Unraveling the instability of Nitrogen-Doped carbon during BPA treatment by peroxymonosulfate Activation: Effect of free radical grafting

Abstract

Nitrogen-doped carbon has been established as an effective catalyst for peroxymonosulfate (PMS) activation to remove pollutants from water. However, the easy deactivation during the reaction process limits its potential for widespread application. In this study, nitrogen-rich carbocatalysts was synthesized by two-step pyrolysis and used to activate PMS for degradation of bisphenol A (BPA). The nitrogen-rich catalysts calcined at 900 ℃ with the amount of 2 mg degraded more than 80 % of 20 mg/L BPA in 20 min and the degradation of TOC has reached 65 %, showing excellent catalytic performance. Based on free radical quenching experiments and electron spin resonance (ESR), the non-radical process played a key role in BPA degradation. The characterization results of fresh and used catalysts suggested that the instability of the nitrogen-rich carbon materials resulted from the grafting reaction between free radicals on the graphite carbon site of the N-doped carbon materials and the intermediate degradation products of BPA, which covered the active sites of the catalysts. This new discovery elucidates the reason of N-doped carbon materials deactivation in PMS oxidation and provides a complementary for the reaction mechanism of carbon catalysis.