Depressing Effect of Dichromate and Permanganate on Pyrite Flotation

摘要

The mechanisms of pyrite depression by potassium salts of dichromate and permanganate have been investigated through flotation tests, measurements of reagent uptake and measurements of redox potential, etc. Both depressants had similar depressing effects and effectively depressed pyrite flotation at pH 9. At pH 6, pyrite depression with permanganate was insufficient while dichromate strongly depressed.Collector (KAX) was found to be mostly consumed irrespective of flotation pH or depressant used. Both depressants oxidized pyrite surface in flotation pulp, resulting in precipitates on the surface of pyrite, which composed of the oxidation-reduction reaction products. When dichromate was used, the amounts precipitated of Cr species at pH 6 where pyrite flotation was significantly depressed was larger than that at pH 9 where pyrite depression was inferior to pH 6 Also, in the case of permanganate the amounts precipitated of Mn species at pH 9 where significant depression occurred was much larger than that at pH 6 where insufficient depression occurred. Accordingly, it is considered that mechanisms of depression with both depressants were related to the formation of precipitates on the pyrite surface.It was concluded from material balance and Eb-value that the precipitates by which pyrite flotation was depressed were basic chromium sulfate and Mn_2O_3 or Mn_3O_4 in the case of dichromate and permanganate, respectively.