin, and Redlich–Peterson models. Based on equilibrium adsorption data, the Langmuir, Freundlich, and Temkin constants were determined to be 2.265, 56.82, and 148.56 at pH 7.5 and 25°C, respectively. The method was applied for cobalt ion determination from human plasma and sea water sample.

Properties of Chelating Sorbent Prepared by Modification of Silica Gel with Polyaniline and Acid Alizarin Violet N

A new chelating sorbent was prepared, by synthesizing the surface of silica gel with a very thin layer of polyaniline, and then the thus obtained carrier was impregnated with Acid Alizarin Violet N. The stability of the resulting chelating sorbent and the sorption of selected metal ions was investigated. The sorbent was used for the purification of tap water and distilled water from some heavy metal ions and for additional purification of aqueous solutions of KCl from trace amounts of heavy metals. An effective method of regenerating the column with the chelating sorbent obtained is proposed. For regeneration 5% aqueous ammonia solution was used; then the column had to be conditioned with hydrochloric acid. It was found that the method does not destroy the sorbent skeleton.

A siliceous support grafted with poly[1-(N,N-bis-carboxymethyl)amino-3-allylglycerol-co-dimethylacrylamide] brushes for removal of nickel from environmental samples

A system for the determination of nickel(II) after preconcentration on chelating adsorbent and elution with nitric acid is presented in this article. The adsorbent was synthesized by grafting the chelating polymer poly[1-(N,N-bis-carboxymethyl)amino-3-allylglycerol-co-dimethylacrylamide (poly(AGE/IDA-co-DMAA)) to silica gel. Ni(II) recoveries were above 92% when using 0.5 mol L−1 nitric acid as eluting agent. The sorption capacity of the functionalized sorbent was 12.2 mg g−1. The chelating sorbent can be reused for at least 15 cycles without any significant change in sorption capacity. The developed method was utilized for preconcentration and determination of Ni(II) in sea water samples by flame atomic absorption spectrometry. The 3σ detection limit and 10σ quantification limit for Ni(II) were found to be 0.5 and 1.7 µg L−1, respectively. The equilibrium adsorption data of Ni(II) on modified sorbent were analyzed using Langmuir, Freundlich, Temkin, and Redlich–Peterson models. Based on equilibrium adsorption data, the Langmuir, Freundlich, and Temkin constants were determined as 0.0346, 1.286, and 53.73, respectively, at pH 4.5 and 20°C.