Removal of mercury from gold cyanide solution by dissolved air flotation

The removal of mercury from mercury cyanide complexes from the processing streams of gold cyanidation circuits was studied by dissolved air flotation (DAF) at laboratory scale. Selective aggregation of mercury was carried out after precipitation of the complexes with sodium dimethyl dithiocarbamate (NaDTC), coagulation with colloidal hydroxides of La and Fe, and flocculation with a polymer (Bufloc 606). Removal of the mercury was achieved by dissolved air flotation of the aggregates formed. Results showed almost complete removal (>98%) of Hg from dilute solution and the process efficiency was dependent on system solution and interfacial chemistry, overall aggregation phenomena and operating parameters.