Photo-assisted electrochemical degradation of ciprofloxacin using DSA® anode with NaCl electrolyte and simultaneous chlorine photolysis

Abstract

This study aimed to investigate and improve the performance of the photo-assisted electrochemical process (PAEC) for the degradation of ciprofloxacin (CIP) and the production of active chlorine species (ACS), using a DSA® (Dimensionally stable anodes) electrode, NaCl as the supporting electrolyte and UV radiation provided by a high-pressure mercury lamp (UVC). The performance of the system was assessed by monitoring the CIP concentration, ACS, chemical oxygen demand (COD), total organic carbon (TOC), and phytotoxicity tests. The effect of operational parameters, such as current density, NaCl concentration, volumetric flow, and initial pH of the solution were evaluated. Under operating conditions of j = 60.7 mA/cm2, [NaCl] = 0.3 mol/L, qv = 10 mL/min, and pH = 5, complete removal of CIP was achieved in 5 min and, with only 1 h of electrolysis, removal of approximately 60% TOC and 65% COD was obtained. The PAEC process promoted greater mineralization of the solution in relation to the isolated techniques and the phytotoxicity tests indicated that, despite the high salinity of the effluent (0.3 mol/L NaCl), the PAEC process (UVC 250 W) did not generate an increase in toxicity of the treated solution. The elucidated CIP degradation mechanism indicates that the piperazine group was the most attacked site of the molecule. Furthermore, the identified intermediates show that CIP was gradually destroyed, generating compounds with a lower risk of increasing bacterial resistance proliferation.