Enhancement effect among a UV, persulfate, and copper (UV/PS/Cu2+) system on the degradation of nonoxidizing biocide: The kinetics, radical species, and degradation pathway
2019
Abstract Reverse osmosis concentrate (ROC) generally contains highly toxic and biorefractory organic pollutants. In this study, various oxidation systems, including UV, persulfate (PS)/Cu 2+ , UV/PS, and UV/PS/Cu 2+ , were evaluated for the degradation of nonoxidizing biocides, which are commonly used in reverse osmosis systems for preventing biofouling. The results showed that UV/PS/Cu 2+ had an enhancement effect among UV, PS, and Cu 2+ . Compared with UV/PS, the degradation efficiency of UV/PS/Cu 2+ increased 4.4%–22.2% for dodecyl trimethyl ammonium chloride (DTAC) and 19%–37.6% for dodecyl dimethyl benzyl ammonium chloride (DDBAC). The k obs of DTAC and DDBAC by UV/PS/Cu 2+ were approximately 1.5–2 times higher than those of the UV/PS system, which were examined to be 0.569 and 0.602 min −1 , respectively. The contributions of SO 4 •− , HO • , and other way on the degradation of DTAC and DDBAC in the UV/PS/Cu 2+ system were observed to be 77.0%, 1.0%, and 22.1% for DTAC and 55.3%, 1.0%, and 12.0% for DDBAC, respectively, at pH 7. The effect of humic acids (HAs) and natural organic matter (NOM) considerably impeded the degradation of DTAC (50 and 54%) and DDBAC (47 and 69%) when the concentration of HAs and NOM was 1 and 10 mg/L, respectively. The degradation of DTAC by various metals was enhanced in the order Cu 2+ > Fe 2+ > Mg 2+ > Mn 2+ at 0.1 mg/L, whereas that of DDBAC was Cu 2+ > Mg 2+ > Zn 2+ > Fe 2+ > Mn 2+ .
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