Selective depression mechanism of locust bean gum in the flotation separation of chalcopyrite from pyrite in a low-alkalinity media

Conventional inorganic depressants are widely used to separate pyrite in the flotation process of chalcopyrite, however, their widespread use entails some inevitable disadvantages, such as low-selectivity, additional costs, and especially hypertoxicity. In this work, we tested locust bean gum (LBG), a natural polysaccharide polymer, as a selective depressant in the Cu-Fe flotation separation. Micro-flotation tests suggested that at a slurry pH of 8.0, the addition of LBG dramatically depressed the floatability of pyrite while having a negligible depressive effect on chalcopyrite. The results of surface adsorption experiments, contact angle and zeta potential measurements showed that the adsorption of LBG on the pyrite surfaces was stronger than that on the surfaces of chalcopyrite. Moreover, XPS and FT-IR analyses further suggested that LBG was adsorbed on the pyrite surfaces by physical adsorption. The acid/base interactions, hydrogen bonding, and the attraction between the hydrophobic sections of both LBG and pyrite surfaces, were considered as the potential mechanisms in the adsorption of LBG on pyrite.