Surface features and flotation behaviors of spodumene as influenced by acid and alkali treatments

Abstract

Surface dissolution was proved as a fundamental phenomenon in the flotation of spodumene. This study presents an improved understanding of surface dissolution behavior and the corresponding surface states involving consideration of topography, chemical species distribution, as well as oleate adsorption at spodumene surface treated by sodium hydroxide (NaOH) and hydrochloric acid (HCl). Micro-flotation results showed that spodumene flotation was activated with NaOH treatment but was depressed with HCl treatment when sodium oleate was used as a collector. AFM imaging revealed variations in surface topography, indicative of different dissolution behaviors. Water rinsing treatment increased flotation response of NaOH-treated spodumene but had no effect in the case of HCl treatment. Colloidal substances precipitated at surface conditioned in NaOH solution as evidenced from in-situ AFM, and appeared to be unfavorable for oleate adsorption. Chemical states of elements at surface were influenced by treatments, and larger relative contents of Al and unsaturated Al at surface with NaOH treatment were revealed by XPS as compared with that treated by HCl. Density functional theory calculations indicated that unsaturated Al was favorable for oleate adsorption. It seems the relative content of unsaturated Al at surface influenced by acid and alkali treatments dominates the extent of oleate adsorption.