Surface crystal chemistry in selective flotation of spodumene (LiAl[SiO3]2) from other aluminosilicates

The characteristic surface crystal chemistry of spodumene (LiAl[SiO3](2)) is found to be the major contributing factor for the selectivity in the common industrial flotation of the mineral with oleate collector (CH3(CH2)(7)CHCH(CH2)(7)COO-Na+) from other pegmatic aluminosilicates such as muscovite (K2Al4[Al2Si6O20](OH,F)), feldspar (4K[AlSi3O8]), and quartz (SiO2). Crystallographically, the surface Al site on {110} cleavage plane of spodumene was found to be the most favorable site for the selective chemisorption of oleate, while those in other pegmatic aluminosilicates are buried deep inside the crystallographic unit cells of the minerals, making them unavailable for oleate adsorption. A typical surface of a mineral contains many different surface atomic sites with different broken bonds, depending on the crystal planes. The surface can also be very heterogeneous due to the omnipresent crystal defects of various kinds, and/or due to the inherent anisotropic crystal structure of many minerals. The surface chemical properties of a mineral-collector system, such as surface charge, wettability, and adsorption of the collectors, should be understood in terms of the specific surface atomic sites. In the present study, various surface chemical investigations were carried out on oleate-spodumene systems, including the aqueous chemistry of oleate collector and spodumene-water systems, the effect of acidic and alkaline leaching of spodumene during various surface chemical investigations, X-ray photoelectron spectroscopy, electrophoretic mobility, oleate adsorption study, infrared spectroscopy, contact angle measurements, and Hallimond flotation study. The results of these surface chemical investigations indicate that the chemisorption of an anionic oleate collector on the surface aluminum sites of the negatively charged spodumene surface was responsible for the best selective flotation at pH 8 from other aluminosilicates. (C) 2003 Elsevier B.V. All rights reserved.