Ultrasonic role to activate persulfate/chlorite with foamed zero-valent-iron: Sonochemical applications and induced mechanisms.

The novel system, consisting of composite oxidants (persulfate/chlorite, SO/ClO) and stationary phase activator (zero-valent-iron foam, Fe) 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 SO, ClO, and Fe 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 Fe by sonicate-polishing during the process of ClO co-activating SO. US and Fe were affected by fluid eddy on activating SO/ClO. The Fe had slight effect on the temperature of US bubble-water interface but the addition of ClO lowered it. The partitioning capacity of the above US reactive zone increased during the reaction. US and ClO could enrich the kinds of degradation intermediates. The contributions of free radicals (ClO-based radicals, sulfate radicals (SO), and hydroxyl radicals (OH)) and non-free radicals (ClO, and O = Fe from ionic Fe under "-O-O-" of SO and cyclic adjustment reaction of ClO) 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.