Novel resins for the selective extraction of gold from copper rich ores

The recovery of gold from copper rich ores proves problematic when conventional cyanidation and commercially available standard or gold selective resins are employed. The use of ammonia/cyanide as the lixiviant enhances gold leaching and much improved gold recoveries are possible when a specially designed resin is employed. By considering the geometry of the metal cyanide/ammonia complexes present it was possible to design and prepare a resin with a suitably hindered cationic site. Successful synthesis of the resin was confirmed by microanalysis, IR and NMR spectroscopy, and ion exchange techniques. Testing this new resin with conventional cyanide leachates and with ammonia/cyanide leach solutions revealed selectivities in the range 0.88 to 0.96 for the conventional solution and 11 to 19 for the ammonia/cyanide system, with excellent gold loadings. These values can be compared to conventional and current gold selective resins which have selectivity ratios for these solutions of 0.3 to 0.7 and 1 to 3 respectively. Once loaded, this new resin could be fully eluted in less than ten bed volumes of eluent, while retaining its loading and selectivity characteristics. The effects of different resin matrices were also investigated.