Differential depression of calcium lignosulfonate on chalcopyrite and molybdenite flotation with collector kerosene

Abstract

Molybdenite is the main mineral for molybdenum extraction, which coexists with chalcopyrite in porphyry copper deposits. However, the separation of molybdenite from chalcopyrite by flotation uses large amounts of toxic depressants, causing financial, health and environmental concerns. In this study, an environmentally friendly depressant, calcium lignosulfonate, with a low price was explored to depress chalcopyrite in the presence of kerosene, a collector widely used to float molybdenite. Adsorption isotherms of calcium lignosulfonate on chalcopyrite and molybdenite surfaces and contact angles of chalcopyrite, molybdenite’s basal planes and edge planes in the absence and presence of calcium lignosulfonate and kerosene were determined to understand the adsorptions of calcium lignosulfonate on heterogeneous chalcopyrite and molybdenite surfaces and the subsequent interactions with kerosene. It was found that calcium lignosulfonate effectively depressed chalcopyrite flotation, but had little depression effect on molybdenite because the adsorption density of calcium lignosulfonate on chalcopyrite was significantly higher than that on molybdenite. Calcium lignosulfonate molecules were uniformly adsorbed on chalcopyrite and molybdenite despite the heterogeneous surfaces. In fact, calcium lignosulfonate adsorbed on polar metal ion sites of chalcopyrite surfaces, blocking the adsorption of kerosene from adsorbing on hydrophobic sulphur-rich phases. Analogously, calcium lignosulfonate adsorbed on polar edge planes of molybdenite with little interference with the adsorption of kerosene on hydrophobic basal planes.