Enhanced separation of pyrite from high-sulfur bauxite using 2-mercaptobenzimidazole as chelate collector: Flotation optimization and interaction mechanisms

The existence of sulfide minerals (mainly pyrite) limits the use of high-sulfur bauxite in the production of Bayer alumina. In this work, the reverse flotation desulfurization using 2-mercaptobenzimidazole (MBI) as the collector was studied by L-9(3(4)) orthogonal tests. The interaction mechanisms of MBI with pyrite were investigated by advanced analysis technologies including scanning electron microscopy, Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), contact angle testing and zeta potential analysis. Results indicate that the sulfur content of bauxite is decreased from 2.87% to 0.26% by one roughing and one cleaning flotation under the optimized conditions of collector dosage of 100 g/t, activator dosage of 60 g/t, frother dosage of 200 g/t and pulp pH at 3. MBI exhibits superior hydrophobic behavior on the pyrite surface under the acid solution than under the alkaline solution, which favors the flotation of pyrite under the acidic condition. The zeta potential, FTIR and XPS results reveal that the interaction mechanisms of MBI with pyrite are electrostatic forces and chelation by forming N-Fe-S coordination bonds. MBI is an efficient collector of pyrite in the flotation desulfurization of high-sulfur bauxite and is expected to be used in other oxide or sulfide ores to separate pyrite.