Enhanced photolytic and photooxidative treatments for removal of selected pharmaceutical ingredients and their degradation products in water matrices

Abstract

Photolytic and photooxidative degradations of diclofenac (DICL), naproxen (NAPR) and carbamazepine (CARB) were compared by a conventional low-pressure mercury-vapor lamp with λmax = 254 nm and a vacuum UV (VUV) one, emitting also at 185 nm (in 11%) in ultra-pure water (UPW) and municipal wastewater (WW) spiked with 5 × 10−6 M for each drug. Almost complete photolytic and photooxidative degradations were observed by VUV irradiation for all three compounds in 2 min. About 75% decrease in the total organic carbon content was determined in UPW irradiated samples spiked at the 2–5 × 10−5 M levels in 15 min. Effective degradations of DICL, NAPR and CARB were achieved in spiked WW by photolysis and photooxidation (PhO) at 185 nm (11%) within 1, 2 and 10 min, respectively. Several aromatic degradation products of DICL, NAPR and CARB were identified by quadrupole time-of-flight mass spectrometer hyphenated to an ultra-high performance liquid chromatograph after preconcentration with off-line solid phase extraction upon irradiation of the UPW matrix spiked with the selected drugs at 254 nm. For several degradation products, chemical structures differing from those previously reported have been proposed. Moreover, acridine has not yet been reported as photodegradation product for DICL. Degradation pathways have been also proposed. Almost complete degradation of DICL, NAPR and CARB as well as their degradation products by VUV + PhO in WW took place in 5, 10 and 30 min, respectively. However, the total organic content decreased by only 25% in the WW sample.