Photo-catalytic degradation of ofloxacin with UV/ ZnO / KI process: Performance, kinetic, energy consumption and the pathway

Abstract

This study was aimed to evaluate the improvement of ofloxacin (OFX) photocatalytic degradability in the presence of an exogenous reductant. For this purpose, potassium iodide (KI) (as an exogenous reductant) was added into the UV/ZnO (UZ) reaction environment and the photocatalytic process efficiency in presence and absence of KI reductant was compared with each other. Four evaluation criteria to compare the efficiency of different processes were included: degradation rate, the observed rate of OFX degradation (robs), the energy consumption and the total cost of system. The degradation rates of OFX by UV alone and UZ were obtained 20% and 54%, respectively. The maximum degradation rate (95%) was observed when KI reductant agent was added in the UZ reaction environment (UZI). Kinetic studies also revealed the superiority of UZI process than UV alone and UZ processes. The kinetic study indicated the observed rate of the OFX degradation (robs) for UZI process was 13.65 and 3.73 times than that of UV alone and UZ processes, respectively. The energy consumption values for UV alone, UZ and UZI were estimated 103.02 kWh/g−1, 27.25 kWh/g−1 and 7.68 kWh/g−1, respectively. In addition, the total cost of system for UZI was lower compared to the other processes (UV alone and UZ). Investigation of the reaction mechanism indicated eaq- and •OH radicals have the main role in the degradation of OFX. No spectrum related to OFX and products containing fluoride was detected in the sample taken from the UZI process effluent after 30 min