Insight into the mechanism of peracetic acid activation by corn straw-derived biochar as efficient green activator mediating electron transfer: Crucial role of carbonyl functional group

Abstract

Efficient and economical activator for enhancing peracetic acid (PAA) to generate reactive species is greatly critical for elevating the removal efficiency of the recalcitrant organic compounds in the water and wastewater treatment. Corn straw-derived biochar (CBC) is prepared by pyrolysis method with ample oxygen-containing functional group and defective structures working as an efficient electron transfer medium, which can promote PAA activation for the tetracycline (TC) degradation. In the CBC/PAA system, the TC degradation rate can reach 97.7 % within 30 min of reaction. The high performance of the CBC/PAA system is mainly attributed to the combined process of the free radical and the non-free radical pathway. According to the electrochemical experiments and density functional theory (DFT) calculation, carbonyl functional group (C=O) plays a crucial role for PAA activation. The electron-rich group C=O can not only transfer electrons from carbon networks and TC to PAA, but also provide electrons to directly activate PAA due to the presence of lone pair electrons. Moreover, the TC degradation pathways guided by radical and non-radical mechanisms are elucidated, and the toxicity changes of intermediate products are evaluated. In this study, a low-cost and efficient process combining PAA and biochar based on electron transfer mechanisms is proposed, guaranteeing the rapid TC degradation.