Al-caustic starch coordination compounds: A new depressant for fine calcite

Abstract

The flotation separation of scheelite from fine calcite is difficult due to the larger specific surface area and higher activity with flotation collectors. The selectivity of caustic starch as the depressant is poor, due to the -OH functional group reacting with the similar Ca2+ active sites of scheelite and calcite. In this paper, a novel structure of Al-caustic starch is prepared by the reaction of Al3+ and caustic starch, which has a new functional group of -CH2-O-Al2+. The Al-caustic starch is an effective depressant for the fine calcite particles, contributing to the efficient flotation separation of scheelite from the fine calcite particles. All the flotation kinetics of scheelite and fine calcite is first-order uniform distribution model, and the flotation rate of calcite decreases significantly after the treatment of Al-caustic starch. The zeta potential of Al-caustic starch is much higher than that of caustic starch, and Al-caustic starch can selectively change the surface charge of fine calcite, instead of scheelite. The X-ray photoelectron spectroscopy (XPS) spectrum of Al-caustic starch appears the peak of Al atom, which chemisorb on the calcite surface and make the peak of characteristic atoms shift. Moreover, Al-caustic starch reacts with the anion of CO32- on fine calcite surface, instead of cation of Ca2+, which obviously improves the selective adsorption on mineral surface.