Promoted degradation of ofloxacin by ozone integrated with Fenton-like process using iron-containing waste mineral enriched by magnetic composite as heterogeneous catalyst

Abstract

In this study, a heterogeneous catalyst derived from iron-containing waste mineral was enriched by magnetic composite (Fe3+/Fe2+) at modification ratio of 5 % for the highest mineralization of ofloxacin (OFL) by ozone/Fenton system. A comparative study between O3, perozone (H2O2) and O3/Fenton systems in mineralization of ofloxacin (OFL) under various solution pH, H2O2 dosages, initial OFL concentrations and catalyst (MFS-5) dosages was performed. Adding Fenton reagent (H2O2/MFS-5) into ozonation system gave the highest OFL removal efficiency of 70 % at optimal operational conditions of pH 9, catalyst dosage of 1.5 g/L, H2O2 dosage of 100 mg/L with initial OFL concentration of 100 mg/L due to synergistic effect of O3 and Fenton reagent. The catalyst's properties were evaluated through BET, SEM image, EDS and mapping data, FTIR and XRD. The main mineralization mechanism of OFL was through hydroxyl radicals (⁎OH) which were formed during ozonation process because FeO, Fe3O4 and SiO2 in the MFS-5's constituent accelerated decomposition of O3 and promoted reaction rate with H2O2. The catalyst exhibited a good reusability and stability after five consecutive runs with negligible change in mineralization efficiency of OFL and a very low leached iron amount into solution. Besides, there was an efficient improvement of biodegradability of real pharmaceutical wastewater after treatment by O3/Fenton with 71 % and 62 % removal of COD and TOC, respectively. These findings indicated utilizing magnetic-modified waste iron mineral as heterogeneous catalyst in combination with H2O2 and O3 achieved high efficiency and feasibility in removal of OFL antibiotic from real pharmaceutical wastewater.