Pyrrolic N-rich biochar without exogenous nitrogen doping as a functional material for bisphenol A removal: Performance and mechanism

Abstract Nitrogen configurations doped in carbon matrix serve as the catalytically active sites for the metal-free activation of persulfates (peroxydisulfate PDS, and peroxymonosulfate PMS). Herein, a series of pyrrolic N-rich biochars (BDKx, where x represents the pyrolysis temperature) were facilely prepared by using waste bean dregs as the feedstocks. The resulted BDK900 possessed ultra-high specific surface area (SBET, > 3000 m2 g-1). Accordingly, it exhibited superior catalytic activity in PDS activation, as evidenced by the efficient removal of bisphenol A (BPA, 1358.4 mg g-1) with 0.05 g L−1 BDK900 and 5 mM PDS. Surface-bound radicals and electron-transfer mechanism were discovered to contribute to the BPA oxidation, during which BDK900 played vital roles in PDS activation, BPA accumulation, and regulating electron shuttle from BPA to PDS. Overall, this study sheds new light on the rational design of N-rich biochar and develops a low-cost technology toward remediation of BPA-contaminated wastewater.