Removal of Cu(II) from aqueous solutions by recycled tire rubber

A batch adsorption system was applied to study the adsorption of Cu(II) ions from aqueous solutions by crumb rubber. The effects of pH ranging from 1.5 to 7.0, contact time ranging from 6 to 96 h and initial metal concentration ranging from 1 mg L^− 1 to 50 mg L^− 1 on the removal of Cu(II) were studied. Results show that adsorption of Cu(II) is pH-dependent and the best results are obtained at pH = 6.0. Results also show that copper uptake is accompanied by displacement of zinc and therefore probably involves an ion exchange type mechanism. Langmuir and Freundlich adsorption models were applied to describe the isotherms and isotherm constants. Equilibrium data agreed very well with the Langmuir model. Results clearly show that crumb rubber is an effective adsorbent for the removal of Cu(II) from aqueous solutions.     

Regeneration of spent bleaching earth and its adsorption of copper (II) ions from aqueous solutions

This study was designed to provide a comprehensive investigation into heat and acid reactivation of spent bleaching earth (SBE) and adsorption of Cu(II) ions from aqueous solutions. Heat treatment was the master variable in SBE regeneration. Dilute acid treatment did not constitute an effective SBE reactivation protocol for this purpose. Solvent extraction of residual oil using excess methylethyl ketone followed by heating at 370 °C was, therefore, the most effective reactivation procedure. Highly adsorptive materials with > 98% removal of Cu(II) ions from solution were obtained. Thus, > 80% Cu adsorption was reversible at SBE silicate sites because of their higher proportion in the adsorbent.     

Adsorption behavior of estrogenic compounds on carbon nanotubes from aqueous solutions: Kinetic and thermodynamic studies

In this study different estrogenic compounds, estrone (E1), 17β-estradiol (E2), and 17a-ethinylestradiol (EE2), were removed from the model and real solution by the newly emerged multi-walled carbon nanotubes. The effects of different factors which affect the removal process were studied and optimized for efficient removal. The kinetics of E1, E2, and EE2 adsorption on MWCNTs were analyzed using different kinetic models and the results showed that the removal was mainly a pseudo-second-order process. The thermodynamic study showed the spontaneity and exothermic nature of the removal process, with negative entropy.     

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.     

Enhanced removal of nickel(II) ions from aqueous solutions by SDS-functionalized graphene oxide

In this paper, a one-pot and easy-to-handle method at room temperature without additional chemicals for the modification of graphene oxide (GO) with surfactant is found. Removal of nickel (II) ions from aqueous solutions by GO and surfactant (sodium dodecyl sulphate) modified graphene oxide (SDS-GO) was studied spectrophotometrically at room temperature as a function of time, initial concentration and pH. Adsorption capacity of the adsorbent was increased dramatically (from 20.19 to 55.16 mg/g found by Langmuir model) due to the functionalization of the surface by SDS. The driving force of the adsorption of Ni(II) ions is electrostatic attraction and Ni(II) ions adsorbed on the GO surface chemically besides ion exchange.     

Application of kinetic,isotherm and thermodynamic models for the adsorption of Co(II) ions on polyaniline/polypyrrole copolymer nanofibers from aqueous solution

The aim of this research is to investigate sorption characteristics of polyaniline/polypyrrole copolymer nanofibers (PANI/PPy copolymer nanofibers) for the removal of Co(II) ions from aqueous solution. The adsorbent is characterized using FE-SEM, TEM, FTIR, TGA, DSC and BET surface area. The sorption of Co(II) ions by batch method is applied and the optimum conditions are investigated. In optimum condition, removal efficiency was 99.68% for 100 mg L⁻¹ Co(II) solution. It is found that temperature has a positive effect on the removal efficiency. It can be concluded that PANI/PPy copolymer nanofibers are potentially able to removal of Co(II) ions from aqueous solutions.     

Selective adsorption behavior of ion-imprinted magnetic chitosan beads for removal of Cu(II) ions from aqueous solution

Heavy metal ion is one of the major environmental pollutants. In this study, a Cu(II) ions imprinted magnetic chitosan beads are prepared to use chitosan as functional monomer, Cu(II) ions as template, Fe₃O₄ as magnetic core and epichlorohydrin and glutaraldehyde as crosslinker, which can be used for removal Cu(II) ions from wastewater. The kinetic study shows that the adsorption process follows the pseudo-second-order kinetic equations. The adsorption isotherm study shows that the Langmuir isotherm equation best fits for the monolayer adsorption processes. The selective adsorption properties are performed in Cu(II)/Zn(II), Cu(II)/Ni(II), and Cu(II)/Co(II) binary systems. The results shows that the IIMCD has a high selectivity for Cu(II) ions in binary systems. The mechanism of IIMCD recognition Cu(II) ions is also discussed. The results show that the IIMCD adsorption Cu(II) ions is an enthalpy controlled process. The absolute value of ΔH (Cu(II)) and ΔS(Cu(II)) is greater than ΔH (Zn(II), Ni(II), Co(II)) and ΔS (Zn(II), Ni(II), Co(II)), respectively, this indicates that the Cu(II) ions have a good spatial matching with imprinted holes on IIMCD. The FTIR and XPS also demonstrates the strongly combination of function groups on imprinted holes in the suitable space position. Finally, the IIMCD can be regenerated and reused for 10 times without a significantly decreasing in adsorption capacity. This information can be used for further application in the selective removal of Cu(II) ions from industrial wastewater.     

Polymeric hydrogels obtained using a redox initiator: Application in Cu(II) ions removal from aqueous solutions

Poly(acrylic acid‐co‐acrylamide) hydrogels were prepared via free‐radical solution polymerization, crosslinked with ethylene‐glycol‐dimethacrylate, potassium persulfate/ammonium bisulfite as the initiator, and applied in the removal of Cu(II) ions from aqueous solutions. Molar ratios of acrylamide/acrylic acid moieties and the amount of crosslinking agent were varied to determine the swelling capacities of hydrogels and maximum metal uptake. Polymerization kinetics was investigated by ¹H‐NMR. Hydrogel physicochemical properties were characterized by nitrogen sorption measurements, elemental analysis, FTIR, and X‐ray photoelectron spectroscopy (XPS). Swelling results indicated that hydrogels were swollen up to 27,500%. Hydrogels showed equilibrium Cu(II) adsorption capacities of 211.7 mg g^?1 and fast kinetics (～20 min). Langmuir isotherm fitted adsorption equilibrium data. FTIR and XPS results helped in elucidating the presence of monodentate copper complex on the surface of hydrogels. A simple synthesis route of hydrogels using the redox initiator suggests the potential application in the removal of toxic metals from aqueous streams. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 39933.     

Boron removal from aqueous solutions by ion-exchange resin: Batch studies

In this study, boron removal from aqueous solutions was examined using Dowex 2 × 8 anion exchange resin. The sorption behaviour of resin was investigated as a function of pH, contact-time and temperature, initial boron concentration of solution, resin dosage and effect of other ions. The maximum sorption value for boron was observed at pH 9. The percent removal of boron decreased as temperature and initial boron concentration increased. The presence of other ions in solutions affected the sorption of boron significantly. The Langmuir isotherm was used to describe observed sorption phenomena. The maximum sorption capacity of Dowex 2 × 8 was determined as 16.98 mg B/g at pH 9 and 25°C. The quantitative stripping of boron from resin was obtained with 0.5 M H₂SO₄ or 0.5 M HCl solutions at 25°C. A generalised ion exchange kinetic model was applied to fit the kinetic data obtained by using the Dowex 2 × 8 and the rate-determining step is determined as film-intraparticle diffusion.     

Adsorption of Cu(II) ions from aqueous solutions on modified chrysotile: Thermodynamic and kinetic studies

The adsorption of Cu(II) ions by modified chrysotile from aqueous solution was investigated under different experimental conditions. The Langmuir and Freundlich equations were introduced to describe the linear forms about the adsorption of Cu(II) ions on the surface of modified chrysotile, and it was found that the adsorption equilibrium process was well described by the Langmuir isotherm model with the maximum adsorption capacity of 1.574 mmol/g at 333 K. The thermodynamic parameters (ΔG⁰, ΔH⁰ and ΔS⁰) for adsorption on modified chrysotile were also determined from the temperature dependence. The influences of specific parameters such as temperature, pH value and initial concentration for the kinetic studies were also examined. The adsorption follows a pseudo-second order rate law.     

A modified cellulose adsorbent for the removal of nickel(II) from aqueous solutions

A series of adsorption studies was carried out on a glycidyl methacrylate‐ modified cellulose material functionalised with imidazole (Cellulose‐g‐GMA‐Imidazole) to assess its capacity in the removal of Ni(II) ions from aqueous solution. The study sought to establish the effect of a number of parameters on the removal of Ni(II) from solution by the Cellulose‐g‐GMA‐Imidazole. In particular, the influence of initial metal concentration, contact time, solution temperature and pH were assessed. The studies indicated a Ni(II) uptake on the Cellulose‐g‐GMA‐Imidazole sorbent of approximately 48 mg g^?1 of nickel from aqueous solution. The adsorption process fitted the Langmuir model of adsorption and the binding process was mildly endothermic. The kinetics of the adsorption process indicated that nickel uptake occurred within 400 min and that pseudo‐second order kinetics best describe the overall adsorption process. Nickel(II) adsorption, recovery and re‐adsorption studies indicated that at highly acidic pH values the adsorbent material becomes unstable, but in the range pH 3–6, the adsorbent is stable and shows limited but significant Ni(II) recovery and re‐adsorption capability. Copyright © 2006 Society of Chemical Industry     

A chelating cellulose adsorbent for the removal of Cu(II) from aqueous solutions

Regenerated cellulose wood pulp was grafted with the vinyl monomer glycidyl methacrylate (GMA) using ceric ammonium nitrate as initiator and was further fuctionalised with imidazole to produce a novel adsorbent material, cellulose‐g‐GMA‐imidazole. All cellulose, grafted cellulose and functionalized cellulose grafts were physically and chemically characterized using a number of analytical techniques, including elemental analysis, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential thermal analysis, and scanning electron microscopy. The cellulose‐g‐GMA material was found to contain 1.75 mmol g^?1 epoxy groups. These epoxy groups permitted introduction of metal binding functionality to produce the cellulose‐g‐GMA‐imidazole final product. Following characterization, a series of adsorption studies were carried out on the cellulose‐g‐GMA‐imidazole to assess its capacity in the removal of Cu²⁺ ions from solution. Cellulose‐g‐GMA‐imidazole sorbent showed an uptake of ～70 mg g^?1 of copper from aqueous solution. The adsorption process is best described by the Langmuir model of adsorption, and the thermodynamics of the process suggest that the binding process is mildly exothermic. The kinetics of the adsorption process indicated that copper uptake occurred within 30 min and that pseudo‐second‐order kinetics best describe the overall process. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 2006     

Water purification of removal aqueous copper (II) by as-grown and modified multi-walled carbon nanotubes

This study compares aqueous copper (II) adsorbed onto as-grown and modified carbon nanotubes (CNTs), using H₂SO₄ and H₂SO₄/KMnO₄ processes. H₂SO₄ and H₂SO₄/KMnO₄ modifications reduced pH_iep and Fourier Transform Infrared Spectroscopy (FTIR) analysis revealed that some functional groups were formed on modified CNTs. The adsorption capacity of copper (II) onto modified CNTs was greater than that of as-grown CNTs, especially at pH 6. The results demonstrate that the modified processes increased the adsorption capacity because the functional groups were generated on the modified surfaces of the CNTs. Additionally, the adsorption capacity of copper (II) onto as-grown and modified CNTs both increased with temperature, and the results indicated that the Langmuir isotherm fitted the experimental data well. Simulation results indicated that the ΔH⁰ values of as-grown, H₂SO₄-modified CNTs and H₂SO₄/KMnO₄-modified CNTs were 4.83, 14.37 and 29.92 kJ/mol, respectively. Based on ΔH⁰, the adsorption of Cu²⁺ onto H₂SO₄/KMnO₄-modified CNTs is suggested to proceed simultaneously by physisorption and chemisorption but that onto as-grown and H₂SO₄-modified CNTs may proceed only by physisorption.     

Adsorption of Cu(II) from aqueous solutions by tannins immobilized on collagen

Novel adsorbents were prepared by immobilizing tannins on collagen fibre matrices. Their adsorption properties, including adsorption equilibrium, adsorption kinetics, and column adsorption kinetics to Cu(II) were investigated. Immobilized Myrica rubra tannin and black wattle tannin exhibited significantly higher adsorption capacity than larch tannin and the adsorption isotherms of these three immobilized tannins can be described by the Freundlich model. Detailed adsorption studies of immobilized black wattle tannin to Cu(II) indicated that temperature had little effect on the adsorption isotherms whereas the effect of pH was significant. Adsorption rate data fitted well to a pseudo‐second‐order rate model, and the adsorption capacity calculated by this model was consistent with the result of actual measurement at relatively higher adsorption temperatures. Immobilized black wattle tannin also had excellent column adsorption kinetic properties and high binding capacity. The adsorptivity of the column was stable even after repeated adsorption–desorption cycles. Copyright © 2004 Society of Chemical Industry     

New polymeric structures designed for the removal of Cu(II) ions from aqueous solutions

New polymeric structures obtained by chemical transformations of maleic anhydride/dicyclopentadiene copolymer with triethylenetetraamine, p‐aminobenzoic acid, and p‐aminophenylacetic acid were used for the removal Cu(II) ions from aqueous solutions. The experimental values prove the importance of the chelator nature and of the macromolecular chain geometry for the retention efficiency. The retention efficiency (η_r), the retention capacity (Q _e ), and the distribution coefficient of the metal ion into the polymer matrix (K _d ) are realized by evaluation of residual Cu(II) ions in the effluent waters, by atomic adsorption. Also are discussed the influence of pH, the thermal stability of the polymer, and their polymer–metal complex, as well as the particular aspects regarding the contact procedure and the batch time. Based on the polymers and polymer–metal complexes characterization a potential retention mechanism is proposed. All polymer supports as well theirs metal–complexes are characterized by ATD and FTIR measurements. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1397–1405, 2007     

Cellulose-graft-polyacrylamide/hydroxyapatite composite hydrogel with possible application in removal of Cu (II) ions

Cellulose-graft-polyacrylamide/hydroxyapatite composite hydrogels of different weight ratios were prepared through a suspension polymerization method. Physical and chemical characteristics of the composite were investigated by Fourier transform infrared spectroscopy and scanning electron microscopy. The swelling behaviors of the composite hydrogels were investigated under varying conditions of time, temperature and pH. The optimized swelling capacity in standard conditions was found to be 5197% per gram of the hydrogel. The prepared hydrogel has the potential to be used for ion adsorption in water treatment. Such a possibility was examined through adsorption of copper (II) ions from an aqueous solution. The effects on adsorption of varying the time, pH, and initial concentration of copper (II) solution as well as some thermodynamic parameters were also investigated. The maximum adsorption capacity was found to be 175 mg per gram of composite hydrogel in dried state. The mechanism of adsorption was well presented using a pseudo-second-order kinetic model. Finally, the mercury-loaded hydrogel was regenerated without losing its original activity and stability.     

Adsorption of Cu(II) ions from an aqueous solution by crosslinked amphoteric starch

The adsorption process of Cu(II) ions from aqueous solutions by crosslinked amphoteric starch with quaternary ammonium and carboxymethyl groups was investigated. The adsorption capacity was found to be dependent on the solution pH, the dose of the crosslinked amphoteric starch, and the initial concentration of Cu(II) ions. Moreover, the adsorption capacity increased with an increasing degree of substitution (DS) of the carboxymethyl groups. The adsorption followed a Freundlich adsorption isotherm. The adsorption process was endothermic, and the thermodynamic parameters were calculated at different DS values. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 728–732, 2004     

Removal of Cu(II) from aqueous solutions by chelating starch derivatives

Two chemically modified starch derivatives, crosslinked amino starch (CAS) and dithiocarbamates modified starch (DTCS), were prepared and used for the removal of Cu(II) from aqueous solutions. CAS was found to be effective for the adsorption of Cu(II), which tended to form a stable amine complex. Adsorption of Cu(II) onto DTCS was higher than that onto CAS. Experiments showed that the adsorption processes of Cu(II) on both CAS and DTCS were endothermic, and followed Freundlich isothermal adsorption. For both adsorbents, dynamic modeling of their adsorption showed that the first‐order reversible kinetic model described the adsorption process. The adsorption rate constants of CAS and DTCS were 1.578 and 10.32 h^?1, respectively. From the results of the thermodynamic analysis, free energy ΔG, enthalpy ΔH, and entropy ΔS of the adsorption process were calculated. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3881–3885, 2004     

Competitive adsorption of Pb, Cu and Cd ions from aqueous solutions by multiwalled carbon nanotubes

The individual and competitive adsorption capacities of Pb²⁺, Cu²⁺ and Cd²⁺ by nitric acid treated multiwalled carbon nanotubes (CNTs) were studied. The maximum sorption capacities calculated by applying the Langmuir equation to single ion adsorption isotherms were 97.08 mg/g for Pb²⁺, 24.49 mg/g for Cu²⁺ and 10.86 mg/g for Cd²⁺ at an equilibrium concentration of 10 mg/l. The competitive adsorption studies showed that the affinity order of three metal ions adsorbed by CNTs is Pb²⁺>Cu²⁺>Cd²⁺. The Langmuir adsorption model can represent experimental data of Pb²⁺ and Cu²⁺ well, but does not provide a good fit for Cd²⁺ adsorption data. The effects of solution pH, ionic strength and CNT dosage on the competitive adsorption of Pb²⁺, Cu²⁺ and Cd²⁺ ions were investigated. The comparison of CNTs with other adsorbents suggests that CNTs have great potential applications in environmental protection regardless of their higher cost at present.     

Mercury(II) removal from aqueous solutions by adsorption on multi-walled carbon nanotubes

Our aim was to test how MWCNTs can be used as a new adsorbent for mercury(II). Multi-walled carbon nanotubes (MWCNTs) have been used for removal of mercury from aqueous solutions. Mercury removal from aqueous solutions by batch adsorption was investigated. Equilibrium isotherms, such as Freundlich, Langmuir, Temkin, Harkins-Jura, were tested. Kinetic studies based on Lagergren first-order, pseudo-second-order and Elovich rate expressions were done. The batch experiments were conducted at three different temperatures (17, 27 and 37 °C) and different pHs of the initial solution. Error function analysis shows that mercury(II) removal obeys pseudo-second order kinetics and Freundlich isotherm equation. Finally, the effects of solution pH and temperature on the adsorption were studied.