Catalytic Ozonation Of Bezafibrate In Water By Cobalt-doped Red Mud

Bezafibrate (BZF) is a typical pollutant on behalf of pharmaceutical and personal care products (PPCPs) and it would be a potential threat for the aquatic environment, because its residues in effluent are frequently detected in all types of surface water. However, the conventional sewage treatment process is difficult to remove BZF completely. Therefore, heterogeneous catalytic ozonationis is able to develop the BZF degradation compared with the sole ozonation, ensuring to further protect water environmental quality and safety.Red mud (RM) that contains oxides of Fe, Al, Ti, is a solid industrial waste of alumina extraction process from the bauxite through the Bayer process. In this study, RM was used as the basic raw material for synthesis of the efficient catalyst by cobalt modification. The optimization on preparation conditions of RM loading Co oxides (Co/RM) was achieved by Plackett-Burman (P-B) and Response Surface Methodology (RSM) statistical experimental design. The optimum values for preparation conditions of Co/RM catalysts was the cobalt mass fraction of4.14%, calcination temperature of389℃, impregnation temperature of60℃, drying temperature of80℃and calcination time of4.0h. Under this condition, the catalyst showed the best catalytic activity. In addition, catalyst was characterized by N2adsorption-desorption test, XRD, FT-IR, XPS and UV-Vis, indicating that the key active site of Co/RM was Co3O4that formed on the surface of RM.The removal efficiency of BZF by catalyzed ozonation with RM and Co/RM were55%and70.6%, respectively. Cobalt loadings affected the catalytic activity significantly, while8.54%loading of cobalt showed the best catalytic activity; high ozone dosage and dosage of catalyst were both not good for BZF degradation; the presence of phosphate in water showed a significant inhibition on the performance; solution pH exhibited a remarkable influence on the removal efficiency and the surface pHpzc of the catalyst might be an important factor. When the solution pH was close to the pHpzc of the catalyst, the maximum observed catalytic contribution was achieved; Co/RM still showed catalytic activity when the effluent used as a background and the removal efficiency was66.6%.To explore the catalytic reaction mechanism of catalytic ozonation by RM and Co/RM, tert-butanol was as a probe to study the ratio between the direct and indirect oxidation. Also, the decomposition rate of ozone and ozone consumption efficiency were studied in detailed. Results above showed that the hydroxyl radical (·OH), ozone molecules and catalyst adsorption were contribute the removal of BZF, but· OH was the major one. Furthermore,22of the intermediates generated during this process were identified and degradation pathways were proposed. The two catalysts (Co/RM and RM) had no other active composition leaching. Detoxification and reuse were also achieved in this reaction process, suggesting that Co/RM catalyst was safe and could be had the certain application prospect for waste water treatment.