China Nonferrous Metallurgy

To tackle the difficulty of cost-effective iron recovery from copper slag, where iron predominantly occurs as iron olivine intimately bound with SiO₂, pyrolyzed waste-plastic char was adopted as the reductant. The char was blended with copper slag to form composite pellets, which were subjected to isothermal thermogravimetric tests at 1000~1250℃. During reduction the char supplies both solid carbon and in-situ-generated CO and H₂; the real-time mass loss of the pellets was recorded and converted to the reduction fraction. The results show that: the reduction course follows a three-dimensional gas-diffusion mechanism (Ginstling-Brushtein model), yielding an apparent activation energy of 82.67kJ mol-1; the metallization rate rises sharply with temperature between 1000 and 1200℃, reaching 78.3% after holding at 1200℃ for 30min; further heating produces liquid phases that block porosity and slightly decrease the metallization degree; compared with conventional coke reduction, an equivalent metallization rate can be achieved at temperatures 50~100℃ lower, indicating that the “dual-reductant” effect of the plastic char lowers the energy barrier, shortens holding time and mitigates high-temperature sintering/encapsulation. Overall, carbothermic reduction of copper slag with pyrolyzed waste-plastic char enhances iron recovery, cuts fuel consumption and CO2 emissions, and enables the co-valorization of two solid wastes. The kinetic parameters obtained provide a data basis for industrial furnace optimization, continuous feeding and subsequent magnetic-separation process design. Future work will evaluate char quality variability and pilot-scale feasibility to advance the industrial application of this low-carbon recovery route.