Ultrasonic role to activate persulfate/chlorite with foamed zero-valent-iron: Sonochemical applications and induced mechanisms
Qihui Xu, Hong Zhang, Haoran Leng, Hong You, Yuhong Jia, Shutao Wang
Abstract
The novel system, consisting of composite oxidants (persulfate/chlorite, S2O82−/ClO2−) and stationary phase activator (zero-valent-iron foam, Fe0f) driven by ultrasonic (US) field, was applied to treat the triphenylmethane derivative effectively even at low temperature (≈ 289 K). By comparisons of sub-systems, the US roles to S2O82−, ClO2−, and Fe0f were seriatim analyzed. US made the reaction order of multi-component system tend to within 1 (leading to de-order reaction), and widened pH activating range of the Fe0f by sonicate-polishing during the process of ClO2− co-activating S2O82−. US and Fe0f were affected by fluid eddy on activating S2O82−/ClO2−. The Fe0f had slight effect on the temperature of US bubble-water interface but the addition of ClO2− lowered it. The partitioning capacity of the above US reactive zone increased during the reaction. US and ClO2− could enrich the kinds of degradation intermediates. The contributions of free radicals (ClOx-based radicals, sulfate radicals (SO4−), and hydroxyl radicals (OH)) and non-free radicals (ClO2, and O = FeIV/V from ionic Fe under “-O-O-” of S2O82− and cyclic adjustment reaction of ClO2−) processes by sonochemical induction were equally important by corresponding detection means. Especially, real-time and online high-resolution mass spectrum by self-developing further confirmed the chain transfers of different free radicals due to US role. The findings expanded the application of sono-persulfate-based systems and improved understanding on activation mechanism.