Carbon and hydrogen isotopic evidence for atrazine degradation by electro-activated persulfate: Radical contributions and comparisons with heat-activated persulfate.

The activation ways of persulfate (PS) were dominate for pollutant degradation and energy consumption. For the first time, this research compared electro-activated PS and heat-activated PS from the perspective of isotope fractionation, in order to "fingerprinted" and precisely interpretate reaction contributions and degradation pathways. As results, PS can be electrochemically activated with atrazine (ATZ) removal rates of 84.8% and 88.8% at pH 4 and 7. The two-dimensional isotope plots (Ʌ) values were 6.20 at pH 4 and 7.46 at pH 7, rather different from that of SO -dominated process with Ʌ value of -4.80 at pH 4 and -23.0 at pH 7, suggesting the weak contribution of SO. ATZ degradation by electro-activated PS was controlled by direct electron transfer (DET) and ·OH radical, and ·OH (derived from PS activation) played the crucial role with contributing rate of 63.2%-69.1%, while DET and ·OH (derived from electrolysis of HO) contributed to 4.5-7.9% and 23.0%-30.8%, respectively. This was different from heat activation of PS, of which the latter was dominated by SO with contributions of 83.9%-100%. The discrepant dominating reactive oxygen species should be responsible for their different degradation capabilities and pathways. This research provided isotopic interpretations for differences of PS activation mode, and further efforts can be made to realize the selective degradation by enhancing the specific reaction process.