Green separation of galena from molybdenite by flotation using DL-dithiothreitol as a depressant

Abstract

Developing an environment-friendly depressant to separate galena from molybdenite by flotation remains greatly challenging. Herein, the nontoxic DL-dithiothreitol (DLD) was used as a galena depressant in a molybdenite–galena flotation system. Flotation experiments showed that a recovery difference of 88.45 % was achieved in a binary mixed-mineral system with a DLD dosage of 40.00 mg/L at pH 8.00, indicating that DLD significantly reduced the floatability of galena while barely altering that of molybdenite. The adsorption mechanism of DLD on the surfaces of galena and molybdenite were investigated by various characterization techniques. Results showed that DLD can coordinate with unsaturated lead ions on the galena surface through its sulfhydryl groups. DLD stably adsorbed onto the galena surface because of the presence of chemical bonding (Pb–S), which significantly changed the surface potential of galena. Molybdenite cannot chemisorb DLD because only saturated sulfur atoms were exposed on its cleavage surface. Hence, the selective adsorption of DLD enhanced the hydrophilicity of the galena surface without affecting the hydrophobicity of the molybdenite surface. Evidently, DLD was a high-performance and promising industrial application of galena depressant. This study provided new insights into the separation of molybdenite and galena, thereby facilitates the sustainable development of the mining industry.