Photoactivation of peroxymonosulfate by wood pulp cellulose biochar/g-C3N4 composite for diclofenac degradation: the radical and nonradical pathways

Metal-free photocatalysts have attracted growing concern recently. Herein, the composites combining g-C3N4 with wood pulp cellulose biochar (WPBC/g-C3N4) were synthesized to effectively activate peroxymonosulfate (PMS) under visible light for the degradation of diclofenac (DCF). The incorporation of WPBC endowed g-C3N4 with enhanced visible light absorption, improved charge separation capability, reduced electrical conductivity, and increased photocatalytic and PMS activation capability. Based on quenching tests, electron paramagnetic resonance (EPR), electrochemical analysis and solvent exchange experiments, both radical and nonradical mechanisms were proposed. Radical species including center dot OH, h(+), center dot O-2(-) were identified to contribute to DCF degradation. The O-1(2) and electron transfer were the dominant nonradical pathways for DCF degradation. Moreover, the common influencing factors were examined, and DCF concentration was the most influential factor based on principal component analysis. Generally, the composites exhibited good reusability during consecutive runs. Based on HPLC/MS analysis, four intermediates were detected and the possible DCF degradation pathway was proposed. This work provided a potential strategy based on metal-free WPBC/g-C3N4 for the photocatalytic activation of PMS to effectively degrade emerging contaminants in wastewater. [GRAPHICS] . Highlights center dot Wood pulp cellulose biochar (WPBC) improved the catalytic performance of g-C3N4 via both radical and nonradical mechanisms. center dot The photoelectrical properties and PMS activation capability were improved by WPBC. center dot WPBC/g-C3N4 presented high stability for multiple runs.

Automated summary

Metal-free WPBC/g-C3N4 composites were synthesized to effectively activate PMS for the degradation of DCF. The composites demonstrated enhanced visible light absorption, improved charge separation capability, and increased photocatalytic and PMS activation capability. Both radical and nonradical mechanisms were proposed for DCF degradation. The composites exhibited good reusability and a possible degradation pathway for DCF was proposed.