Abstract:An efficient process based on chlorination roasting with CaCl₂ was proposed to recover zinc from copper smelting slag. The reaction mechanism and the kinetics of the chlorination process were investigated by thermodynamic calculation, thermogravimetry and differential scanning calorimetry (TG-DSC) analysis and X-ray diffraction (XRD) methods. The results demonstrated that the temperatures of oxidative decomposition of CaCl₂ and chlorination of all Zn-containing phases were above 774.3 and 825 °C, respectively. The chlorination roasting process was divided into four stages: precipitation of adsorbed water, extraction of crystallized water, oxidation of Fe-containing phases, and chlorination volatilization of zinc. The average apparent activation energies of the iron oxidation and zinc chlorination were 101.70 and 84.4 kJ/mol, respectively. The most probable mechanism function for the iron oxidation process was the Avrami-Erofeev model (n=2). Zinc chlorination followed the shrinking unreacted core model, and the chemical reaction was the rate-controlling step.

Key words: copper smelting slag; chlorination roasting; CaCl₂; thermodynamics; kinetics; iron; zinc