Studies on syntheses and properties of chelating resins based on chitosan

Chelating resins have some good adsorption properties for some metal ions, especially for several noble metal ions. Thus to retrieve rare metals using chelating resins is always an interesting project for chemistry researchers. In this study we synthesized a series of chelating resins based on chitosan and investigated adsorbing capacities, adsorption rates, and adsorption selectivities for Ag(I), Au(III), Pd(II), Pt(IV), Cu(II), Hg(II), and Zn(II). The results indicate that the resins have remarkable adsorbing capacities and adsorption rates for four noble metal ions and Hg(II). For instance, one of the resins adsorbs Au(III) and the adsorbing capacity is up to 7.11 mmol/g. However, the adsorbing capacities of the resins for Cu(II) and Zn(II) are much less than for the noble metal ions. Finally, x-ray photoelectron spectroscopy studies of a chelating resin and its metal chelates were made. The result reveals that the basis of the chelations is a chemical process. © 1996 John Wiley & Sons, Inc.     

The Application of 2,6-Bis(4-Methoxybenzoyl)-Diaminopyridine in Solvent Extraction and Polymer Membrane Separation for the Recovery of Au(III), Ag(I), Pd(II) and Pt(II) Ions from Aqueous Solutions

The work describes the results of the first application of 2,6-bis(4-methoxybenzoyl)-diaminopyridine (L) for the recovery of noble metal ions (Au(III), Ag(I), Pd(II), Pt(II)) from aqueous solutions using two different separation processes: dynamic (classic solvent extraction) and static (polymer membranes). The stability constants of the complexes formed by the L with noble metal ions were determined using the spectrophotometry method. The results of the performed experiments clearly show that 2,6-bis(4-methoxybenzoyl)-diaminopyridine is an excellent extractant, as the recovery was over 99% for all studied noble metal ions. The efficiency of 2,6-bis(4-methoxybenzoyl)-diaminopyridine as a carrier in polymer membranes after 24 h of sorption was lower; the percentage of metal ions removal from the solutions (%R_s) decreased in following order: Ag(I) (94.89%) > Au(III) (63.46%) > Pt(II) (38.99%) > Pd(II) (23.82%). The results of the desorption processes carried out showed that the highest percentage of recovery was observed for gold and silver ions (over 96%) after 48 h. The results presented in this study indicate the potential practical applicability of 2,6-bis(4-methoxybenzoyl)-diaminopyridine in the solvent extraction and polymer membrane separation of noble metal ions from aqueous solutions (e.g., obtained as a result of WEEE leaching or industrial wastewater).     

Synthesis and adsorption properties of magnetic resin microbeads with amine and mercaptan as chelating groups

Three magnetic chelating resins containing amino and mercapto groups were prepared by the suspended condensation polymerization of 2‐chloroethoxymethyl thiirane with diamines. The magnetic resins were microbeads whose diameter was in the range of 10 to 45 μm. The structure of the resins was characterized by XPS, IR, and elemental analysis. Their adsorption properties for Hg(II), Au(III), Pd(II), Pt(IV), Ag(I), Cu(II), Zn(II), and Pb(II) were investigated. The experimental results show the magnetic resins have high affinity for Hg(II) and noble metal ions. In the competitive adsorption, the resins predominantly adsorbed Hg(II) or Pd(II) in the coexistence of Cu(II), Zn(II), and Mg(II). Desorption of Pd(II) loaded on the resins was studied by using 2M hydrochloric acid solution containing 1% thiourea as desorbent. A high desorption ratio (up to 96.5%) was observed, and repeated adsorption/desorption operations showed the probability of repeated use of the magnetic resins. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1587–1592, 2001     

A preliminary evaluation on the use of the cyclam functionalized resin for the noble metals sorption

A new resin has been prepared through a reaction between the vinylbenzyl chloride–divinylbenzene copolymer and the 1,4,8,11-tetraazacyclotetradecane (cyclam). This resin has been investigated after the characterization of the FTIR, batch and the dynamic sorption behavior of Au(III), Pt(IV) and Pd(II) ions took place. The sorption has been optimized with respect to HCl solutions. The maximum sorption properties were achieved from the solution of 0.1 M HCl. The sorption of Au(III), Pt(IV) and Pd(II) ions during a dynamic procedure in the presence of the 20-fold excess metals i.e. Cu, Fe, Ni resulted in an outcome of up to 400 mg of noble metals per gram of dry resin. The study of the noble metal loading was carried out over a wide range of the HCl concentration and in media of various multicomponent solutions of common metals.     

NEW XANTHIC ACID DERIVATIVES AS POTENTIAL REAGENTS IN THE SOLVENT EXTRACTION OF PRECIOUS METAL IONS: EXTRACTION OF PALLADIUM(II) WITH 13-BIS(0-BUTYLXANTHATO)PROPANE

ABSTRACT

Two series of new xanthic acid derivatives namely, the bis (O-butylxanthato) alkanes ( abbreviated as BBXAs or simply as bis-xanthates in this paper) have been synthesized in connection with the solvent extraction of precious metal ions. From an aqueous medium containing 0.1 M NaC10₄ (1 M=l mol dm^-3), these compounds exhibited high selectivity for extraction of Pd(II) and Ag(I) in dichloroethane, over most of the base metals as well as Pt(IV) and Au(III) ions. Towards Pd(II) and Ag(I) ions, the bis compounds act as SS chelating agents where the stabilities of the extractable complexes are determined by the length of the alkylene chain existing between the donor atoms. Pd(II) extraction has been studied in detail taking 13-bis(O-n-butylxanthato)propane (BnBXP) as the representative member of the series of bis-xanthates synthesized in this work. The extraction of palladium(II) was found to be quite slow in pure chloride medium. But, a mixed acid medium containing H₂SO₄ or HNO₃ in the presence of smaller amount of chloride ion provided optimum reversible extraction of palladium in dichloroethane, where Pd(II) forms 1:1 extractabic complexes with BnBXP. Pd(II) extraction is described in terms of the aqueous phase compositions, extraction and back-extraction data, extraction equilibrium, selectivity considerations and probable mechanisms of extraction.     

Synthesis and properties of poly-Schiff base containing bisthiazole rings

Poly-Schiff base containing bisthiazole rings (TAPDA) has been prepared from terephthalaldehyde and 2,2′-diamino-4,4′-bisthiazole. It was found that the TAPDA polymer film is permeable to H₂, O₂, and N₂ and can be converted into an electrical conductor by pyrolysis at high temperature in nitrogen. TAPDA is a novel chelate polymer. The complex of Cu(II) with TAPDA was readily obtained; and the noble metal ions Au(III), Pt(IV), Pd(II), and Ag(I) can be adsorbed quantitatively by the TAPDA powder. © 1997 John Wiley & Sons, Inc. J Appl Polym Sci 64: 2309–2315, 1997     

Polyacrylate Ion Exchangers in Sorption of Noble and Base Metal Ions from Single and Tertiary Component Solutions

Two polyacrylic resins of different types such as Purolite S-984 (macroporous, chelating with a polyacrylic matrix supporting functional groups of the polyamine type) and Amberlite IRA-478RF (gel, intermediate polyacrylic anion exchanger with the tertiary amine and quaternary ammonium functional groups) were applied in removal of palladium(II) metal ions from HCl and HCl – HNO₃ solutions. Its sorption behaviors for base (Co(II), Ni(II), Cu(II), Ni(II)) and other noble metal (Pt(IV), Au(III)) ions, kinetics, and equilibrium studies were carried out in detail. The obtained results indicate that the resin is characterized by high sorption capacity and good kinetics of the sorption process. For the elution, the solutions of various reagents, that is, HCl, HNO₃, H₂SO₄, NaOH, NH₄OH, (NH₂)₂CS were studied as regards the complete release of the metal ions retained by the resin. Gold(III) could be eluted quantitatively from the loaded resin whereas Pd(II) and Pt(IV) could not by means of the applied eluting agent.     

Electrolyte solutions in liquid ammonia—IX. Electrodeposition and electrodissolution of metals from their salts

Anodic dissolution and cathodic deposition of 20 transition metals in acidic solutions in liquid ammonia has been surveyed. The early transition metal elements Ti, Zr, V Nb, Mo and W form high oxidation-state insoluble amido complexes during anodic oxidation. Soluble ammines of normal metal oxidation states are produced with Cr(III), Mn(II), Fe(II), Co(III), Ni(II), Cu(II), Ag(I), Zn(II), Cd(II) and Hg(II) (Mn dissolves spontaneously). The metals Ru, Pd, Pt and Au only dissolve slightly after prolonged electrolysis. Anodic enrichment of Au in its alloys is unlike that in aqueous solution; in ammonia both Cu and Ag can be simultaneously depleted from a 9 carat gold alloy. Cathodic reduction of metal-bearing solutions follows wide variations of behaviour. Fe and Ru ammines reduce to amido-complexes with concomittant hydrogen evolution, but Cr is not reduced. Solutions of Mn, Co, Ni, Pd, Pt, Ag, Au, Zn, Cd and Hg give metallic cathode deposits under differing conditions. Electrodeposition is potential dependent for Ni, Cu and Ag; metal plate at low potentials, and powders at high potentials. The two different products are the result of reduction of species with different degrees of solvation.     

Quaternary Amine Modified Persimmon Tannin Gel: An Efficient Adsorbent for the Recovery of Precious Metals from Hydrochloric Acid Media

Persimmon tannin was chemically modified to prepare a quaternary amine type of adsorption gel, named as quaternary amine modified persimmon tannin (QAPT) gel. The QAPT gel has been used to investigate the adsorption behaviors for Au(III), Pd(II), and Pt(IV) from HCl media. It was found that the gel exhibited good selectivity towards precious metals over a wide concentration range of HCl. However, it exhibited poor affinity towards base metals such as Cu(II), Fe(III), Ni(II), and Zn(II). The adsorption isotherms of the gel for precious metal ions were described by the Langmuir model. The maximum adsorption capacities for Au(III), Pd(II), and Pt(IV) were evaluated as 4.16, 0.84, and 0.52 mmol g^?1, respectively. Although the anion exchange is the main mechanism for the adsorption of anionic species of Au(III), Pt(IV), and Pd(II), adsorption of Au(III) is followed by subsequent reduction, which results in the extraordinary high adsorption capacity for Au(III). Adsorption behavior of QATP gel for Au(III) was also compared to that of the persimmon tannin, the feed material.     

Reactive polymers, 47. Sorption properties of the reaction product of macroporous poly (glycidyl methacrylate-co-ethylene dimethacrylate) with 8-aminoquinoline

The sorption of Fe(III), Al(III), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Au(III), Pd(II), Pt(IV), and Hg(II) ions on a sorbent prepared by reacting the copolymer of glycidyl methacrylate and ethylene dimethacrylate with 8-aminoquinoline was investigated. Gold and palladium are strongly absorbed in hydrochloric acid. Results of static and dynamic tests indicate the possibility of separation of Au(III) and Pd(II) from Pt(IV) and from the other metal ions investigated in the study. The sorption of Hg(II) by the polymer increases in nitric acid.     

Adsorption of Silver and Gold Ions from their Aqueous Solutions using a Magnetic Chelating Resin Derived from a Blend of Bisthiourea/Thiourea/Glutaraldehyde

A magnetic chelating resin was obtained from copolymerization of a blend of bisthiourea/thiourea/glutaraldehyde in the presence of magnetite (Fe₃O₄). The uptake of Ag(I) and Au(III) by the resin using batch and column techniques was studied. The maximum uptake capacity showed 6.2 and 5.78 mmol/g for Ag(I) and Au(III), respectively. Breakthrough curves showed critical bed height values of 0.03 cm and 0.04 cm for Ag(I) and Au(III), respectively, indicating the higher affinity of resin to Ag(I) relative to Au(III). Regeneration of the resins was achieved using acidified thiourea at efficiency of 98% over five cycles with no appreciable change in durability. The investigated resin was found to be able to remove 13 different metal ions from a real wastewater matrix at efficiency of 91%.     

Preparation and adsorption properties of chelating resins from thiosemicarbazide and formaldehyde

A novel chelating resin was synthesized in just one step under mild synthetic conditions. The synthesis was carried out through the copolymerization of thiosemicarbazide and formaldehyde in an aqueous solution. The adsorption properties for some noble metal ions were investigated. The results showed that the resin had high adsorption selectivity for Au(III) and Ag(I). The adsorption capacities for the two metal ions reached up to 7.3 and 11.8 mmol/g, respectively. The adsorption rate for the two metal ions in a dilute solution was 99.9%. The adsorption fit first‐order kinetics, and an isothermal adsorption study indicated that it corresponded to Langmuir monomolecular layer adsorption. The change in the bonding energy during the chelating process was investigated with X‐ray photoelectron spectroscopy. The study revealed that nitrogen and sulfur atoms of the resins were electron donors and metal ions were electron acceptors in the process. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

CHARACTERISATION OF METALFIX-CHELAMINE AND ITS APPLICATION IN PRECIOUS METAL ADSORPTION

ABSTRACT

The physical and chemical characteristics of the chelating resin Chelamine, which contains a pentamine ligand, are investigated in order to consider its application in the separation of precious metals- Adsorption isotherm experiments for Pt, Pd and Au and kinetic experiments were carried out under batch procedures. The resin presents a high level of adsorption selectivity for Pt(IV), Au(III) and Pd(II) giving a capacity of 2.8 mmol/g, 3.1 mmol/g and 2.0 mmol/g respectively. Acidic solutions, complexing agents, lipophilic anions and ammonia were used for metal elution. NaClO₄ solutions are the most effective eluting agents for Pt(IV) while thiourea is the best stripping agent for both Pd(II) and Au(III). Selective separation of the three metals can be achieved by sequential elution from the resin with NaClO₄ solutions in different HCl concentrations and thiourea 0.5 M.     

LIQUID-LIQUID EXTRACTION OF Ag(I), Hg(II), Au(III) AND Pd(II) BY SOME OLIGOTHIA MACROCYCLIC LIGANDS INCORPORATING AROMATIC AND HETEROAROMATIC SUBUNITS*

ABSTRACT

A series of hydrophobic tri- to hexa-dentate sulfur containing macrocyclic ligands incorporating aromatic and heteroaromatic subunits have been studied with respect to their extraction properties toward Ag(I), Hg(II), Au(III), and Pd(II) in aqueous//organic systems. The stoichiometry of extracted species and their extraction constants have been determined. The different ligands are compared with structure related open-chain compounds. The influence of substitution, solvent, and anion on the extraction equilibrium is also discussed providing a basis for future design of selective extractants and for die development of improved separation methods. The extractability of the various metal ions strongly depends on the nature and the number of donor atoms of the corresponding ligands and on the properties of the metal ion itself. In some cases, simple open-chain ligands show extraction properties comparable to the present macrocycles. A trithia crown with incorporated benzo subunit highly prefers Ag(I) to Hg(II). Furthermore a distinct selectivity for Au(ni) and Hg(II) over Pd(II) with pyridine substituted macrocycles was found.     

Properties and application of poly(acrylphenylamidrazone‐phenylhydrazide) chelating fiber for enrichment–separation of trace gold and ruthenium from solution samples

An ICP‐OES method using a new poly(acrylphenylamidrazone‐phenylhydrazide) chelating fiber to enrich and separate trace Au(III) and Ru(III) ions from solution samples is established. The results show that 50–500 ng/mL of Au or Ru ions can be enriched quantitatively by 0.1 g of the fiber at pH 4, with recoveries > 96%. The ions can be desorbed quantitatively with 10 mL of 4 M HCl and 3.0% CS(NH₂)₂ solution from the fiber column, with recoveries > 97%, and 200–1000‐fold excesses of Cu(II), Zn(II), Ca(II), Mg(II), Mn(II), Cr(III), Fe(III), Ba(II), and Al(III) caused little interference in the determination of these ions by ICP–OES. The chelating fiber can be reused eight times, and the recoveries are all > 95%. The relative standard deviations for enrichment and determination of 50 ng/mL of Au and Ru are in the range 1.8–1.9% (1.9% for Au and 1.8% for Ru). The recoveries of trace Au and Ru ions added to real waste water and alloy samples are 96–98%. The concentration of each ion found in the alloy samples was in good agreement with that provided by the plant. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 81: 2656–2660, 2001     

Syntheses and characterization of polystyrene‐supported 2,5‐dimercapto‐1,3,4‐thiodiazole and its sorption behavior for Pd(II), Pt(IV), and Au(III)

A type of chelating resin crosslinking polystyrene‐supported 2,5‐dimercapto‐1,3,4‐thiodiazole (also called bismuththiol I, BMT), containing sulfur and nitrogen atoms, was prepared. The structure of PS‐BMT was confirmed by FTIR, elemental analysis, and X‐ray photoelectron spectroscopy (XPS). Adsorption of Pd(II), Pt(IV), and Au(III) was investigated. The capacity of PS‐BMT to adsorb Pd(II) and Pt(IV) was 0.190 and 0.033 mmol/g, respectively. The adsorption dynamics of Pd(II) showed that adsorption was controlled by liquid film diffusion and that the apparent activation energy, E_a, was 32.67 kJ/mol. The Langmuir model was better than the Freundlich model in describing the isothermal process of Pd(II), and the ΔG, ΔH, and ΔS values calculated were ?0.33 kJ/mol, 26.29 kJ/mol, and 87.95 J mol^?1 K^?1, respectively. The mechanisms of adsorption of Pd(II), Pt(IV), and Au(III) were confirmed by XPS. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 631–637, 2006     

Studies of syntheses and adsorption properties of chelating resin from thiourea and formaldehyde

Chelating resins are useful substances in industry because of their extraordinary adsorption properties for specific metal ions. In this study, a new type of chelating resin is synthesized simply by reaction between thiourea and formaldehyde. The synthetic conditions and the structure of the product are approached and the adsorbing capacities for 11 metal ions, adsorbing rates, and selectivities investigated. The results of the experiments show that the resin has high adsorbing capacities for Ag(I): 13.1 mmol/g, and for Au(III): 6.95 mmol/g. Adsorbing rates are close to 100% in dilute solution. Isothermal adsorbing study reveals that the adsorption is monomolecular layer adsorption process. It is hopeful for the resin to be used for concentrating and retrieving Ag(I) and Au(III) ions from their dilute solutions in industry. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 3127–3132, 2001     

Synthesis,characterization and polychelatogenic properties of poly[(2‐acrylamido‐2‐methyl‐1‐propane sulfonic acid)‐co‐(methacrylic acid)]

Poly(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid), poly(methacrylic acid), and five copolymers of poly[(2‐acrylamido‐2‐methyl‐1‐propanesulfonic acid)‐co‐(methacrylic acid)] were synthesized by radical polymerization and obtained in yields >97%. The polymers were characterized by FT‐IR, [¹H]NMR, and [¹³C]NMR and studied by means of the Liquid‐phase Polymer‐based Retention (LPR) technique. The metal ion retention ability of the copolymers for Cu(II), Cd(II), Co(II), Hg(II), Ni(II), Zn(II), Cr(III) and Ag(I) was investigated at different pH values because of their environmental and analytical interest. The retention profiles of the copolymers were compared with those of the corresponding homopolymers and retention of metal ions was found to increase with increasing pH. © 2001 Society of Chemical Industry     

Synthesis of chemically modified chitosan with 2,5‐dimercapto‐1,3,4‐thiodiazole and its adsorption abilities for Au(III), Pd(II), and Pt(IV)

A new chemically modified chitosan hydrogel with 2,5‐dimercapto‐1,3,4‐thiodiazole (CTS‐DMTD) has been synthesized. The structure of CTS‐DMTD was confirmed by elemental analysis and FTIR. It was found that adsorption capacities were significantly affected by the pH of solution, with optimum pH values of 3.0 for Au(III), 2.0 for Pd(II) and Pt(IV). The saturated adsorption capacities were 198.5 mg/g for Au(III), 16.2 and 13.8 mg/g for Pd(II) and Pt(IV), respectively. Langmuir and Freundlich isotherm adsorption models were applied to analyze the experimental data. The results showed that adsorption isotherms of Pd(II) and Pt(IV) could be well described by the Langmuir equation. The adsorption kinetic investigations indicated that the kinetic data correlated well with the pseudo‐second‐order model. The recovery experimental data showed that CTS‐DMTD had a higher affinity toward Au(III), Pd(II), and Pt(IV) in the coexistence system containing Cu(II), Fe(III), Cd(II), Ni(II), Mg(II), and Zn(II). The studies of desorption were carried out using various reagents and the optimum effect was obtained using thiourea. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009     

The Interaction of Noble Metal With La1–xSrxMnO3 (001) Surface and Catalytic Role for Oxygen Adsorption: A Density Functional Theory Study

Adsorption mechanisms of noble metals (Ag, Pd, Pt) on MnO₂‐terminated (001) surface and their catalytic role for oxygen adsorption have been investigated using the first‐principles density functional theory calculations. The analysis of the adsorption energies reveals that the energetically favorable configuration for Ag and Pd adsorption is at the O site, whereas one for Pt adsorption is at the Mn site. Pt atom exhibits the largest adsorption energy, followed by Pd and Ag atoms. Both bond population and PDOS (partial density of states) analysis confirm the formation of adatom–O–Mn bonds. Adsorption is accompanied by a charge transfer between adatoms and surface atoms. Significantly, we predict that the order on the increase of O₂ adsorption energy follows the Pd > Ag > Pt due to pre‐adsorbed noble metal atoms. The calculated bond length and bond population of O₂ molecule demonstrate that pre‐adsorbed noble metal atoms facilitates O₂ molecule dissociate to O atoms, thus contributing to the surface oxygen diffusion process. Our calculations identify an important catalytic role of noble metal in LSM‐based catalysts, which may improve electrochemical performance for SOFCs cathodes.