The Study On The Combined Treatment Of Cr（Ⅵ） And Sulfite In Water By Modified MOFs And TiO₂

With the rapid development of global industrialization,water pollution problem has become increasingly serious in recent years.More and more researchers have focused on the development of efficient water treatment techniques in order to improve water utilization efficiency.Therefore,this work has successfully prepared two new solid material,uio-66（MOFs）and TiO₂,via a facile one-pot hydrothermal method and explore the optimum preparation conditions,modification methods and reaction conditions via batch experiments.Cr（Ⅵ）solutions and sulfite solutions are prepared as simulated wastewater.The samples were also characterized by XRD,BET,SEM,XPS,UV-ⅥS DRS and some other analysis techniques.In MOFs adsorption experiments,uio-66 shows the best adsorption ability among other materials,whose adsorption capacity of Cr（Ⅵ）can reach 17.7 mg/g at the pH of 6.When the doping amount of Cu is fixed at 10%,the adsorption capacity can be increased to 30.7 mg/g,showing a successful modification.XRD and SEM characterizations shows that uio-66 was prepared with a complete structure.XPS and BET characterizations shows that Cu ions was inserted into the frameworks and become new metal centers,improving the surface area and pore volume.Via the TiO₂ photocatalytic experiments,optimum hydrothermal temperature and time are proved to be 180℃and 8 hours.The optimum reaction pH is 3.After 150min reaction,the reduction efficiency of Cr（Ⅵ）by virgin TiO₂ can reach 60.0%,far more than that of TiO₂ prepared by sol-gel method（3.1%）.When 0.5%Cu was doped,the reduction efficiency of Cr（Ⅵ）can be increased by 13.4%,with more Cr（III）ions detected in solution.When treating sulfite solution（2 g/L）using 0.5Cu-TiO₂,the oxidation efficiency can reach above 90%after 90 min reaction,30%more than that without catalysts.XRD and XPS characterizations shows that TiO₂ was prepared with a anatase phase and Cu ions was successfully inserted into the grains.UV-ⅥS DRS characterizations shows the Cu doped TiO₂ has a better adsorption of visible light.To treat Cr（Ⅵ）solutions with a high concentration（50 mg/L）,the combination of 10Cu-uio-66 and 0.5Cu-TiO₂ was used.Both dosage is fixed at 1g/L.The finial removal efficiency of Cr（Ⅵ）can reach 91.8%,with about 30%Cr（Ⅵ）ions reduced.