Upcycling Electroplating Sludge into NiO/CaO Catalysts: A Waste-to-Value Approach for High-Performance CO 2 Gasification of Biochar

Nickel-rich electroplating sludge, a hazardous waste generated by the electroplating industry, exhibits significant recycling potential and economic value. The use of electroplating sludge to prepare catalysts for CO 2 capture and biochar gasification has rarely been reported. In this study, a sustainable method is proposed for recovering Ni-containing electroplating sludge by synthesizing Ni-CaO composite metal oxide catalysts, which enhance the catalytic gasification of biochar with CO 2 . The effects of various reaction conditions on CO release and CO 2 conversion rates were systematically investigated. According to the results, the optimized Ni-CaO-2 catalyst (30 wt % loading) exhibited outstanding catalytic performance, achieving a peak CO release rate of 114.8 mL/min/g and a CO 2 conversion rate of 62.3% at 850 °C, which was 1.6 times that of the conventional CaO catalyst. The incorporation of Ni improved gasification performance through the redox effect of Ni 2+ /Ni 3+, which induced the formation of oxygen vacancies, thereby promoting CO 2 activation. This approach not only facilitates the recycling of hazardous electroplating sludge but also contributes to carbon emission reduction, providing a sustainable strategy for waste utilization and environmental protection.