LAUSR

Abstract Sewage sludge, an unavoidable by-product of industrial wastewater treatment, is facing multitudinous challenges in drawing a cost-effective compromise between environmental and economic acceptance. The aim of this research is to produce high-quality energy materials by utilizing hazardous waster as precursors. A novel inorganic-organic composite flocculant was first manufactured and used as an efficient binary-coagulant for enhanced dyes removal and Fe-containing textile sludge (TS-Fe) production from dyeing wastewater. Then, three-dimensional interconnected hierarchical porous iron-nitrogen doped carbon materials (TS-Fe-N-C) were fabricated by pyrolysis of TS-Fe to realize the resource recovery. Upon accurate control the composition of TS-Fe-N-C, the optimal TS-Fe-N-C-0.23 has excellent performance for oxygen reduction reaction (half-wave potential of 0.837 V), oxygen evolution reaction (overpotential of 0.328 V at 10 mA cm-2), and hydrogen evolution reaction (overpotential of 0.144 V at 10 mA cm-2). Moreover, Zn-air battery and water splitting device based on TS-Fe-N-C-0.23 electrodes displayed satisfactory energy density (770.0 mAh g-1), power density (120.5 mW cm-2), and low water splitting voltage (1.70 V @ 10 mA cm-2). This study suggests that rational design of flocs by conventional wastewater treatment technologies is an effective strategy for optimizing the composition of sludge and boosting the additional value to the sludge-derived biochar product.