Separation of platinum, palladium and rhodium from aqueous solutions using ion exchange resin: A review

Preconcentration and separation of palladium(II) and platinum(IV) on a dithizone anchored poly(vinylpyridine)-based chelating resin

Dithizone, one of the specific reagents for the determination of gold, was coupled to cross-linked poly(vinylpyridine) and was used for the preconcentration of nanogram levels of gold. The polymeric support was characterized as regards the extent of dithizone coupling and its thermal properties. The support was also used under batch and column conditions for the preconcentration of gold. Various conditions such as pH, temperature, flow rate and column parameters were optimized for the maximum amount of gold loading. A gold loading of 240 mg per gram of support was achieved under the optimized conditions. Mixtures of 0.2 mol dm–3 HCl and 2.0% thiourea (1 + 1) and of 5.0 mol dm–3 HCl and 1.0 mol dm–3 HNO3(1 + 1) could elute gold quantitatively. Separation of gold from binary and ternary mixtures of platinum, copper and mercury was achieved without any cross-contamination.

Dithizone-anchored poly(vinylpyridine) as a chelating resin for the preconcentration and separation of gold(III) from platinum(IV), copper(II) and mercury(II)

A novel 1,2,4,5-tetrazine functionalized polymer P-Tz was successfully synthesized by the reaction of an aminomethylated macroporous polystyrene-DVB-copolymer (P-Am) with 3-bromo-6-phenyl-1,2,4,5-tetrazine. The proposed structure of the functional groups of P-Tz was confirmed by synthesis of the model compound benzyl-(6-phenyl-1,2,4,5-tetrazine-3-yl)-amine and comparative FTIR-spectroscopic investigations. An application of P-Tz as a redox polymer is not possible due to the cleavage of the tetrazine groups under reducing conditions. Metal sorption and desorption studies of the resin P-Tz were carried out and the results compared with the properties of the weak base anion exchanger P-Am. Evidence is given that the secondary amine spacer of P-Tz influences markedly its over all sorption properties, i.e., the tetrazine-modified resin shows in dilute hydrochloric acid typical anion-exchange properties towards precious metal ions. Compared with the starting polymer P-Am the selectivity sequence found for P-Tz, Pd(II) > Au(III) ⪢ Ir(IV) > Os(IV) > Pt(IV) > Ru(III) > Rh(III), revealed a significantly higher selectivity for Pd(II) which is established even in the presence of an excess of base metals. The results of desorption studies obtained by applying perchloric acid and thiourea as eluting agents led to the assumption that palladium is strongly N-coordinated by the functional tetrazine groups and the secondary amine spacer as well. This hypothesis is confirmed by the structural characterization of a Pd(II)-chelate which is formed during solvent extraction using a monomolecular tetrazine analogue.

Synthesis and characterization of a 1,2,4,5-tetrazine-modified ion-exchange resin

We report on the synthesis and reactivity of a polymer-supported o-phenylenediamine hydrochloride ligand, PS-PDHC, using macroporous 6% crosslinked polystyrene-divinylbenzene beads The PS-PDHC ligand was found to be highly selective to AuCl4− ions in strongly acidic solutions in the presence of other precious metal ions, PdCl42−, PtCl42−, RhCl63−, and RuCl52− (selectivity values: 25, Au/Pd; 75, Au Pt ; 7, Au Rh ; 22, Au Ru ) as well as other transition metal ions, Fe 3+, Cr3+, CU2+, Nit+, and Mn2+ The sorption capacity, selectivity, kinetics of removal and recovery, and solution isotherms have been determined for AuCl4− ions in competition with the above-mentioned metal ions The relative ease of formation of the anionic complex in 05 M HCI, AuCl4− was thought to be the primary reason for its selective ability to bind to the PS-PDHC ligand by an anion-exchange mechanism Therefore, the effect of the HCI concentration on the kinetics of AuCl4− ion removal from solution was also investigated to clearly show that raising the pH from 0 to 5 caused a dramatic decrease in rate The AuCl4− ion can be recovered quantitatively from the PS-PDHC beads using a 5% thiourea solution in 01 M HCl, allowing the polymer-supported ligand to be reused

Polymer pendant ligand chemistry, 4. Recovery of precious metal ions from strongly acidic solution with a polymer-supported o-phenylenediamine hydrochloride ligand

Studies on macroporous cross-linked polyacrolein-styrene resin I. Synthesis of polyacrylic aldehyde-hydrazone and polyacrolein-phenylhydrazone resins and their chelating properties for gold and platinum group metals

A. Kettrup

Papers

Studies on macroporous cross-linked polyacrolein-styrene resin I. Synthesis of polyacrylic aldehyde-hydrazone and polyacrolein-phenylhydrazone resins and their chelating properties for gold and platinum group metals