Effect and mechanism of xanthan gum on the flotation separation of pyrite and micro-fine chlorite

Chlorite is a common magnesia silicate gangue mineral in copper-nickel sulfide ores. Fine chlorite minerals are difficult to effectively inhibit in the flotation separation process, resulting in excessive MgO content in the concentrate. This work investigated the feasibility of separating pyrite and fine-grained chlorite using xanthan gum as a depressant. Single-mineral flotation tests showed that under the butyl xanthan system, the floatability of pyrite was good, and the flotation recovery of chlorite reached about 30%. Under neutral and weakly alkaline conditions, adding xanthan gum selectively inhibited the flotation of chlorite. Artificial mixed minerals flotation test results indicated that xanthan gum was effective in removing chlorite minerals during pyrite flotation. Adsorption tests illustrated that the adsorption amount of xanthan gum on the surface of chlorite was significantly higher than that on the surface of pyrite, and the turbidity and foam entrapment test results indicated that xanthan gum flocculated chlorite to a certain extent, thereby decreasing its entrainment. Zeta potential results illustrated that the interaction between xanthan gum and chlorite surface was stronger than that between xanthan gum and pyrite. The results of infrared spectroscopy confirmed that xanthan gum was chemically adsorbed on the chlorite mineral surface, and its mechanism was attributed to the chemical interaction between the -COOH groups of xanthan gum and magnesium ions on the chlorite surface, ​thus achieving the removal of chlorite during pyrite flotation.