Preparation And Catalytic Reduction Performance Of Ni-based Nanocomposites

The rapid development of chemical industry leads to a sharp increase in the discharge of industrial wastewater,the water resources that human survival environment is seriously polluted,so it is urgent to solve the problem of water pollution.In the water source pollution,nitrophenol pollutants and organic dyes have the most prominent influence.Among of them,4-nitrophenol（4-NP）is a highly toxic organic pollutant with strong stability and difficult degradation,it will attack the nervous system of organisms,liver,kidney and so on.It is carcinogenic and teratogenic,and does great harm to the environment and life.The organic dye wastewater is the most abundant in water pollution environment,which has the characteristics of complex composition,poor biodegradability,high toxicity and high chroma.And it seriously affects water quality and the life of aquatic organisms.Cr（Ⅵ）in water is highly toxic,carcinogenic and teratogenic,and will be enriched in organisms through the food chain,causing serious damage to organisms.How to effectively remove and degrade the organic and inorganic pollutants in the above water bodies is an urgent research task for researchers.Catalytic reduction reaction has the advantages of mild reaction conditions,high degradation rate,simple operation and low cost.It is a promising sewage treatment technology.Nickel is cheap and easy to prepare,and its outermost electronic structure is the same as that of precious metals palladium and platinum,and its chemical properties are comparable to those of precious metals.The single nickel nanoparticles are active and easy to agglomerate,which can not exert the best catalytic activity.Nickel-based nanocomposites prepared with carbon-based materials as support have become a new favorite of catalyst materials.In this thesis,in order to improve the catalytic activity of nickel-based nanocomposites,nickel-based nanocomposites were prepared by one-step thermal polymerization and their catalytic reduction activity was studied.The main research contents and conclusions are as follows:（1）Using nickel acetate tetrahydrate and melamine as the main raw materials,g-C₃N₄@Ni hollow nanotube composite was prepared by simple thermal polymerization method at 600℃by adjusting the dosage of melamine（2.0 g,2.5 g,3.0 g）.The nanocomposites were characterized by X-ray diffraction（XRD）,Fourier Infrared Conversion Spectroscopy（FTIR）,Laser Raman spectroscopy（Raman）,Scanning electron microscopy（SEM）,transmission electron microscopy（TEM）,BET surface area measurement（BET）,X-ray photoelectron spectroscopy（XPS）and so on..The results show that the catalytic reduction performance of4-NP by g-C₃N₄@Ni＿2.5 hollow nanotube composite containing 2.5 g melamine is the best,the reaction rate constant is 0.366 min^-1,and shows good cyclic stability.The catalyst also showed significant catalytic reduction activities for m-nitrophenol（3-NP）,o-nitrophenol（2-NP）,Methylene blue（MB）,Rhodamine B（Rh B）,Orange G（OG）and Azurin B（AB）.（2）Using the g-C₃N₄@Ni＿2.5 hollow nanotubes with the largest specific surface area as the carrier,the supported g-C₃N₄@Ni-Ag hollow nanotube composites were prepared by photochemical reduction method by adjusting the addition amount of Ag NO₃（1%,3%,5%）,and the materials were characterized by XRD,FTIR,Raman,SEM,TEM,BET and XPS.The results of catalytic reduction experiments show that g-C₃N₄@Ni-Ag＿1 nanocomposites with1%Ag loading have the best catalytic reduction performance of 4-NP,and the reaction rate constant is 1.953 min^-1,and shows good cyclic stability.The catalyst also has significant catalytic reduction activity against 3-NP,2-NP and organic dyes（MB,Rh B,OG,and AB）.（3）Using nickel acetate tetrahydrate and melamine as the main raw materials,g-C₃N₄@Ni₃C-Ni core-shell nanocomposites were prepared by simple thermal polymerization method at 500℃by adjusting the dosage of melamine（2.0 g,2.5 g,3.0 g）.The materials were characterized by XRD,FTIR,Raman,SEM,TEM,BET and XPS.The experimental results show that the g-C₃N₄@Ni₃C-Ni＿2.5 core-shell nanocomposite prepared with melamine dosage of 2.5 g has the best catalytic reduction performance of 4-NP,the catalytic rate constant is 0.643 min^-1,and shows good cyclic stability.In addition,the catalyst also has high catalytic reduction activity on 3-NP,2-NP and organic dyes（MB,Rh B,OG,AB）.（4）CN@Ni₃S₂nanocomposites were prepared from 5-sulfosalicylic acid dihydrate,nickel acetate tetrahydrate and oxalic acid by controlling the presence of melamine pyrolysis gas as protective atmosphere.The composites were characterized by XRD,FTIR,Raman,SEM,TEM,BET and XPS.The experimental results show that CN@Ni₃S₂composite prepared with melamine pyrolysis gas as protective atmosphere has the best catalytic reduction performance of 4-NP,and the reaction rate constant is 3.459 min^-1.It also shows good cyclic stability.The catalyst also has good catalytic reduction activity against 3-NP,2-NP and organic dyes（MB,Rh B,OG,and AB）.The catalyst has obvious catalytic reduction effect on Cr（Ⅵ）.In this paper,several exploratory experimental studies have been carried out with the goal of catalytic reduction and degradation of organic and inorganic pollutants in water by nickel-based nanocomposites.this research work provides a reliable theoretical and experimental basis for the simple preparation of non-precious metal catalysts and deep degradation of pollutants in water.It has important scientific research value for the research and development of new reduced catalyst and its application in the field of sewage treatment.