Study On Preparation And Photocatalysis Of Palygorskite/Metal Oxide Composites

Water is an important resource in the human world,and clean drinking water is the foundation for human survival.However,a large number of pollutants are discharged into the water with the rapid development of industrialization.Dyes and metal ions are the main components of water pollution.A hot issue that is to remove dyes and metal ions with high efficiency and environmental protection has attracted wide attention.Nowadays,the methods of removing pollutants include flocculation,ion exchange,adsorption,photocatalytic degradation,electrochemistry,etc.Combining multiple methods to improve the efficiency of removing pollutants is the current trend of removing pollutants.In this thesis,several palygorskite/metal oxide composites were prepared by using palygorskite with low cost,non-toxicity and good environmental compatibility as raw materials.Degradation of anionic dyes,adsorption dyes and metal ions,the main work is as follows:1.Using zinc nitrate,magnesium nitrate,aluminum nitrate,palygorskite,and urea as raw materials,palygorskite/Zn-Mg-Al metal hydroxides?PGS/Zn-Mg-Al LDH?,calcined palygorskite/Zn-Mg-Al metal oxide composite?PGS/Zn-Mg-Al LDO?.The photocatalytic performance of the composite materials was used to probe by malachite green under simulated visible light,3%PGS/Zn-Mg-Al?4:1:1?LDO was the best.20 mg3%PGS/Zn-Mg-Al?4:1:1?LDO photocatalytic degradation of 30 mL 20 mg/L malachite green was better,and the decolorization rate was 97.44%.The main active group is·O₂^-.The cycle was catalyzed 11 times,and the removal rate was still 95.1%.The composite material not only has good photocatalytic ability for the cationic dyes rhodamine B,methylene blue,crystal violet,malachite green,but also has excellent adsorption performance for anionic dyes?acid fuchsin and methyl orange?.And it can adsorb Pb²⁺,Cu²⁺,Ni²⁺in water.The composite material utilizes photocatalysis and electrostatic adsorption to simultaneously remove cationic dyes and anionic dyes in wastewater,and has more selectivity to remove wastewater and improves the removal efficiency.2.Using zinc chloride,magnesium chloride,chromium chloride,and palygorskite as raw materials,a series of palygorskite/Zn-Mg-Cr metal hydroxides?PGS/Zn-Mg-Cr LDH?were prepared with one-pot hydrothermal method.After calcination at high temperature,palygorskite/Zn-Mg-Cr metal oxides?PGS/Zn-Mg-Cr LDO?were obtained in different proportions.The results show that 10%PGS/Zn-Mg-Cr-3 LDO has the best photocatalytic effect under simulated visible light,and has good photocatalytic ability for most cationic dyes.The photocatalytic degradation of malachite green by the composite material was studied in particular.20 mg 10%PGS/Zn-Mg-Cr-3 LDO photocatalytic degradation of 30 mL 10 mg/L malachite green was better,and the decolorization rate was 97.47%and the main active group is·O₂^-.Due to the positive electrical properties of the composite material,it exhibits excellent adsorption performance for the anionic dye?acid fuchsin?.The adsorption process of acid fuchsin was in accordance with the pseudo-second-order kinetic model,mainly chemisorption.3.Palygorskite/Zn-Mg-Bi metal hydroxides?PGS/Zn-Mg-Bi LDH?was prepared by hydrothermal method as precursors,and the corresponding palygorskite/ZnO-MgO-Bi₂O₃ was obtained after calcination composite material?PGS/Zn-Mg-Bi LDO?.The structure,morphology,specific surface area and optical properties of the composite material were characterized by XRD,FT-IR,SEM,BET,Uv-vis and PL.Under simulated visible light,5%PGS/Zn-Mg-Bi?1:1:1?LDO has the best photocatalytic effect,and has good cationic dyes?such as rhodamine B,methylene blue,crystal violet,and malachite green?.The photocatalytic ability is focused on the process of photocatalytic degradation of malachite green,and·O₂^-is the main active group.The electrostatic effect of 5%PGS/Zn-Mg-Bi?1:1:1?LDO shows good adsorption performance for anionic dyes?such as acid fuchsin and methyl orange?,and the adsorption process of acid fuchsin and methyl orange both were in accordance with the pseudo-second-order kinetic model,mainly chemisorption.