Influence of formic acid on photocatalytic degradation of diclofenac in water

Diklofenak je često korišten nesteroidni, protuupalni, antipiretički lijek dostupan u nizu komercijalnih pripravaka u obliku tableta ili gela. Nakon korištenja, lijek dospijeva u komunalne otpadne vode iz kojih ga je nemoguće u potpunosti ukloniti klasičnim metodama obrade te dospijeva u okoliš zbog čega se nastoje pronaći metode koje bi ga u potpunosti uklonile i time spriječile onečišćavanje okoliša. Fotokatalitički procesi pokazali su se učinkovitima za uklanjanje diklofenaka. U ovom radu je istraživan mehanizam fotokatalitičke razgradnje farmaceutika u vodi. U tu svrhu primijenjeni su UV-A/TiO2 i UV-A/TiO2/H2O2 procesi za razgradnju diklofenaka. Doprinos različitih mehanizama u ukupnoj učinkovitosti fotokatalitičkog procesa obrade voda ispitivan je dodatkom mravlje kiseline i natrijevog formijata kao inhibitora fotogeneriranih šupljina, h+. Mravlja kiselina se pokazala kao neprikladan inhibitor h+ mehanizma razgradnje diklofenaka zbog prirode onečišćivala, tj. precipitacije u kiselim uvjetima. Primjenom natrijeva formijata postignut je visok stupanj inhibicije, što nam govori o velikom doprinosu fotogeneriranih šupljina ukupnoj učinkovitosti istraživanih fotokatalitičkih procesa.Diclofenac is common used non-steroidal, anti-inflammatory, antipyretic drug, available under a number of trade names in the form of tablets or gel. After therapeutic usage, drug is released in municipal wastewater and conventional wastewater treatment methods are found not to efficient for diclofenac removal. Consequently, diclofenac can be detected in the environment; therefore scientific research is aimed to wastewater treatment methods able to remove pollutant as diclofenac to prevent environmental pollution. Photocatalysis is found to be one of the most effective processes for diclofenac removal. In this research the mechanism of photocatalytic degradation of pharmaceuticals in water was studied. For this purpose UV-A/TiO2 and UV-A/TiO2/H2O2 processes for diclofenac removal were applied. Contribution of particular degradation mechanism to overall process efficiency was examined with an addition of formic acid and sodium formiate as photo generated hole, h+ scavengers. Formic acid isn’t appropriate h+ scavenger, due diclofenac precipitation in acidic conditions. On the other hand, when applying sodium formiate, high inhibition rate was achieved, speaking in favor to important role of photo generated holes in photocatalytic processes efficiency