| The necessity of wastewater treatment of industrial dye pollutants gains more and more attention.Complete degradation of refractory dyes is a difficult problem and a hot spot.In recent years,multi-phase photocatalytic technology applied in the degradation of dye wastewater,which has been widespread researched because of its strong oxidizing and universally applicability.In this paper,nano-sized zinc oxide photocatalysts were prepared by a method with polymer assisted and freeze-drying process,then the zinc oxide was modified by ion doping.Aiming to degrade methyl orange and remazol brilliant blue R,the performance of photocatalysts and mechanism of degradation were studied.Firstly,the effects of initial concentration of dye,input of photocatalysts mass,pH and light source on the photocatalytic degradation of methyl orange were investigated.The optimum conditions for single factor experiments were as follow.The initial concentration of methyl orange was 10 mg·L-1,the mass concentration of zinc oxide was 400 mg·L-1,in weak acid or strong alkaline conditions,and under 365 nm main wavelength of ultraviolet light.The prediction model of the secondary polynomial response surface was established by Box-Behnken method,which indicated the relationship between degradation rate of methyl orange and the initial concentration,the mass concentration of zinc oxide and pH value.The model could predict the 95%of the response value,and the variance results showed that the interaction between the initial concentration of dye and the photocatalyst mass concentration was most significant.Following,zinc oxide was doped with aluminum,ferric,cobalt,cerium and lanthanum ions,respectively.Among them,the prepared Al-doped ZnO exhibited excellent activity than ZnO.For 10 mg·L-1 methyl orange and 60 mg-L-1 active brilliant blue,the degradation degree can reach to 97%within 1 hour,much higher than zinc oxide which about 65%degree in 2 hours.XRD shows that doping aluminum ions makes the particle size smaller.The SEM image of 8 wt%doping shows it changes the surface morphology of ZnO.Finally,the kinetic equation of the photocatalytic reaction of ZnO and Al-doped ZnO to degrade methyl orange was studied by using the model of Langmuir-Hinshelwood.Samples of different degradation times of methyl orange and remazol brilliant blue R were analyzed by liquid chromatography method. |
