| Bismuth vanadate (BiV04) is a visible-light driven semiconductor photocatalyst. In spite of its excellent photocatalytic activity, its application for treating wastewater is still restricted due to the difficulty to separate BiVO4 particles from treated water.However, immobilization of BiVO4 onto various substrates to recycle the particles leads to great decrease of effective surface area of the photocatalysts and finally the reduction of the activities. How to prepare BiVO4 photocatalyst with easy recovery and excellent activity has always been an challenge.Since magnetic nanopaticles possesses huge surface areas and excellent recovery, we developed BiVO4/Fe3O4 magnetic composite which is different mass ratio with BiVO4 to Fe3O4 by imparting magnetic properties of Fe3O4 onto BiVO4 photocatalyst via ultrasonic irradiation and investigated on the photocatalytical activities.The as-prepared samples were characterized using analytical techniques of XRD, TEM, DRS and BET. In order to test the photocatalytic activities of as-prepared BiVO4/Fe3O4 composite particles, photodegradation of methylene blue (MB) in water has been chosen as a test reaction. The result indicated that the optimal weight ratio of BiVO4 to Fe3O4 is 5:1. The photodegradation rate of MB by such composite is highest and 92.0%in 5 h. The photocatalytic degradation of methylene blue (MB) was studied including the effects of photocatalyst dosage, initial concentration, pH value and the existence of electron acceptors on photocatalytic degradation. The results indicated that after 5 h the methylene blue was totally degraded with initial concentration of MB at 10mg/L, dosage of catalyst at 2.0g/ml, pH value at 11 and the existence of K2S2O8. The photocatalyst can be recycled with a little decrease of photocatalytic activity and the degradation rate of methylene blue was still higher than 80%after three cycles.
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