Metallurgical chromium slag is a hazardous by-product generated during the production of chromium salts and metallic chromium, containing significant amounts of leachable Cr(VI), which poses severe environmental and human health risks. To address this challenge, this study presents an integrated “alkaline roasting, water leaching with impurity removal, glucose reduction and vacuum calcination” process for its direct preparation to nano-pigment-grade Cr2O3. The reduction process was systematically optimized by investigating the effects of critical parameters: glucose dosage, HCl concentration, reduction temperature and time. Optimal conditions were established as 2.5 g of C6H12O6, 20 mL of 12 M HCl, 55 °C and 4 h, achieving the Cr(VI) reduction efficiency of 99.66%. Comprehensive characterization of the final product via XRD, SEM-EDS and XRF confirmed its high quality. The Cr2O3 exhibited a purity of 99.31%, well-developed crystallinity and a uniform sub-micron particle size distribution, fully meeting industrial standards for pigment applications. By substituting conventional hazardous reductants with glucose, this route demonstrates enhanced safety, environmental compatibility and cost-effectiveness. The proposed methodology not only provides a practical and scalable solution for the valorization of hazardous chromium slag but also contributes to the advancement of green processing technologies in the metallurgical sector, supporting the transition towards a circular economy.
Li et al. (Fri,) studied this question.