Synthesis And Application Of New Materials For Adsorption And Photocatalytic Degradation Of Dyes

With the rapid population growth,industrialization,urbanization,agricultural activities and excessive use of chemicals have caused more and more serious water pollution problems.In the industries causing water pollution,the dye wastewater discharged from the printing and dyeing industry is one of the important sources of pollution.There are more than 10000 kinds of dyes,most of which are azo dyes.These dyes are easily found even at low concentrations in water and can reduce photosynthesis in the aquatic environment by preventing the penetration of light and oxygen.In addition,azo dyes have a complex aromatic structure that has direct and indirect toxic effects on humans.Therefore,from the perspective of health protection and resource conservation,the removal of azo dyes is of great significance to humans and the environment.At present,there are many mature methods for removing dyes.These methods include physical methods,biological methods,and chemical methods.Among them,the adsorption methods in physical methods and the photocatalytic methods in chemical methods are used in purification efficiency,operation process,and economic benefits.All aspects have great advantages.These two methods are based on the continuous development of functional materials.Therefore,the focus of this paper is to develop new materials.Based on the literature,several new materials were synthesized as high-efficiency and high-utility sewage treatment agents.The azo dye molecules were used as targets,and their removal ability was explored by adsorption and photocatalysis.The main research work is as follows:1.Firstly,Fe₃O₄ nanoparticles were prepared by solvothermal method,and then2,4-diaminophenol-co-formaldehyde（DAPF）polymer was coated on the surface of Fe₃O₄ to synthesize core-shell structure magnetic nanomaterials.The structure and composition of the sample Fe₃O₄@DAPF were characterized by SEM,TEM,XRD and FT-IR.With Fe₃O₄@DAPF as adsorbent,the adsorption properties of three anionic dyes:amaranth（AM）,orange Ⅱ（OR-Ⅱ）and acid red 18（AR-18）were investigated,and the initial pH of the solution,the initial dye concentration adsorption time etc on the adsorption properties were also studied.In addition,the adsorption isotherm,adsorption kinetics and thermodynamics were studied,and the adsorption mechanism of Fe₃O₄@DAPF was discussed.Because of its fast adsorption kinetics,high adsorption capacity and easy separation,Fe₃O₄@DAPF has become a more competitive adsorption material.2.g-C₃N₄/TCAP was synthesized by thermal polymerization of urea carbonitride as precursor and 2-amino-1,1,3-tricyanyl-1-propylene（TCAP）as copolymer at 550℃.The morphology,structure,specific surface area and optical properties of g-C₃N₄/TCAP were characterized by XRD,SEM,TEM,XPS,FI-IR and PL.The photocatalytic degradation and stability of orange Ⅱ（OR-Ⅱ）under visible light by g-C₃N₄/TCAP were evaluated.The effects of photocatalytic dosage,pH,doping amount and other experimental conditions on photocatalytic activity were systematically studied.At the same time,the role of different active species in the degradation process was also investigated,and the photodegradation mechanism was discussed.3.The g-C₃N₄/TCAP/CdS heterojunction composite photocatalyst was prepared by in situ deposition of semiconductor photocatalyst CdS on g-C₃N₄/TCAP via simple successive ionic layer adsorption and reaction（SILAR）process.The structure,morphology and optical properties of the samples were characterized by means of SEM,XPS,FI-IR and PL.With orange Ⅱ as organic dye and g-C₃N₄/TCAP/CdS as photocatalyst under visible light,the effects of photocatalytic dosage,pH and CdS loading on photocatalytic activity were systematically studied.At the same time,the role of different active species in the degradation process was also investigated,and the mechanism of photodegradation was proposed.The composite heterojunction photocatalyst has high catalytic activity and stability for the degradation of OR-Ⅱ.