Effective mineralization of quinoline and bio-treated coking wastewater by catalytic ozonation using CuFeO/Sepiolite catalyst: Efficiency and mechanism.

In this study, CuFeO nanocomposite loaded on natural sepiolite (CuFeO/SEP) was prepared by the citrate sol-gel method. CuFeO/SEP was characterized by X-ray diffraction, Brunauer-Emmett-Teller adsorption analysis, scanning electron microscopy, and energy dispersive spectroscopy. The CuFeO/SEP composite was stable and showed an excellent catalytic activity for ozonation. The efficiency of quinoline mineralization in the catalytic ozonation with CuFeO/SEP was 90.3%, and this value was 5.4 times higher than that of the uncatalyzed ozonation (16.8%). The quinoline mineralization followed a pseudo first-order kinetics with all the catalysts. The rate constant for the mineralization of quinoline by ozonation in the presence of CuFeO/SEP was 0.0885 min, which was 16.7 times higher than that in ozone alone (0.0053 min). Radical scavenging tests revealed that hydroxyl radical (OH) and superoxide radical (O) were the reactive oxygen species (ROS) in the quinoline degradation. In the presence of CuFeO/SEP, ozone and hydrogen peroxide were rapidly converted into the ROS. Although neutral and alkaline pH were more beneficial for the quinoline mineralization, CuFeO/SEP exhibited significant catalytic activity even under acidic conditions. Meanwhile, five-cycle successive tests suggested that CuFeO/SEP was recyclable and hence, stable. Furthermore, the feasibility of the catalytic ozonation for the treatment of biologically treated coking wastewater was evaluated. The catalytic ozonation resulted in 57.81% total organic carbon removal efficiency at 60 min, which was 2.9 times higher than that in the uncatalyzed ozonation (19.99%).