Dissolution in Plural Minerals-Water System and Its Effects on Interfacial Phenomena and Flotation of Each Mineral

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Salt-type minerals such as fluorite, calcite and bastnaesite have higher solubilities in water. When salt-type minerals coexist, the ions derived from these minerals markedly affect the surface and flotation properties of each other. In this study, special apparatus and methods developed by the authors were used to investigate the phenomena occurring in the mixed minerals system. The main results were as follows: (1) All results(flotation, zeta potential, etc.) obtained in the binary minerals system of fluorite and calcite differed from those in the singular mineral systems. The difference was caused by the effect of the ionic species dissolved from both minerals in the aqueous solution. This was interpreted in terms of the surface precipitation and/or surface reaction between both minerals and the dissolved ionic species. The results of chemical thermodynamic calculations showed that the fluorite phase was more stable than the calcite phase below pH 8.3-9.3, where the calcite surface in the binary minerals system became similar to that of fluorite. Above this pH range, the reverse phenomenon was observed. (2) N-oleoylsarcosine, sodium octadecylsulfate and n-tallow-1,3-diaminopropane dioleate(TDO) reacted selective- ly with the constituent ions of salt-type minerals, and these surfactants can be used as collector in flotation of bastnaesite, monazite, fluorite, barite and calcite. High flotation recovery was obtained in the pH range where TDO is present as ampho-ion, and a possible explanation for its adsorption on salt-type minerals was presented. (3) Because TDO did not react with main ions in flotation pulp, TDO was an effective collector for selective flotation of salt-type minerals.