Efficiency and mechanism of macroporous poly(vinylthiopropionamide) chelating resin for adsorbing and separating noble metal ions and determination by atomic spectrometry

Abstract

A macroporous poly(vinylthiopropionamide) chelating resin was synthesized from spherical poly(vinyl chloride) resin particles and used for the enrichment and separation of trace noble metal ions. Trace Au(III), Pt(IV) and Pd(II) in sample solutions can be enriched quantitatively in the range 5 M HClpH 9 with recoveries > 96%, and the recovery of trace Ir(IV) at pH 1–9 was > 93%; however, the adsorption of Rh(III) and Ru(III) at pH 3–6 was < 16%. When Au, Pt, Pd and Ir ions were adsorbed by the resin at a flow-rate of 4 ml min −1, the recoveries of Au, Pt, Pd eluted with 6% thiourea-1 M HCl and Ir with 6 M HCl were > 96%. The adsorption capacity of the resin was 978 ng g −1 for Au, 288 mg g −1 for Pt, 455 mg g −1 for Pd and 10 mg g −1 for Ir. When the resin was reused ten times, the recoveries of the above ions on enrichment were still > 92% and a 100-fold excess of other ions caused little interference in the determination of the ions. The eluted ions were determined by inductively coupled plasma atomic emission spectrometry (ICP-AES). The lowest concentrations determined were 0.040 μg ml −1 for Au, Pt and followed by Zeeman-effect atomic absorption spectrometry or ICP-AES were in good agreement with the certified values. The structures of the resin, investigated by Fourier transform IR spectrometry and electron spectroscopy revealed that Au, Pt and Pd ions were chelated mainly with the thioketo form of the thiorpropionamide group in the resin, forming a quadridentate chelate.