| Due to the complex and diverse types of organic pollution wastewater,it is difficult to treat it.Synthesis of novel and efficient catalysts for the degradation of organic pollutants in water is considered to be an effective method for water pollution treatment.However,most common semiconductor materials have intrinsic problems such as narrow utilization of visible light and difficulty in separating photogenerated carriers,which affect their catalytic performance.Therefore,it is necessary to find and construct photocatalysts with excellent catalytic performance.BiVO4 is a twodimensional layered semiconductor with a small band gap,approximately 2.4 eV.It has a good response to visible light,and has a suitable valence band position,exhibiting excellent photocatalytic activity.However,its powder has problems such as easy agglomeration of particles and difficulty in recovery,which seriously limits its large-scale industrial application.Due to its excellent magnetic properties,the introduction of spinel ferrite CuFe2O4 into semiconductor photocatalyst systems can effectively solve such problems,providing a way for future large-scale applications.In this paper,BiVO4 was prepared by EDTA-assisted hydrothermal method,and CuFe2O4 and CuFe2O4/BiVO4 composites were prepared by hydrothermal method.Characterization methods such as X-ray diffraction and scanning electron microscopy were used to characterize BiVO4 prepared under different synthesis conditions and CuFe2O4/BiVO4 composite photocatalyst samples synthesized by hydrothermal method with different CuFe2O4 addition amounts,and their photocatalytic activity was tested.The main research content includes the following aspects:(1)BiVO4 powder was prepared by EDTA-assisted hydrothermal method,by which microcrystallites with high crystallinity and uniform shape can be obtained,they have good visible light catalytic activity.The effects of different pH values of precursor solution,hydrothermal time,and hydrothermal temperature on the crystal phase composition,micromorphology,and photodegradation efficiency of BiVO4 were studied.Studies on the synthesis of BiVO4 under different pH conditions have shown that strong acidic conditions may inhibit the nucleation and growth of BiVO4 grains,while a milder acidic environment is conducive to the nucleation and preferential orientation growth of BiVO4 grains.At pH=4,BiVO4 preferentially grows along the(121)crystal surface,which allows BiVO4 to have larger upper and lower surfaces,a thinner thickness,and a two-dimensional micrometer lamellar microstructure,it has higher specific surface area and more active sites,so it has better catalytic performance.Research on BiVO4 synthesized at different hydrothermal times has shown that a hydrothermal time of 5 hours is beneficial for the formation of BiVO4.Shorter hydrothermal time can lead to insufficient crystal growth and the difficult formation of grains with uniform size and regular morphology,while too long hydrothermal time can lead to excessive crystal growth and agglomeration,which can reduce photocatalytic efficiency.The research on BiVO4 synthesized at different hydrothermal temperatures has shown that the crystallinity and crystalline morphology of BiVO4 was continuously improved with the increase of temperature.At 180℃,it has better crystallinity and a more uniform and regular two-dimensional sheet shape,thus possessing higher catalytic activity.Therefore,the BiVO4 photocatalyst prepared under the conditions of precursor solution pH=4,hydrothermal time 5 hours,and hydrothermal temperature 180℃ has relatively best performance.(2)CuFe2O4 was prepared by hydrothermal method,with a cubic shape of about 100 nm in grain size,good crystallinity,and uniform particles.Based on the above,CuFe2O4/BiVO4 composite photocatalysts with different CuFe2O4 additions were synthesized by hydrothermal method.The results showed that the five samples with a CuFe2O4 addition of 10%-50%exhibited certain photocatalytic performance,with degradation efficiencies of 39.8%,40.5%,43.7%,58.1%,and 51.0%for 120 minutes,respectively.With the increase of the amount of CuFe2O4 added,the degradation efficiency of the composite materials first increased and then decreased within 120 minutes,reaching the highest when the amount of CuFe2O4 added was 40%.At this time,the BiVO4 crystal grows into a thin,small,square sheet shape with a relatively large specific surface area.CuFe2O4 mostly adheres to the surface of the BiVO4 crystal with a large number of hanging bonds,providing a wealth of active sites for the entire catalytic process,and forming good contact with CuFe2O4,thereby forming a heterojunction structure. |
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