Effect of calcium hypochlorite on flotation separation of covellite and pyrite

The effect of calcium hypochlorite (Ca(ClO)2) on the flotation separation of covellite and pyrite with ammonium dibutyl dithiophophate (ADD) has been investigated through micro-flotation tests, zeta-potential measurements, infrared spectroscopy (IR) analyses, adsorption measurements and X-ray photoelectron (XPS) analyses. The flotation results illustrate that Ca(ClO)2 depressed pyrite selectively and had little effect on covellite at pH 10. The zeta-potential measurements indicate that a potential change occurred on covellite and pyrite because of the adsorption of ADD. The selective adsorption of Ca(OH)+ on pyrite causes a sharp decrease in the negative potential. In addition, adsorption studies and IR analyses demonstrate that the adsorption of ADD on pyrite is strongly inhibited by Ca(ClO)2, whereas that on covellite is affected only slightly. Furthermore, XPS analyses confirm that pyrite is preferentially oxidized by Ca(ClO)2 to form CaSO4 and Fe(OH)3 on its surface; thus, the adsorption of ADD on pyrite is prevented, resulting in the depression of pyrite. [Display omitted] •Selective separation of covellite from pyrite was achieved by flotation.•Ca(ClO)2 selectively depressed the flotation of pyrite rather than that of covellite.•Pyrite surface was oxidized by Ca(ClO)2 to prevent ADD adsorption.•Oxidative mechanism of pyrite was proposed based on electrochemical theory.