Preconcentration and determination of chromium in water with flame atomic absorption spectrometry by thiourea-formaldehyde as chelating resin

Thiourea-formaldehyde chelating resin is synthesized simply and rapidly from thiourea and formaldehyde by condensation polymerization and characterized by IR spectra and studied for the preconcentration and determination of trace Cr(III) ion from solution samples. The optimum pH value for sorption of the metal ion was 6.5. The sorption capacity of resin for Cr(III) was determined. The chelating resin can be reused for 20 cycles of sorption-desorption without any significant change in sorption capacity. A recovery of 96% was obtained for the metal ion with 0.5M HNO₃ as eluting agent. The equilibrium adsorption data of Cr(III) on modified resin were analyzed by Langmuir, Freundlich and Temkin models. Based on equilibrium adsorption data the Langmuir, Freundlich and Temkin constants were determined as 0.016, 0.040 and 0.074 at pH 6.5 and 20°C. The method was applied for chromium ion determination from river water sample.     

Modification and characterization of amberlite XAD-2 with calcein blue for preconcentration and determination of copper(II) from environmental samples by atomic absorption spectroscopy

A chelating resin is produced by coupling a dye calcein blue to Amberlite XAD-2 through an azo spacer. The resulting resin has been characterized by FT-IR, elemental analysis, thermogravimetric analysis (TGA) and scanning electron microscopy (SEM) studied for the preconcentration and determination of trace Cu(II) from solution samples. The optimum pH for adsorption of copper ions was 6. The sorption capacity of functionalized resin is 27 mg·g⁻¹. The chelating resin can be reused for 10 cycles without any significant changes in sorption capacity. A recovery of 100% was obtained for Cu(II) when eluted with 0.5 M nitric acid. Scatchard analysis revealed that homogeneous binding sites were formed in the resin. The equilibrium adsorption data of Cu(II) on modified resin were analyzed by Langmuir, Freundlich and Temkin models. Based on equilibrium adsorption data the Langmuir, Freundlich and Temkin constants were determined 0.036, 2.196 and 0.348 at pH 6 and 20 °C, respectively. The method was applied for Cu(II) assay in environmental samples.     

Synthesis,characterization, and application of amberlite XAD‐2‐ salicylic acid‐ iminodiacetic acid for lead removal from human plasma and environmental samples

A new chelating resin is prepared by coup‐ling 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 (TGA), and scanning electron microscopy (SEM) and studied for the preconcentration and determination of trace Pb (II) ion from human biological fluid and environmental water samples. The optimum pH value for sorption of the metal ion was 5. The sorption capacity of functionalized resin is 67 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% was obtained for the metal ion with 0.5M nitric acid as eluting agent. The profile of lead 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 Pb (II) on modified resin were analyzed by Langmuir, Freundlich, Temkin, and Redlich‐Peterson models. Based on equili‐brium adsorption data the Langmuir, Freundlich, and Temkin constants were determined 0.428, 20.99, and 7 × 10⁻¹² at pH 5 and 20°C. The method was successfully applied for determination of lead ions in human plasma and sea water sample. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Modification and characterization of poly (ethylene terephthalate)‐grafted‐acrylic acid/acryl amide fiber for removal of lead from human plasma and environmental samples

A new fibrous adsorbent was prepared by grafting acrylic acid/acryl amide (AA/AAm) comonomers onto poly (ethylene terephthalate) (PET) fibers. The resulting sorbent has been characterized by Fourier transform infrared (FT‐IR), elemental analysis, thermogravimetric analysis (TGA), FT‐Raman, and scanning electron microscopy (SEM) and studied for the preconcentration and determination of trace Pb (II) ion from human biological fluid and environmental water samples. The optimum pH value for sorption of the metal ion was 8. The sorption capacity of functionalized resin is 44.1 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 100.2% was obtained for the metal ion with 0.5M nitric acid as eluting agent. Effect of grafting yield, shaking time, shape of sorbent, and pH of the medium on adsorption of the metal ion were investigated. Scatchard analysis revealed that the homogeneous binding sites were formed in the polymers. The equilibrium adsorption data of Pb (II) on modified fiber were analyzed by Langmuir, Freundlich, Temkin, and Redlich‐Peterson models. Based on equilibrium adsorption data, the Langmuir, Freundlich, and Temkin constants were determined as 0.236, 10.544, and 9.497 at pH 8 and 20°C, respectively. The method was applied for lead ions determination from human plasma and sea water sample. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Iminodiacetic acid‐containing polymer brushes grafted onto silica gel for preconcentration and determination of copper(II) in environmental samples

Silica gel has been modified by silylation with 3‐mercaptopropyltrimethoxysilane followed by graft polymerization of dimethylacrylamide and (N,N‐bis‐carboxymethyl)amino‐3‐allylglycerol‐co‐dimethylacrylamide, synthesized via the reaction of allyl glycidyl ether with iminodiacetic acid. The sorbent, poly(AGE/IDA‐co‐DMAA)‐grafted silica gel, has been characterized by FTIR, elemental analysis, thermogravimetric analysis (TGA), FT‐Raman, and scanning electron microscopy and studied for the preconcentration and determination of trace amounts of Cu(II) ion in environmental water samples. The optimum pH value for quantitative sorption of Cu(II) in batch mode was 5.5 and desorption was achieved, using 0.5 mol L^?1 nitric acid. The sorption capacity of functionalized sorbent is 32.3 mg g^?1. The chelating sorbent was reused for 15 sorption–desorption cycles without any significant change in sorption capacity. The profile of copper uptake by the sorbent reflected good accessibility of the chelating sites in the poly(AGE/IDA‐co‐DMAA)‐grafted silica gel. Scatchard analysis demonstrated homogeneous nature of binding sites. The equilibrium adsorption data of Cu(II) on modified sorbent were analyzed by Langmuir, Freundlich, Temkin, and Redlich–Peterson models. Based on equilibrium adsorption data, the Langmuir, Freundlich, and Temkin constants were determined as 0.0665, 4.26, and 8.34, respectively, at pH 5.5 and 20°C. Adsorption isotherms were analyzed at different temperatures to obtain free energy, enthalpy, and entropy of adsorption. The method was applied for Cu(II) determination in sea water samples. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Ghezeljeh nanoclay as a new natural adsorbent for the removal of copper and mercury ions:Equilibrium,kinetics and thermodynamics studies

Heavy metal determination was carried out by applying the solid phase extraction (SPE) method in batch mode followed by atomic absorption spectroscopy (AAS) and inductively coupled plasma atomic emission spectrosco-py (ICP-AES) from aqueous solutions using Ghezeljeh montmoril onite nanoclay as a new natural adsorbent. The Ghezeljeh clay is characterized by using Fourier Transform Infrared (FT-IR) Spectroscopy, Scanning Electron Mi-croscopy–Energy Dispersive Spectrometry (SEM–EDS) and X-ray Diffractometry (XRD) and X-ray Fluorescence (XRF). The results of XRD and FT-IR of nanoclay confirm that montmoril onite is the dominant mineral phase. Based on SEM images of Ghezeljeh clay, it can be seen that the distance between the plates is Nano. The effects of varying parameters such as initial concentration of metal ions, pH and type of buffer solutions, amount of ad-sorbent, contact time, and temperature on the adsorption process were examined. The effect of various interfer-ing ions was studied. The adsorption data correlated with Freundlich, Langmuir, Dubinin–Radushkevich (D–R), and Temkin isotherms. The Langmuir and Freundlich isotherms showed the best fit to the equilibrium data for Hg(I ), but the equilibrium nature of Cu(II) adsorption has been described by the Langmuir isotherm. The kinetic data were described with pseudo-first-order, pseudo-second-order and double-exponential models. The adsorp-tion process follows a pseudo-second-order reaction scheme. Calculation ofΔG0,ΔH0 andΔS0 showed that the nature of Hg(II) ion sorption onto the Ghezeljeh nanoclay was endothermic and was favored at higher temper-ature, and the nature of Cu(II) ion sorption was exothermic and was favored at lower temperature.     

Heavy metals adsorption on some iminodiacetate chelating resins as a function of the adsorption parameters

The adsorption properties of some novel chelating resins (CRs) bearing iminodiacetate groups for removal of heavy metal ions like: Cu(II), Co(II) and Ni(II) from aqueous solutions comparative with the commercial resin Amberlite IRC-748 have been studied in this work by a batch equilibrium technique. Quantitative analysis for adsorption was conducted using UV–vis spectroscopy to investigate the kinetics, adsorption isotherm and thermodynamics of the removal process considering equilibration time, pH, metal ion concentration and temperature as controlling parameters. The metal adsorption capacities, at pH 5, were in the order Cu(II) > Ni(II) > Co(II), for both the CR with 10 wt.% DVB (CR-10) and the commercial resin Amberlite IRC-748. The adsorption capacities on CR-10 were higher for Ni(II) and Co(II) ions, but lower for Cu(II) ions compared with Amberlite IRC-748. Both Freundlich and Langmuir isotherms well fitted on the adsorption results of Cu(II), Ni(II) and Co(II) ions on all iminodiacetate resins.     

Synthesis and analytical application of a chelating resin based on a crosslinked styrene/maleic acid copolymer for the extraction of trace‐metal ions

A new chelating polymer sorbent was synthesized through the copolymerization of styrene and maleic anhydride in the presence of divinyl benzene as the crosslinking agent, followed by hydrolysis. This polymeric resin, bearing O donor groups, had the advantage of being stable in basic and saline media, unlike its linear analogue. This newly developed chelating matrix has a high resin capacity for metal ions such as Cr, Fe, Ni, Cu, and Pb. Various physicochemical parameters, such as the pH, volume, and flow rate, and the interference effect on metal uptake were studied. The sorption capacities of the crosslinked resin for Cr(III), Fe(III), Ni(II), Cu(II), and Pb(II) were 10.2, 14.3, 14.2, 15.4, and 8.8 mg/g, respectively. A high recovery of 98% was obtained for all the metal ions with 2N HCl as the eluting agent. The chelating resin was characterized by swelling studies, Fourier transform infrared, elemental analysis, X‐ray studies, and thermal analysis. The Langmuir and Freundlich adsorption isotherms were used to validate the metal‐uptake data. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 1771–1779, 2004     

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.     

Adsorption isotherms,kinetic, and desorption studies on removal of toxic metal ions from aqueous solutions by polymeric adsorbent

Adsorption of Cd(II), Co(II), and Ni(II) on aminopyridine modified poly(styrene‐alt‐maleic anhydride) crosslinked by 1,2‐diaminoethane as an ion exchange resin has been investigated in aqueous solution. Adsorption behavior of these metal ions on the resin was studied by varying the parameters such as pH (2–6), adsorbent dose (0–4.0 g/L), contact time (0–240 min), and metal ions concentration (20–300 mg/L). Adsorption percentage was increased by increasing each of these parameters. The isotherm models such as: Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich were used to describe adsorption equilibrium. The results showed that the best fit was achieved with the Langmuir isotherm equation, yielding maximum adsorption capacities of 81.30, 49.02, and 76.92 mg/g for Cd(II), Co(II), and Ni(II), respectively. The pseudo‐first‐order, pseudo‐second‐order, and intra‐particle diffusion kinetics equations were used for modeling of adsorption data and it was shown that pseudo‐second‐order kinetic equation could best describe the adsorption kinetics. The intra‐particle diffusion study revealed that external diffusion might be involved in this case. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 41642.     

Kinetic,thermodynamic and equilibrium studies on the removal of copper ions from aqueous solutions by natural and modified clinoptilolites

This paper presents the adsorption of Cu(II) ions from aqueous solution on Na and Fe-modified clinoptilolite. The copper adsorption experiments were performed in a batch system considering an optimum contact time of 24 h. Changes in the surfaces and structure were characterized by SEM data. According to the SEM results, it was anticipated that the removal efficiency of Fe-modified clinoptilolite was the highest compared with the natural and Na-modified clinoptilolites. Adsorption of Cu(II) ions by modified clinoptilolites was investigated as a function of the initial Cu(II) concentration, solution pH, and temperature. According to the results, the maximum adsorbed Cu amount onto Fe-modified was 19.40mg/l at the optimum operating condition with a pH value of 5.5 and temperature of 60 °C. According to the thermodynamic evaluations, positive ΔS and negative ΔG were found for the adsorption process showing that the adsorption reaction is a spontaneous process and more favorable at high temperatures. Sorption data have been interpreted in terms of Langmuir and Freundlich, Temkin and Dubinin-Radushkevich. The adsorption equilibrium was best described by the Langmuir adsorption isotherm. In addition, according to the Sips model, the sorption of Cu(II) ions on the Fe-modified clinoptilolite was found to be heterogeneous. The kinetic study showed that the Fe-modified clinoptilolite followed the pseudo-second order model. The results indicated that the clinoptilolite-rich tuff in its iron oxide form could be efficiently used for the removal of copper from aqueous solutions.     

Adsorption properties of a chelating resin containing hydroxy group and iminodiacetic acid for copper ions

A chelating resin, PSGI, was synthesized by the radical polymerization of GMA‐IDA, DVB, and styrene for the removal of Cu(II), Co(II), and Cd(II) from an aqueous solution. The characteristic functional groups and chemical composition of PSGI were analyzed by Fourier transform infrared spectroscopy and elemental analysis of C, H, and N. The equilibrium adsorption capacities of PSGI from their single‐metal ion solutions were 1.46 mmol/g for Cu(II), 1.02 mmol/g for Co(II), and 1.10 mmol/g for Cd(II). The adsorption isothermal of Cu(II) by PSGI followed the Langmuir isotherm. Increasing the concentration (0–0.1 M) of KCl in Cu(II) solution affected the adsorption behavior slightly. Within the pH range of 2–5.5, decreasing the pH of the Cu(II) solution did not produce remarkable changes in the equilibrium adsorption capacities. The adsorption capacities of PSGI for Cu(II) did not cause significant change during the repeated adsorption–desorption operations. The competitive adsorption tests verified that this resin had good adsorption selectivity for Cu(II) with the coexistence of Co(II) and Cd(II). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 94: 2123–2130, 2004     

Preparation and characterization of an IPN type chelating resin containing amino and carboxyl groups for removal of Cu(II) from aqueous solutions

A novel IPN type chelating resin, amino-functionalized poly (glycidyl methacrylate)/poly (acrylic acid), (pGMA/pAA), was synthesized by a combination of serial reactions including, conventional radical polymerization, amination and photopolymerization. To assess the efficacy and characteristics of the resin in removal of Cu (II), batch adsorption experiments were carried out, and the effects of different parameters such as contact time, adsorbent dosage, initial metal ion concentration, temperature, and pH on the adsorption process were investigated. The results showed that 0.5 g/L dosage and pH 5 are the optimum values to achieve the maximum adsorption capacity and the adsorption kinetic of Cu (II) was well represented by pseudo-second-order kinetic model. In addition, it was found that the adsorption was mainly controlled by the film diffusion mechanism, along with a considerable contribution of the intra-particle diffusion mechanism, and Langmuir, Freundlich and Dubinin–Radushkevich (D–R) isotherm models can be used for interpreting the adsorption process. Moreover, FT-IR analysis results and the mean free energies of adsorption clearly indicate that the ion exchange and chelation mechanisms took place as dominating mechanisms simultaneously during the adsorption process. It was also found to be that IPN resin could be used at least four times without losing its original activity.     

Batch adsorptive removal of copper ions in aqueous solutions by ion exchange resins: 1200H and IRN97H

The removal of copper from aqueous solution by ion exchange resins, such as 1200H and IRN97H, is described. Effect of initial metal ion concentration, agitation time and pH on adsorption capacities of ion exchange resins was investigated in a batch mode. The adsorption process, which is pH dependent, shows maximum removal of copper in the pH range 2–7 for an initial copper concentration of 10 mg/L. The experimental data have been analyzed by using the Freundlich, Langmuir, Redlich-Peterson, Temkin and Dubinin-Radushkevich isotherm models. The batch sorption kinetics have been tested for a first-order, pseudo-first order and pseudo-second order kinetic reaction models. The rate constants of adsorption for all these kinetic models have been calculated. Results showed that the intraparticle diffusion and initial sorption into resins of Cu(II) in the ion exchange resins was the main rate limiting step. The uptake of copper by the ion exchange resins was reversible and thus has good potential for the removal/recovery of copper from aqueous solutions. We conclude that such ion exchange resins can be used for the efficient removal of copper from water and wastewater. This paper is dedicated to Professor Hyun-Ku Rhee on the occasion of his retirement from Seoul National University.     

Sorption of Zn(II) and Pb(II) ions in the presence of the biodegradable complexing agent of a new generation

The macroporous chelating ion exchangers containing different functional groups i.e. Purolite S-920, Purolite S-930 and Lewatit TP-208 have been used in the sorption process of Zn(II) and Pb(II) ions. The effect of the presence of biodegradable, environmentally friendly aminopolycarboxylate chelating agent, trisodium salt of methylglycinediacetic acid (MGDA) on its sorption capacity was also examined. The investigations were carried out by the static method. Besides the effect of initial concentration of Zn(II) and Pb(II) and the complexing agent the research concerns the influence of solution pH, phase contact time on effectiveness of sorption. The equilibrium and kinetics of Zn(II)–MGDA and Pb(II)–MGDA complexes sorption were obtained and fitted using the Langmuir, Freundlich, Temkin and Dubinin–Radushkevich (D–R) models as well as the pseudo first and pseudo second order kinetic models. The intraparticle diffusion model was also used. The results showed that the sorption processes of Zn(II) and Pb(II) complexes with MGDA on Purolite S-920, Purolite S-930 and Lewatit TP-208 followed well the pseudo second order kinetics.     

Adsorption of Ni(II) on ion exchange resin: Kinetics, equilibrium and thermodynamic studies

This article describes the ion exchange of a heavy metal Ni(II) from aqueous solutions onto a Dowex HCR-S, cationic resin. Batch adsorption studies were conducted to evaluate the effect of various parameters such as pH, resin dose, stirring speed, temperature, contact time and initial Ni(II) concentration on the removal of Ni(II). Adsorption rate increased with the increase in initial nickel concentration, stirring speed and temperature. Equilibrium adsorption isotherms were measured for the single component system, and the experimental data were analyzed by using Langmuir, Freundlich, Elovich, Temkin, Khan, Sips, Toth, Koble-Corrigan and Radke-Prausnitz isotherm equations. The Sips equation appears to fit the equilibrium data. Different models were tested for their applicability. Adsorption kinetic data were modeled using the Lagergren pseudo-first-order, Ho??s pseudo-second-order and Elovich models. It was found that Ho??s pseudo-second-order model could be used for the prediction of the system??s kinetics. Thermodynamic activation parameters such as ??G*, ??S* and ??H* of the adsorption of Ni(II) on Dowex HCR-S cationic resin were also calculated.     

Comparative adsorption isotherms and modeling of nickel and cobalt citrate complexes onto chelating resins

The sorption characteristics of nickel and cobalt-organic acid complexes on two commercial chelating resins (Purolite S930 and S950) were compared. Purolite S390 is based on an iminodiacetic funtional group and S950 is an aminophosphonic acid resin. Batch equilibrium adsorption tests of these resins were examined and compared using various metal citrate concentrations (15–2000 mg/L) and solution pH. The solution pH of complex solutions was varied by preparing metal solutions in 0.01, 0.1, 0.5 and 1.0 M of citric acid. Equilibrium adsorption data were fitted to empirical isotherm models; linear, Langmuir, Freundlich and Redlich–Peterson (R–P) equations to establish the mechanism for the uptake of the metal complexes onto the resins. Our study showed that nickel-citrate complex adsorption exhibited both monolayer and multilayer adsorption; the mechanism on both resins varying with acid concentration, whereas cobalt complex adsorption was independent of acid concentration but the mechanism of metal loading was found to be influenced by the nature of the resins.     

The adsorption behavior of Cu(II), Pb(II), and Co(II) of ethylene vinyl acetate‐clinoptilolite nanocomposites

In this study, ethylene vinyl acetate (EVA) was mixed with clinoptilolite (C), a natural zeolite, to prepare EVA‐C nanocomposites. The films were characterized by SEM‐EDS, XRD, and FT‐IR, and heavy metal removal was studied using the batch technique. The effects of the initial pH value and concentration of solutions, contact time, and filler dosage on the adsorption capacity of the composites were investigated. To study the influence of pretreatment on the filler, clinoptilolite was activated using KCl, NaCl, and HCl. Adsorption results show that equilibrium was reached after 24 h, and that sorption reached its maximum at pH values between 5 and 7. The selectivity trend was observed to be Pb > Cu > Co, which was consistent for both single and mixed metal‐ion solutions. Pretreatment significantly increased adsorption capacity of the composite, but was dependent on the conditioning reagent. Nanocomposites filled with HCl‐activated particles demonstrated a high adsorption capacity of between 70 and 80% for all three metals, while KCl‐activated particles were the least efficient with a maximum adsorption capacity of 69% for Pb(II), 54% for Cu(II) and 48% for Co(II). The adsorption data were then fitted to both Langmuir and Freundlich isotherms over the entire concentration range, and the Langmuir isotherm showed a better fit of the experimental sorption data than the Freundlich isotherm. The results obtained show that this simple methodology which can be up‐scaled has great potential for the preparation of a wide variety of similar particle‐filled adsorbent nanocomposites in other environmental remediation applications. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Adsorption properties of poly(acrylaminophosphonic-carboxyl-hydrazide)type chelating fiber for heavy metal ions

In this article, the adsorption properties of poly(acrylaminophosphonic-carboxyl-hydrazide) chelating fibers for Cu(II), Cd(II), Co(II), Mn(II), Pb(II), Zn(II), Ni(II), and Cr(III) are investigated by a batch technique. Based on the research results of binding capacity, adsorption isotherm, effect of pH value on sorption, and adsorption kinetics experiments, it is shown that the poly(acrylaminophosphonic-carboxyl-hydrazide) chelating fibers have higher binding capacities and good adsorption kinetic properties for heavy metal ions. The sorption of the metal ions on the chelating fibers is strongly dependent on the equilibrium pH value of the solution. The adsorption isotherms of Cu(II) and Cd(II) on the chelating fiber exhibit a Langmuir-type equation. The adsorbed Cu(II), Cd(II), Zn(II), and Pb(II) could be eluted by diluted nitric acid. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 70: 7–14, 1998     

向日葵秸秆对U（Ⅵ）和Cu（Ⅱ）的选择吸附特性

以分别含有单一的U（Ⅵ）、Cu（Ⅱ）溶液以及U（Ⅵ）、Cu（Ⅱ）混合溶液为吸附质,系统探讨了pH值、吸附剂量、温度、时间和初始离子浓度对向日葵秸秆吸附效果的影响。采用准二级动力学模型、Langmuir、Freundlich和Langmuir-Freundlich等温吸附模型对实验数据进行拟合,从分配系数和分离因子角度对吸附选择性进行分析,并对吸附机理进行探讨。结果表明：向日葵秸秆对U（Ⅵ）和Cu（Ⅱ）的吸附分别是自发的吸热和放热反应;吸附动力学均符合准二级动力学模型,即化学吸附为控速步骤;单离子体系下U（Ⅵ）和Cu（Ⅱ）的吸附等温线分别符合Langmuir-Freundlich和Langmuir等温吸附模型;复配体系下,当干扰Cu（Ⅱ）浓度≥60 mg·L^-1时,U（Ⅵ） 的吸附等温线可用Langmuir-Freundlich模型描述;而当干扰U（Ⅵ）浓度≥200 mg·L^-1时,Cu（Ⅱ）的吸附等温线可用Langmuir模型描述。当溶液中同时存在U（Ⅵ）和Cu（Ⅱ）两种离子时,离子间存在竞争吸附,且向日葵秸秆对U（Ⅵ）具有更高的选择性,这与金属本身的特性有关。向日葵秸秆吸附前后的SEM、EDX和FT-IR图谱表明,吸附U（Ⅵ）和Cu（Ⅱ）的主要方式为络合和离子交换。