Structure-performance relationship of biochar for direct degradation of organic pollutants

Abstract Recently, most of biochar materials are used as adsorbents to adsorb pollutants or as catalysts for oxidants ( e.g. H 2 O 2 , persulfate, O 3 ) to degrade organic pollutants via free radical pathway and nonradical pathway. Actually, the property of electron transfer endows biochar with direct degradation capability, which is overlooked. However, the structure-performance relationship of biochar for direct degradation of organic pollutants still remains unclear. Besides, the distinction between adsorption, direct degradation, and indirect degradation is also very ambiguous. Therefore, this study employed quantification tests, electrochemical tests and correlation analysis to address this gap. The results show that both the direct and indirect degradation behavior occurred in the system of biochar with different types of organic pollutants. The direct degradation capacity of biochar was highly related to the electron-donating capacity. Additionally, the C–O groups, O–H groups, and graphitic structure promoted the electron transfer for the direct degradation of organic pollutants. Generally speaking, the direct degradation of biochar in our study reached up to 40% ± 10% in the whole degradation performance of both the direct and indirect degradation. Moreover, biochar maintained stable direct degradation performance even after five cycles (~ 100%). This study provides a new insight into the property of biochar in wastewater treatment, rather than adsorbent or catalyst.