Hydrochar as sustainable redox catalyst for advanced oxidation processes-based wastewater treatment

Abstract Hydrochar-based catalysts (HBCs) are one example of carbon-based catalysts and four forms of hydrochar-based catalysts have been reported in environmental remediation, including pristine hydrochar (HC), heteroatom-doped hydrochar (HA-HC), metal-doped hydrochar (M-HC), and metal-heteroatom co-doped hydrochar (M-HA-HC). However, research on HBCs and their catalytic performance in advanced oxidation processes remains limited and this is attributed to low specific surface area and poor porosity, low aromatization and carbonization degrees, and inadequacy of literature on its production methods for enhanced advanced oxidation processes (AOPs). Herein, we aimed to discuss the activation mechanisms of the selected oxidants ( i.e. , peroxymonosulfate (PMS), peroxydisulfate (PDS), ozone (O 3 ), and hydrogen peroxide (H 2 O 2 )) by different HBCs, characteristics of emerging pollutants, and synthesis conditions ( i.e. , biomass type, temperature and residence time, reaction solvent, in situ air stream, post-treatment, and external dopants) that influence the desirable properties of catalysts, comprehensively highlighting their enhanced potential as effective activators for AOPs-based wastewater treatment.