Adsorption of copper(II) and EDTA‐chelated copper(II) onto granular activated carbons

Waste streams generated by electroless copper plating in the printed circuit boards manufacturing industry often contain copper complexed by strong chelating agents such as EDTA. The consequence of metal complexation by chelating agents is that alternative treatment to chemical precipitation is often necessary to achieve the low metal concentrations required by increasingly stringent environmental regulations. This paper examines the feasibility of using activated carbon to remove EDTA‐chelated copper(II) species as well as free copper(II) ions from aqueous solution. The adsorption characteristics of copper(II) and EDTA‐chelated copper(II) on two granular activated carbons prepared from coal and coconut shell were evaluated. Adsorption equilibrium data of copper(II) on the two carbons corresponded well to the Langmuir model. The coconut shell‐based carbon exhibited a greater adsorption capacity for copper(II) than the coal‐based carbon under similar experimental conditions. Solution pH had a considerable influence on copper(II) adsorption by the two carbons. Low adsorption levels of copper(II) at pH 3 and high adsorption levels in the pH range of 4–6 were observed. However, a reverse adsorption trend was observed when the chelating agent EDTA was added to the copper(II) solution. Adsorption of EDTA‐chelated copper(II) by the two carbons was higher at pH 3 than at pH 6. The contrasting adsorption behaviour of copper(II) ions and EDTA‐chelated copper(II) species can be readily explained in terms of electrostatic interaction in that solution pH influences the surface charge of the carbons as well as the charge property of copper(II) ions and EDTA‐chelated copper(II) species. © 2000 Society of Chemical Industry     

The Adsorption and Desorption Characteristics of EDTA-Chelated Copper Ion by Activated Carbon

Abstract

This paper addresses the effect of EDTA, a strong agent, on the removal of copper ion from solutions using activated carbon adsorption. Experimental studies indicate the presence of EDTA significantly altered the adsorption behavior of copper on the activated carbon due to the formation of copper chelate species in the solution. The adsorption isotherms and kinetics were found to be strong functions of solution pH and the ratio of copper ion and EDTA concentrations. Adsorption of EDTA-Cu chelates was found to be more favorable than those of free copper ion and unbound EDTA species in the solution. Experimental results indicated that the desorption of chelated copper ion from activated carbon by NaOH and HClO⁴ solutions was influenced by the initial adsorption conditions. A significantly higher quantity of copper ion was recovered with HClO⁴ than with NaOH. Combining the adsorption and desorption data of copper and EDTA, and an understanding of the species distribution of copper in the presence of EDTA, the behavior of the adsorption of EDTA-chelated copper on the activated carbon was described. The predominant adsorbed copper species was the chelated form, CuEDTA^2-, which can be adsorbed on activated carbon surfaces with either the Cu end or the EDTA end bonding directly to the surface.     

A new metal chelate sorbent for glucose oxidase: Cu(II)- and Co(II)-chelated poly(N-vinylimidazole) gels

Poly(N-vinylimidazole) (PVIm) gels were prepared by irradiating a binary mixture of N-vinylimidazole (VIm)–water in a ⁶⁰Co-γ source having 4.5 kGy/h dose rate. In the glucose oxidase (GOx) adsorption studies, affinity gels with a swelling ratio of 1100% for PVIm and 40 and 55% for Cu(II)- and Co(II)-chelated PVIm gels, respectively, at pH 6.5 in phosphate buffer were used. FTIR spectra were taken for PVIm and Cu(II)- and Co(II)-chelated PVIm, and glucose oxidase adsorption on these gels, to characterize the nature of the interactions in each species. The results show that PVIm–glucose oxidase interaction is mainly electrostatic and metal ion–chelated PVIm gel–glucose oxidase interaction is of coordinate covalent nature. Cu(II) and Co(II) ions were chelated within the gels via amine groups on the imidazole ring of the gel. Different amounts of Cu(II) and Co(II) ions [maximum 3.64 mmol/g dry gel for Cu(II) and 1.72 mmol/g dry gel for Co(II)] were loaded on the gels by changing the initial concentration of Cu(II) and Co(II) ions at pH 7.0. GOx adsorption on these gels from aqueous solutions containing different amounts of GOx at different pH was investigated in batch reactors. GOx adsorption capacity was further increased when Cu(II) and Co(II) ions were attached [up to 0.53 g GOx/g dry Co(II)-chelated PVIm gels]. More than 90% of the adsorbed GOx was desorbed in 5 h in desorption medium containing 1.0M KSCN at pH 7.0 for plain gel and 0.05M EDTA at pH 4.9 for metal-chelated gel. Nonspecific glucose oxidase adsorption on/in the metal ion–chelated PVIm gel was investigated using 0.02M of phosphate buffer solution. The nonspecific GOx adsorption was determined to be about 18% for PVIm and 8% for the metal ion–chelated PVIm gels. The ionic strength effect was investigated both on PVIm and on the metal ion–chelated PVIm gels for the glucose oxidase adsorption. It was found that ionic strength was more effective on the PVIm gel because of the electrostatic interaction between protonated gel and the deprotonated glucose oxidase side chain. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 446–453, 2001     

Arsenic adsorption on Ti‐pillared montmorillonite

BACKGROUND: Arsenic pollution in drinking water has been found in most countries. Arsenate (As(V)) and arsenite (As(III)) are two major forms of inorganic arsenic species, and the latter is the more toxic. The removal of arsenic ions from water has attracted increased attention, and therefore further understanding and development of techniques for removal of arsenic ions are required. RESULTS: Adsorption of arsenate and arsenite from aqueous solutions using Ti‐pillared montmorillonite (Ti‐MMT) was investigated as a function of contact time, pH, temperature, coexisting ions, and ionic strength. The adsorption of both arsenate and arsenite were temperature and pH dependent, indicating different adsorption mechanisms. The effect of coexisting ions on the adsorption was also studied and, among the ions investigated, only phosphate had a noticeable influence on the adsorption of arsenate, while the effect of other ions was negligible. A pseudo‐second‐order chemical reaction model was obtained for both arsenate and arsenite; adsorption isotherms of arsenate and arsenite fitted the Langmuir and Freundlich isotherm models well. X‐ray diffraction (XRD) and X‐ray photoelectron spectroscopy (XPS) were used to study the nature of surface elements before and after adsorption. CONCLUSIONS: This work demonstrates that Ti‐pillared montmorillonite is an efficient material for the removal of arsenate and arsenite from aqueous solutions. Experimental parameters such as contact time, solution pH, temperature, initial concentration, coexisting ions, and ionic strength have been optimized. Copyright © 2010 Society of Chemical Industry     

Low cost adsorbents obtained from ash for copper removal

We investigated the utilization of ash and modified ash as a low-cost adsorbent to remove copper ions from aqueous solutions such as wastewater. Batch experiments were conducted to determine the factors affecting adsorption of copper. The influence of pH, adsorbent dose, initial Cu²⁺ concentration, type of adsorbent and contact time on the adsorption capacity of Cu²⁺ from aqueous solution by the batch adsorption technique using ash and modified ash as a low-cost adsorbent were investigated. The optimum pH required for maximum adsorption was found to be 5. The results from the sorption process showed that the maximum adsorption rate was obtained at 300 mg/L when a different dosage of fly ash was added into the solution, and it can be concluded that decreasing the initial concentration of copper ion is beneficial to the adsorption capacity of the adsorbent. With the increase of pH value, the removal rate increased. When the pH was 5, the removal rate reached the maximum of over 99%. When initial copper content was 300 mg/L and the pH value was 5, the adsorption capacity of the zeolite Z 4 sample reached 27.904 mg/g. The main removal mechanisms were assumed to be the adsorption at the surface of the fly ash together with the precipitation from the solution. The adsorption equilibrium was achieved at pH 5 between 1 and 4 hours in function of type of adsorbent. A dose of 1: 25 g/mL of adsorbent was sufficient for the optimum removal of copper ions. For all synthesized adsorbents the predominant mechanism can be described by pseudo-second order kinetics.     

Removal of Copper (II) Ions from Aqueous Solutions using Na‐mordenite

Abstract

The potential to remove copper (II) ions from aqueous solutions using Na‐mordenite, a common zeolite mineral, was thoroughly investigated. The effects of relevant parameters solution pH, adsorbent dose, ionic strength, and temperature on copper (II) adsorption capacity were examined. The sorption data followed the Langmuir, Freundlich, and Dubinin‐Radushkevich (D‐R) isotherms. The maximum sorption capacity was found to be 10.69 mg/g at pH 6, initial concentration of 40 mg/dm³, and temperature of 40°C. Different thermodynamic parameters viz., changes in standard free energy (ΔG⁰), enthalpy (ΔH⁰), and entropy (ΔS⁰) have also been evaluated and the results show that the sorption process was spontaneous and endothermic in nature. The dynamics of the sorption process were studied and the values of rate constant of adsorption, rate constant of intraparticle diffusion were calculated. The activation energy (E_a) was found to be 11.25 kJ/mol in the present study, indicating a chemical sorption process involving weak interactions between sorbent and sorbate. The interaction between copper (II) ions and Na‐mordenite is mainly attributable to ion exchange. The sorption capacity increased with the increase of solution pH and the decrease of ionic strength and adsorbent dose. The Na‐mordenite can be used to separate copper (II) ions from aqueous solutions.     

Removal of Cu2+ and Pb2+ ions from aqueous solutions by starch-graft-acrylic acid/montmorillonite superabsorbent nanocomposite hydrogels

In this study, the removal of copper(II) and lead(II) ions from aqueous solutions by Starch-graft-acrylic acid/montmorillonite (S-g-AA/MMT) nanocomposite hydrogels was investigated. For this purpose, various factors affecting the removal of heavy metal ions, such as treatment time with the solution, initial pH of the solution, initial metal ion concentration, and MMT content were investigated. The metal ion removal capacities of copolymers increased with increasing pH, and pH 4 was found to be the optimal pH value for maximum metal removal capacity. Adsorption data of the nanocomposite hydrogels were modeled by the pseudo-second-order kinetic equation in order to investigate heavy metal ions adsorption mechanism. The observed affinity order in competitive removal of heavy metals was found Cu²⁺ > Pb²⁺. The Freundlich equations were used to fit the equilibrium isotherms. The Freundlich adsorption law was applicable to be adsorption of metal ions onto nanocomposite hydrogel.     

Removal of Copper in Aqueous Solution by Apple Wastes

Abstract

Removal of copper from a solution was investigated to evaluate the cation-exchange capacities of apple residues from agricultural wastes. The effects of solution pH, ionic strength, co-ion, ligands, initial metal concentrations, and particle size of apple residues were studied. The optimal pH range for copper removal by apple residues was shown to be from pH 5.5 to 7.0, and the maximum percentage of copper removal was 91.2%. Increasing ionic strength, up to 0.1 N, has little effect on metal uptake. The presence of co-ions such as lead decreases the removal capacity of copper as expected. The presence of ligands, such as EDTA and ammonia, also reduces metal removal efficiency due to the formation of a metal-ligand complexation in solution. Equilibrium of copper sorption was established very rapidly initially and decreased markedly after 1 hour. Equilibrium isotherms of copper fit the Langmuir equation adequately. Column experiments showed that the dynamic capacity of chemically modified apple residues was four to five times higher than that of raw residues which contained acidic groups such as carboxylic and phenolic functional groups. The adsorbed copper ions were completely recovered with three bed volumes of 0.5 N HCl. Thus, modified apple residues could be applied successfully for metal removal from wastewater.     

双甘膦修饰磁性四氧化三铁纳米微球吸附DNA的研究

用双甘膦(PMIDA)修饰磁性四氧化三铁纳米微球(MNP)并负载Zn2+制得了PMIDA-Zn2+修饰磁性微球吸附剂。考察了吸附溶液的pH值、离子强度、吸附时间、吸附温度等因素对DNA吸附的影响。结果表明,当吸附剂用量为10mg、pH值为5.0、离子强度(NaCl浓度)为2.0mol.L-1、吸附时间为20min、吸附温度为35℃时,吸附率可达80%,吸附容量为21mg.g-1。被吸附的DNA用3.5%的氨水能完全洗脱。将PMIDA-Zn2+修饰磁性微球用于玉米DNA的提取,所得DNA纯度较高,效果令人满意。     

Enhanced adsorption and recovery of Pb(II) from aqueous solution by alkali‐treated persimmon fallen leaves

Persimmon fallen leaves were employed to prepare a renewable and low‐cost biosorbent named as NPFL. Effects of initial pH, contact time, initial Pb(II) concentration, coexisting metal ions, and ionic strength on adsorption of Pb(II) from aqueous solution by NPFL were studied in detail. Enhanced removal capacity of NPFL toward Pb(II) was observed, and the maximum adsorption capacity was evaluated as 256 mg g^?1 by Langmuir modeling calculation. The fast adsorption process and the well‐fitted kinetics data with pseudo‐second‐order model indicated that chemisorption is the main rate‐limiting step for the adsorption process. NPFL had superior adsorption selectivity for Pb(II) from aqueous solution with coexisting metal ions. Characterization of NPFL and adsorption mechanism (electrostatic attraction, ion exchange, and chelation) were performed using XRD, SEM‐EDS, FT‐IR, XPS, and TGA. The results suggested that NPFL could be utilized as a potential candidate for the preconcentration of Pb(II) recovery and its removal in practice. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43656.     

Poly(vinyl alcohol)/polyethyleneimine (PVA/PEI) blended monolithic cryogel columns for the depletion of haemoglobin from human blood

We have synthesized PVA/PEI monolithic cryogel columns chelated with Cu²⁺ ions as a model adsorbent, which is capable of binding haemoglobin (Hb) from human blood. The goal of this study is to perform the depletion of Hb via a single and easy process to be useful in proteomic studies. PVA/PEI-Cu²⁺ cryogel columns were subjected to adsorption studies of Hb from both aqueous solution and human plasma to evaluate the extent of interaction between cryogel columns and Hb. The effects of experimental parameters, such as pH, Hb equilibrium concentration, adsorption time, temperature, and ionic strength, on Hb adsorption capacity were investigated.     

Reticulated vitreous carbon cathodes for metal ion removal from process streams part II: Removal of copper(II) from acid sulphate media

The performance of cells with reticulated vitreous carbon cathodes for the removal of low levels of copper ions from aqueous, acidic sulphate media is described. During the batch recirculation of nitrogen-sparged, sodium sulphate solutions, pH 2, the copper ion concentration may be reduced from 10 p.p.m. to <0.5 p.p.m. or from 2.5 p.p.m. to <0.1 p.p.m. with overall current efficiencies of 84% and 42%, respectively. The influence of solution flow rate through the cathode and the choice of the grade of the reticulated carbon is discussed. The removal of copper ions from solutions of low ionic strength, saturated with air and/or containing chloride ion is also investigated.     

模拟酸雨中离子强度与pH值影响土壤缓冲力

酸雨是一种强电解质溶液,它与土壤接触发生液-固反应,酸雨的离子强度对土壤中电性吸附的各种离子起着至关重要的作用.本试验通过运用两种离子强度的模拟酸雨溶液,分别进行四种pH值的模拟酸雨淋滤试验,探讨离子强度与氢离子浓度对土壤缓冲力的影响.结果发现,氢离子浓度和离子强度越大,土壤的缓冲能力就越弱.     

Sorption equilibrium of Cr(VI) ions on oak wood charcoal (Carbo Ligni) and charcoal ash as low-cost adsorbents

The aim of this study is to demonstrate the potential of oak wood charcoal (WC) and oak wood charcoal ash (WCA) as a low-cost adsorbent for environmental protection applications of Cr(VI) ion. The influence of contact time, solution pH, initial metal concentration, amount of adsorbent and ionic strength on the removal of Cr(VI) ion was studied. The adsorption of Cr(VI) with (WC) and (WCA) was investigated in a batch arrangement. The Cr(VI) ions sorbed onto the adsorbents were determined by a UV-Visible Spectrophotometer. The sorption of Cr(VI) on the adsorbent surface depends strongly on the pH and Cr(VI) ion-sorption increased with a decreasing pH until pH 2 and increase in the concentration of this metal in solution phase. The adsorption of Cr(VI) was higher between pH 2.0 and 2.5 for both adsorbents. The Freundlich adsorption isotherm was used to describe observed sorption phenomena. The maximum adsorption capacity of 30.10 mg of Cr(VI)/g for (WC) and 46.17 mg of Cr(VI)/g for (WCA) was obtained at pH of 2 and 2.5 respectively.     

pH对壳聚糖螯合铜(II)的螯合机理及稳定常数的影响

用紫外分光光度法研究了pH值对壳聚糖螯合Cu(II)的影响。通过显微图像、X衍射图谱及红外光谱对沉淀物进行分析。结果表明，随体系pH值增加，壳聚糖碳链上的活性基团与铜离子的螯合能力增强。溶液体系pH=5~6时，螯合物的稳定常数最大值为1.1×108；当pH接近7时，部分螯合产物析出导致稳定常数降低。酸性条件下pH值的变化对螯合物的配位比(n)无明显影响，壳聚糖–铜螯合物的配位比n=2。通过调节pH值可使溶液中壳聚糖铜螯合物析出，随pH增加，Cu2+浓度降低，当pH约为9时，Cu2+浓度达最小值1.5 mg/L。壳聚糖的主要活性基团–NH2与铜离子发生螯合，反应生成壳聚糖-铜。     

Surface modification of rubber (Hevea brasiliensis) leaves for the adsorption of copper ions: kinetic,thermodynamic and binding mechanisms

BACKGROUND: This research describes the adsorption of copper ions from aqueous solutions following the modification of rubber (Hevea brasiliensis) leaves with formaldehyde solution. The main objectives of this research were to identify the binding mechanisms of copper ions on the chemically modified rubber leaves by spectroscopic techniques and to investigate the effects of several important physicochemical parameters such as pH, copper concentration, contact time, adsorbent dose and temperature on copper removal. RESULTS: Based on a kinetic study, the pseudo‐second‐order model was found to fit the experimental results well, while the Boyd kinetic model indicated that the rate‐determining step was due to film diffusion. Adsorption isotherms were modelled by the Langmuir and Freundlich isotherm equations, with the former providing a better fit for the data. Based on the Langmuir model, the maximum adsorption capacities of Cu(II) ions at 300, 310 and 320 K were 8.36, 8.61 and 8.71 mg g^?1, respectively. Thermodynamic parameters such as the Gibbs free energy (ΔG°), enthalpy (ΔH°) and entropy changes (ΔS°) were calculated. The adsorption process was spontaneous as the values of ΔG° were negative, and endothermic as higher adsorption capacities were recorded at higher temperatures. More than 80% of copper ions bound on the adsorbent were able to be desorbed using 0.02 mol L^?1 HCl, HNO₃ and EDTA solutions. Besides ion exchange, surface complexation could also play a major role in copper binding. CONCLUSION: Due to its relative abundance and satisfactory adsorption capacity, the modified rubber leaves can be considered as a good low‐cost adsorbent for removing copper ions from dilute aqueous solutions. Copyright © 2008 Society of Chemical Industry     

Kinetic and equilibrium modeling of liquid‐phase adsorption of lead and lead chelates on activated carbons

The sawdust (SD) waste generated in the timber industry was converted to a low‐cost activated carbon (SDAC) using a simpler and cheaper activation process, single‐step steam pyrolysis activation. The possibility of utilizing SDAC for the removal of lead (Pb(II)) in the absence of ligands and nitrilotriacetic acid (NTA) and ethylenediaminetetraacetic acid (EDTA) chelated Pb(II) complexes from the liquid phase was examined and the results were compared with those for commercial activated carbon (CAC). SDAC shows a high adsorption capacity for Pb(II) and Pb(II) chelates compared with CAC. The extent of adsorption of Pb(II) and Pb(II) chelates on activated carbons was found to be a function of solution pH and species distribution of Pb(II) and Pb(II) chelates. The optimum pH range for the removal of Pb(II) in the absence of ligands by SDAC was 6.5–8.0, whereas its maximum removal by CAC was observed at pH 6.5. In the presence of ligands, the extent of Pb(II) adsorption was enhanced in the pH range 2.0–5.0 and was reduced significantly in the pH range 6.0–8.0. The maximum uptake of Pb(II) chelates for both carbons was observed at pH 5.0. Kinetic models such as pseudo‐first‐order, pseudo‐second‐order and pore diffusion were tested to investigate the adsorption mechanism. Batch kinetic studies showed that the adsorption of Pb(II) from aqueous solutions with and without ligands could be best described by a psuedo‐first‐order model for both carbons. The effect of pH on the adsorption isotherms of Pb(II) and Pb(II) chelates was also investigated. The applicability of the Langmuir and Freundlich isotherms, established for various initial concentrations of the adsorbate and for different pH values, was tested at 30 °C. Copyright © 2003 Society of Chemical Industry     

Preparation of amidoximated polyester fiber and competitive adsorption of some heavy metal ions from aqueous solution onto this fiber

In this study, a fibrous adsorbent containing amidoxime groups was prepared by graft copolymerization of acrylonitrile (AN) onto poly(ethylene terephthalate) (PET) fibers using benzoyl peroxide (Bz₂O₂) as initiator in aqueous solution, and subsequent chemical modification of cyano groups by reaction with hydroxylamine hydrochloride in methanol. The grafted and modified fibers were characterized by FTIR, TGA, SEM, and XRD analysis. The crystallinity increased, but thermal stability decreased with grafting and amidoximation. The removal of Cu(II), Ni(II), Co(II), Pb(II), and Cd(II) ions from aqueous solution onto chelating fibers were studied using batch adsorption method. These properties were investigated under competitive conditions. The effects of the pH, contact time, and initial ion concentration on the removal percentage of ions were studied. The results show that the adsorption rate of metal ions followed the given order Co(II) > Pb(II) > Cd(II) > Ni(II) > Cu(II). The percentage removal of ions increased with initial ion concentration, shaking time, and pH of the medium. Total metal ion removal capacity was 49.75 mg/g fiber on amidoximated fiber. It was observed that amidoximated fibers can be regenerated by acid without losing their activity, and it is more selective for Pb(II) ions in the mixed solution of Pb‐Cu‐Ni–Co‐Cd at pH 4. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

Removal of Cadmium from Aqueous Solution Using Adsorptive Bubble Separation Techniques

Abstract

Cadmium ion was removed from aqueous solutions using adsorptive bubble separation techniques. The effect of pH, coagulant and activator concentrations, and ionic strength on separation efficiency was studied. Adsorbing colloid flotation using ferric hydroxide and aluminum hydroxide as the coprecipitant and sodium lauryl sulfate as the collector and frother was found to be very effective provided that the ionic strength of the solution was no greater than 0.01 M. The residual cadmium concentration was less than 0.02 ppm after foaming for 10 min from a solution containing 20 ppm cadmium initially. Effective separation can be achieved from solutions containing 0.1 M NaNO₃ or 0.05 M Na₂SO₄ when zinc ion is used as the activator. The results of foam flotation were compared with the zeta potential of the floc. It was found that the zeta potential of the floc decreases with increasing ionic strength of the solution. The zeta potential of the floc is more positive when activators (aluminum and zinc ions) were added, which presumably gives the floc a stronger affinity for anionic surfactant adsorption, resulting in better separation efficiency. Adsorbing colloid flotation becomes less effective with increasing inert salt concentration of the solution; this effect can be compensated for to quite a large extent with the aid of activators, and the applicability of foam separation techniques for heavy metal removal from wastewater is thus greatly extended     

Removal of Co2+ Ions from Aqueous Solution by Ferrite Process

Abstract

A mathematical model was developed to investigate the characteristics of Co²⁺ removal by the pre-formed ferrite process. In this study, surface adsorption, hydrolysis-precipitation, and ion exchange were considered as Co²⁺ removal mechanisms, and incorporated into the model. In addition, a series of batch experiments was performed to remove Co²⁺ ions from aqueous solution, and the removal characteristics of Co²⁺ were analyzed by considering equilibrium pH, shaking time, ionic strength, and the effect of EDTA and Ca²⁺ as a chelating agent and a competing cation, respectively. Finally, the model proposed in this study was applied to the given experimental system, and it turned out that the pH-edge could be successfully predicted by the model. The experimental results were well-fitted by a Freundlich isotherm, and the standard enthalpy change of the reaction was 25.02 kJ·mol^?1. The removal efficiency was slightly diminished by increasing the ionic strength and the initial concentration of Co²⁺; however, the effect of the competing cation, Ca²⁺, was negligible.