Sodium cyanide and Nokes reagent are commonly used depressants to reject iron, copper, and lead sulfide minerals for the flotation recovery and upgrading of molybdenite concentrate. With the ever increasing cost of reagents and more stringent regulations, it is necessary that these depressants are used as efficiently and effectively as possible. Therefore, a study was undertaken to investigate the effects of concentration and conditioning time of two depressants—sodium cyanide and Nokes reagent—at different levels of pH on the rejection of sulfide impurities from the molybdenite concentrate. This paper discusses the experimental methods used and the results obtained to date on this ongoing investigation.
A representative sample of the first-stage cleaner flotation feed in the mill was obtained for this study. The sample assayed 6.2 percent MoS2, 13.5 percent FeS2, 0.108 percent Cu, and 0.026 percent Pb. The bench-scale flotation tests were performed in a 4.5-liter Denver D12 flotation machine. Concentrates were collected at cumulative times of 3, 5, and 7 minutes of flotation, and flotation products were assayed for MoS2, Cu, Pb, and FeS2.
Three series of tests were performed to investigate the following:
- effect of conditioning time of depressants,
- effect of pH, and
- effect of depressant addition rates on the