Waste to Energy Storage: Fe-Doped ZnO/Carbon Anodes Synthesized From Galvanizing Flue Dust

Zinc, in a complex form, is one of the main components of the flue dust formed during the hot-dip galvanizing (HDG). Its disposal not only causes economic losses but also poses significant environmental challenges. In alignment with circular economy, the utilization of such industrial residues in value-added applications becomes vital. Herein, using HDG flue dust as an input material, a novel approach for synthesizing Fe-doped ZnO/carbon-based composite anode materials for lithium-ion batteries (LIBs) is proposed. In this scope, a three-step process comprising neutral leaching, calcination, and ball milling is employed for the fabrication. Neutral leaching is optimized to enrich the hot-dip galvanizing (HDG) flue dust residue with zinc and iron while simultaneously reducing the concentrations of ammonia and chlorine. The optimal leaching conditions (95.7 wt% Zn retention efficiency) are determined to be 80°C, a solid to liquid ratio of 1:100, and a leaching time of 1 h at 750 rpm. Later, the solid residue is subjected to thermal treatment at 500°C for 4 h, resulting in Fe-doped ZnO powder. Lastly, the synthesized Fe-doped ZnO powder is mechanically ball-milled with activated carbon (AC) at three different weight ratios: Fe-ZnO:C = 1:1, 2:1, and 3:1. Fe-ZnO:C = 3:1 achieves the highest capacity and the best retention: at the 1st and 100th cycles, it delivers 1760.72 and 592.68 mAh g⁻¹, respectively. The enhanced performance of the composite is attributed to its unique properties in morphology, structure, and chemistry. (Figure presented.).