Coagulation of fines in fluorite froth flotation

Abstract

Fluorite, a valuable mineral in the metallurgical industry, can be found together with silicates, carbonates and oxides in ore deposits. Commercial concentrates with more than 95 % of CaF₂ are obtained processing the mineral in flotation plants and using oleic acid as fluorite collector. Depressor reagents such as sodium silicate, tannin and sodium carbonate are commonly employed to allow the oleic acid selective performance. These reagents cause a dispersant effect separating the solid-liquid solution on tailing plants. Fine particles in the recovered water enter the circuit and affect the flotation efficiency. The effect of coagulant ions was studied as a method to clarify the returned water. The problem of the presence of these ions is related to its reactions with the collector by the formation of compounds and possibly on the selectivity. Variable quantities of Al³⁺, Fe³⁺ and Ca²⁺ ions were added to the flotation to evaluate its effect on the fluorite recovery, in the selectivity and in solids content in recirculation water. Results show that some ions fail to improve water quality and are detrimental to flotation. On the contrary, some ions contribute to reduce fine content in suspension. Therefore, although there is a recovery reduction, such effect can be counteracted increasing the collector consumption a little.