A Sustainable Strategy for Co-Melting of Electroplating Sludge and Coal Gasification Slag: Metals Recovery and Vitrified Product Valorization

The high concentrations of heavy metals in electroplating sludge (ES) result in its dual properties as both hazardous waste and a potential secondary resource. Effective strategies are urgently needed for the simultaneous detoxification and utilization of ES. In this study, a sustainable strategy for co-melting of ES and coal gasification slag (CGS) was proposed. By optimizing the mass ratio of ES to CGS (m(ES)/m(CGS) = 1) and adding 7.5 wt% B2O3, a low-temperature vitrification system was established at 1250 °C, enabling the recovery of 97.31 ± 0.61% Cu, 99.17 ± 0.43% Ni, and 81.84 ± 0.33% Fe in the alloy phase within 90 min. Melt structure analysis indicated that CaO and [BO3] promoted the depolymerization of the silicate network, facilitating the amorphous phase transition and enhancing fluidity. Meanwhile, residual carbon from CGS functioned as a reductant, reducing metal minerals in the mixture to form alloys that were simultaneously separated during co-melting. Compared with the raw sample, heavy metals in the vitrified product were effectively immobilized, exhibiting low risk of heavy metal leaching. Furthermore, high-value-added glass-ceramic materials were successfully prepared from the vitrified product. Therefore, the proposed strategy could serve as a sustainable solution for the treatment of ES and CGS.