Aplicação dos processos oxidativos, redutivos e (foto)eletroquímicos na degradação de fármacos em meio aquoso

Abstract

A detailed investigation on the efficiency of several processes in promoting the degradation of some organic microcontaminants, from the class of the emerging pollutants, in water was performed. The following substances were tested: clofibric acid, atenolol, carbamazepine (drugs), folic acid (a vitamin compound) and ethinyl estradiol (a hormone). For the degradation of these emerging pollutants, several processes (advanced oxidation, reductive, electrochemical and photoelectrochemical) were used. To determine the presence of degradation products, the reactions were monitored by various analytical techniques, mainly electrospray ionization mass spectrometry (ESI-MS). Measurements of total organic carbon (TOC) revealed the degree of mineralization obtained. Thus, it was found that the ozonolysis and heterogeneous Fenton system (usingthe iron/ hematite composite), examples of advanced oxidation processes, showed high efficiency to deplete ethinylestradiol (100 % for both systems), carbamazepine (100 % and 50 % for ozonolusis and heterogeneous fenton system, respective) and folic acid (100 % for both systems), but with low mineralization rates. Monitoring by ESI-MS(direct infusion) revealed the presence of products from the ozonolysis ofcarbamazepine and ethinyl estradiol. Based on the data from ESI-MS (m/z ratio of ionic species formed from substances in solution) and MS/MS (fragmentation profile of such ionic species), degradation routes for both substances could thus be proposed. It was also evaluated the efficiency of reductive processes, using zero valence metals (Feo and Zno) in the presence of H2O2, on the degradation of the following analytes: clofibric acid, atenolol, carbamazepine and ethinyl estradiol. Whereas thesystem Zno/H2O2 displayed undesirably low degradation rates, much better and promising results were achieved when the Feo/H2O2 system was employed, especially for ethinylestradiol (until 80 %). Furthermore, degradation products could not be detected via HPLC-MS monitoring.Finally, evaluated the electrochemical and photoelectrochemical processes were those that produced the best results among all the methods investigated. The analytes (clofibric acid, carbamazepine and ethinyl estradiol) were depleted with degradation and mineralization rates close to 100% after relatively short exposure times (less 20 min).The analytical techniques employed (direct infusion ESI-MS and HPLC-UV) to monitor such processes revealed once more no degradation products