| As a common semiconductor photocatalyst,Ti O2 and Zn Fe2O4 can generate strong ability of oxidation and reduction of electronic carriers and hole carriers when the visible light is diffracted,and become popular materials in the field of photocatalysis.However,Ti O2 can only absorb ultraviolet wavelengths and its catalytic efficiency is not high because of the band gap energy and high electron hole recombination rate,which severely limits it further development.In addition,because of the low valence band potential of Zn Fe2O4,the activity of direct removal of organic matter is not high.To overcome the inherent shortcomings of Ti O2 and Zn Fe2O4 semiconductor materials,we used the method of surface modification,recombination,and calcination to study Ti O2 and Zn Fe2O4 semiconductor composite materials.(1)A series of composite photocatalysts Ti O,Ti O2/Pd and Ti O2/Pd O were prepared by hydrothermal method,sol-gel process and calcination method using Tetrabutyl titanate and palladium chloride as raw materials.The UV diffuse reflection results showed that the bandgap energy of Ti O2/Pd and Ti O2/Pd O are 3.05 e V and2.47 e V,smaller than Ti O2.The photocatalytic activity of the catalyst under visible light irradiation was investigated by using rhodamine B(Rh B)as a dyestuff template,the results show that,30 mg Ti O2/Pd O in 40 minutes to 50 m L 30 mg/L of Rh B degradation rate was 100%,and the degradation rate of Ti O2 is only 76.23%.The active species which play the main role in the photocatalytic degradation process were the superoxide radical and the hydroxyl radical.(2)Four kinds of Zn Fe2O4 photocatalysts were prepared via a combination of coprecipitation,and calcination methods by using Zn SO4·7H2O and Fe SO4·7H2O as raw materials.The UV diffuse reflection results showed that the band gap of Zn Fe2O4 increases significantly compared with the reported Zn Fe2O4.The photocatalytic activity of the catalyst under visible light irradiation was investigated by using rhodamine B(Rh B)as a dyestuff template,the results show that,compared with other three kinds of catalysts,the Zn Fe2O4 prepared under 400 °C(ZFOC400)calcination conditions has the best photocatalytic activity,30 mg ZFOC400 in 150 minutes to 50 m L 20 mg/L of Rh B degradation rate was 96.6%,and the photocatalytic degradation process was found to follow the pseudo-first-order kinetics.The active species which play the main role in the photocatalytic degradation processwere the superoxide radical,hydroxyl radical and hole.(3)Based on the above Ti O2/Pd O and Zn Fe2O4,four kinds of ternary Zn Fe2O4/Ti O2/Pd O composite photocatalysts were successfully prepared by using various amounts of Ti O2/Pd O.The UV diffuse reflection results showed that the band gap of Zn Fe2O4/Ti O2/Pd O and Zn Fe2O4 is almost unchanged,but the specific surface area is obviously reduced.The photocatalytic activity of the catalyst under visible light irradiation was investigated by using rhodamine B(Rh B)as a dyestuff template,the results show that,1% Zn Fe2O4/Ti O2/Pd O showed the best photocatalytic activity compared with the other three catalysts,30 mg 1% Zn Fe2O4/Ti O2/Pd O in 120 minutes to 50 m L 20 mg/L of Rh B degradation rate of 74.5%,but its catalytic efficiency was significantly lower than Zn Fe2O4.(4)Using Fe(NO3)3·9H2O and Zn(NO3)2·6H2O as the raw materials,five kinds of ternary Zn Fe2O4/Fe2O3/Zn O composite photocatalyst were synthesized successfully by hydrothermal method and high temperature calcination.The UV diffuse reflection results showed that the band gap of Zn Fe2O4/Fe2O3/Zn O increases significantly compared with the pure phase Zn Fe2O4.The photocatalytic activity of the catalyst under visible light irradiation was investigated by using rhodamine B(Rh B)as a dyestuff template,the results show that,the Zn Fe2O4/Fe2O3/Zn O prepared under500 °C(ZFO500)calcination conditions has the best photocatalytic activity,30 mg ZFO500 in 60 minutes to 50 m L 20 mg/L of Rh B degradation rate was 95.7%,and the photocatalytic degradation process was found to follow the pseudo-first-order kinetics.The active species which play the main role in the photocatalytic degradation process were the superoxide radical and the hydroxyl radical. |
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