Bench-scale reactor for Cefadroxil oxidation and elimination of its antibiotic activity using electro-generated active chlorine

The Cefadroxil (CFDX) degradation and its associated antibiotic activity (AA) are analyzed on Sb₂O₃ doped Ti/RuO₂-ZrO₂ anodes electro-generating active chlorine (Cl₂-active). The influence of the following parameters: (i) current density (ii) CFDX concentration (iii) volumetric flow and (iv) initial pH is evaluated in a filter-press FM01-LC reactor to account for controlling factors of the system. The CFDX removal is improved when HClO predominate in solution due to its higher oxidation potential, co-assisted with the presence of Cl₂ (pH = 2), while the CFDX molecule undergoes a slight acid hydrolysis. The contaminant destruction is controlled by the kinetics arising between the active chlorine species adsorbed on the electrode surface (HClO_ads) and the pollutant, since the increase of flow rate in the reactor does not improve the abatement whatsoever. The total CFDX concentration and its antibiotic activity can be eliminated after 15 min using electro-generated active chlorine at the following operating conditions: 0.05 mol L⁻¹ NaCl, natural pH (5.5), 3 mA cm⁻² and 4 L min⁻¹. The energy consumption is considerably influenced by the cell voltage and the presence of active chlorine and H⁺ concentrations. An important biodegradability degree of the final byproducts is produced by active chlorine species, while only two intermediates of cefadroxil oxidation (CFDX-I-1 and CFDX-I-2) are detected after 2 h of treatment using high-performance liquid chromatography (HPLC).