Surface chemistry of xanthan gum interactions with bastnaesite and fluorite during flotation

Abstract

Rare earth (RE) minerals are resources crucial to mining strategies. In particular, bastnaesite is a major mineral from which rare earth elements (REEs), especially light rare earth elements (LREEs), can be extracted. However, the separation of bastnaesite and fluorite via flotation is challenging owing to their similar physical and chemical properties. In this study, xanthan gum (XG) was evaluated as a novel depressant of bastnaesite and fluorite in an octyl hydroxamic acid (OHA) system. The flotation behavior and surface chemistry by which the XG interacted with the bastnaesite and fluorite were investigated via analyses of micro-flotation tests, adsorption density measurements, zeta potentials, Fourier transform infrared spectra (FTIR), and X-ray photoelectron spectra (XPS). The micro-flotation results showed that the XG was an efficient selective depressant for the fluorite but had minimal impact on the bastnaesite. The results of the adsorption density and zeta potential analyses indicated that the adsorption of the XG occurred on both the bastnaesite and fluorite surfaces. They also indicated that the XG hindered the subsequent adsorption of the OHA on the surface of the fluorite, but the OHA was able to attach to the surface of the bastnaesite. The results of the FTIR and XPS analyses revealed that in the interaction between the XG and fluorite, chemical and hydrogen bonding adsorption occurred via complexation between the –COO- and –OH groups within the XG and the Ca or F sites on the surface of the fluorite, whereas only hydrogen bonding and electrostatic attraction occurred between the XG and bastnaesite surface. These results provide a more robust theoretical basis and sound guidance for the selection of effective depressants in the flotation separation of bastnaesite and fluorite.