Inhibiting mechanisms and applications of novel Al-starch for ultrafine gangue minerals based on experimental and computational study

Abstract

Ultrafine gangue minerals of calcite and chlorite seriously affect the flotation of valuable mineral, and its inhibition is difficult to achieve using conventional depressants. This study finds the Al-starch colloidal depressants can inhibit the flotation of ultrafine calcite and chlorite, which significantly increases the grade of valuable minerals in concentrates of actual ores. When the chemisorption of Al-starch is occurred on mineral surface, the zeta potential of calcite decreases whilst that of chlorite increases. With the treatment of Al-starch, the initial functional group peaks of Fourier transform infrared spectroscopy measurement on the surface of calcite and chlorite are shifted, and the new O-Al functional group is generated. Meanwhile, the X-ray photoelectron spectroscopy measurement peaks of O1 s atom is changed, and the Al2p atom peak is generated. Furthermore, the optimal structure of Al-starch is O1—Al—O6, and the optimal adsorptive configuration on calcite (104) surface, hydroxyl-terminated and silica-terminated chlorite (001) surface are (Og1 Og2)—Al—(Om1 Om2), (Og1 Og2)—Al—(Oh1 Oh2 Oh3) and Og2—Al—(Om1 Om2 Om3 Og4) with adsorptive energy of − 678.50 kJ/mol, − 353.49 kJ/mol and − 475.05 kJ/mol, respectively. During the adsorption, the 3 s and 3p orbitals of Al on Al-starch accept the 2 s and 2p electrons of O atom on mineral surface.