SODIUM DITHIONITE AS A PYRITE DEPRESSANT IN GOLD ORE FLOTATION

Abstract

Sodium dithionite (Na2S2O4) is a widely used reducing agent to control pulp potential (Eh) and pyrite depressant in sulfide ore flotation. In this study, the pyrite depressant effect of sodium dithionite on gold ore flotation was investigated at pH 8 and pH 10.5 comparatively in terms of gold, chalcopyrite, and pyrite recoveries and grades. The presence of sodium dithionite resulted in a drop of approximately 50–70 mV in the Eh values, regardless of the studied pH values, confirming the reducing effect of sodium dithionite. The effects of sodium dithionite on gold and chalcopyrite grades and recoveries were quite limited, especially at pH 10.5. At pH 8, the utilization of sodium dithionite slightly decreased gold and chalcopyrite recovery and grades, while the decrease in pyrite recovery and grades was remarkable. Both pyrite recovery and grade were reduced from 79.5% to 54.7% and 15.3% to 10.7% by the utilization of sodium dithionite at pH 8. In conclusion, it is considered that the selective flotation of gold and chalcopyrite from pyrite can be achieved at a lower pH accompanied by a slightly reduced Eh by the utilization of sodium dithionite.