Surface chemistry considerations in the flotation of bastnäsite

• Bastnäsite IEP (2 samples) determined electrophoretically and electroacoustically.
• Reagent selectivity for bastnäsite vs. quartz: benzohydroxamate > NaOL > Flotinor SM15.
• Benzohydroxamic acid found to selectively float bastnäsite from quartz at pH 9.

Bastnäsite is the chief valuable mineral in two of the world’s largest rare earth (RE) mineral deposits and is also found in a number of new RE deposits currently under development. This work used electrophoretic and electroacoustic zeta potential measurements to identify the interaction between bastnäsite and several different collectors. The results of these measurements were then compared with microflotation of bastnäsite and quartz, a common RE gangue mineral. Zeta potential measurements of bastnäsite determined the isoelectric point of bastnäsite to occur at approximately pH 6.3 (via electrophoretic measurement) and pH 8.1 (via electroacoustic measurement). Sodium oleate and Flotinor SM15 (a commercial phosphoric acid ester) are both shown to chemically adsorb onto the bastnäsite surface. Zeta potential measurements of bastnäsite with benzohydroxamic acid indicate significant adsorption, especially from pH 5 to pH 10. The microflotation results show that all three collectors were able to successfully recover bastnäsite. SM15 is the least selective collector as it floats both quartz and bastnäsite whereas benzohydroxamic acid is able to selectively float bastnäsite at pH 9. The recovery of bastnäsite using benzohydroxamic acid is also shown to be highly dependent on frother selection. The optimum pH of flotation for all three collectors occurs at pH 9.