Upcycled CuS/magnetic slag composites: A circular economy strategy for flue gas mercury remediation

Gaseous mercury (Hg⁰) emissions from industrial sources remain a pressing global environmental challenge, with conventional sorbent-based technologies limited by high costs and secondary contamination risks. This study introduces a sustainable waste-to-resource strategy, upcycling two underutilized industrial byproducts—iron-rich copper slag flotation tailings (CSFT) and acidic copper etching wastewater (ACEW)—into magnetic CuS-embedded sorbents via sulfurization-hydrothermal synthesis. By using CSFT as a stable magnetic matrix and ACEW as a copper precursor, this approach delivers dual benefits: efficient Hg⁰ capture and sustainable waste valorization. Under optimized conditions (pH 11, Cu/S molar ratio of 1:5, and ACEW dosage of 6 mL), the synthesized CuS-embedded composite demonstrates exceptional Hg⁰ removal performance, with a 27.7-fold increase in specific surface area compared to the acid-treated matrix. The composite achieves 99 % removal efficiency within 2 h under N₂ and maintains over 80 % efficiency across three regeneration cycles. While its regeneration capacity remains inferior to that of magnetic sulfide-based sorbents synthesized from pure reagents, a techno-economic analysis reveals a 90 % cost reduction (material cost of 175 RMB/kg, energy consumption of 46.2 kWh) compared to conventional counterparts. This integrated strategy bridges mercury pollution control and industrial waste management, offering a scalable, cost-effective solution for atmospheric Hg⁰ remediation.