One-Electron Oxidant-Induced Transformations of Aromatic Alcohol to Ketone Moieties in Dissolved Organic Matter Increase Trichloromethane Formation.

Radicals in advanced oxidation processes (AOPs) degrade micropollutants during water and wastewater treatment, but the transformation of dissolved organic matter (DOM) may be equally important. Ketone moieties in DOM are known disinfection byproduct precursors, but ketones themselves are intermediates produced during AOPs. We found that aromatic alcohols in DOM underwent transformation to ketones by one-electron oxidants (using SO 4 •- as a representative), and the formed ketones significantly increased trichloromethane (CHCl 3 ) formation potential (FP) upon subsequent chlorination. CHCl 3 -FPs from aromatic ketones (Ar-CO-CH 3 , average of 22 mol/mol) were 6-24 times of CHCl 3 -FPs from aromatic alcohols (Ar-CH(OH)-CH 3 , average of 0.85 mol/mol). At a typical SO 4 •- exposure of 7.0 × 10 -12 M·s, CHCl 3 -FPs from aromatic alcohol transformation increased by 24.8%-112% with an average increase of 53.4%. Notably, SO 4 •- oxidation of aliphatic alcohols resulted in minute changes in CHCl 3 -FPs due to their low reactivities with SO 4 •- (∼10 7 M -1 s -1 ). Other one-electron oxidants (Cl 2 •- , Br 2 •- ,and CO 3 •- ) are present in AOPs and also lead to aromatic alcohol-ketone transformations similar to SO 4 •- . This study highlights that subtle changes in DOM physicochemical properties due to one-electron oxidants can greatly affect the reactivity with free chlorine and the formation of chlorinated byproducts.