Thermal decomposition of pyrometallurgical copper slag by oxidation in synthetic air

Abstract

The purpose of this study was to investigate the possibility of separating pyrometallurgical copper (fayalite) slag by oxidation in a synthetic air atmosphere into ferrous and silicate phases suitable for resources to be recovered from them. Isothermal oxidation kinetics and the most probable reaction models are studied in the temperature range of 773 to 1173 K using thermogravimetric analysis data and the classical Johnson—Mehl—Avrami—Yerofeev—Kolmogorov (JMAYK) equation. Depending on the model applied, the activation energies of fayalite slag oxidation in the temperature range of 773—973 K were: D1: 37.55 kJ mol-1; D2: 43.27 kJ mol-1; D3: 50.52 kJ mol-1; and D4: 45.65 kJ mol-1. Depending on the model applied, the activation energies of fayalite slag oxidation in the temperature range of 1073—1173 K were: F1: 20.48 kJ mol-1; R2: 20.45 kJ mol-1; R3: 20.18 kJ mol-1; A2: 21.54 kJ mol -1 and A3: 22.34 kJ mol-1. The transformation of fayalite to hematite and amorphous silica was completed after 1435, 1350 and 1080 s at temperatures of 1073, 1123 and 1173 K, respectively. The following oxidation products were identified by X-ray diffraction: (1) fayalite, hematite and magnesioferrite (Fe2MgO4) in the temperature range 773 to 973 K; and (2) hematite and magnesium iron oxide (Mg1.55Fe 1.6O4) in the temperature range of 1073 to 1173 K.