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 andsludge content fluorite ore. Part of calcite and most of fluorite were separated with sludge byfloating in the conventional conditions through a first step rougher, and then fluorite and calcitewere separated by a second step rougher. First step rougher was carried out in alkaline pulp withoutany depressant to pull off most of the sludge and the second step rougher was carried in weak acidconditions with NSO_H as depressant. Several stage of cleaning flotation was also needed to obtaindesirable concentrate. Desirable fluorite concentrate could be produced by a process of one stagegrinding-two step rougher-two stage scavenging and five stage cleaning flotation. The content ofCaF_2 in concentrate is 95.37 per cent with a recovery of 76.61 per cent, and the content of CaCO_3 inconcentrate is 3.06 per cent. Theoretical study showed that Si(OH)_4 and SiO_2(OH)_4~(2-) were the maincomponents which could depress calcite minerals in modified sodium silicate and the sequence ofdepress ability was SiO_2(OH)_4~(2-)>Si(OH)_4>HSiO_3~-. The depress ability was mainly due to differentadsorption ability of Si(OH)_4 and SiO_2(OH)_4~(2-) between different minerals. Those had strongadsorption ability could have a firm adsorption and much more adsorption capacity, thus could beeasily depressed. Minerals that had no or less adsorption of Si(OH)_4 and SiO_2(OH)_4~(2-) were not easilydepressed or could not be depressed. As the adsorption capacity of calcite to Si(OH)_4 and SiO_2(OH)_4~(2-)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 Ca~(2+), Mg~(2+) ions.