Perpared And Photocatalyst Properties Investigation Of Ni(C)-based Nanocapsules

As the rapid development of our country’s economy, sewage disposal has received wide attention. Photocatalyst has strong oxidation ability, and most of the organic matter can be degraded into CO₂ and H₂ O. However, it is generally more difficult to be separated from the reactants and recycled. Photocatalyst has not been widely used in wastewater treatment. In this paper, we prepare magnetic nanocapsule photocatalyst which composite semiconductor materials and magnetic material. It not only has the high efficiency of suspended photocatalyst, but also can be separated and recycled by using magnetic method. The unique characteristics of nano-materials such as little size and quantum effects, improve the photocatalytic ability effectively.First of all, Ni@ZnO nanocapsules are prepared by using plasma DC arc discharge method. The diameter of the nanocapsule particle is 30-50 nm, and it owns obvious core-shell structure. And Ni@ZnO@TiO₂ nanocapsules are prepared by using hydrolysis precipitation method. The core-shell structure is formed by Ni as the core, ZnO as the middle layer, TiO₂ as the shell. Magnetic analysis show that the saturation magnetizations are 27.9Am²/Kg and 23.1Am²/Kg. This has achieved the goal of retrieving photocatalyst by using magnetic separation. Photocatalytic degradation experiments show that the degradation rate of both photocatalyst can reach more than 95% for Rhodamine B under UV light irradiation for 3h, and the degradation rate has small improvement after coated TiO₂.In the second part of this paper, we prepare Ni@C@Bi₂O₃ nanocapsules by using hydrothermal method-liquid phase deposition method. The particle size is 200-250 nm, the inner layer is metal Ni, the middle layer is C, and the outer shell layer is α-Bi₂O₃. The magnetic analysis show that the saturation magnetization of sample B is 13.5Am²/Kg. It can be recycled through the magnetic separation. Photocatalytic performance analysis show that the catalyst has the highest efficiency when the content of Bi₂O₃ is 50%, the degradation rate for Rhodamine B can reach 89.4% under visible light irradiation for 4h, and the degradation rate can reach more than 60% under visible light irradiation for 1h. By comparing the efficiency of catalyst with Ni@C@Bi₂O₃ and Ni@Bi₂O₃, we can get C layer and its’ surface functional groups play an important role in transferring electron in the process of catalytic, suppress the recombination of photogenerating electrons and holes effectively, and improve the photocatalytic efficiency and velocity effectively.Finally in order to further explore the impact of light catalysis by the C layer and its’ surface functional groups, CPNB@GO compounds are prepared by using the organic solvent method-Hummers’ method. The number of functional groups on GO’s surface is changed by changing the addition amount of KMnO₄. Photocatalytic performance analysis show that CPNB@GO（C） has the highest catalytic efficiency, the degradation rate for Cr₂ O₇^2- can reach 85.42% under visible light irradiation for 3h. Experiments show that photocatalytic activity increases gradually with increasing the number of functional groups on GO’s surface. When the number of functional groups increases to a certain amount, GO’s conjugate structure is damaged, or the layered structure of the GO is damaged, and then the catalytic activity is reduced. Compared with the photocatalytic activity of CPNB@GO and CPNB/GO, we can get the conclusion that photocatalytic activity is determined by the synergy effect between GO and CPNB.The above studies show that nanoparticle photocatalyst with metal Ni which is not easy oxidation and has strong magnetism, the semiconductor oxide with high catalytic properties and the C layer which can transfer electronic, can simultaneously satisfy the requirements of magnetic and catalytic properties of catalyst.