Phosphate adsorption by bastnaesite

By Weiping Liu, Xuming Wang, and Jan D. Miller

 Department of Metallurgical Engineering, University of Utah

Bastnaesite is a major mineral resource of importance in the production of rare earth materials. Present flotation practice uses a reagent schedule which typically includes fatty acid of hydroxamic acid as collector. Initial evaluation suggests that phosphate collectors should be a promising collector for bastnaesite flotation. In this regard, the adsorption of phosphate collectors by bastnaesite was examined by Molecular Dynamics Simulations. The phosphate collectors were found to be adsorbed at the bastnaesite (100) surface, specifically, with the phosphate groups in preferred positions with respect to cerium atoms in the crystal structure, as shown in (a) and (b). This phenomenon agrees with the thermodynamic analysis and density functional theory calculation results. Furthermore, the 2-Ethylhexyl phosphate is adsorbed on the bastnaesite surface totally by the polar headgroup, while lauryl phosphate is adsorbed on the bastnaesite surface by the combination of headgroup and hydrophobic attraction between adjacent hydrocarbon chains. However, lauryl phosphate excludes more water due to its longer hydrocarbon chain, thereby imparting higher hydrophobicity compared to the case of 2-Ethylhexyl phosphate as shown in (c). It is expected that the results of this research will enable us to further understand the bastnaesite flotation chemistry using phosphate collectors, with consideration of chemical structure, which includes the hydrophobic surface state, selectivity in flotation, and adsorption phenomena for the sign of alkyl phosphate collector.

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