Depression performance and mechanism of a novel reagent (Pb-starch) for calcite: Experimental and DFT study

The fine calcite is difficult to inhibit due to the high activity and large specific surface area, and its inhibition is the crucial to achieve the flotation separation of valuable minerals. This study releases that the Pb-starch is an effective depressant for calcite flotation to significantly decrease the flotation kinetics, which is better than the effect of starch. The surface charge of calcite obviously increases with the increase of mass ration of Pb2+ ions and starch. The FTIR spectra indicate the starch is chemisorbed on the calcite surface through hydroxyl groups, while the chemisorption of Pb-starch is relied on Pb-O group. Meanwhile, the XPS measurement determines that starch mainly react with the Ca active site, whilst the Pb-starch mainly react with O active site. Furthermore, the single Pb-starch molecule adsorb on the (1 0 4) cleave surface of calcite to form two covalent bonds of Pb2+ and O atom, and the adsorption energy is much less than that of starch. The analysis of electronic property and electrons density confirm during the adsorption, the Pb2+ ions of Pb-starch accept the electrons from O atoms on calcite surface, and the hybrid orbital is the electronic states of Pb 6s6p with that of O 2s2p.