THE CHARACTERISATION OF SILVER SORPTION BY CHELATING RESINS CONTAINING THIOL AND AMINE GROUPS

Abstract

We investigated the sorption capacity towards Ag(I) of three different resins bearing a thiol chelating group, Duolite GT-73, Purolite Thiomethyl and Spheron Thiol, as well as Chelamine, a resin with a tetraethylenepentaamine moiety. The metal sorbed by the resins at 0.01 M HNO₃ follows the order: Purolite Thiomethyl > Duolite GT-73 > Spheron Thiol. As this result does not correlate with the sulphur content of each resin we studied the physical characteristics of the resins in an attempt to find an explanation for this behaviour. In the case of Chelamine, a nitrogen containing resin, silver sorption increases when pH increases, reaching a value of 1.2 mmol/g at pH around 6. A kinetic study of the three polymers with the same functional group (–SH) was also performed in order to discover more about the sorption mechanism. The differences observed between the three polymers are explained taking into consideration the nature of the polymeric matrix and the resin morphology. Finally, we study the elution process of silver and find that, with each resin, thiourea 0.1 M in HNO₃ 0.1 M is the most effective elution agent.