The pH of the pulp was adjusted to 9.5 with NaOH, and the effects of sodium humate on the flotation recoveries of pyrite and
chalcopyrite were determined (see Fig. 3). The results indicated that the flotation recovery of pyrite decreased gradually with an increase in the sodium humate concentration. However, as the concentration of sodium humate increased from 0 to 50 mg/L, the recovery of chalcopyrite remained relatively constant.