The speciation of gold and copper cyanide complexes on ion-exchange resins containing different functional groups

Abstract

Despite the work of many researchers on the use of ion exchange technology for the recovery of gold from cyanide leached slurries, very little work has considered the effect that the chemical structure and hydrophilicity of the functional group may have on the speciation of the sorbed metal cyanide species. The present study investigated the properties of five resins that have the same type of resin matrix but contain a different aliphatic amino functional group. The tested resins include a variety of predominantly weak base resins that contain a small amount of strong base groups. These types of resin are similar to those that are currently being used in resin-in-pulp processes in the former Soviet Union for the recovery of gold (AM-2B). This study used CP/MAS 13C-NMR to determine the chemical structure of the functional group on each synthesised resin. Raman spectroscopy was used in conjunction with FTIR spectroscopy to determine the speciation of copper(I)–cyanide and gold(I)–cyanide on each resin studied. Despite the equilibrium distribution of copper cyanide species in solution it was established that [Cu(CN) 3] 2− predominantly loaded onto all resins studied. However, for resins of a low ionic density the sorption of [Cu(CN) 2] − was also observed. Raman spectroscopy showed that gold cyanide loads onto each resin as the linear [Au(CN) 2] − complex and that no change in speciation was observed in highly saline solutions. The observed phenomena have been used to successfully explain the selective sorption properties of each resin in non-saline and highly saline solutions.