A Review of the Surface Chemistry of Calcite in Rare Earth Flotation Mr. Hao Cui and Dr. Corby Anderson Kroll Institute for Extractive Metallurgy, The George S. Ansell Department of Metallurgical and Materials Engineering, Colorado School of Mines, Golden CO. 80401 Hydroxamate Adsorption Abstract Three Types of Materials Calcite is one of the main gangue minerals associated with rare earth minerals, such as bastnaesite and ancylite. The comprehensive understanding of the surface chemistry of calcite will help us find a way to successfully separate the rare earth minerals from calcite. Thus, this review will present both an electrokinetic feature and common depressants for calcite in the flotation of rare earth minerals. The surface charge for minerals can have a significant effect on flotation behavior.. The surface property of calcite, as an alkaline earth semisoluble mineral, does not only depend on solution pH, but also relyies on the dissolved species... Point of zero charge (PZC), the pH where the zeta potential is zero, is used to illustrate the interfacial property.. A comparison of three types of materials, calcite, bastnaesite and barite is illustrated. In this poster. Figure 1. Hydroxamate adsorption isotherm for calcite, barite and bastnaesite. Calcite Depressants Calcite PZC (pH) Measurement Reference 9.5 Streaming potential D. W. Thompson et al. 1989 8.2 P. Somasundaran et al. 1967 11 Electrophoretic mobility D. W. Fuerstenau et al.1992 10.5 (i.e.p) M. C. Fuerstenau 1968 10 Pradip 1981 5.5 M. S. Smani 1975 8 Martinez-Luevanos et al. 1999) Several depressants, such as lignin sulfonate, sodium carbonate, sodium silicate and sodium metaphosphate, have been thoroughly investigated in the rare earth flotation industry. Different depressants used in the varied flotation plants are listed below: Background Currently, many new rare earth deposits are being developed to meet the demand for the critical products manufactured with rare earths. Calcite is the main gangue mineral associated with most rare earth minerals. It has similar interfacial chemistry features like rare earth minerals which contributes to the difficulty in separation of the rare earth minerals from calcite. Depressant Flotation plant Minerals depressed Lignin sulfonate, sodium carbonate, sodium fluorite Mountain Pass Calcite and barite Sodium silicate, alum, carboxymethyl cellulose Bayan Obo Calcite, silicate, iron-bearing ore The discrepancy in the reported PZCs of calcite might be due to different preparations, measurement methods, mineral compositions, surface structures etc. Objectives Adsorption of Hydroxamic Acid on Calcite Conclusion Summarize points of zero charge (PZC) for calcite. Illustrate the difference for adsorption of hydroxamic acid on calcite and bastnaesite. Show calcite depressants used in the industry of rare earth flotation . The review summarizes PZCs of calcite and common depressants used in the rare earth flotation industry. A comparison with hydroxamate adsorption of calcite and bastnaesite is also present here to illustrate that hydroxamate preferentially adsorbs on bastnaesite, rather than calcite. The stability constants of rare earth hydroxamate is much higher than that of calcium hydroxamate. (M. C. Fuerstenau, 2005). Results from Pradip (1981) shows that hydroxamate adsorption on calcite is significant lower than on bastnaesite. And the free energies of hydroxamate adsorption on calcite and bastnaesite are -28 and -57 KJ/mol, respectively. References Fuerstenau D. W. et al. Colloids and Surfaces, 68(1992) 95-102. Fuerstenau M. C. Annual Meeting of AIME, 1968. Fuerstenau M. C. Innovations in Natural Resource Processing. Edited by Courtney A. Young et al. Society for Mining, Metallurgy and Exploration, Inc. Martinez_luevanos, A. et al. Minerals Engineering, 12(1999) 161-176. Smani M. S. et al. Transactions AIME, 258(1975) 173-176. Somasundaran P. et al. Journal of Colloid and Interface Science, 24(1967) 433-440. Thompson D. W. et al. Journal of Colloid and Interface Science, 131(1989)74-82