Direct UV photolysis of propranolol and metronidazole in aqueous solution

The aim of this work was to study the direct photolysis of two pharmaceuticals: propranolol (PRO) and metronidazole (MET) promoted by ultra violet radiation (UV). For this purpose, 50 and 100 mg L−1 aqueous solutions of PRO and MET were irradiated by two different UV sources: a UV-254 germicidal lamp (UV-C) and a UV-365 black light lamp (UV-A). After 8 h of irradiation, direct UV photolysis promoted substantial pharmaceuticals removal, especially with the use of UV-C radiation (near 50%). However, on average only 12% of the organic matter content was photodegraded. The photo-transformation of both compounds promoted the formation of more biodegradable byproducts. Nevertheless, PRO direct UV-C photolysis produced byproducts with less toxic character while MET irradiation promoted a slight increase of toxicity. Direct photolysis of PRO using solar radiation was proved to be as effective as those runs carried out with the UV-C device. Kinetic constants based on time and UV-C fluency were in a magnitude order of 10−2 h−1 and 10−5 cm2 mJ−1, respectively.