The effect of salinity on the capacity and selectivity of ion exchange resins for gold cyanide

Despite the success of several resin-in-pulp pilot plant operations in the Western World and large scale plants in the former Soviet Union the process of extracting gold from slurries using ion exchange resins is yet to gain recognition as a viable alternative to the carbon-in-pulp process. An experimental research program has investigated the potential use of anion exchange resins containing a variety of quaternary ammonium functional groups in highly saline process water such as that found in Western Australia. The effect of univalent and bivalent ions on gold adsorption has been studied. It was shown that the selectivity of the resin for gold cyanide was enhanced with increasing ionic strength. It has been proposed that the degree of hydration, polarisation and size of the adsorbing species are factors that contribute to the observed change in selectivity of the ion exchange resin at different salinity. It was observed that in highly saline solutions copper cyanide did not load significantly on any of the experimental resins studied. Furthermore, it has been shown that an existing commercial non-selective resin loads no significant amount of copper cyanide under saline conditions. It is proposed that the apparent change in selectivity of resins for gold cyanide is caused by anions that have a stronger affinity for the resin in these highly non-ideal solutions as well as a possible change in the distribution of copper cyanide complexes in solution. The results of this study demonstrate that the selectivity of ion exchange resins in highly saline water is significantly improved and as a consequence the resin-in-pulp process may be more efficient than carbon-in-pulp in process streams of high salinity.