Direct UV photolysis of selected pharmaceuticals, personal care products and endocrine disruptors in aqueous solution

Pharmaceuticals and personal care products (PPCPs), and endocrine disrupting compounds (EDCs) are micropollutants of emerging concern that have been detected in the aquatic environment and in some cases, in drinking water at nanogram per liter levels. The goal of this study was to evaluate the removal of 15 model PPCPs and EDCs from water by direct UV photolysis, using either low (LP) or medium (MP) -pressure mercury vapor arc lamps. Some of the model compounds are either weak bases or weak acids, and therefore, the pK(a) values were determined or confirmed for those compounds using spectrophotometric titrations. The molar absorption coefficients of ionized and non-ionized forms were also determined. The quantum yields at 253.7 nm in phosphate buffer solutions of pH 7.2 were determined to be 0.033 +/- 0.004 for sulfamethoxazole, 0.0035 +/- 0.0008 for sulfachloropyxidazine, 0.006 +/- 0.002 for acetaminophen, 0.34 +/- 0.07 for triclosan, 0.35 +/- 0.14 for estrone, 0.08 +/- 0.05 for 17 alpha-ethinylestradiol, 0.086 +/- 0.012 for ibuprofen. The quantum yield for 4-n-nonylphenol photolysis at 253.7 nm varied with the initial concentration from 0.32 +/- 0.08 at 23 mu g/L to 0.092 +/- 0.006 at 230 mu g/L. The pseudo-first order rate constants determined for direct photolysis at 253.7 nm of the studied micropollutants followed the order: triclosan approximate to sulfamethoxazole >> 4-n-nonylphenol approximate to sulfachloropyridazine approximate to estrone > acetaminophen approximate to 17 alpha-ethinylestradiol approximate to ibuprofen. In contrast to the results observed for the monochromatic radiation (LP lamp), all 15 model compounds photolyzed under exposure to the broadband radiation emitted by the MP lamp. (C) 2015 Elsevier Ltd. All rights reserved.