Selective flotation separation of bastnaesite from calcite using xanthan gum as a depressant

The inability of rare earth and gangue minerals to be efficiently separated by flotation due to their similar physicochemical properties is a major challenge of the rare earth industry. Bastnaesite is one of the principal sources of light rare earth elements. The use of traditional flotation reagents often poses the problem of poisonous wastewater generation. Therefore, we use xanthan gum (XG) as a non-toxic, biodegradable, and cheap depressant to selectively separate bastnaesite from calcite by flotation and probe the corresponding mechanism. Microflotation experiments/zeta potential measurements conducted with/without XG using sodium oleate as a collector demonstrate that at pH 8, XG decreases the flotation recoveries of calcite and bastnaesite by 85.09 and 22.37%, respectively. Further analysis of adsorption behaviour on the mineral surface and possible reagent-mineral interactions shows that selective mineral separation is due to the preferential interaction of XG with Ca ions on the calcite surface and the suppression of oleate ion adsorption thereon due to the steric hindrance of polymeric XG. Hence with regard to the potential of XG in calcium-bearing mineral separation, XG could be as a new depressant for RE mineral flotation.