Removal of cyanide and zinc-cyanide complex by an ion-exchange process

Removal efficiencies of cyanide and a zinc-cyanide complex in solutions were studied by using an ion-exchange process at pH 10.0 and 12.0. An anion-exchange resin, AMBERLITE (R) IRA-402 Cl, was used to perform packed bed continuous experiments. For the initial 200 mg/l cyanide solution, the packed bed gave a cyanide effluent concentration of 0.2 mg/l at 80 bed volumes for both pH 10.0 and 12.0. Comparatively, in the mixture of 200 mg/l cyanide and 100 mg/l zinc, packed bed volumes were obtained as 80 and 90 at pH 10.0 and 12.0, respectively, to have 0.2 mg/l cyanide effluent concentrations. The packed beds were exhausted at 250 and 400 bed volumes for cyanide and zinc-cyanide complex solutions, respectively. Speciation calculations in Zn(II)/cyanide/OH(-) were used to interpret the results. The exchange capacities of the resin were determined as similar to 1.2 and similar to 0.9 meq/ml resin for cyanide and zinc-cyanide complex solutions, respectively, and were independent of pH in the studied pH range.