Mesoporous Bismuth Series Oxide Photocatalyst Study On Preparation And Photocatalytic Properties

Nowadays,under the background of the rapid development of the world,the pollution of the scarce fresh water resources is becoming more and more serious.Due to the stable chemical structure,the organic pollutants are not easy to degrade naturally and are harmful to human beings,which has become the focus of water pollution control in China and even the world.Traditional water treatment methods are difficult to remove,so it is very important to study efficient photocatalytic degradation materials which can effectively adsorb organic pollutants.Bismuth based oxometalates have been widely studied in the field of photocatalyst because of their excellent photocatalytic activity under visible light and ultraviolet light.But at present,bismuth based photocatalytic materials still have the disadvantages of low utilization of visible light energy,low specific surface area,easy recombination of photogenerated electrons and holes,insufficient active sites and insufficient photocatalytic performance.As we all know,mesoporous materials have high specific surface area,Therefore,the synthesis of mesoporous bismuth photocatalytic materials will make up for the deficiency of bismuth photocatalytic materials,increase the specific surface area and active site of the reaction,and greatly improve its photocatalytic performance.Therefore,this study attempts to develop the mesoporous bismuth photocatalyst and explore the best conditions for its formation by taking experiments as the main means.Meanwhile,the photocatalytic performance of the synthesized mesoporous bismuth photocatalyst is analyzed to explore its degradation efficiency of pollutants.Three bismuth photocatalysts,Bi VO₄,Bi PO₄ and Bi₂Mo O₆,were selected for this study.Bi VO₄,Bi PO₄ and Bi₂Mo O₆,with mesoporous structure were synthesized by high temperature hydrothermal method.At the same time,using Bi?NO₃?₃ as the precursor material,hexadecyl trimethyl ammonium bromide?CTAB?as the organic template agent,and two buffer solutions to adjust and control the p H value of the mixed solution to weak acid or neutral conditions,we managed to make its mixture forming micelles.After that,we utilized XRD,TEM,BET,to analyze the phase of photocatalyst,micro pore structure,specific surface area,etc.The results showed that the mesoporous bismuth hydroxyl photocatalysts with pore diameter of 2-50nm were successfully synthesized in this study,and the pore structure successfully synthesized would effectively improve the specific surface area of Bi VO₄,Bi PO₄ and Bi₂Mo O₆.To determine its catalytic efficiency,the study on MB,Rh B degradation under UV light and visible light irradiation is performed with mesoporous structure bismuth catalysts,especially the special hole structure on the performance impact of photocatalytic degradation rate.Results indicate that the degradation rate of MB and Rh B were increased with mesoporous bismuth vanadate photocatalytic materials in the UV and visible light conditions which shows that mesoporous structure can improve the bismuth photocatalytic activity of photocatalyst.Under UV light,for bismuth photocatalyst,the mesoporous structure and non-mesoporous structure show little effect on the degradation of MB.But bismuth showed a stronger light catalytic activity to the degradation of Rh B under the same condation.Among them,the mesoporous Bi PO₄ samples showed the highest adsorption-light catalytic activity,180 min light removal rate reached 95.3%,The photocatalytic apparent rate constant was 1.0453 h^-1.The degradation rates of mesoporous Bi VO₄ and Bi₂Mo O₆ after 180min of light were85.2%and 75.1%,respectively,and the photocatalytic apparent rate constant was0.5571 h^-1and 0.4185 h^-1,respectively.Compared with the non-mesoporous bismuth photocatalysts,the catalytic effects of mesoporous ones were increased by 38.5%,20.2%and 29.7%,respectively.Solutions for Rh B fall in visible light,bismuth photocatalyst also showed a strong photocatalytic activity,mesoporous Bi VO₄ samples showed the highest adsorption-light catalytic activity,180 min light removal rate reached 95.5%,and photocatalytic apparent rate constant was 1.1556 h^-1.Mesoporous Bi₂Mo O₆samples for Rh B,180 min light removal rate reached 92.9%,photocatalytic apparent rate constant was 0.9279 h^-1.Compared with the non-mesoporous bismuth photocatalysts,the catalytic effect were increased by 13%and 12.3%,respectively.It is also necessary and important to study the optimum synthesis conditions of mesoporous bismuth photocatalyst for improving the catalytic efficiency.Therefore,the optimal synthesis conditions of bismuth mesoporous photocatalytic materials were investigated by adjusting the selection of buffer solution,p H of buffer solution,hydrothermal reaction temperature and reaction time.The results show that bismuth vanadate and molybdate photocatalyst are easy to form mesoporous structure when citric acid is used as buffer solution,p H=3.6,hydrothermal reaction temperature is150?,the reaction time is 12h.Bismuth phosphate photocatalytic material is easy to form mesoporous structure in phosphoric acid buffer solution,p H=6.4,6.8,7.0,hydrothermal reaction temperature is 150?,the reaction time is 12h.