Effects of dissolution by alkali treatment on anisotropic surface properties and flotation behavior of spodumene

The effect of dissolution pretreatment of spodumene using NaOH and Na2CO3 was investigated by micro-flotation test, contact angle measurement, XPS, ICP and AFM imaging. The results showed that NaOH treatment activated the spodumene flotation whilst Na2CO3 showed little depression effect. NaOH had more significant activating effect on the spodumene (001) surface than (110) surface. The surface dissolution was confirmed by AFM, showing that weak surface dissolution was observed in ultrapure water and Na2CO3 solution, while there was strong surface dissolution in NaOH solution. Some precipitates coated the surface at the very start in NaOH and Na2CO3 solution, and the precipitates redissolved rapidly in NaOH solution while redissolved very slowly in Na2CO3 solution. The ICP results verified the release of Si, Al and Li from spodumene surface. NaOH treatment gave larger relative contents of Al on spodumene surface than Na2CO3, and the relative contents of Al on the (001) surface increased to a greater extent than on the (110) surface, as revealed by XPS analysis. From the point of crystal structure, the dissolution made more dangling Al exposed on the (001) surface, making it more favor of NaOL adsorption.