| In this thesis,the microwave preparation method,characterization and catalytic properties of four nanocomposite photocatalysts: silver-titanium-zinc,copper-titanium-zinc,silver-magnesium-zinc and silver-manganese-zinc were studied.X-ray diffraction,Fourier infrared spectroscopy,scanning electron microscopy and ultraviolet-visible spectrophotometry were used to characterize the morphology,structure and crystalline phase of the synthesized catalysts.Four synthesized composites were used to photocatalytic degradation of rhodamine B,methylene blue and oily wastewater.The specific experimental contents were as following:(1)Using saturated sodium carbonate solution as a precipitant and four kinds of composite photocatalysts including silver-titanium-zinc,copper-titanium-zinc,silver-magnesium-zinc and silver-manganese-zinc were synthesized by co-precipitation.X-ray diffraction characterization indicated that the crystallinity of the synthesized catalyst was good.By infrared characterization,it was shown that the surface of the synthesized catalyst contained hydroxyl(-OH),M-O bond(M=Zn,Ti,etc)and other groups.By scanning electron microscope characterization,it was confirmed that the synthesized silver-titanium-zinc,copper-titanium-zinc and silver-magnesium-zinc composites were all rod-like structures with a small amount of agglomeration between the particles,and silver-manganese-zinc composires were grape-like structures.Characterization by ultraviolet-visible spectrophotometer proved that the doping of silver,copper,magnesium and manganese can effectively enhance the light absorption performance of the catalyst,and broaden the application range of the catalyst to the visible light region.(2)Using methylene blue as a simulated degradation product,the effects of the following factors on the photocatalytic performance were investigated: optimal reaction conditions for microwave synthesis,optimal silver doping amount,catalyst loading amount,initial concentration of degradation product,catalytic mechanism and catalyst recycling frequency.The traditional water bath method and microwave synthesis method were compared.The results showed that the best conditions for microwave synthesis were that the heating temperature was maintained at 85 ℃,the microwave power was set to 60 W and the continuous heating time was 15 min.When the doping amount of silver was 2 %,0.8 g/L catalyst was added to a 10 mg/L methylene blue solution,and the reaction rate was up to 99.32 % after 50 minutes reaction under a 15 W UV lamp.The degradation accorded with pseudo-first order kinetics.In the process of photocatalytic degradation of methylene blue,there was no obvious difference in the catalytic performance of the silver-titanium-zinc photocatalyst synthesized by the microwave method and the water bath method.Holes played a major role in the process of photocatalytic degradation.After the catalyst was reused five times,the degradation effect did not change significantly.(3)Using methylene blue as a simulated degradation product and copper-titanium-zinc composite as a catalyst.The effects of copper doping amount,catalyst addition amount,initial concentration,pH and other factors on the catalytic performance were investigated.The results showed that when the copper doping amount was 1 %,the pH was 13,and the amount of catalyst was 0.8 g/L,the degradation rate of a 10 mg/L methylene blue solution was up to 96.88 % after 30 minutes reaction under a 500 W visible lamp.(4)Using rhodamine B as a simulated degradation product and silver-magnesium-zinc composite as a catalyst,the catalytic performance of co-doping two metals and single doping one metal was compared.The results showed that after adding 0.4 g/L of silver-magnesium-zinc catalyst to 10mg/L of rhodamine B and irradiating it under 15 W ultraviolet light for 50 min,the degradation rate of rhodamine B was 98.52 %.Under the same conditions,when rhodamine B was treated with silver-zinc and magnesium-zinc catalysts,the degradation rates were 96.10 % and 93.14 % respectively.It was proved that the catalytic effect of two metals co-doped was better than that of one metal alone.The silver-magnesium co-doping had a synergistic effect.(5)The four catalysts,silver-titanium-zinc,copper-titanium-zinc,silver-magnesium-zinc and silver-manganese-zinc were used to treat standard oil components in oily wastewater.The results showed that the four catalysts were excellent in degrading the standard oil.After 5 hours of UV light irradiation,the degradation rates can reach 90.15 %,87.02 %,93.35 %,and 88.95 % respectively.Under the same reaction conditions,the degradation rate was only 83.23 % when using P25.It can be seen that all four catalysts have high practical value. |
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