The Uptake of Gold(I) from Ammonia Leaching Solution by Imidazole Containing Polymeric Resins

Abstract

The polymeric resins containing guanylthiourea, 1-methylimidazole, 2-mercapto-1-methylimidazole ligands have been synthesized from vinylbenzyl chloride-divinylbenzene copolymers and used in the removal of Au(I) from ammonium buffer and ammoniacal thiosulphate solutions. The best gold sorption from ammonium buffer that contains 100 g/dm³ NH₃ · H₂O and 5 g/dm³ (NH₄)₂SO₄, is reached in the case of 1-methylimidazole resin (2) (27.9 mg/g) and all three resins do not have a measurable sorption of copper(II) ammine complexes. The resins display a higher affinity towards gold(I) from ammoniacal thiosulphate solutions than from the ammonium buffer solution. The XPS analysis of gold loaded resins suggests the presence of gold at Au(I) oxidation state, most likely in the form of ionic pair Au(NH₃)₂ ⁺OH⁻ or neutral complex AuNH₃OH and as highly-dispersed metallic gold. The degree of gold desorption is about 50% using 1% potassium cyanide solution in 0.3% hydrogen peroxide solution. Resins retain their capacity towards gold in five consecutive sorption/desorption cycles.

Keywords:

• Desorption
• gold(I)
• imidazole complexes
• polymeric resins
• sorption

ACKNOWLEDGEMENT

We thank Polish Committee for Scientific Research for supporting this work through grant 1 T09B 101 30.