Degradation pathways of atrazine by electrochemical oxidation at different current densities: Identifications from compound-specific isotope analysis and DFT calculation

Current density was the key factor that impacted pollutant degradation by electrochemical oxidation, and reaction contributions at various current densities were non-negligible for the cost-effective treatments of organic pollutants. This research introduced compound specific isotope analysis (CSIA) into atrazine (ATZ) degradation by boron doped diamond (BDD) with current density of 2.5-20 mA/cm(2), in order to provide in-situ and fingerprint analysis of reaction contributions with changed current densities. As results, the increased current density displayed a positive impact on ATZ removal. The.C/ H values (correlations of Delta delta C-13 and Delta delta H-2) were 24.58, 9.18 and 8.74 when current densities were 20, 4, and 2.5 mA/cm(2), with center dot OH contribution of 93.5%, 77.2% and 80.35%, respectively. While DET process favored lower current density with contribution rates up to similar to 20%. What's more interesting, though the carbon and hydrogen isotope enrichment factors (epsilon(C) and epsilon(H)) were fluctuate, the Lambda(C/H) linearly increased accompanied with applied current densities. Therefore, increasing current density was effective due to the larger center dot OH contribution even though side reactions may occur. DFT calculations proved the increase of C-Cl bond length and the delocalization of Cl atom, confirming dechlorination reaction mainly occurred in the direct electron transfer process. While center dot OH radical mainly attack the C-N bond on the side chain, which was more benefit to the fast decomposition of ATZ molecule and intermediates. It was forceful to discuss pollutant degradation mechanism by combining CSIA and DFT calculations. Target bond cleavage (i.e., dehalogenation reaction) can be conducted by changing reaction conditions like current density due to the significantly different isotope fractionation and bond cleavage.

Automated summary

Current density has a significant impact on the degradation of pollutants through electrochemical oxidation, and different current densities contribute to cost-effective treatment of organic pollutants. This research combined compound specific isotope analysis (CSIA) and boron doped diamond (BDD) to study atrazine (ATZ) degradation under different current densities, revealing the reaction contributions. The results showed that increasing current density had a positive effect on ATZ removal, with higher center dot OH contributions at higher current densities. The combination of CSIA and DFT calculations provided valuable insights into the pollutant degradation mechanism and demonstrated the possibility of conducting targeted bond cleavage by altering reaction conditions like current density.