Intermediate accumulation and toxicity reduction during the selective photoelectrochemical process of atrazine in complex water bodies

Abstract

Selective removal of atrazine (ATZ) in wastewater and clarification of the degradation intermediate-toxicity correlation are of great importance. A newly molecularly imprinted, {001} facets-exposed TiO2 (MI-TiO2,001) photoanode with strong catalytic and selective ability was designed. ATZ was selectively removed from pesticide wastewater, reaching 1.9 µg L−1, approximately 1/10 of the concentration achieved with nonselective treatment. This selective removal originated from the preferential adsorption and enrichment of ATZ onto MI-TiO2,001. The highly specific recognition relied on the halogen bond and strong hydrogen bond formed between the Cl atom and triazine ring π orbital of ATZ and the surface -OH group of MI-TiO2,001 as well as the recognition of MI-TiO2,001 to the shape and size of ATZ. The specific interaction leads to different accumulations of intermediates. The correlation of intermediate and toxicity was also discussed. Aquatic toxicity was rapidly reduced through the direct dealkylation path, and due to the accumulation of highly toxic 2‑hydroxy-4-ethylamino-6-isopropylamino-s-triazine, there will be transient fluctuations via the dechlorination-hydroxylation path first. The final product was identified as nearly nontoxic cyanuric acid, the selective accumulation of which indicated that there was almost 100% removal of aquatic toxicity and cytotoxicity with only 9.8% removal of total organic carbon. This work provides new insight into the correlation of pollutant degradation intermediates and changes in toxicity.