Preparation,Characterization And Photocatalytic Performance Of Ag/Ag₃PO₄/CNTs Composite

With the development of industrial and agricultural production,the problem of water pollution is becoming more and more serious,among which organic pollutants and pathogenic microorganisms pose a serious threat to the ecological environment and human health.The characteristics of"green"and"high efficiency"make photocatalysts an important means of environmental governance.It is difficult for a single photocatalytic material to simultaneously eliminate toxic chemicals and pathogenic pathogens in the water.Therefore,the exploration of new bifunctional composite photocatalytic materials has become a research hotspot.Part I:Based on the research of Ag₃PO₄,the Ag/Ag₃PO₄/CNTs composite photocatalytic materials with excellent properties were prepared by the combined method of deposition and precipitation and in situ reduction.The crystal structure,elemental composition and morphology of the materials were analyzed by X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),scanning electron microscopy(SEM)and transmission electron microscopy(TEM).Ag₃PO₄particles present a relatively regular polygon structure with different sizes.Ag and Ag₃PO₄ particles are uniformly distributed on the surface of CNTs,indicating that the prepared Ag/Ag₃PO₄/CNTs was supported composite with CNTs as the carrier.The light absorption performance,photoelectron transfer efficiency and electrochemical performance of the material were evaluated by ultraviolet-visible light absorption spectroscopy(UV-vis),fluorescence spectroscopy(PL),impedance,photocurrent.UV-visible absorption spectrum display that Ag₃PO₄ can only absorb and utilize visible light with wavelength less than 530 nm,while Ag/Ag₃PO₄/CNTs can absorb and utilize visible light with full wavelength range.Fluorescence spectra showed that the peak intensity of Ag/Ag₃PO₄/CNTs was significantly lower than that of Ag₃PO₄ under the illumination of 390 nm excitation light source,which proved that the recombination rate of photo-generated electron-hole pairs of Ag/Ag₃PO₄/CNTs during the photocatalysis process was significantly lower than that of Ag₃PO₄.The impedance and photocurrent test results show that the impedance of Ag/Ag₃PO₄/CNTs is significantly lower than that of Ag₃PO₄,and the photocurrent is significantly improved.That indicates the charge transfer at the Ag/Ag₃PO₄/CNTs interface is faster than that of Ag₃PO₄,and the separation efficiency of photogenerated carriers is improved.Part?:The research on the photocatalytic activity degradation of phenol by Ag/Ag₃PO₄/CNTs composites under visible light and its mechanism.The results of the photocatalytic degradation experiment of phenol showed that the degradation of phenol by Ag/Ag₃PO₄/CNTs reached 91.6%under visible light irradiation for 40 minutes,while the degradation of phenol by Ag₃PO₄ was only 75.9%.At the same time,the kinetic study showed that the degradation rate of phenol followed the first-order kinetic model,and the degradation rate of phenol by Ag/Ag₃PO₄/CNTs(K₁=0.055 min^-1)was much higher than that of Ag₃PO₄(K₂=0.028 min^-1).It can be concluded that the photocatalytic degradation rate and degradation efficiency of Ag/Ag₃PO₄/CNTs composites are significantly improved.The effect of environmental p H and catalyst dosage on the photocatalytic reaction was studied.The results showed that Ag/Ag₃PO₄/CNTs exhibited the best photocatalytic degradation activity in neutral solution and catalyst concentration of 22 g?L^-1.Subsequently,the contribution rates of various active substances to phenol degradation in photocatalysis were studied,the free radical scavenging test showed that in the photocatalytic degradation test of phenol,the contribution of photogenerated electrons to the degradation rate of phenol was 67.36%,indicating that photogenerated electrons played a vital role in the photocatalytic degradation test of phenol.In addition,the effect of the presence of heteroions on the photocatalytic degradation of phenol was also investigated.the heteroion doping test showed that the degradation rate of phenol decreased to 68.5%when phosphate was present in the solution,which may be due to the certain scavenging effect of phosphate on ROS.Finally,the stability of the photocatalytic material was studied,cyclic experiments of photocatalytic degradation of phenol showed that the degradation rate of Ag/Ag₃PO₄/CNTs on phenol decreased from 91.6%to 51.0%after four cycles,indicating that the photocatalytic activity of Ag/Ag₃PO₄/CNTs was slightly increased during the recycling process.Decrease,the stability of the photocatalytic material after compounding is improved.Part?:The bactericidal activity of Ag/Ag₃PO₄/CNTs composite photocatalyst against E.coli and S.aureus under visible light was studied.The results showed E.coli(10⁷ cfu·m L^-1)could be completely inactivated by Ag/Ag₃PO₄/CNTs within 20 min,and the inactivation rate of S.aureus(10⁷ cfu·m L^-1)reached 92%.Meanwhile,the micromorphology of the inactivated Staphylococcus was observed by scanning electron microscopy,the results showed that the bacterial cell membrane gradually contracted and collapsed during the photocatalytic process.Changes in the amount of genetic material in the cells were also studied.It was found that with the photocatalytic reaction,the DNA content in the bacterial cells decreased gradually,which indicated that the ROS further reacted with the genetic material in the cells after the cell rupture.