Lactic acid as selective depressant for flotation separation of chalcopyrite from pyrite and its depression mechanism

Abstract

Inorganic depressants are commonly used in the flotation separation of chalcopyrite from pyrite, but they adversely affect the environment. The use of degradable and environmentally friendly depressants is therefore important. In this work, lactic acid (LA) was used as a suitable and effective depressant for selectively separating chalcopyrite from pyrite at low alkalinity. The mechanism of pyrite depression by LA was investigated by performing micro-flotation tests, surface adsorption experiments, zeta potential measurements, infrared (IR) spectroscopy, time-of-flight secondary-ion mass spectrometry (TOF-SIMS), and X-ray photoelectron spectroscopy (XPS). The micro-flotation tests showed that LA has a clear depressive effect on pyrite, but not on chalcopyrite. Adsorption experiments indicated that LA considerably decreased xanthate adsorption on pyrite surfaces, but had no significant effect on xanthate adsorption on chalcopyrite surfaces. Zeta potential measurements indicated that LA increased the surface potential of pyrite within a wide pH range. New peaks were present in the IR spectrum of the LA-treated pyrite surface. TOF-SIMS and XPS analysis confirmed that LA strongly interacted with Fe sites on the pyrite surface. These results verify that LA is selectively adsorbed on the pyrite surface, therefore chalcopyrite can be separated from pyrite at low alkalinity.