Electrochemical mineralization of the antibiotic levofloxacin by electro-Fenton-pyrite process

Abstract

Levofloxacin is a large spectrum antibiotic from fluoroquinolones family, widely used and detected in natural waters. Here, this drug was degraded by a novel heterogeneous electro-Fenton (EF) process, so-called EF-pyrite, in which pyrite powder in suspension regulates the solution pH to 3.0 and supplies 0.2mM Fe2+ as catalyst to the solution. Trials were performed with a stirred boron-doped diamond (BDD)/carbon-felt cell under O2 bubbling for cathodic H2O2 generation. Hydroxyl radicals formed from water oxidation at the BDD anode and in the bulk from Fenton’s reaction between Fe2+ and H2O2 were the main oxidizing agents. The effect of applied current and antibiotic concentration over the mineralization rate and degree, mineralization current efficiency and specific energy consumption was studied. An almost total mineralization was achieved for a 0.23mM drug solution operating at 300mA for 8h. The kinetic decay of the drug was followed by reversed-phase HPLC and obeyed a pseudo-first-order reaction. Ion-exclusion HPLC analysis of treated solutions revealed that oxalic and oxamic acids, the most persistent final products, were the predominant pollutants remaining in solution at long electrolysis time. Ion chromatography analysis confirmed the release of F−, NO3− and NH4+ ions during levofloxacin mineralization.