Synthesis, flotation performance and adsorption mechanism of 3-(ethylamino)-N-phenyl-3-thioxopropanamide onto galena/sphalerite surfaces

In this paper, a novel β-Oxo thioamide surfactant 3-(ethylamino)-N-phenyl-3-thioxopropanamide (EAPhTXPA) was synthesized and first used as flotation collector for galena and sphalerite. The results of micro-flotation tests showed that EAPhTXPA possessed not only stronger collecting ability but also better selectivity to galena against sphalerite than traditional sulfide collector sodium isobutyl xanthate (SIBX). Adsorption tests indicated that EAPhTXPA could adsorb onto galena surfaces more easily than SIBX, while the adsorption affinity of EAPhTXPA to sphalerite was weaker than that of SIBX. The results of FTIR and XPS spectra demonstrated that there was no chemical bond or new chemical state appeared on sphalerite surfaces after treatment by EAPhTXPA, while Pb-EAPhTXPA complexes were formed on galena surfaces by reaction of EAPhTXPA’s C(S), C(O) and NH groups with surface Pb atoms to build PbS, PbO and PbN bonds. DFT calculations further gave an evidence that the dominated interaction between sphalerite and EAPhTXPA was probably van der Walls forces, and EAPhTXPA reacted with galena by the formation of PbS, PbO and PbN bonds.