Retention Of Metal Ions Research Articles

A solid phase extraction procedure for the determination of Cd(II) and Pb(II) ions in food and water samples by flame atomic absorption spectrometry

A relatively rapid, accurate and precise solid phase extraction method is presented for the determination of cadmium(II) and lead(II) in various food and water samples. Quantitation is carried out by flame atomic absorption spectrometry (FAAS). The method is based on the retention of the trace metal ions on Dowex Marathon C, a strong acid cation exchange resin. Some important parameters affecting the analytical performance of the method such as pH, flow rate and volume of the sample solution; type, concentration, volume, flow rate of the eluent; and matrix effects on the retention of the metal ions were investigated. Common coexisting ions did not interfere on the separation and determination of the analytes. The detection limits (3σb) for Cd(II) and Pb(II) were found as 0.13 and 0.18μgL−1, respectively, while the limit of quantification values (10σb) were computed as 0.43 and 0.60μgL−1 for the same sequence of the analytes. The precision (as relative standard deviation was lower than 4% at 5μgL−1 Cd(II) and 10μgL−1 Pb(II) levels, and the preconcentration factor was found to be 250. The accuracy of the proposed procedure was verified by analysing the certified reference materials, SPS-WW2 Batch 108 wastewater level 2 and INCT-TL-1 tea leaves, with the satisfactory results. In addition, for the accuracy of the method the recovery studies (⩾95%) were carried out. The method was applied to the determination of the analytes in the various natural waters (lake water, tap water, waste water with boric acid, waste water with H2SO4) and food samples (pomegranate flower, organic pear, radish leaf, lamb meat, etc.), and good results were obtained. While the food samples almost do not contain cadmium, they have included lead at low levels of 0.13–1.12μgg−1.

Retention of heavy metal ions on comb-type hydrogels based on acrylic acid and 4-vinylpyridine, synthesized by gamma radiation

Two novel comb-type hydrogels based on pH-sensitive monomers (acrylic acid (AAc) and 4-vinylpyridine (4VP)) were synthesized by gamma radiation. The systems were as follows: a) comb-type hydrogels of an AAc network followed by grafting of 4VP ((net-PAAc)-g-4VP) and b) comb-type hydrogels of an AAc network grafted onto polypropylene (PP) followed by grafting of 4VP (net-(PP-g-AAc)-g-4VP). The equilibrium isotherms and kinetics were evaluated for copper and zinc ions in aqueous solutions. The Zn(II) retention obtained was 480mgg−1 and 1086mgg−1 for (net-PAAc)-g-4VP and net-(PP-g-AAc)-g-4VP, respectively. At concentrations as low as ppm, retention efficiencies of approximately 90% were achieved for Cu(II) on (net-PAAc)-g-4VP and for Zn(II) on net-(PP-g-AAc)-g-4VP. Desorption of the hydrogels was also studied, and the results indicated that they can be used repeatedly in aqueous solutions. For both systems, the adsorption of Cu(II) and Zn(II) obeyed the Freundlich model, indicating heterogeneous sorption, and the retention process occurred by chemisorption. The sorption process follows a pseudo-second-order model.

Loading of VO2+ and Cu2+ to partially oxidized charcoal fines rejected from Brazilian metallurgical industry

Purpose Charcoal is utilized in Brazil for the metallurgical industry. Small size pieces, called charcoal fines, are rejected and sometimes are used to produce energy by burning. This charcoal can be used as soil conditioner to improve retention of metal ions in soil. However, changing the charcoal's surface chemistry via oxidation may increase retention of metal ions.

Sorption properties of chelating polymer–clay nano‐composite resin based on iminodiacetic acid and montmorillonite: water absorbency, metal ion uptake, selectivity, and kinetics

AbstractBACKGROUNDThis paper presents the study of the sorption performance of a novel poly[N‐(4‐vinylbenzyl)‐iminodiacetic acid)‐montmorillonite nano‐composite. The composite was obtained through in situ polymerization of the previously synthesized monomer N‐(4‐vinylbenzyl)‐iminodiacetic acid in the presence of organic‐modified montmorillonite and N,N‐methylene‐bis‐acrylamide.RESULTSThe water uptake of the nanocomposites increased with increasing montmorillonite content. Metal ion retention studies as a function of montmorillonite content showed an unexpected trend in which the adsorption capacities decreased as the montmorillonite content increased. Selectivity experiments reveals that composites present a certain selectivity towards Cu2+ and that montmorillonite content does not provide selectivity to the composite. Kinetic experiments were conducted using a Cu2+ aqueous solution at pH 5.0 and it was observed that after 60 min contact the maximum retention is reached. Kinetics and diffusion models reveal that the metal ion retention occurs mainly at the surface of resin particles, suggesting a film diffusion process.CONCLUSIONThe nano‐composite showed the ability to remove metal ions. The process can be described by a Langmuir isotherm, whereas kinetic studies indicated that the pseudo‐second‐order model could describe the sorption process. The intra‐particle diffusion model suggests that sorption mechanism is film diffusion. © 2013 Society of Chemical Industry

Transition metal cation separations with a resorcinarene-based amino acid stationary phase

A resorcinarene-based macrocyclic ligand functionalized with alanine and undecyl groups (AUA) was synthesized and applied to ion chromatographic separations. The selectivity and separation of transition metal ions on a column packed with AUA adsorbed onto 55% cross-linked styrene-divinylbenzene resin are presented. The upper and lower rims of the resorcinarene were modified with amino acids and -C(11)H(23) alkyl chains, respectively. The four carboxylic acid groups on the upper rim act as cation-exchangers while the four -C(11)H(23) alkyl chains serve to anchor the ligand to the resin surface by the hydrophobic effect. A systematic study of the effect of different eluent components including non-metal-chelating (HNO(3)) and chelating acids (oxalic acid, succinic acid, dipicolinic acid, and citric acid) on the retention of transition metal ions was investigated. Six metal ions (Mn(2+), Co(2+), Ni(2+), Cd(2+), Cu(2+), and Zn(2+)) were separated on the AUA column within a reasonable time with a single eluent gradient using oxalic acid. The separation is compared to that obtained using a commercial column containing carboxylic acid functional groups. The AUA column containing four preorganized carboxylic acid groups showed selectivity for Cu(2+) when no chelating eluent was present, a selectivity which was not observed with the comparison column.

Reactions of Cp2M (M = Ni, V) with dilithium diamido-aryl reagents; retention and oxidation of the transition metal ions

The reactions of dilithium 1,2-diamidobenzene, [1,2-(HN)2C6H4]Li2 (L(1)H2)Li2, and dilithium 1,8-diamidonaphthalene, [1,8-(NH)2C10H6]Li2 (L(2)H2)Li2, with Cp2Ni and Cp2V have been used to obtain the new complexes (L(2)H2)2Ni{Li(THF)2}2 (3), (L(2)H2)3V{Li(THF)2}3 (4) and (L(1)H2)6Ni6·{[(L(1)H2)3(L(1)H)3Ni6Li(THF)](2-)·2[Li(THF)4](+)} (5), in which retention or oxidation of the initial metal(ii) centre is observed. Whereas 3 and 4 contain one transition metal ion within ion-paired structures, 5 has a complicated co-crystalline composition which contains octahedral Ni6-cages constructed from six square-planar (16e) Ni(II) centres.

Comparação da eficiência de três materiais na sorção e difusão dos íons metálicos através de ensaios experimentais e simulação computacional

Com objetivo de obter parâmetros fundamentais do transporte e retenção de íons metálicos em sistemas de contenção, utilizou-se lixiviado sintético, com pH 1 e conhecidas concentrações dos íons cromo, cádmio e cobre. Através de ensaios de sorção e difusão molecular, estudou-se o comportamento dos íons metálicos em solo compactado, solo com 10% de bentonita sódica compactado e solo compactado sobreposto por geomembrana. Foi implementado, no programa MPHMTP (Multi Phase Heat and Mass Transfer Program), as equações que descrevem o comportamento dos íons investigados com parâmetros de ajustes obtidos através dos ensaios de sorção e difusão. A presença da geomembrana minimiza a migração dos metais pelo processo difusivo, sendo que a capacidade de sorção do solo não é exigida em função da presença da geomembrana. Porém a opção solo com bentonita mostrou-se uma alternativa específica predominantemente pela capacidade de sorção do cádmio.

Poly(sodium 4‐styrene sulfonate) and poly(2‐acrylamido glycolic acid) polymer–clay ion exchange resins with enhanced mechanical properties and metal ion retention

AbstractThis research presents the synthesis of novel nanocomposite ion exchange resins based on poly(sodium 4‐styrene sulfonate) and poly(2‐acrylamido glycolic acid). Nanocomposites were synthesized by in situ radical polymerization using organic modified montmorillonite as filler and different clay contents. Loaded resins showed improvements in mechanical properties compared with unloaded resins: specifically, when the nominal montmorillonite content was 2.5 wt%, poly(sodium 4‐styrene sulfonate) nanocomposite increased its shear modulus from 323 to 910 Pa and doubled its elastic recovery ratio, and the yield point was almost 20 times higher than for unloaded resins. In the case of metal ion retention, the effect of pH and clay content were studied for Cd(II), Pb(II), Cu(II), Cr(III) and Al(III) by a batch procedure. Results showed high efficiency, reaching over 80% after only 1 h of contact. Poly(2‐acrylamido glycolic acid) presented a higher pH dependence than poly(sodium 4‐styrene sulfonate). In addition, it was observed that montmorillonite contributes to retention capacity from the increase in distribution coefficients for loaded resins compared with unloaded resins. Copyright © 2011 Society of Chemical Industry

Metal ion sorption properties of water-insoluble resins based on sodium styrene sulfonate and different comonomers

A set of water-insoluble resins based on sodium styrene sulfonate and different comonomers were synthesized. The resins poly(mono-2-(methacryloyloxy)ethyl succinate-co-sodium 4-styrene sulfonate) P(MOES-co-SSNa), poly(2-acrylamido glycolic acid-co-sodium 4-styrene sulfonate) P(AGA-co-SSNa), poly(acrylamide-co-sodium 4-styrene sulfonate) P(AAm-co-SSNa), and poly(2-(dimethylamine)ethyl acrylate-co-sodium 4-styrene sulfonate) P(DMAEA-co-SSNa) were synthesized by solution radical polymerization. The metal ion retention properties were studied by batch procedure for Cd(II), Zn(II), Pb(II), and Hg(II). Resins performance was compared with a poly(sodium 4-styrene sulfonate) (PSSNa) resin in order to evaluate the effect of comonomer on sorption properties. The effect of pH, time, temperature, and maximum retention capacity were studied. In addition, sorption experiments were carried out under competitive ion conditions to study the selectivity of resins. The resins P(AAm-co-SSNa) and P(AGA-co-SSNa), showed the most important differences compared with PSSNa resin, the former present higher sorption and the latter presented selectivity for Hg(II) at pH 2.

Removal-concentration of pollutant metal-ions by water-soluble polymers in conjunction with double emulsion systems: A new hybrid method of membrane-based separation

The effect of reverse emulsion globules stabilized by non-ionic surfactants on metal-ion retention properties of poly(acrylic acid) was studied by continuous enrichment of external aqueous phase in a dead-end filtration system. Double emulsion systems were made by two-steps method confining an acid solution at pH 1.0 in the inside of reverse emulsion. Continuous phase of second dispersion stage was a poly(acrylic acid) solution at pH 6.0. By application of pressure, a divalent metal-ion stream, Cu 2+ and Cd 2+ at pH 6.0 was continuously added from a reservoir. Results indicate that it is possible to increase the maximum retention capacity of retention system above maximum retention capacity of poly(acrylic acid). The increase in the metal-ion retention can be explained via the macromolecular transport of metal-ions through oil phase of double emulsion. In general, a sequence given by linking of metal-ions by the polymer, adsorption of polymer on liquid–liquid interface, transporting of metal-ion and functional group regeneration is suggested and associated to the increases of overall system retention. Combination of water-soluble polymer and double emulsion systems appears as a novel alternative to remove and concentrate pollutant metal-ions in aqueous solution.

Metal ion retention by emulsion liquid membrane coupled to liquid-phase polymer-based retention

The capacity of polyelectrolytes (PELs) to enhance the metal ion retention in a double emulsion system (DES) was studied by diafiltration. Our results indicate that PELs can increase the maximum retention capacity of DES as functional groups of polymer are being saturated. Increase of retention can be explained by interaction between reverse emulsion globules and metal–polymer species formed in solution. Assuming an inert membrane, if the amount of added metal ion is lower than the polymer’s maximum retention capacity, then the retention system behaves as if the polymer was the single retainer element in the filtration cell. For poly(acrylic acid), retention/adsorption and transport/regeneration processes were strongly associated to changes in hydrophilic–lipophilic balance of polymer chains; whereas for poly(vinyl sulfonic acid) and poly(sodium 4-styrensulfonate), these processes were mainly associated to screening of surface charge density of macromolecule in solution.

Metal-ion retention properties of water-soluble amphiphilic block copolymer in double emulsion systems (w/o/w) stabilized by non-ionic surfactants

Metal-ion retention properties of water-soluble amphiphilic polymers in presence of double emulsion were studied by diafiltration. Double emulsion systems, water-in-oil-in-water, with a pH gradient between external and internal aqueous phases were prepared. A poly(styrene-co-maleic anhydride) (PSAM) solution at pH 6.0 was added to the external aqueous phase of double emulsion and by application of pressure a divalent metal-ion stream was continuously added. Metal-ions used were Cu2+ and Cd2+ at the same pH of polymer solution. According to our results, metal-ion retention is mainly the result of polymer–metal interaction. Interaction between PSMA and reverse emulsion globules is strongly controlled by amount of metal-ions added in the external aqueous phase. In addition, as metal-ion concentration was increased, a negative effect on polymer retention capacity and promotion of flocculation phenomena were produced.

Metal Ion Removal Properties of Water‐Insoluble Functional Polymers

AbstractSummary: Resins containing sulfonic acid groups by radical polymerization were synthesized. The metal ion retention properties were studied by batch and column methods for the polluting metal ions Cd(II), Pb(II), and Hg(II).pH exercises an important effect on the retention: the metal ion sorption increases with increases in the pH. The maximum retention capacity was determined after three contacts at optimum pH. Resin R1 obtained the highest value 1.207 mmol/g resin for Cd(II). Different eluent reagents were used to recover the resin. Resin R1 loaded with Pb(II) was completely recovered using 4 M HCl as stripping reagent.

Use of Biopolymers for the Removal of Metal Ion Contaminants from Water

AbstractSummary: Naturally abundant biosorbants such as chitin and chitosan are recognized as excellent metal ligands, forming stable complexes with many metal ions, and serving as effective protein coagulating agents. Chitosan is a heteropolymer made of D‐glucosamine and a small fraction of N‐acetyl‐D‐glucosamine residues. Therefore, the adsorption ability of chitosan is found to be much higher than that of chitin, which has relatively fewer amino groups. Zeolites are crystalline microporous aluminosilicates with ion exchange properties suitable for a wide range of applications in catalysis and separation of liquid and gaseous mixtures. Incorporation in chitosan membranes is an effective method to control the diffusion outside the zeolite crystals and appropriately designed composite systems can find numerous opportunities for applications in wastewater treatment. In this paper we present the synthesis of zeolite‐chitosan and zeolite‐ethyl cellulose composites by encapsulation of clinoptilolite using a gelling solution of chitosan or an ethyl cellulose solution in ethyl acetate. The adsorption process of Cu2+ and Cd2+ on some adsorbents was investigated: clinoptillolite tuff (0.05 mm), chitosan flakes, ethyl cellulose, zeolite‐chitosan and zeolite‐ ethyl cellulose composites. Zeolite‐chitosan composites have been prepared by encapsulation of zeolites by a gelling solution of chitosan. Micrometric crystals of clinoptillolite were dispersed in a 3% chitosan solution in 1% aqueous acetic acid. The chitosan gel was formed and the zeolite crystals were encapsulated during the gelling process. The same procedure was used to obtain zeolite – ethyl cellulose composites. Study of the metal ion retention properties of different adsorbent materials was carried out using a steady state regime. The concentration of heavy metal ions in supernatant was determined by the atomic absorption spectrophotometric method. Adsorption isotherms of metal ions on adsorbents were determined and correlated with common isotherm equations such as Langmuir and Freundlich models.

Polymer enhanced membrane filtration of metals: retention of single and mixed species of metal ions based on adsorption isotherms

The binding and retention of single metal ions and mixtures of metal ions with polyethylenimine (PEI) was studied using polymer enhanced ultrafiltration (PEUF). Using a highly branched chain form of PEI (Sigma Aldrich 181979) with an average molecular weight 750,000 and approximately 60,000, ultrafiltration experiments were carried out in the stirred dead-end ultrafiltration mode. The results of the binding studies show that the Langmuir isotherm offers a good description of the binding process. At pH 5.5, the maximum polymer binding (Q max) and binding affinity constant (K L) were determined according to Langmuir isotherms. It was observed that the maximum amount of metal ions bound to the polymer for Cu2+, Zn2+, Ni2+ and Cd2+ decreased substantially in solutions containing mixtures of metal ions when compared to the values obtained for single metal ion solutions. For Cr6+ and Co2+ no significant decrease was seen. These data indicate that the binding capacity of Cr6+ and Co2+ remain constant in competit...

Separation of lanthanides and actinides on a bistriazinyl pyridine coated reverse phase column

Abstract The retention behaviour of uranium, thorium, americium and lanthanides has been investigated, using a reverse phase C18 column modified with 2,6-bis(5,6-dipropyl-1,2,4-triazin-3-yl)pyridine (n-Pr-BTP) with the aim of investigating rapid lanthanide-actinide separations by HPLC technique. Nitric acid and α-hydroxy isobutyric acid (α-HIBA) have been employed as the mobile phase. The influence of mobile phase pH and concentration on the retention of metal ions has been studied. The aim of this study is to investigate the use of BTP coated reverse phase columns as analytical columns for the fast separation of the minor actinides from the lanthanides in the high-level waste (HLW), and to explore whether such columns can be used on a preparative scale for the purification and the recovery of minor actinides from the high-level waste (HLW). It was observed that reverse phase columns modified with BTP showed greater affinity for actinides but exhibited no retention for lanthanides and the lanthanide-actinide separations could be achieved in nitric acid mobile phase, without the need for complexing agents. Americium was separated from the lanthanides with good peak profile and baseline resolution in both nitric acid as well as α-HIBA as the mobile phase. Based on this, the separation of americium from the lanthanides in the HLW was also demonstrated. The retention of a significant amount of thorium by the column in breakthrough studies also indicated that these columns can be used for preparative scale purification of the actinides.

Polymer-enhanced ultrafiltration: counterion distribution and its relation with the divalent metal-ion retention properties by sulfonic acid polyelectrolytes

The distribution of divalent counterions and its relation with the retention properties of sulfonic polyelectrolytes were analyzed, and the results were interpreted under the light of the counterion condensation theory using two-zone model and Donnan’s equilibria. In this regard, poly(vinyl sulfonic acid) and sodium poly(styrene sulfonate) solutions at pH 6.0 were diafiltered by the liquid-phase polymer-based retention technique. Metal-ion retention and distribution around polyelectrolyte chains were obtained from the diafiltration experiment as well as the maximum retention capacity (MRC) for each polymer. The MRC values obtained were 0.30, 0.15, 0.21, and 0.26 mmol of metal-ion per mmol of polymer for PVSA–Cu2+, PVSA–Cd2+, PSS–Cu2+ and PSS–Cd2+, respectively. The excess of ions added, the volume in the inside cell, and the order of addition of the ions contacted with the polymer were important factors defining the form of the retention profile.

Sorption Properties of Metal Ions onto Poly-.GAMMA.-glutamic Acid Nanofiber

Poly-γ-glutamic acid(γ-PGA)is a natural polymer that is widely recognized as a component in the viscous filaments of fermented soybean (natto). γ-PGA is known for its superior biodegradability‚ biocompatibility‚ water retention and sorption of metal ions. We used oxazoline component polymer(OXA) for crosslinking agent and prepared γ-PGA nanofiber from γ-PGANa by the electrospinning with a non-toxic water solvent system. In this study, we evaluated metal sorption characteristics of γ-PGA/OXA webs. At low concentration solution of copper ions‚ the γ-PGA material dissolved and didn’t cohere‚ but γ-PGA/OXA webs shrank by the sorption of metal ions, and salt precipitated on its surface. When γ-PGA/OXA webs contained OXA with a very small or a large quantity‚ its sorption rate or sorption ability was decreased. A tendency was found to adsorb divalent or trivalent metal ions, and reflect the shrinkage of the γ-PGA/OXA web.

Chemically modified silica gel with thiol group as an adsorbent for retention of some toxic soft metal ions from water and industrial effluent

In this study, functionalized silica with mercaptopropyl groups were synthesized. These materials have been characterized by powder X-ray diffraction and FT-IR spectroscopy. We have shown that silica gel (SG) particles with a surface functionalization of thiol group (S–H) are an effective adsorbent material for toxic soft metal ions such as Hg 2+, Pb 2+ and Cd 2+, which effectively bind to the thiol ligands. The ability of the thiol modified silica gel (TMSG) to remove heavy metal ions was studied by the method of continuous variation of two process variables: Initial heavy metal concentration (mg L −1) in distilled water and the contact time of adsorbent and solutions in water and industrial effluent. The experimental data were fitted into three kinetic models: Lagergren, pseudo-second order and Elovich. The experimental isotherm data were analyzed using Langmuir, Freundlich, Sips, Redlich–Peterson and Temkin isotherms. Six error functions were used to treat the adsorption data using nonlinear optimization techniques for evaluating the fit of the model equations. Error analysis showed that the Langmuir and Redlich–Peterson isotherms best fit the ions adsorption data on TMSG and the pseudo-second order kinetic model described the adsorption process.

Characterization and use of Moringa oleifera seeds as biosorbent for removing metal ions from aqueous effluents

Moringa oleifera seeds were investigated as a biosorbent for removing metal ions from aqueous effluents. The morphological characteristics as well as the chemical composition of M. oleifera seeds were evaluated using Fourier Transform Infrared (FT-IR) Spectroscopy, Thermogravimetric Analysis (TGA), X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The FT-IR spectra showed the presence of lipids and protein components. Scanning electron micrographs showed that Moringa seeds have an adequate morphological profile for the retention of metal ions. The results suggest that M. oleifera seeds have potential application in Cd(II), Pb(II), Co(II), Cu(II) and Ag(I) decontamination from aqueous effluents.