Efficient degradation of 2,3,5-trimethylpyrazine by catalytic ozonation over MnOx supported on biochar derived from waste tea leaves

In this study, a series of biochars derived from waste tea leaves and loaded with MnOx (Mn-nWT) was fabricated for use in heterogeneous catalytic ozonation (HCO). Excellent degradation of 2,3,5-trimethylpyrazine (TMP) was achieved. Characterization data indicated that Lewis acid sites, including multivalent Mn sites, oxygen vacancies and surface hydroxyl groups, were the main active sites responsible for the HCO activity of Mn-nWT. The Mn-nWT catalysts exhibited superior HCO activity compared with bulk biochar and MnOx under various experi-mental conditions. In particular, 0.05 g L-1 Mn-5WT gave 95.3% degradation of 5 mu M TMP in 30 min at pH 7.0. Reactive oxygen species (mainly center dot OH) generated from catalytic decomposition of ozone by Mn-nWT contributed to the enhanced HCO performance. The second-order degradation rate constants of TMP with O3 and center dot OH are 2.3 +/- 0.13 and (7.3 +/- 1.31) x 109 M-1 s-1. The reusability and stability of Mn-5WT was demonstrated by outstanding TMP degradation efficiency (88.8%), negligible metal dissolution and minor differences in physical characterization after four cycles. Additionally, the impacts of water matrices (catalyst dose, ozone dose, pH, temperature, carbonate and natural organic matter) on the Mn-5WT HCO process were investigated thoroughly. This study found that loading of metal oxides onto biochar synergistically promoted the HCO process by enhancing the physical and chemical properties.

Automated summary

In this study, MnOx loaded biochars derived from waste tea leaves were fabricated and demonstrated excellent degradation efficiency of 2,3,5-trimethylpyrazine (TMP) through heterogeneous catalytic ozonation (HCO) process. The active sites responsible for the HCO activity were identified as Lewis acid sites, including multivalent Mn sites, oxygen vacancies, and surface hydroxyl groups. Mn-nWT catalysts showed superior HCO activity compared to bulk biochar and MnOx. The impacts of water matrices on the Mn-5WT HCO process were thoroughly investigated.