Degradation of diclofenac in water by direct photolysis using different irradiation sources

Sve veća prisutnost različitih onečišćujućih tvari, pa tako i lijekova, tj.farmaceutika u vodi, izaziva zabrinutost stručnjaka ali i cjelokupne javnosti. Primjena farmaceutika u današnjem životu je vrlo česta, te oni negdje u konačnici moraju završiti. Dio njih završi u prijemnicima putem otpadnih voda, dio putem metabolita. Za velik dio farmaceutika još uvijek nisu razvijene adekvatne metode uklanjanja, što je naravno, potrebno unaprijediti. Posljednjih se godina sve više unaprjeđuju napredni oksidacijski procesi (AOP), putem kojih se učinkovito mogu ukloniti različita onečišćivala. Na novu listu prioritetnih onečišćivala je između ostaloga uvršten i diklofenak (DCF), te je time označen kao prioritetna opasna tvar. Stoga je potrebno detaljnije razmotriti svojstva diklofenaka, njegovu prisutnost i zadržavanje u prijemnicima, učinak na okoliš, kao i mogućnosti njegova uklanjanja i razgradnje, što je proučavano u ovom radu. Konkretno se u ovom radu proučavala učinkovitost razgradnje DCF-a primjenom direktne fotolize uz UV-A365 i UV-C254 tipove zračenja. Utvrđeno je da se diklofenak brže i uspješnije razgrađuje uz pomoć UV-C254 zračenja, gdje je postignuto njegovo potpuno uklanjanje za samo 9 minuta, dok je uz pomoć UV-A365 zračenja za isti učinak bilo potrebno čak 29 sati. Nadalje, utvrđeno je da kinetika mineralizacije uz UV-C zračenje ima pseudo-linearni trend. Također je utvrđeno da otopina DCF-a nije biorazgradiva s obzirom da je omjer BPK5/KPK=0.043, koji bi za biorazgradivu otopinu iznosio ≥0,4. Također, pokazalo se da se primjenom direktne fotolize biorazgradivost ne mijenja značajno, te da isto tako da ne dolazi niti do smanjenja toksičnosti, iako trend promjene ukazuje na mogućnost smanjenja produljenjem vremena obrada u oba slučaja.The presence of various pollutants, including pharmaceuticals, in water increases continuously, causing the serious concern of water experts and scientists, but general public as well. The application of pharmaceuticals in every day life is very spread, and in such manner, their concentrations in environment increase as well. As pharmaceuticals pertain to the class of new pollutants, the methods for their removal from the environment are still under development. Recently, the application of advanced oxidation processes is under consideration to be further developed and integrated in the water purification system with the goal to remove pharmaceuticals. The latest EU Directive from the water quality and management sector, which includes the list of 45 priority substances, classified diclofenac (DCF) as “new potential priority substances” by including it to the “watch list”. Hence, the environmental fate and behavior of DCF, as well as effective treatment methods for its complete removal should be investigated, which was actually the topic of this work. Within this work, the effectiveness of direct photolysis, applying UV-C and UV-A irradiation sources, for DCF degradation was investigated. It was established that DCF photolysis kinetics is much faster under UV-C irradiation; 9 minutes was necessary to completely degrade DCF in water. On the other hand, in the case of UV-A light 29 hours was needed for the same result. Furthermore, the mineralization followed pseudo-linear trend, indicating on the zero-order kinetics in the investigated treatment period. The initial DCF solution was nonbiodegradable with BOD5/COD ratio of 0.043, far below biodegradability limit of 0.4. It was established that photolytic treatment did not improve DCF biodegradability during the observed treatment period, while in the case of toxicity certain changes during the treatment indicated on the nature of formed by-products and their correlation with the overall toxicity