Study On Adsorption And Degradation Of Congo Red By MgZnCr-TiO₂ Hydrotalcite Composite Visible Light Catalyst

Photocatalytic oxidation is considered to be a green oxidation technique for no chemical oxidants is added.In the paper,MgCl₂,ZnCl₂,CrCl₃.6H2O,TiO₂,NaOH and anhydrous Na2CO₃ as raw materials and the new nanophotocatalyst MgZnCr-TiO₂ was successfully prepared by co-precipitation under different molar ratio of metals?Mg:Zn:Cr?and the loaded amount of TiO₂.X-ray diffraction,scanning electron microscopy,transmission electron microscopy,Raman sprctrum and the Brunauer Emmett Teller nitrogen adsorption measurement were used to characterize the MgZnCr-TiO₂.Congo Red was selected as target contaminant for its wide use,biodegradable resistance and even toxicity to some organisms.The adsorption and photocatalytic oxidation property of MgZnCr-TiO₂ catalyst has been studied,and the results are as follows:1.The structure of MgZnCr-TiO₂ is layered structure and it has the characteristic diffraction peaks of hydrotalcite;2.The specific surface area of MgZnCr-TiO₂?1:1:2-0.05?is 170.3364 m2/g;3.Langmuir model fitted well the adsorption isotherm with the value of R2 0.9765,the maximum adsorption capacity was 526.32 mg/g,and the adsorption followed pseudo second order kinetic by MgZnCr-TiO₂?1:1:2-0.05??the molar ratio of Mg,Zn and Cr was 1:1:2,the mass of TiO₂ was 0.05 g?.The study of adsorption thermodynamics shows that the adsorption of Congo Red by MgZnCr-TiO₂?1:1:2-0.05?is a spontaneous endothermic reaction.4.The photocatalytic oxidation of Congo Red was used to determine the photocatalytic performance of MgZnCr-TiO₂?1:1:2-0.05?under visible light irradiation,and the removal rate of Congo Red reached 98%after reaction for 40 min.5.The degradation mechanism of Congo Red by MgZnCr-TiO₂?1:1:2-0.05?was proposed,MgZnCr-TiO₂?1:1:2-0.05?was excited by visible light,and the electrons on the valence band were excited and then migrated to the conduction band,the electrons reacted with O₂ and product superoxide radicals with strong oxidative at the same time the holes on the valence band are also strong oxidative,the superoxide radicals and holes can degrade Congo Red.The MgZnCr-TiO₂?1:1:2-0.05?was stable after five cycles of the nanoparticles for adsorption and oxidation of Congo Red.Compared to the adsorption,photocatalysis removed Congo Red fundamentally and it is expected to be an effective way to eliminate Congo Red.