Study On The Preparations And Properties Of G-C₃N₄/BIOX Visible Light Composite Photocatalyst

Organic pollution is the biggest problem in the current water environment,the traditional water treatment method has been unable to degrade some pollutants.Photocatalyst treatment of wastewater has energy saving,environmental protecting and other advantages,but the traditional photocatalyst TiO₂ has other low utilization rate of visible light.The new visible light catalyst material g-C₃N₄ can decompose organic components in visible light,but its visible light response region is narrow and electron-hole is easy to be compounded.In this paper,in order to overcome the disadvantages of g-C₃N₄,The optimum calcination temperature of g-C₃N₄ was screened by a series of characterization and catalytic properties.Then,BiOX（X=Br,I）and g-C₃N₄ were selected by in-situ deposition method to improve the photocatalytic activity.Carbon-nitrogen double bond（C=N）and carbon-nitrogen triple bond（C≡N）in the g-C₃N₄molecular structure were relatively completed at calcination temperature of 550℃and the crystal structure was loose and porous which was easy for the adhesion and growth of other photocatalysts.Compared with 520℃and 580℃,the photocatalytic activity was the highest at 550℃,at which the degradation rate of methylene blue was 69%.After five photocatalytic tests,the degradation rate was maintained at 58%and the stability was the highest.So in the preparation of photocatalyst,g-C₃N₄ calcinated under 550℃was used as the raw material.The introduction of BiOBr does not alter the original crystal structure of the g-C₃N₄catalyst material,and BiOBr is successfully attached to the surface of g-C₃N₄,both of which are embedded together and have grown into g-C₃N₄/BiOBr.The photocatalytic activity of g-C₃N₄/BiOBr was the best when the mass ratio was 1:1 and the degradation rate of methylene blue was 98%.After five times of photocatalytic cycling tests,it could be maintained at 90%.The results showed that the photocatalytic activity of g-C₃N₄/BiOBr was the best when the initial concentration of methylene blue was 10mg/L,the concentration of photocatalyst was0.5g/L,the temperature was 35℃,the light intensity was 500W and the nass ratio was1:1.The composite catalyst g-C₃N₄/BiOI not only retained the crystal structure of g-C₃N₄,but also was added with the phase structure of BiOI.The photocatalyst BiOI was petal-like,about1000nm in size.g-C₃N₄ was bonded to BiOI.The photocatalytic activity of g-C₃N₄/BiOI was the best when the mass ratio of g-C₃N₄/BiOI was 1:1,and the degradation rate of methylene blue was 91.3%.After five times of photocatalytic cycling tests,it could be maintained at 80%.The single factor control experiment showed that the photocatalytic activity of g-C₃N₄/BiOI was the best when the initial concentration of methylene blue was 10mg/L,the concentration of photocatalyst was 0.8g/L,the temperature was 35℃,the light intensity was 500W and the nass ratio was1:1.The photocatalytic activity of g-C₃N₄/BiOBr was higher than that of g-C₃N₄/BiOI under the optimum experimental conditions.