Abstract:Lime (CaO) and sodium humate (NaHA) were used as the combined depressant for arsenopyrite pre-treated by CuSO₄ and butyl xanthate. Micro-flotation tests show that the combined depressant CaO and NaHA achieved the selective depression of arsenopyrite. Closed-circuit lab-scale test results indicate that the synergistic effect of CaO+NaHA achieved a satisfactory flotation separation of sphalerite and arsenopyrite, for which the Zn grade and recovery of Zn concentrate were 51.21% and 92.21%, respectively. Contact angle measurements, adsorption amount measurements and X-ray photoelectron spectroscopy analysis indicate that the dissolved calcium species (mainly as Ca²⁺) were adsorbed on the mineral surfaces, thereby promoting NaHA adsorption. Moreover, the surface of the arsenopyrite absorbed more amount of calcium species and NaHA than that of the sphalerite, thereby accounting for the strong hydrophilic surface of arsenopyrite. The adsorption of NaHA on arsenopyrite was mainly chemical adsorption through its carboxyl groups and Ca atoms, whereas that on sphalerite surface was relatively weak.

Key words: sphalerite; arsenopyrite; Zn-As bulk concentrate; flotation separation; lime; sodium humate