A novel surfactant 2-(benzylthio)-acetohydroxamic acid: Synthesis, flotation performance and adsorption mechanism to cassiterite, calcite and quartz

In order to improve the floatability of cassiterite, a novel surfactant 2-(benzylthio)-acetohydroxamic acid (BTHA) was synthesized and first used as flotation collector to selectively separate cassiterite from calcite and quartz. The flotation performance and adsorption mechanism of BTHA to cassiterite were studied by micro-flotation tests, zeta potential measurements, solution chemistry analysis, XPS and DFT calculations. The results of micro-flotation tests showed that BTHA possessed not only stronger collecting ability than either octanohydroxamic acid (OHA) or benzohydroxamic acid (BHA) under weak alkaline conditions, but also better selectivity to cassiterite against calcite and quartz. The results of zeta potential and solution chemistry analysis suggested that BTHA could produce co-adsorption between molecules and ions on the surface of cassiterite. The results of XPS spectra demonstrated that Sn-BTHA complexes were formed on cassiterite surfaces while no chemical bond or new chemical state emerged on calcite or quartz surfaces after BTHA treatment. DFT calculations provided further evidence that the BTHA interacted with cassiterite mainly through C O and OH in hydroxamate groups and S atoms in BTHA had certain electronic supply abilities which would promote the flotation of cassiterite.