Two analytical approaches quantifying the electron donating capacities of dissolved organic matter to monitor its oxidation during chlorination and ozonation
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Electron-donating activated aromatic moieties, including phenols, in dissolved organic matter (DOM)partially control its reactivity with the chemical oxidants ozone and chlorine. This comparative studyintroduces two sensitive analytical systems to directly and selectively quantify the electron-donatingcapacity (EDC) of DOM, which corresponds to the number of electrons transferred from activated aro-matic moieties, including phenols, to the added chemical oxidant 2,20-azino-bis(3-ethylbenzothiazoline-6-sulphonate) radical cation (i.e., ABTSþ). Thefirst system separates DOM by size exclusion chroma-tography (SEC) followed by a post-column reaction with ABTSþand a spectrophotometric quantificationof the reduction of ABTSþby DOM. The second system employsflow-injection analysis (FIA) coupled toelectrochemical detection to quantify ABTSþreduction by DOM. Both systems have very low limits ofquantification, allowing determination of EDC values of dilute DOM samples with<1 mg carbon per liter.When applied to ozonated and chlorinated model DOM isolates and real water samples, the twoanalytical systems showed that EDC values of the treated DOM decrease with increasing specific oxidantdoses. The EDC decreases detected by the two systems were in overall good agreement except for onesample containing DOM with a very low EDC. The combination of EDC with UV-absorbance measure-ments gives further insights into the chemical reaction pathways of DOM with chemical oxidants such asozone or chlorine. We propose the use of EDC in water treatment facilities as a readily measurableparameter to determine the content of electron-donating aromatic moieties in DOM and thereby itsreactivity with added chemical oxidants.
|Publication status||Published - 2018 Jun 27|