Adsorption mechanism of H2O/oleate on α-quartz (101) surface with Al and Fe impurities/cations: DFT study and experimental verification

Flotation is an indispensable approach for efficiently separating gangue minerals from phosphate rock, with significant implications for the development and utilization of mineral resources in a highly efficient and sustainable manner. The Al and Fe elements are incorporated as impurity defects within quartz crystals, which alter the physicochemical properties of quartz minerals and subsequently influence their flotation behavior. The present study investigated the impact of Al and Fe impurity defects on the crystal structure, electronic characteristics, and surface wettability of α-quartz through density function theory (DFT). The calculation results suggest that the α-quartz with impurity defects alter the structure crystal and electronic structure properties of α-quartz. The presence of impurity defect further raises the adsorption energy of the H₂O molecule and decreases the interaction between the α-quartz (101) surface and the H₂O molecule. In addition, the wettability of α-quartz (101) hydrated surface treated with Al³⁺ and Fe³⁺ and its adsorption effect on the H₂O molecule or oleate ion (OL^-) were studied by DFT and experimental. The findings testify that OL^- can be adsorbed on α-quartz (101) hydrated surface via Al³⁺ and Fe³⁺, thereby enhancing the hydrophobicity of quartz surface and improving natural flotation recovery. The computational prediction was validated by experimental results. Consequently, the existence of Al and Fe impurities/cations can improve the surface wettability of α-quartz, which is conducive to enhancing the natural floatability and provides valuable guidance for the flotation process.