Enhancement of xanthate adsorption on lead-modified and sulfurized smithsonite surface in the presence of ammonia

Abstract

The contribution of ammonia to the sulfurization of Cu and Zn oxide minerals has been widely investigated, but the practical role of ammonia in the xanthate adsorption that directly determines the flotation of minerals has not been clearly confirmed. In this work, the promotion performance of NH3·H2O for xanthate adsorption onto the smithsonite surface was visually exhibited through adsorption density detection and the relating adsorption mechanism was revealed in terms of adsorption behavior and structure. Ultraviolet–visible spectroscopy and infrared spectroscopy tests showed that NH3·H2O treatment significantly increased the adsorption density of xanthate, with an increasing value of approximately 0.52 mg/m2 on the smithsonite surface at the initial xanthate concentration of 300 mg/L. With NH3·H2O treatment, the zeta potential of smithsonite particles increased, which was attributed to the chemisorption of Zn–NH3 complex cations on the mineral surface; such increased potential enhenced the proximity and adsorption probability for xanthate anions on the mineral surface through electrostatic attraction. X-ray photoelectron spectroscopy and time-of-flight secondary ion mass spectrometry analysis indicated that Pb–xanthate was the main xanthate product chemisorbed onto the Pb-modified and sulfurized smithsonite surface; NH3·H2O effectively increased the number of Pb sites on the surface and facilitated the transformation of the Pb(II)–S state to the Pb(II) xanthate state, resulting in an increase of Pb–xanthate content on smithsonite surface. Thus, NH3·H2O improved the hydrophobicity and increased the flotation recovery of smithsonite by approximately 10% in the Pb ion-modified sulfurization–xanthate system.