Is waste-derived catalyst mediated electro-Fenton a sustainable option for mitigating emerging contaminants from wastewater?

Heterogenous electro-Fenton (H-EF)-based technologies are incredibly potent in mitigating recalcitrant emerging contaminants from different wastewater matrices. The H-EF process facilitates Fenton's oxidation at circumneutral pH and also enable catalyst recycling. However, heterogeneous solid catalysts are often synthesised from expensive and virgin precursors, making H-EF treatment expensive and unsustainable. In this regard, synthesising these catalysts from waste material could be a judicious alternative with multiple environmental and economic benefits. Already in H-EF systems, nitrogen-containing porous biochar has exhibited exceptional H₂O₂ selectivity replacing conventional carbon catalysts, while metallic scraps have been efficiently repurposed to substitute the virgin metal components of heterogenous catalysts. In addition, life cycle assessments have affirmed that repurposed waste catalysts can substantially lower the adverse environmental impacts of H-EF systems. Hence, this opinion article explicitly focuses on materials explored for synthesising waste-derived Fenton catalysts and their most recent application in the remediation of emerging contaminants from wastewater.