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.     

Preparation of aminoalkyl celluloses and their adsorption and desorption of heavy metal ions

Aminoalkyl celluloses (AmACs) were prepared from 6-chlorodeoxycellulose and aliphatic diamines H₂N(CH₂)_mNH₂ (m = 2, 4, 6, 8). Their adsorption and desorption of divalent heavy metal ions such as Cu²⁺, Mn²⁺, Co²⁺, Ni²⁺ and their mixtures were also investigated in detail. Adsorption of metal ions on AmACs was remarkably affected by the pH of the solution, the metal ion and its initial concentration, and also the number of methylene units in the diamines. No adsorption of metal ions occurred on AmACs in strongly acidic solutions. However, metal ions were adsorbed rapidly on AmACs from weakly acidic solutions and the amount of adsorption increased with increasing pH. The effectiveness of AmACs as adsorbents decreased with increasing length of the methylene moiety, and AmACs from ethylenediamine (m = 2) was most effective. The adsorption of metal ions on AmACs was in the order Cu²⁺ > Ni²⁺ > Co²⁺ > Mn²⁺. Accordingly, their behavior followed the Irving-Williams series and Cu²⁺ ions were preferentially adsorbed from solutions containing metal ion mixtures. The adsorbed ions were easily desorbed from the AmACs by stirring in 0.1 M HCl.     

Adsorption of zinc, cadmium and mercury ions from aqueous solutions on an activated carbon cloth

The adsorption of zinc, cadmium and mercury ions from aqueous solutions on an activated carbon cloth was studied as a function of their concentrations and solution pH. For that purpose, pertinent adsorption isotherm data was collected at different pH values. The amount of adsorbed zinc and cadmium ions increases while the amount of adsorbed mercury remains constant with an increase in the equilibrium pH of the solution. The adsorption mechanisms of metal ions on activated carbon cloth are discussed. Under the conditions investigated, these primarily involve adsorption of monovalent cations (Zn and Cd) or precipitation of metal hydroxides (Cd and Hg) on the activated carbon cloth tested.     

Preparation and adsorption properties of poly(N‐vinylformamide/acrylonitrile) chelating fiber for heavy metal ions

In this article we report a new chelating fiber that was prepared from a hydrolyzate of poly(N‐vinylformamide/acrylonitrile) by a wet‐spinning method. This fiber contains chelating groups, such as amidine groups, amino groups, cyano groups, and amide groups, with high densities. We examined the chelating abilities for several metal ions with this fiber, and present the morphological merit of the fibrous product compared with the globular resin. Based on the research results, it is shown that the fiber has higher binding capacities and better adsorption properties for heavy metal ions than the resin. The pH value of the metal ion solution shows strong influences on the adsorption of the metal ions. The maximum adsorption capacities of the fiber for Cu²⁺, Cr³⁺, Co²⁺, Ni²⁺, and Mn²⁺ are 112.23, 88.11, 141.04, 108.06, and 73.51 mg/g, respectively. In mixed metal ions solution, the fiber adsorbs Cr³⁺, Cu²⁺ and Co²⁺ efficiently. The adsorbed metal ions can be quantitatively eluted by hydrochloric acid. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 85: 1378–1386, 2002     

A model for the adsorption of single metal ion solutes in aqueous solution onto activated carbon produced from pecan shells

Adsorption isotherms for activated carbon made from pecan shells have been obtained at 25 °C and an approximate pH of 3 for a number of metal ion solutes. It was found that the Slips and Freundlich equations were satisfactory for explaining the experimental data. The correlation of metal ion adsorption with the solute parameters of metal ion electronegativity and first stability constant of the metal hydroxide was investigated. In the case of most of the metal ions studied, higher electronegativities and stability constants corresponded to the higher adsorption levels of metal ions onto the activated carbon. A correlation was developed that predicts the constants of the Freundlich equation from the selected parameters of the metal ions, and thus can predict the adsorption isotherms at constant pH. The developed correlation gives results with acceptable deviations from experimental data. A procedure is proposed for obtaining similar correlations for different conditions (temperature, pH, carbon type and dosage). The ratio of equivalent metal ions adsorbed to protons released is calculated for the studied metal ions over a range of concentrations. In most cases, particularly at low concentrations, this ratio is close to one, confirming that ion exchange of one proton with one equivalent metal ion is the dominant reaction mechanism.     

Electrochemical studies of the interaction between a modified activated carbon surface and heavy metal ions

Cyclic voltammetric studies of the influence of surface chemistry on the electrochemical behaviour of powdered activated carbon electrodes (PACE) in the presence of selected heavy metal ions (Pb²⁺, Hg²⁺, Cd²⁺) in bulk solution and pre-adsorbed on carbon were carried out. The variety of surfaces was achieved via the modification of carbon samples by heat treatment under vacuum and in an oxygen/ammonia atmosphere, as well as oxidation with conc. nitric acid. The chemical structures of the modified carbon surfaces were characterised by XPS and standard pH-titration. The adsorption capacities of the modified carbon samples towards the heavy metal ions in question were estimated. The mechanisms of adsorption processes of metal species on carbon surfaces were analysed and described on the basis of their electrochemical behaviour. The nature of the interactions between the modified carbon surfaces and adsorbed cations is discussed.     

Activated carbon surface modifications by adsorption of bacteria and their effect on aqueous lead adsorption

The adsorption of Escherichia coli on different activated carbons has been studied. The activated carbon samples used have been characterized, determining their surface area, pore size distribution, elemental analysis, mineral matter analysis and pH of the point of zero charge. The adsorption capacity of these carbons increased with their hydrophobicity and macropore volume. The number of bacteria adsorbed on the demineralized activated carbon in a solution of pH value equal to the iso‐electric point of the carbon was negligible. However, in the presence of cations the proportions of bacterial cells adsorbed were 87.8% (Fe³⁺), 54.7% (Ca²⁺) and 24.8% (Mg²⁺) respectively. This increase in adsorption capacity in the presence of electrolytes has been explained on the basis of both the reduction in electrostatic free energy and the increase in cell surface hydrophobicity due to the metal bound by some compounds of the cell membrane. When the solution pH was intermediate between the pH values of the point of zero charge of the carbon and bacteria the number of bacteria adsorbed increased due to the attractive interactions between the carbon and bacteria. The adsorption of bacteria on activated carbons decreased the porosity and increased the negative charge density of the latter. Depending on the experimental conditions used, the presence of bacteria can enhance the capacity of activated carbons to adsorb lead. © 2001 Society of Chemical Industry     

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.     

Studies of selective adsorption resin. XXIV. Preparation and properties of macroreticular chelating resins containing both polyethylenepolyamine side chains and mercapto groups

The macroreticular chelating resins containing both polyethylenepolyamine side chains and mercapto groups were prepared by the reaction of 2,3-epithiopropyl methacrylate-divinylbenzene macroreticular copolymer beads with polyethylene-polyamine. The adsorption behavior of metal ions on the obtained resins was then investigated. The amination of the macroreticular copolymer beads could effectively be carried out by treatment of the polymer beads with polyethylenepolyamine in organic solvent (benzene, terahydrofuran) or in the absence of organic solvent at 80°C or 100°C for 60 min. It was found that the adsorption capacity of the resins for metal ions is not only affected by the ion exchange capacity of the resins but also by the porosity of the resins. Hg²⁺, Ag⁺, and Cu²⁺ were effectively adsorbed on the resins even at a pH below 3, whereas Co²⁺, Ni²⁺, and Cd²⁺ were adsorbed at a pH above 3, Mn²⁺ at a pH above 7, and Ca²⁺ at a pH above 8. These metal ions adsorbed on the resins could easily be eluted with dilute mineral acid solution or dilute mineral acid solution containing thiourea.     

Investigation of adsorption of lead,mercury and nickel from aqueous solutions onto carbon aerogel

Recently a new form of activated carbon has appeared: carbon aerogel (CA). Its use for the removal of inorganic (and especially metal ions) has not been studied. In the present study, the adsorption of three metal ions, Hg(II), Pb(II) and Ni(II), onto carbon aerogel has been investigated. Batch experiments were carried out to assess adsorption equilibria and kinetic behaviour of heavy metal ions by varying parameters such as agitation time, metal ions' concentration, adsorbent dose and pH. They facilitated the computation of kinetic parameters and maximum metal ion adsorption capacities. Increasing the initial solution pH (2–10) and carbon concentration (50–500 mg per 50 cm³) increases the removal of all three metal ions. A decrease of equilibrium pH with an increase of metal ion concentration led us to propose an adsorption mechanism by ion exchange between metal cations and H⁺ at the carbon aerogel surface. Carboxylic groups are especially involved in this adsorption mechanism. Langmuir and Freundlich isotherm models were used to analyse the experimental data of carbon aerogel. The thermodynamics of the metal adsorption was also investigated for the practical implementation of the adsorbent. The sorption showed significant increase with increase of temperature. Kinetics models describing the adsorption of Hg(II), Pb(II) and Ni(II) ions onto carbon aerogel have been compared. Kinetics models evaluated include the pseudo‐first order and second order model. The parameters of the adsorption rate constants have been determined and the effectiveness of each model assessed. The result obtained showed that the pseudo‐second order kinetic model correlated well with the experimental data and better than the pseudo‐first order model examined in the study. Mass transfer coefficients obtained can be useful in designing wastewater treatment systems or in the development of environmental technologies. Copyright © 2005 Society of Chemical Industry     

Copper and strontium adsorption by a novel carbon material manufactured from pecan shells

A novel carbon material (PS276a) was produced from pecan shells, a waste product of the agricultural industry. Preparation of this material involved the impregnation of the pecan shell feedstock with a phosphoric acid solution. Activation was followed by a water wash and a sodium hydroxide treatment. The carbon produced was characterized by adsorption of N₂ and revealed a pore structure with an average pore diameter of 74.8 Å. Equilibrium sorption isotherms prepared for this carbon demonstrate that it has a significantly higher capacity for copper and strontium sorption than that of a commercial material used for comparison. A maximum of 95 mg Cu²⁺ and 180 mg Sr²⁺ are adsorbed per gram of this carbon at pH 3.6 and 8.5, respectively. Demonstrated process advantages of this carbon material and preparation technique include low temperature manufacture, in-situ regeneration potential, and adsorbate recovery capability.     

Removal of metal ions using lignite in aqueous solution—Low cost biosorbents

Turkish lignite can be used as a new adsorption material for removing some toxic metals from aqueous solution. The adsorption of lignite (brown young coals) to remove copper (Cu²⁺), lead (Pb²⁺), and nickel (Ni²⁺) from aqueous solutions was studied as a function of pH, contact time, metal concentration and temperature. Adsorption equilibrium was achieved between 40 and 70 min for all studied cations except Pb²⁺, which is between 10 and 30 min. The adsorption capacities are 17.8 mg/g for Cu²⁺, 56.7 mg/g for Pb²⁺, 13.0 mg/g for Ni²⁺ for BC₁ (Ilg?n lignite) and 18.9 mg/g for Cu²⁺, 68.5 mg/g for Pb²⁺, 12.0 mg/g for Ni²⁺ for BC₂ (Beysehir lignite) and 7.2 mg/g for Cu²⁺, 62.3 mg/g for Pb²⁺, 5.4 mg/g for Ni²⁺ for AC (activated carbon). More than 67% of studied cations were removed by BC₁ and 60% BC₂, respectively from aqueous solution in single step. Whereas about 30% of studied cations except Pb²⁺, which is 90%, were removed by activated carbon. Effective removal of metal ions was demonstrated at pH values of 3.8–5.5. The adsorption isotherms were measured at 20 °C, using adsorptive solutions at the optimum pH value to determine the adsorption capacity. The Langmuir adsorption isotherm was used to describe observed sorption phenomena. The rise in temperature caused a slight decrease in the value of the equilibrium constant (K_c) for the sorption of metal ions. The mechanism for cations removal by the lignite includes ion exchange, complexation and sorption. The process is very efficient especially in the case of low concentrations of pollutants in aqueous solution, where common methods are either economically unfavorable or technically complicated.     

Adsorption of heavy metal ions in ternary systems onto Fe(OH)3

The adsorption behavior of amorphous Fe(OH)₃ has been studied in multicomponent metal system. The metal ions uptake in the ternary system is lower than in the single system, suggesting that certain sites on the surface of the solid are blocked due to competition. The selectivity trend in the ternary system is observed to be Ni²⁺>Zn²⁺>Cd²⁺ which is, however, lost with increase in the temperature of the aqueous solution. Further, the observed selectivity trend is neither related to electronegativity of the metal ions nor to the pH of the hydrolysis, but has been found dependent on charge to radius ratio. The metal ions adsorption is found to increase with pH, while the converse is true with the rise in temperature. The uptake of metal ions data has been interpreted in terms of stoichiometry, binding constants and adsorption capacities. The negative values of ΔG show that uptake of metal ions is favored at lower temperatures, indicating that the adsorption mechanism essentially remains ion exchange in nature.     

Synthesis of a polyacrylamide chelating resin and applications in metal ion extractions

A series of differently crosslinked polyacrylamide chelating resins were prepared, using N,N′-methylene-bis-acrylamide as the crosslinking agent. The crosslinked resins were functionalized by the reaction with ethylene diamine to get amino group capacities varying from 4.2 to 1.1 mequiv/g. The maximum adsorption capacities of the lightly crosslinked resin for Fe³⁺, Fe²⁺, Ni²⁺, and Cu²⁺ are 3.62, 4.22, 1.48, and 1.67 mequiv/g, respectively. The adsorbed metal ions can be quantitatively desorbed. The adsorption rate and the influence of pH on the adsorption of metal ions were examined. The resins can be used for the separation between different metal ions as well as the ions in different valence states (e.g., Fe³⁺ and Fe²⁺). The resin is amenable for continuous process and can be regenerated several times.     

Removal of Cs1+, Sr2+ and Co2+ from aqueous solutions by adsorption on natural clinoptilolite

The adsorption properties of local clinoptilolite (Serbia) towards Cs⁺, Co²⁺, and Sr²⁺ were investigated by batch equilibration technique. The influence of equilibration time, initial metal cation concentration, solution pH and presence of EDTA on these properties was studied and discussed. Kinetic data were found to be well fitted with pseudo-second order kinetic model. Cs⁺ is preferably adsorbed by the natural clinoptilolite, followed by Sr²⁺ and Co²⁺. The Langmuir adsorption isotherm was used to determine the adsorption capacities from both single and mixed metal solutions. At pH range of 3–12 the adsorption of Cs⁺ remains almost constant, while at low pH (2–3) the adsorption is lesser. At initial pH range of 2–10 adsorption of Sr²⁺ remains approximately stable, whereas at initial pH > 10 adsorption increases significantly. The adsorption of Co²⁺ is low at low pH but increased remarkably with increasing pH and precipitated at pH > 8. Cs⁺ adsorption on the clinoptilolite was not affected by the presence of EDTA, while the presence of EDTA hinders the adsorption of Co²⁺ and Sr²⁺ on clinoptilolite.     

REMOVAL OF Cd2+, Cu2+, AND Ni2+ METALS FROM SIMULATED WASTEWATER IN SINGLE AND COMPETITIVE SYSTEMS USING LOCAL IRAQI PHOSPHATE ROCKS

The equilibrium uptake of cadmium (Cd²⁺), copper (Cu²⁺), and nickel (Ni²⁺) ions, both singly and in combination, by local Iraqi phosphate rocks (PR) was studied in a batch system. The phosphate rock was characterized using BET, FT-IR, XRD, and SEM techniques. Adsorption isotherms were developed for both the single and ternary-component systems and expressed by the mono- and multicomponent Langmuir, Freundlich, Redlich-Peterson, and Dubinin-Radushkevich adsorption models; model parameters were estimated by the nonlinear regression method using STATISTICA version 6 software. To understand the action of metals uptake, factors influencing the adsorption of the heavy metals including pH, initial metal ion concentration, weight of the adsorbent, mixing speed, contact time, and temperature were investigated. It was found that the mono- and multicomponent adsorption equilibrium data fitted very well to the Langmuir model with high determination coefficient (R ²). The maximum loading capacities (q _max) were 70.852, 53.372, and 48.045 mg/g for Cd²⁺, Cu²⁺, and Ni²⁺ respectively. However, in the ternary system the loading capacity decreased because of competition between ions to binding sites of the adsorbent. Adsorption data were modeled using the pseudo-first- and pseudo-second-order kinetic and intraparticle diffusion models. It was seen that the pseudo- first-order kinetic equation could best describe the adsorption kinetics. Thermodynamic parameters showed that the adsorption of investigated heavy metals onto PR was endothermic and spontaneous in nature and the process is physiosorption. Fourier transform-infrared spectroscopy (FT-IR) analysis indicated that carboxylic (C?O), phosphine (p-H), and hydroxyl (–OH) groups in PR played an important role in the adsorption process. In conclusion, PR was found suitable as an abundant adsorbent for removal of the selected metal ions from aqueous solutions.     

Synthesis of chelating resins with iminodiacetic acid and its wastewater treatment application

The chelating resins have high potential applications for the selective removal and recovery of metal ions from industrial waste solutions. The hydrophilic acrylate monomer with the iminodiacetic acid chelating group was prepared from glycidyl methacrylate and iminodiacetic acid at 60°C. The microbeads, prepared from acrylate monomer with the iminodiacetic acid chelating group, were employed by inversion suspension polymerization. In the pH range of 2–6, a reasonably good equilibrium sorption capacity is maintained for Cr³⁺ (ca. 2.7 mmol/g) and Cu²⁺ (ca. 1.8 mmol/g) in the chelating resins. The adsorption of Cd²⁺ and Pb²⁺ on microbeads is clearly affected by the pH of the solution, such that these ions' adsorption capacity increased with the pH of the aqueous solution. The adsorption of Cd²⁺ (ca. 1.25–1.87 mmol/g) and Pb²⁺ (ca. 0.99–1.89 mmol/g) showed a maximum at approximately pH = 5 and 6, respectively. The adsorption isotherms of Cr³⁺ and Cu²⁺ adsorbed on microbeads were following the Langmuir isotherm, but the adsorption behavior of Cd²⁺ and Pb²⁺ were not. The concentration of alkaline earth–metal cations on the range of 0–200 ppm had no influence on metal ions adsorbed capacity of chelating resins. Additionally, NTA (nitrilotriacetic acid) had no significant influence on metal ion adsorption by chelating resins. Furthermore, phenol pollutant can be adsorbed effectively by metal ions chelated microbeads; therefore, the microbeads were useful not only in recovering metal ions but also in the treating phenol pollutants in wastewater. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 84: 1353–1362, 2002; DOI 10.1002/app.10243     

碱金属离子在树脂上的动态吸附行为

选取4种Na型树脂（D001、D113、Ls-1000、Ls-5000）为吸附剂,通过动态吸附法研究其对碱金属混合溶液的动态吸附行为,重点考察了其中铷、铯的分离性能,并考察了溶液pH、溶液组成、流速及树脂类型等对分离性能的影响。研究发现,中性条件下对铷、铯的吸附量顺序为离子交换树脂>螯合树脂。强酸性树脂D001对碱金属离子的亲和顺序为Cs+>Rb+>K+>Li+,其余3种树脂均为Cs+相似文献   

Nonionic adsorption of aromatic amino acids on a cation-exchange resin

Nonionic adsorption of aromatic amino acids on a cation-exchange resin (Dowex 50W-X8) was studied. At low concentrations, phenylalanine and tyrosine were adsorbed on the resin by monovalent ion-exchange process. Deviation from stoichiometric ion exchange became large as phenylalanine and tyrosine concentrations increased. On the other hand, aliphatic amino acids, glycine and alanine, were adsorbed on the resin by monovalent ion-exchange process. In column breakthrough experiments, the bed capacities for phenylalanine and tyrosine were higher than those for metal ions (Na⁺, Pb²⁺, and Ni²⁺) and the aliphatic amino acids. The increased capacities may be due to nonionic interaction between the aromatic amino acids and the polystyrene resin matrix. The nonionic interaction could be suppressed in 25% ethanol solution.     

Formation of Mixed Complexes of Type Phosphate-Ca-Dye

Many of the complex biological properties of hydroxylapatite HA are related to the multiple exchange capacities inside the HA structure, including formation of vacancies to accommodate ions with other valencies, in particular carbonate ions and alkali and other metal ions of biological importance. We have recently illustrated the possibilities of using HA to remove various textile dyes from industrial waste waters by co-precipitation with HA. Most dyes can be treated efficiently and the HA adsorbent can be regenerated for reuse following thermal treatment in air to burn of the organic materials adsorbed. However, important facts point to a situation more complex than simple adsorption. To elucidate the mode of action of HA on the removal of dyes or organic matter in general, we investigated the interactions of alizarinsulfonate ARS with calcium and phosphate ions in solution as a function of pH and dye/mineral fraction. Alizarin or its salt is thus regarded as a model compound for more complex dyes, which led us to investigate the way calcium ions interact simultaneously with phosphate and ARS. We report here the observation of the formation of mixed complexes of the type phosphate-Ca-dye which demonstrate the competition for calcium ions between phosphate and organic ligands.