Photodegradation Performance And Mechanism Of Typical Carboxylic PPCPs In Water By UV Irradiation

Pharmaceutical and personal care products (PPCPs), as a class of emerging organic pollutants, have been widely concerned in recent ten years. Though the concentrations of the detected PPCPs in aqueous environment are low, the PPCPs still have potential risks to human body and ecosystem due to its pseudo-persistent, and bioaccumulative Both conventional drinking water and waste water treatment process are not effective for the PPCPs removal. Therefore, other effective water treatment process should be explored to completely remove such organic contaminants. In this paper, eight typical carboxylic PPCPs including ibuprofen (IBP), naproxene (NPX), ketoprofen (KTP), flurbiprofen (FLBP), diclofenac acid (DCF), meclofenamic acid (MCFN), fenoprofen (FNPF), and oxaprozin (OPX) were selected as the target contaminants, the photodegradation kinetics of these eight selected PPCPs were studied. In addition, the influencing factors, photo-byproducts, photodegradation pathways and mechanisms of FLBP and MCFN during UV irradiation were studied.The HPLC analysis methods of IBP, NPX, KTP, FLBP, DCF, MCFN, FNPF, and OPX were established. The stablished methods were carried out to detect the samples taking from Qiangtang River, in which DCF and MCFN were detected.The photodegradation kinetics of these eight selected PPCPs are fit well with the pseudo-first-order kinetics. The photodegradation rate constant (k) of IBP, NPX, KTP, FLBP, DCF, MCFN, FNPF, and OPX are0.0055,0.0165,0.019,0.1966,0.1983,0.1818,0.0215, and0.1101min-1, respectively.Parameters affecting the photodegradation processes of FLBP and MCFN including reaction temperature, initial concentration, initial solution pH, humic acid concentration and inorganic ions were studied through the single factor experiments. Significance analysis and regression analysis were carried out to investigate the influencing factors through SPSS(Statistics Package for Social Science). Results showed that the apparent degradation rate constant (k) increased with the increasing reaction temperature for FLBP, while the temperature had little influence on the photodegradation of MCFN. The increasing initial concentration and humic acid had an adverse effect on the photodegradation for both FLBP and MCFN. It was found that the weak acidic environment (pH=6-7) boasted the best performance for both FLBP and MCFN degradation. The inorganic ions had different effects on the photodegradation of FLBP and MCFN. The inorganic ions had no influence on the photodegradation of MCFN, while had different sensitivity to different ions on the photodegradation of FLBP. The model of photodegradation rate constant (k) and main influencing factors of FLBP and MCFN were built through regression analysis.The intermediate products during photodegradation of FLBP and MCFN were identified by TOC, LC/MS, IC analysis, and photodegradation pathways were proposed. The TOC results showed the target contaminants were not mineralized, though the removing rate of contaminants were above99%, indicating the formation of many unknown photoproducts. It was found that the F atom in the FLBP molecule and the Cl atom in the MCFN molecule could be easily and completely falled off from benzene ring, forming the F-and Cl-in water. In the experiment, the main mechanisms of FLBP photodegradation are the drop of F atom, decarboxylation and hydroxylation. While in MCFN photodegradation, besides the drop of C1atom and hydroxylation, the dechlorination and cyclization reaction were observed.