Enhancing degradation of atrazine by Fe-phenol modified biochar/ferrate (VI) under alkaline conditions: Analysis of the mechanism and intermediate products

In this study, Fe-phenol modified biochar was prepared to enhance atrazine (AT) degradation by ferrate (Fe(VI)) under alkaline conditions, and the properties, mechanism and transformation pathways were extensively investigated. Degradation experiments showed that Fe-phenol modified biochar was more beneficial for improving the oxidation capacity of Fe(VI) than unmodified biochar, and the biochar with a molar ratio of Fe3+ to phenol of 0.1:5 (BC-2) showed the best promoting effect, and more than 94% of AT was removed at pH = 8 within 30 min. Moreover, the rate of oxidation (k(app)) of AT by Fe(VI) increased 1.86 to 4.11 times by the addition of BC-2 in the studied pH range. Fe(V)/Fe(IV) and center dot OH were the main active oxidizing species for AT degradation in the Fe(VI)/BC-2 group and contributed to 70% and 24%, respectively, of degradation. The formation of center dot OH and Fe(V)/Fe(VI) was mainly due to the persistent free radicals and reducing groups on the surface of BC-2. AT was oxidized to 12 intermediate products in the Fe(VI)/BC-2 group through 5 pathways: alkyl hydroxylation, dealkylation, dichlorination, hydroxylation, alkyl dehydrogenation and dichlorination. Compared with those of the initial solution, the total organic carbon content and toxicity after the reaction decreased by 32.8% and 19.02%, respectively. Therefore, the combination of Fe-phenol modified biochar and Fe(VI) could be a promising method for AT removal.

Automated summary

The Fe-phenol modified biochar enhanced the degradation of atrazine by Fe(VI) under alkaline conditions. Fe(V)/Fe(IV) and ·OH were identified as the main active oxidizing species, contributing to 70% and 24% of degradation, respectively. The combination of Fe-phenol modified biochar and Fe(VI) showed promising potential for atrazine removal with significant reduction in total organic carbon content and toxicity.