Study On The Preparation And Photocatalytic Property Of BiPO₄

Environmental pollution has become one of the most serious problems that human beings have to face urgently in the new century. Photocatalytic will replace traditional control technology due to its advantages of full use of sunlight and completely degrading pollutants without secondary pollution. As a new type of inorganic nonmetal salt of oxy-acid photocatalyst, BiPO4 has attracted more and more people’s attention because of its higher photocatalytic activity and lower cost. However, because of its wide band gap, BiPO4 can have a certain response only under ultraviolet condition, which seriously hinders the utilization of sunlight. In recent years, BiV04 and Bi2MoO6 have been studied widely in light of its high photocatalytic activity under ultraviolet condition. But the application of production is limited, due to its high cost and low efficiency. BiVO4/BiPO4 and Bi2MoO6/BiPO4 were prepared based on the research on optimal preparation of BiPO4 by hydrothermal method. The main results are as follows:(1) We explored the synthesis of bismuth phosphate by using hydrothermal method. The results are as follows:When the heat preservation temperature rose, bismuth phosphate degradation rate of methylene blue first increased and then decreased under ultraviolet conditions. When the temperature was 170℃, the shape of bismuth phosphate was regular nanorod and the degradation performance was best to 67.1%. When the reaction time was from 3 hours to 24 hours, the degradation rate of bismuth phosphate into methylene blue increased gradually. While the reaction time was from 24 hours to 72 hours, the degradation rate of bismuth phosphate into methylene blue decreased gradually. So when the reaction time was 24 hours, the degradation rate of bismuth phosphate into methylene blue was the highest and the shape was best. The smaller pH value of the reaction environment was, the higher the degradation properties of bismuth phosphate was. At the same time, its shape appeared regular nanorod, and its crystallinity was the highest. When the reaction environment pH=l, degradation rate of bismuth phosphate was 99.9%.(2) Different V.P molar ratios of BiVO4/BiPO4 composites were synthesized by a simple one-pot hydrothermal method. The results are as follows. When the ratio of the BiVO4/BiPO4 composites was less than 3:7, the BiVO4/BiPO4 composites degradation rate of methylene blue were enhanced with an increasing amount of BiVO4 under visible light. The results showed that the BiVO4/BiPO4 composite ratio for V:P=3:7 possessed the highest photocatalytic activity. The BiVO4/BiPO4 composite ratio for V:P =3:7 possessed the maximal k value of 0.0034 min-1. It is 20.7 times of the pure BiPO4.(3) Bi2MoO6/BiPO4 composites were successfully synthesized via a simple one-pot hydrothermal method. The results are as follows. The Mo:P=3:4 sample shows the highest degradation rate of methylene blue at different molar ratios under visible light. Different pH values have a considerable effect on the composites. When the pH value is 9, the sample shows the highest photocatalytic activity.