A combined advanced oxidation process: Electrooxidation-ozonation for antibiotic ciprofloxacin removal from aqueous solution

Abstract

In this study, degradation of ciprofloxacin (CIP) was performed by the electrooxidation process (EOP) using the Ti/PbO2 anode and the synergistic impact of a combined electrooxidation-ozonation process (EOOP) was investigated. Antibiotic decomposition and its mineralization were studied by means of high-performance liquid chromatography (HPLC) and COD test and operating parameters: pH, current density, initial antibiotic concentration and contact time were surveyed separately in both processes; also, we calculated energy consumption and mineralization current efficiency. At the initial concentration of 0.12mM, CIP was decomposed (by 70%) via three pathways: direct and indirect electrooxidation on electrode surface and electrodegradation by physisorbed OH and under the following conditions: contact time 120min and current density 32mA/cm2. By contrast, the fourth and fifth pathway happens in EOOP by ozone, which increased the removal efficiency higher than 94% under the following conditions: contact time 90min and current density 24mA/cm2. It should be noted that COD removal required longer contact times, which were 50 and 90% in 180 and 150min for the EOP and EOOP, respectively. Voltammetry studies illustrated that CIP and formed intermediates were degraded completely. The combined system of the EOOP had a higher performance and required a lower current density and longer electrode durability as well as lower energy consumption. All this makes it a suitable measure to be considered as a cost-effective process for antibiotic containing wastewaters.