Study On Synthesis And Visible Light Photocatalytic Activity Of Ag₃PO₄ Composite Photocatalysts

Semiconductor photocatalytic technology is considered to be one of the most potential environmental treatment technology in the 21 st century.Silver phosphate?Ag₃PO₄?has received extensive attention as a new type of highly efficient visible light photocatalyst.However,the pure Ag₃PO₄ is slightly soluble in water and susceptible to photocorrosion generated elemental silver under light irradiation,which reduce its photocatalytic activity and stability,and limit the application in the field of environmental treatment technology.Therefore,this research use graphene oxide?GO?and carbon nanotubes?CNTs?with excellent conductivity as a carrier,using precipitation method to synthesize Ag₃PO₄ composite photocatalyst.Rhodamine B?Rh B?was selected as a target pollutant to evaluate the photocatalytic performance and stability of phtotcatalyst;meanwhile,we studied the photocatalytic degradation effect on organic pollutants?bisphenol A?BPA?and polybrominated diphenyl ethers?PBDEs??over photocatalysts.A series of GO/Ag₃PO₄ composite photocatalysts were synthesized using ion exchange-chemical precipitation method with different GO content.The crystal structure,morphology and optical property of samples were characterized by XRD,SEM,TEM,Raman,UV-Vis and PL.The results showed that the photocatalyst was well-crystallized and excellent optical properties.The results of photocatalytic degradation of Rh B that GO/Ag₃PO₄?7%?exhibited the best photocatalytic efficiency,its reaction kinetics constant?0.03433 min-1?is 2.5 times than Ag₃PO₄,and the sability of catalyst was also improved.The Ag₃PO₄/AgBr/CNTs composite photocatalysts were prepared using precipitation method with the assistance of CNTs as carrier and hexadecyl trimethyl ammonium bromide?CTAB?as surfactant.The photocatalyst were analyzed by XRD,SEM,TEM,XPS,Raman and UV-Vis characterization methods.The results showed that the samples were well-crystallized and had an enhanced visible light absorption.Under visible light irradiation,the Ag₃PO₄/AgBr/CNTs composite had the excellent degradation efficiency of Rh B when the mass of CNTs was 0.009 g;free radicals capture experiments showed that the main active species in the photocatalytic reaction process were holes?h+?and superoxide anion?·O2-?.The photocatalytic degradation efficiency of BPA by two kinds of composites was also researched.The results showed that BPA can be completely degraded and transformed into CO2 and H2 O after 60 min visible light irradiation.Free radicals capture experiments showed that h+ and ·O2-were the main active species roles in the photocatalytic degradation of BPA by GO/Ag₃PO₄,but all three actives species played the important roles in the photocatalytic degradation of BPA by Ag₃PO₄/AgBr/CNTs?h+ > ·O2-> ·OH?.However,the stability of Ag₃PO₄/AgBr/CNTs was not better than GO/Ag₃PO₄ in terms of degradation of BPA.We also studied the photocatalytic reduction degradation of BDE-209 with GO/Ag₃PO₄.The results indicated that the degradation ratio of BDE-209 was 97.33% with GO/Ag₃PO₄ after 8 h visible light irradiation,being the 3 times that in the Ag₃PO₄ system?33.07%?;We found that the content of GO,the dosage of GO/Ag₃PO₄ and pH of reaction system had influence on degradation of BDE-209 in some degree with different reaction conditions,GO/Ag₃PO₄ exhibited excellent photocatalytic activity in neutral environment.The intermediates of degradation over BDE-209 were analyzed by GC-MS,the results indicated that the main reason that BDE-209 could be degraded efficiently was the multi-electron reduction process.Therefore,GO has a great application prospect in the field of semiconductor photocatalytic technology and environmental treatment technology as a carrier of the semiconductor composite photocatalyst.