UV and solar photo-degradation of naproxen: TiO2 catalyst effect, reaction kinetics, products identification and toxicity assessment

• Published in: Journal of hazardous materials 2016-03, Vol.304, p.329-336
• Main Authors: Jallouli, Nabil, Elghniji, Kais, Hentati, Olfa, Ribeiro, Ana R., Silva, Adrián M.T., Ksibi, Mohamed
• Format: Article
• Language: English
• Subjects: Acute toxicity; Animals; Catalysis; Chemical oxygen demand (COD); Chromatography, High Pressure Liquid; Eisenia andrei; Kinetics; Mass Spectrometry; Naproxen; Naproxen - chemistry; Naproxen - toxicity; Oligochaeta - drug effects; Photocatalysis; Photolysis; Soil Pollutants - toxicity; Sunlight; Titanium - chemistry; Titanium - radiation effects; Ultraviolet Rays; Water Pollutants, Chemical - chemistry; Water Pollutants, Chemical - toxicity
• ISSN: 0304-3894; 1873-3336
• DOI: 10.1016/j.jhazmat.2015.10.045

[Display omitted] •Degradation kinetics and mineralization rate of naproxen (NPX) were studied.•Direct photolysis and TiO2/UV approaches were evaluated.•The formation of by-products was followed by UHPLC-DAD-MS.•Ecological risk assessment of NPX-treated solutions was assessed using E. andrei. Direct photolysis and TiO2-photocatalytic degradation of naproxen (NPX) in aqueous solution were studied using a UV lamp and solar irradiation. The degradation of NPX was found to be in accordance with pseudo-first order kinetics, the photocatalytic process being more efficient than photolysis. The NPX removal by photolysis (pHinitial 6.5) was 83% after 3h, with 11% of chemical oxygen demand (COD) reduction, whereas the TiO2-UV process led to higher removals of both NPX (98%) and COD (25%). The apparent pseudo-first-order rate constant (kapp) for NPX degradation by photolysis ranged from 0.0050min−1 at pH 3.5 to 0.0095min−1 at pH 6.5, while it was estimated to be 0.0063min−1 under acidic conditions in photocatalysis, increasing by 4-fold at pH 6.5. Ultra High Performance Liquid chromatography (UHPLC) coupled with a triple quadrupole detector and also a hybrid mass spectrometer which combines the linear ion trap triple quadrupole (LTQ) and OrbiTrap mass analyser, were used to identify NPX degradation products. The main intermediates detected were 1-(6-methoxynaphtalene-2-yl) ethylhydroperoxide, 2-ethyl-6-methoxynaphthalene, 1-(6-methoxynaphtalen-2-yl) ethanol, 1-(6-methoxynaphtalen-2-yl) ethanone and malic acid. Solar photocatalysis of NPX showed COD removals of 33% and 65% after 3 and 4h of treatment, respectively, and some reduction of acute toxicity, evaluated by the exposure of Eisenia andrei to OECD soils spiked with NPX-treated solutions.