A green method for selective separation of molybdenite and pyrite via electrochemical oxidation pretreatment-flotation and its mechanism

Abstract

Electrochemical oxidation (EO) has received widespread attention as a green and non-polluting oxidation treatment. In this paper, we used EO to pretreat pyrite and molybdenite, and then flotation was adopted to separate them. The flotation behavior of the pyrite and molybdenite was studied by micro-flotation tests, and the mechanism for the flotation separation of them was explored via XPS, zeta potential, water contact angle and electrochemistry, etc. The flotation results showed that the floatability of pyrite declined sharply after EO treatment, while that of molybdenite was not affected. In the flotation experiments of artificially mixed ores with various mass ratios, the recoveries of pyrite and molybdenite in the concentrates varied considerably. The mechanism analysis showed that pyrite had a drastic decrease in floatability due to the generation of hydrophilic products of Fe(OH)3, FeOOH and Fe2(SO4)3 covered on its surface in the EO process. Additionally, the oxidation products further hindered the adsorption of the collector of sodium butylxanthate on the pyrite surface. However, the generated MoO42- and SO42- of molybdenite were rapidly dissolved in the pulp during the EO process, allowing its original surface and floatability to be maintained. Therefore, EO pretreatment could generate a great variance in surface properties of pyrite and molybdenite, resulting in an efficient separation of pyrite and molybdenite via subsequent flotation. The work provided a green and environmentally-friendly alternative method to achieve efficient separation of pyrite and molybdenite.