Application and Mechanism of Modified Sodium Silicate on Fluorite Ore Flotation

摘要

A new type of depressant and a new process were used in floatation test of a high-carbonate and sludge content fluorite ore. Part of calcite and most of fluorite were separated with sludge by floating in the conventional conditions through a first step rougher, and then fluorite and calcite were separated by a second step rougher. First step rougher was carried out in alkaline pulp without any depressant to pull off most of the sludge and the second step rougher was carried in weak acid conditions with NSOH as depressant Several stage of cleaning flotation was also needed to obtain desirable concentrate. Desirable fluorite concentrate could be produced by a process of one stage grinding-two step rougher-two stage scavenging and five stage cleaning flotation. The content of CaF2 in concentrate is 95. 37% with a recovery of 76. 61%, and the content of CaCO3 in concentrate is 3.06%. Theoretical study showed that Si(OH)4 and SiO2(OH)42-were the main components which could depress calcite minerals in modified sodium silicate and the sequence of depress ability was SiO2(OH)42-> Si(OH)4 >HSiO3-. The depress ability was mainly due to different adsorption ability of Si(OH)4 and SiO2(OH)42-between different minerals. Those had strong adsorption ability could have a firm adsorption and much more adsorption capacity, thus could be easily depressed. Minerals that had no or less adsorption of Si (OH) 4 and SiO2 (OH)42~ were not easily depressed or could not be depressed. As the adsorption capacity of calcite to Si(OH)4 and SiO2(OH)42-was much more than that of fluorite, the sodium silicate could selectively depress calcite mineral. Modified sodium silicate could also selectively depress silicate minerals activated by Ca2+, Mg2+ ions.