Wencui Chai,Yanfang Huang,Weijun Peng,Guihong Han,Yijun Cao,Jiongtian Liu
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.
Stepwise separation of multi-species with a single type of chemical additives (such as surfactants) is an auspicious but challenging issue in many engineering processes as one surfactant usually lacks the ability to interact with different components. One promising strategy is to develop an environment-responsive surfactant, which possesses various functional groups to anchor target constituents under different environmental conditions. In this work, we have prepared a pH-responsive surfactant (2-(benzylthio)-acetohydroxamic acid, BTHA) possessing two pH-switchable groups (i.e., thioether and hydroxamate) that can selectively interact with different target substances, thus enabling stepwise and efficient separation of a three-component mineral system. The single in-house synthesized BTHA is successfully applied to the sequential separation of pyrite, diaspore, and kaolinite from high-sulfur bauxite by simply tuning the solution pH. Specifically, under the acidic condition (pH 6.0), the hydroxamate group of BTHA is deactivated, thus only the thioether groups can directionally interact with pyrite and enable the selective flotation recovery of pyrite to 85.9%. When the solution pH is subsequently increased to 8.0, the active hydroxamate group of BTHA can tightly chelate with diaspore and result in its efficient separation from kaolinite. The bifunctional surfactant exhibits strong and selective interactions with target substrates via pH modulation, allowing the adsorption selectivity and efficient stepwise separation, which provides an innovative paradigm for the development of novel surfactants with diverse applications in the mineral, metallurgical, chemical, and renewables recycling industry.
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