Abstract: In order to explore the activation mechanism of Cu²⁺ on cassiterite， the monomineral flotation experiment of cassiterite was carried out in the styrene phosphonic acid （SPA） flotation system. The results show that Cu²⁺ has activation effect on cassiterite in the pH range of 2.0~7.4. Under the conditions of pH=4， SPA dosage of 250 mg/L and Cu²⁺ dosage of 4 ×10^-3 mol/L， the flotation recovery rate of cassiterite is 11 percentage points higher than that without Cu²⁺. The results of electrodynamic potential detection and XPS analysis showed that Cu²⁺ could increase the reaction site of SPA on the surface of cassiterite by adsorption or substitution， thus increasing the adsorption amount of SPA on the surface of cassiterite and activating cassiterite. The results are of great significance for the flotation recovery increase of cassiterite resources.

Key words: Cassiterite, Styrene phosphonic acid（SPA）, Cu²⁺, Activation, Mechanism