| Disinfection of drinking water is one of the most effective for public health, it can remove most of the pathogenic microorganisms and prevent the epidemics. However, in the process of drinking water disinfection, some disinfection byproducts may arise and pose a potential threat to human health. Bromate is a typical byproduct of drinking water disinfection, because of its carcinogenicity to human, bromate has been classified as2B carcinogens by the World Health Organization (WHO) and also be strictly regulated by many countries. In2004, the WHO had revised the limit bromate of drinking water from25μg/L to10μg/L. Thus, developing an effective method to remove the bromate in drinking water is imperative.Catalytic hydrogenation method has been considered as one of the promising technologies for bromate removing beacause of its high efficiency, nonbyproducts, and convenience to industrialization&good selectivity compare to normal means. But relevant study and catalysts are scarce. In this paper, catalysts were prepared with two different kinds of mesoporous materials, and its application in bromate reduction was studied in details. To investigate the properties of the catalysts, many characterization methods were performed, such as N2adsorption-desorption, X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), H2chemical adsorption, Transmission electron microscopy (TEM) and etc. The main results have been obtained as follows:(1) The mesoporous carbon nitride supported Palladium catalyst (Pd/MCN) was systhesied via impregnation method with PdCl2as precursor and MCN as support. Characterization results indicated that the Pd/MCN has excellent BET surface area (802.67m2/g), well-ordered mesoporous structure, and the Pd particles were well dispersed on the surface of MCN; the point of zero charge of Pd/MCN is around8.0. The experimental results revealed that the adsorption of the bromate was the prerequisite step of the bromate hydrogenation reduction as a result of the reaction in accordance with the Langmuir-Hinshelwood mechanism. Pd/MCN exhibited higher catalytic activity in the reduction of bromate compare to Pd/AC and Pd/CMK. For the Pd/MCN,0.78125mM bromate will be fully reduced in50min at the catalyst concentration is0.03g/L, and increasing the Pd loading amount and catalyst concentration will enhance bromate reduction efficiency. The bromate reduction was strongly pH-dependent and coexsting ions will suppress the hydrogenation process.(2) The magnetic catalyst (Pd/MCM-41-NH2) was synthesized with amino-functionalized magnetic mesoporous silica (MCM-41-NH2) as support and PdCl2as precursor. Characterization results revealed that the amino groups were successfully grafted onto the support’s surface, the Pd/MCM-41-NH2has huge BET surface area, well-ordered mesoporous structure, and the catalyst can be easily separated from water with the magnetization of6.2620emu/g. The experimental results showed that the bromate reduction on Pd/MCM-41-NH2was also accordance with the Langmuir-Hinshelwood mechanism. Pd/MCM-41-NH2exhibited highr catalytic efficiency compared with the catalysts prepared using non-porous silicon materials (SiO2&SiO2-NH2) as support. The catalytic activity of Pd/MCM-41-NH2for reached the maximum when the ratio of MCM-41and silylating reagent dosage was1:0.25. After recycled for5times, the catalysts can still remain its80.75%activity, indicating that the catalyst has excellent stability and can be reused.In conclusion, the bromate can be effectively removed by mesoporous supported Pd catalyst via catalytic hydrogenation. The technology of hydrogenation can be hopefully served as an efficient way for remove bromate and other similar pollutants. |
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