Enhanced charge transfer over sustainable biochar decorated Bi2WO6 composite photocatalyst for highly efficient water decontamination

ABSTRACT As a green and efficient technology, photocatalysis has practical application value, especially in terms of remediating environmental contamination issues. Biochar, the carbon material derived from sustainable calcined biomass waste, has attracted attention for its efficient adsorption capacity for pollutants. Herein, nitrogen(N)-doped biochar is prepared from sawdust biomass and dexterously coupled with Bi 2 WO 6 to synthesize a range of Bi 2 WO 6 /N-doped biochar composites (BWO/N x -BC), which are successfully utilized for photodegradation of chlorpyrifos (CPs). After introducing N atoms, BWO/N3-BC improves conductivity of electrons while maintaining strong adsorption properties, effectively preventing the charge recombination. BWO/N3-BC demonstrates high efficiency in ultrafast photodegradation of recalcitrant pesticides, destroying 99.0% of CPs in only 0.5 h. Besides, the degradation rate constants are 2.91 and 12.13 times higher than those of pure BWO and N3-BC, respectively. Given the complexity of real water environments, the effects of different operating parameters on photocatalytic activity are explored. Free radical scavenging assay and electron paramagnetic resonance are employed to uncover the key active species (•O 2 – , •OH, and h + ), with •O 2 – being the predominant contributor, and the synergistic enhancement mechanism of adsorption-photodegradation of BWO/N3-BC is successfully revealed. Also, the intermediates of CPs are identified by HPLC-MS, and three possible degradation pathways are proposed. In addition, the ecotoxicity of CPs and their intermediates are evaluated by ecotoxicity test ( E. coli culture) and Toxicity Evaluation Software Tool. This work may provide an opening for environmental remediation via photocatalysis integrated with waste biomass high-value valorization.