Preparations Of Metal Oxides On Layered Double Hydroxides Materials And The Research On Dye Wastewater Treatment

Because of their unique physical and chemical properties,such as high specific surface area,memory effect,layered structures and good anion exchange capacities,the layered double hydroxides(LDHs)had been widely used as adsorbents,catalysts,catalyst supports and so on.In view of serious environmental pollution problems brought by industrial dye wastewater,this thesis used the preparation of metal oxides on layered double hydroxides materials and its application in dye wastewater treatment as the research topic,then focused mainly on the preparation of Mg-Al-CO3-LDHs and synthesis of LDHs supported catalysts which consisted of metal oxides(such as CeO2,ZnO and TiO2)and calcined LDHs.At last,the adsorption properties and photocatalytic degradation on dye wastewater was studied.The Mg-Al-CO3 layered double hydroxides were prepared by the co-precipitation method with the mixture of NaOH and Na2CO3 as precipitated agent and nitrate as cationic sources and their adsorption characteristics had been examined to remove malachite green.The XRD pattern confirmed they had the formation of layered nanoparticles structure,which were also observed by SEM.The results of adsorption experiments indicated that calcined LDO had a significant ability to removal malachite green from the solution.The maximum equilibrium capacity and removal rate of malachite green were 558.55 mg/g and 99.14%respectively at 25? when the solution volume and concentration was respectively 250 mL and 1000 mg/L at pH = 3.85 and the additive amount of Mg-Al-LDO was 45 mg.Ce02 coated the calcined Mg-Al-LDO with Ce02/Mg-Al-LDO different mass rations were prepared by the co-precipitation method with cerium nitrate as cerium sources,and the adsorption characteristics of Ce02/Mg-Al-LDO had been studied to remove malachite green.The results showed that CeO2/Mg-Al-LDO had a good ability to remove malachite green from the solution.The maximum equilibrium capacity and removal rate of malachite green were 694.05 mg/g and 97.17%respectively at 25? when the solution volume and concentration was respectively 100 mL and 250 mg/L at pH = 3.85 and the additive amount of Ce02/Mg-Al-LDO was 35 mg.The regeneration for reuse of Ce02/Mg-Al-LDO after the adsorption of malachite green was feasible at least four times,which indicated that Ce02/Mg-Al-LDO was a reusable and good performance adsorbent material.ZnO coated the calcined Mg-Al-LDO with ZnO/Mg-Al-LDO different mass ratio were synthesized by co-precipitation method with zinc acetate as zinc sources,and they were characterized by X-ray diffraction and scanning electron microscope.Photocatalytic activities of the resultant composites were evaluated by the photocatalytic decomposition of methylene blue under UV light irradiation.The XRD pattern demonstrated the mixed crystals which consisted of LDO layer structure and wurtzite structure of ZnO.The SEM confirmed the nanoparticles of ZnO were coated on calcined Mg-Al-LDHs successfully.The initial concentration of methylene blue,catalyst dosage,initial pH and other factors were investigated.The decolorization of methylene blue solution with ZnO/Mg-Al-LDO increased by the catalyst dosage increasing,and decreased by the initial concentration of the solution increasing.The regeneration for reuse of ZnO/Mg-Al-LDO after the adsorption was feasible at least four times,which indicated that ZnO/Mg-Al-LDO was a kind of reusable and high performance photocatalyst material.TiO2 coated the calcined Mg-Al-LDO with TiO2/Mg-Al-LDO different mass ratio were prepared by co-precipitation method with tetrabutyl titanate as titanium sources.The XRD pattern confirmed that they had anatase of R-TiO2 and layer structure of LDO,and the SEM showed that nanopowders of TiO2 were coated on calcined Mg-Al-LDO successfully.Photocatalytic experiments showed the best photocatalytic activity of Ti02/Mg-Al-LDO catalyst for catalytic degradation of malachite green,which was related to the catalyst dosage,initial dye concentration and other factors.The XRD pattern and FITR showed the structure of Ti02/Mg-Al-LDO after reuse in adsolrption of the malachite green did not change significantly.It indicated Ti02/Mg-Al-LDO was a good reusable photocatalyst.LDHs have good adsorption performance.They can be used as photocatalyst materials when they are loaded metal oxide,why LDHs are applied to photocatalyst field nowdays.From the above,LDHs have a good prospect in dye wastewater treatment.