Selective depression of copper-activated sphalerite by polyaspartic acid during chalcopyrite flotation

Environmentally friendly flotation reagent, polyaspartic acid (PAPA), was tested as a potential selective depressant in the flotation separation of chalcopyrite and Cu-activated sphalerite. The depression mechanism of PAPA was revealed by contact angle measurements, Zeta potential measurements, Fourier transform infrared spectroscopy (FT-IR) analysis and inductively coupled plasma (ICP) measurement. The micro-flotation tests with single minerals showed that PAPA selectively depressed Cu-activated sphalerite, while chalcopyrite remained floatable. Moreover, a concentrate containing 31.40% Cu with a recovery of 92.43% was obtained in flotation tests of artificially mixed minerals. Results of contact angle measurements, Zeta potential measurements and FT-IR spectrum revealed that PAPA exerted a much stronger adsorption on Cu-activated sphalerite surface than on chalcopyrite surface, preventing the further adsorption of sodium diethyl dithiocarbamate (DDTC) on its surface. ICP measurements indicated that PAPA had an excellent complexing ability with Cu2+ in flotation pulp, weakening the activation of Cu species on sphalerite surface and producing selective depression.