Electrochemical Combustion of the Antibiotic Levofloxacin By Electro-Peroxone Process

Abstract

Over the last years pharmaceuticals have been receiving a lot of attention as emergent pollutants worldwide. These compounds can reach the environment through many vias, i.e. excretion in urine and faeces of humans and livestock, household disposal or hospital wastes and their concentration in water can vary between ng L-1 to mg L-1 [1]. Despite their low concentration these persistent organics can have adverse effects on the environment, for this reason its elimination is a big concern. Different processes have been tried to remove these compounds from water among which are the electrochemical advanced oxidation processes (EAOP´s) like electroFenton (EF), photo electroFenton (PEF), solar photo electroFenton (SPEF) and electro-peroxone (E-peroxone) [1]. E-peroxone is a relatively new process that employs two reactants, the electrogenerated hydrogen peroxide (via O2 reduction in acidic media) and ozone to produce homogeneous hydroxyl radicals [2]. The E-peroxone process has been studied for the removal of several pharmaceuticals showing great potential in their elimination from water [3]. This work deals with the removal of the antibiotic Levofloxacin (LVN) from synthetic wastewater using the E-peroxone process. The electrolyzes were performed in a laboratory flow plant containing 1.5 dm3 of solution having 50 mg dm-3 of LVN and 0.05 M NaSO4 as background electrolyte at pH 3; a Ti-Ir-Sn-Sb oxides was used as anode and a graphite felt on top of carbon cloth was used as gas diffusion cathode [4], where compressed air was fed at 0.36 psi of pressure. The trials were conducted at a constant cathodic potential (Ecat ) of -0.3 V vs SHE at a volumetric rate (Q) of 1.5 dm3 min-1. The results showed a chemical oxygen demand (COD) decay of 70 % at 6 hours of electrolysis. The influence of current density, O3 feed and initial concentration of LVN on the rate of degradation of LVN and mineralization current efficiency was also analyzed. Finally, the by-products of LVN were followed by chromatographic techniques to propose a reaction pathway. [1] Sirés I., Brillas., E. Remediation of water pollution caused by pharmaceutical residues sed on electrochemical separation and degradation technologies: A review. Environmental International, 40 (2018) 212-229. [2] Li X., Wang Y., Yuan S., Li Z., Wang B., Huang J., Deng S., Yu G. Degradation of the anti-inflammatory drug ibuprofen by electro-peroxone process. Water Research, 63 (2014) 81-93. [3] Wang H., Zhan J., Yao W., Wang B., Deng S., Huang J., Yu G., Wang Y. Comparison of pharmaceutical abatement in various water matrices by conventional ozonation, peroxone (O3/H2O2), and an electro-peroxone process. Water Research, 130 (2018) 127-138. [4] Pérez T., Coria G., Sirés I., Nava J.L., Uribe A.R. Electrosynthesis of hydrogen peroxide in a filter-press flow cell using graphite felt as air diffusion cathode. Journal of Electroanalytical Chemistry, 812 (2018) 54-58.