No abstract

Research efforts on advanced oxidation processes (AOPs) have long been focused on the fundamental chemistry of activation processes and free radical reactions. Little attention has been paid to the chemistry of the precursor oxidants. Herein, we found that the precursor oxidants could lead to quite different outcomes. A counterintuitive result was observed in the photoreduction of bromate/iodate: the combination of H 2 O 2 and UV enhanced the reduction of bromate/iodate, whereas the addition of persulfate to the UV system led to an inhibitory effect. Thermodynamic and kinetic evidence suggests that the reduction of bromate in UV/H 2 O 2 was attributable to the direct reaction between HOBr and H 2 O 2 . Both experimental determination and kinetic simulation demonstrate that the reaction between HOBr and H 2 O 2 dominated over the • OH-mediated reactions. These results suggest that H 2 O 2 possesses some particular redox properties that distinguish it from other peroxides. The prototypical UV/H 2 O 2 process is not always an AOP: it can also be an enhanced reduction process for chemicals with intermediates that are reducible by H 2 O 2 . Considering the increasing interest in persulfate-based AOPs, the results of this study identify some novel advantages of the classical H 2 O 2 -based AOPs.

Selective inhibition of photosynthesis is a fundamental strategy to solve the global challenge caused by harmful cyanobacterial blooms. However, there is a lack of specificity of the currently used cyanocides, because most of them act on cyanobacteria by generating nontargeted oxidative stress. Here, for the first time, we find that the simplest β-diketone, acetylacetone, is a promising specific cyanocide, which acts on Microcystis aeruginosa through targeted binding on bound iron species in the photosynthetic electron transport chain, rather than by oxidizing the components of the photosynthetic apparatus. The targeted binding approach outperforms the general oxidation mechanism in terms of specificity and eco-safety. Given the essential role of photosynthesis in both natural and artificial systems, this finding not only provides a unique solution for the selective control of cyanobacteria but also sheds new light on the ways to modulate photosynthesis.