Sonophotocatalytic treatment of ofloxacin in secondary treated effluent and elucidation of its transformation products

Abstract

The extent of the degradation of ofloxacin in secondary treated effluents by means of sonolysis, photocatalysis, sonocatalysis and their combined application, sonophotocatalysis, in order to investigate the potential synergistic effect between sonolysis and photocatalysis was addressed. Various parameters affecting the treatment efficiency including TiO2 loading, solution pH, sparging gas, addition of H2O2, and ultrasound acoustic power were investigated. Consequently, this work reports on the successful attempt to develop a sonophotocatalytic process, firstly designed for OFX degradation in a model solution, and further applied to the treatment of a real wastewater effluent. Sonophotocatalysis was generally faster than the respective individual processes presumably due to the enhanced formation of reactive radicals. The optimum operating parameters for the sonophotocatalytic degradation of ofloxacin were determined. Kinetic analysis has indicated that the sonophotocatalytical degradation of ofloxacin can be expressed by pseudo-first-order reaction. For the study of the ofloxacin degradation, the catalyst loading of TiO2 was varied in the range of 0.5–4g/L, whereas the initial concentration of the pollutant was 10mg/L. Ofloxacin degradation increased slightly with increasing the H2O2 concentration, with an optimum level of H2O2 concentration at 0.14mM/L. It was found that an increase in acoustic intensity was proportional to an increased efficiency of the sonophotocatalytic degradation of ofloxacin. Twenty transformation products have been proposed as a result of the sonophotocatalytic process. A possible degradation pathway has been developed.