Effects Of Low-Molecular-Weight Organics On The Photoreduction Of Bromate In Water

Reduction of bromate to bromide is of great significance for the remediation of bromate-containing waters. In natural water, some low-molecular-weight organics (LMWOs) ubiquitously coexist with bromate. However, LMWOs-mediated photoreduction of bromate has been rarely studied. Herein, we found that acids (formic acid, acetic acid, pyruvic acid, lactic acid, and oxalic acid), aldehydes (formaldehyde and acetaldehyde), alcohols (tert-butyl and isopropyl), ketones (acetone, 2,3-butanedione, acetylacetone (AA), and 2,5-hexanedione), and quinones (hydroquinone and benzoquinone) could all enhance the photoreduction of bromate under UV irradiation. The mechanisms of LMWOs-mediated photoreduction of bromate were systematically elucidated. Special attention was paid to AA, because the photolysis of AA generates most of the other tested aliphatic LMWOs. The presence of LMWOs exerted complicated effects on the formation of disinfection byproducts (DBPs): On the one hand, the presence of AA inhibited the formation of hypobromous acid (HBrO), which is believed to be helpful to control the potential formation of DBPs, because HBrO is a key precursor of halogenated DBPs. On the other hand, the LMWOs possibly functioned as precursors of organic halogens. The results here may help us to better understand the fate of bromine species in the natural aquatic environment.