Adsorption of Pb(II)/benzohydroxamic acid collector complexes for ilmenite flotation

In this work, the flotation performance of separately added Pb2+ ions and benzohydroxamic acid (BHA) was compared with that of Pb2+/BHA (Pb-BHA) complexes, and the possible adsorption mechanism on the ilmenite surface was investigated by conducting single-mineral flotation tests as well as zeta potential, ultraviolet (UV) spectroscopy, microcalorimetry, Fourier transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analyses. The results of mineral flotation testing revealed that Pb-BHA complexes exhibited better flotation characteristics as compared to those of their sequentially dosed components, while the collection properties of these complexes depended on their compositions. Thus, the complexes with Pb2+/BHA molar ratios equal to 1:2 and 1:1 exhibited much higher ilmenite collection efficiencies and wider effective pH ranges than those of the complexes with Pb2+/BHA ratios of 2:1 and 3:1. Furthermore, the obtained zeta potentials indicated that the resultant Pb-BHA complexes with a Pb2+/BHA molar ratio of 1:1 were slightly positively charged. After increasing its magnitude, the zeta potential of ilmenite shifted toward positive values. Large amounts of Pb2+ ions in solution were possibly adsorbed on the surface of ilmenite, which suppressed the adsorption of Pb-BHA species. The obtained UV spectra showed that varying the Pb2+/BHA ratio strongly affected the compositions of the produced complexes. The results of microcalorimetry analysis indicated that the adsorption heats (similar to Delta H-ads) of the utilised reagents could be ranked in the order of Pb2+ < BHA < Pb-BHA, suggesting that Pb-BHA species exhibited the highest affinities to the ilmenite surface. Finally, the obtained FTIR and XPS spectra revealed that Pb-BHA complexes were adsorbed on the ilmenite surface more strongly than their individual components.