Ozonation of cyanide with emphasis on gold mill wastewaters

Mass transfer ami treatability studies were conducted in a stirred Danckwerts cell to investigate the ozonation of 1) simple cyanide, NaCN, and 2) cyanides found in the barren bleed of Giant Yellowknife Mines Limited. A theoretical analysis of the simultaneous absorption and reaction of ozone in a NaCN solution was used to calculate an overall second order rate‐constant for the reaction with ozone. The order of magnitude value at 23°C is 10 4 to 10 5 L/(mol.s). Enhancement factors for the ozonation of the barren bleed are in the range of 80 to 300 for bulk total cyanide concentrations of about 38 to 195 mg/L respectively. Attainable treatment levels for cyanide and thiocyanate and stoichiometric relationships are presented along with an economic assessment for an ozone installation for the Giant Yellowknife Mines Limited case.