Processing of residual gold (III) solutions via ion exchange

The processing of gold (III)-hydrochloric acid solutions by the anionic ion exchange Lewatit MP-64 resin has been investigated. The influence of several variables such as the temperature, the hydrochloric acid and metal concentrations in the aqueous solution and the variation of the amount of resin added has been studied. Moreover, a kinetic study performed in the uptake of gold (111) by Lewatit MP-64 shows that either the film-diffusion and the particle-diffusion models fit the adsorption process on the resin. Results obtained from batch experiments were applied to a continuous system using a vertical column. The loaded resin could be eluted by an acidic thiourea solution at 20 degrees C Various systems were investigated to precipitate gold from eluants, only the use of sodium borohydride allowed to accomplish the recovery of the metal from the pregnant solutions. Gold was recovered as fine particles, which were characterised by means of optical and scanning electron microscopy.