Recovery of Fine Particles of Rare Earth Minerals by Liquid-Liquid Extraction Method.

In order to recover fine particles of rare-earth minerals from beach sand by the liquid-liquid extraction method, fundamental studies were carried out using several kinds of surfactants such as oleate, alkylsulfate, alkylbenzenesulfonate and alkylammonium salts. Isooctane and water were used as two liquid phases. Monazite, xenotime, zircon and quartz were chosen as test samples. The percent recovery of each of these minerals was determined in terms of pH of aqueous solution, type of surfactant and concentration of surfactant.Zeta potential variations were measured as a function of pH for each of these minerals to determine its isoelectric point (IEP). In the pH range below the IEP of the mineral where the mineral particles were positively charged, high recoveries were obtained when the anionic surfactant was used at its proper concentrations.To evaluate an oil-wettability of the mineral surface, contact angles in the monazite/isooctane/water system in the presence of the surfactant were measured. Interfacial tensions between isooctane and surfactant solution were also measured. Work of adhesion was then determined. The recovery variations were closely correlated with the work of adhesion.