Biochar, a carbon-based material derived from biomassBiomass is a complex biological organic or non-organic solid product derived from living or recently living organism and available naturally. Various types of wastes such as animal manure, waste paper, sludge and many industrial wastes are also treated as biomass because like natural biomass these More residues, is gaining prominence for its environmental sustainability and multifaceted applications. Notably, biochar-bound persistent free radicals (biochar-PFRs) play a crucial role in environmental remediation, particularly in the transformation of contaminants in wastewater treatment processes. Despite their potential, the comprehensive understanding of the redox activity of biochar-PFRs, including their mechanisms of consumption and regeneration, presents a significant challenge.

Biochar-PFRs are generated during the pyrolysisPyrolysis is a thermochemical process that converts waste biomass into bio-char, bio-oil, and pyro-gas. It offers significant advantages in waste valorization, turning low-value materials into economically valuable resources. Its versatility allows for tailored products based on operational conditions, presenting itself as a cost-effective and efficient More of biomass and are distinguished by their unpaired electrons. These radicals are capable of mediating redox reactions, leading to the degradation of various pollutants. The review delves into the intricacies of these processes, highlighting both non-free radical and free radical pathways. Moreover, it sheds light on the regeneration of biochar-PFRs, which can be triggered by metal cations, reactive oxygen species, and ultraviolet radiations.

A significant challenge in assessing the redox activity of biochar-PFRs lies in the interference caused by components with unpaired electrons and the limitations posed by scavengers and extractants. To address this, the review proposes practical strategies for accurately determining the redox activity of biochar-PFRs.

In conclusion, the review calls for further research to fill existing knowledge gaps and enhance the application of biochar-PFRs in environmental remediation. By providing a comprehensive analysis of the redox activity of biochar-PFRs, this review aims to offer valuable insights for scientists and practitioners in the field, paving the way for innovative solutions to wastewater treatment and pollutant transformation.