| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 47101 | Applied Catalysis B: Environmental | 2011 | 9 Pages |
The mineralization of antibiotic sulfamethoxazole (SMX) of concentrations up to 300 mg L−1 was examined by photoelectro-Fenton (PEF) using an activated carbon fiber (ACF) cathode with UVA (365 nm) irradiation. Comparative mineralization has been studied by different methods: RuO2/Ti anodic oxidation (AO), AO in the presence of electrogenerated H2O2 (AO-H2O2), AO-H2O2 in the presence of UVA (AO-H2O2-UVA), and both the electro-Fenton (EF) and PEF processes. PEF treatment at a low applied current of 0.36 A yields a faster and more complete depollution with 80% of the TOC removed after 6 h of electrolysis. The higher oxidative ability of the PEF process can be attributed to the additional hydroxyl radicals (OH) produced by the photo-Fenton reaction. The 63% mineralization in the case of EF treatment was due to the formation of short intermediates, such as carboxylic acids, which were difficult to oxidise with OH. In the AO-H2O2-UVA process, about 36% of the TOC was removed after 6 h electrolysis, while 28% of the TOC was removed in the AO-H2O2 process. SMX is only slightly mineralized by the AO process, with only 25% of the TOC removed. HPLC–MS analysis allowed for up to six aromatic reaction products to be identified during the SMX degradation in the PEF process, mainly formed from the hydroxylation of the aromatic ring or/and isoxazole ring, accompanied by the substitution of the amine group (on aromatic cycle) or methyl group (on isoxazole ring) by OH. The carboxylic acids generated, including oxalic, maleic, oxamic, formic and acetic acids, were detected by ion-exclusion chromatography. The initial organic nitrogen was mainly converted into NH4+ along with a very small proportion of NO3− ion. Considering all the oxidation intermediates and end products for SMX degradation in the PEF process, a general mineralization mechanism by OH and UVA was proposed.
Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideResearch highlights▶ High efficient photoelectro-Fenton process using activated carbon fiber cathode was developed. ▶ Rapid electrogeneration of H2O2 and complete mineralization of antibiotic sulfamethoxazole were achieved. ▶ Aromatic intermediates and carboxylic acids generated, as well as inorganic end product were measured. ▶ A comprehensive SMX degradation pathway involving OH and UVA is proposed.
