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The effects of lead ions on the flotation performance of the cassiterite system have been investigated using microflotation tests. Adsorption experiments, X-ray photoelectron spectroscopy (XPS), contact angle measurement, and zeta (ζ)-potential measurements were conducted. Octanohydroxamic acid and lead ion solution speciation simulations were used. These were used to correlate surface properties of lead-activated with cassiterite flotation performance. Flotation results indicate that the addition of lead ions activates the cassiterite flotation. The addition of lead ions enhanced the adsorption of octanohydroxamic acid on cassiterite, and the wetting characteristic of cassiterite decreased in the presence of octanohydroxamic acid and the addition of lead ions. ζ-Potential measurements and solution chemistry analyses confirmed that flotation recovery of the cassiterite increases due to Pb­(OH)+ and Pb3(OH)4 2+ sites on the cassiterite surface. XPS results indicated the adsorption of octanohydroxamic acid onto the cassiterite surface was through chemisorption, which combined with lead ions changed the chemical properties of the cassiterite surface.

The existence of metal ions should not be ignored in both hydrometallurgy and flotation. In this study, the effects of Ca2+, Mg2+ and Fe3+ on the flotation performance of cassiterite using octanohydroxamic acid (OHA) as the collector were investigated by micro-flotation tests, X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) spectroscopy, contact angle, zeta (ζ) potential measurements and atomic force microscopy (AFM) imaging. The results of the flotation and contact angle experiments showed that the addition of Ca2+, Mg2+ and Fe3+ significantly decreased both the recovery and contact angle of cassiterite with pH ranged from 6.0 to 12.0 in the presence of OHA collector. ζ-Potential measurements, solution chemistry analysis and FTIR measurements indicated that the flotation recovery of the cassiterite declined due to the CaOH+, MgOH+ and Fe(OH)3 sites on the cassiterite surface. XPS results indicated that the chemisorption of OHA and calcium ions on the cassiterite surface finally changed its chemical properties. The AFM images also revealed that new species Fe(OH)3 of Fe3+ formed and adsorbed on the cassiterite surface at pH 9.0. The adsorption of Fe(OH)3 reduced the adsorption of OHA on the cassiterite surface, thus the hydrophobicity of cassiterite was deteriorated.

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