Biochar in hydroxyl radical-based electrochemical advanced oxidation processes (eAOPs) – Mechanisms and prospects

Electrochemical advanced oxidation processes (eAOPs) with in-situ generation and activation of H2O2, as used in the conventional Fenton process, are an attractive solution for the removal of recalcitrant organic pollutants in wastewater, given that they are considered sustainable, cost-efficient, versatile and easy to operate. Biochar possesses outstanding and tunable physicochemical properties, such as high electrical conductivity, large specific surface area, large number of functional groups and high stability, arousing extensive interest in acting as an electrocatalyst or electrode material in eAOPs. In this review, firstly, the desirable physicochemical properties of biochar for its application as catalyst or electrode material in EAOPs are summarized. Secondly, the mechanisms for electrocatalytic in-situ generation and activation of H2O2 by biochar in EAOPs are presented, providing deeper insights into the process and mechanisms for organic pollutants degradation by EAOPs. Moreover, modification strategies to improve the performance of biochar in EAOPs are addressed. Finally, the remaining challenges and perspectives for the application of biochar in EAOPs are discussed.