Preparation And Performance Of Yb-P-TiO₂/SiO₂/NiFe₂O₄Nano-photocatalyst With

To resolve the problems of nano-TiO2in wastewater treatment such as low solarutilization, low quantum efficiency, and difficult recovery, Yb-P-TiO2/SiO2/NiFe2O4nano-composite photocatalyts with magnetic separation and visible light response wereexploited, which could offer novel high-performance photocatalytic materials for thetreatment of environmental pollutants.First of all, magnetic nickel ferrite nanoparticles were prepared by liquid phasecatalytic conversion method using iron nitrate, nickel nitrate, and sodium hydroxide asraw materials. Iron and nickel contents in magnetic nickel ferrite nanoparticles weredeteminied by experiment, and the prepariton conditions of nickel ferrite wereoptimized as follows: The amount of Fe2+catalyst was n(Fe2+): n(Fe3+)=0.015; theinitial pH of the reaction solution was about9.6; the reflux time was3h, n(Fe2+):n(Fe3+) of nickel ferrite was closest to2:1. The sample prepared under optimalconditions was calcined at200℃,300℃,400℃. Their photocatalytic activities wereevaluated by degradation of4-chlorophenol (4-CP) under simulated sunlight irradiation,which increased from1.97%to34.5%. The effects of the amount of dispersant,ultrasonic dispersion time on the dispersion were researched. The results showed thatwhen the mass ratio of sodium hexametaphosphate to the nickel ferrite powders is18%,and ultrasonic dispersion time is40min, nickel ferrite particles can be well dispersed inwater.Yb-P-codoped anatase-TiO2nano-sheets were successfully synthesized from TiCl4hydrolysis by a hydrothermal method. The effect mechanisms of Yb-P-codoping on thesurface physicochemical properties and photocatalytic activities of TiO2were discussedbased on the results of XRD, TEM, BET, XPS, FTIR, DRS and PL analysis. Thephotoactivities of as-prepared samples towards the degradation of4-chlorphenol inaqueous solution under simulated sunlight irradiation followed the order of TiO2<Yb-TiO2<P25<P-TiO2<Yb-P-TiO2, indicating the production of synergetic effect byYb-P-codoping. P-doping played a crucial role on both the inhibition transformation ofTiO2from anatase to rutile and the improvement of surface texture properties. Yb3+ions could capture photogenerated electrons to form Yb2+, and then tend to release them intoacceptor such as O2adsorbed on the surface to produce·O2–, thus effectively inhibitingthe recombination of photogenerated charge carriers. The improved light absorptionproperty of Yb-P-TiO2was attributed to narrowing of the band gap owing to thecooperative effect of energy levels hybridized by the3p orbits of P atoms and the2porbits of O atoms and energy levels of oxygen vaccancies. Yb-P-codoping could furtherinhibit the recombination of photogenerated electrons and holes, enhancing the quantumefficiency, and further increase the surface hydroxyl, which was in favor of the captureof photogenerated holes and information of strong oxidative hydroxyl free radicals. Allabove factors were beneficial to the enhanced photocatalytic activity of Yb-P-TiO2.SiO2/NiFe2O4nanoparticles were prepared through Na2SiO3hydrolyzation bysol-gel method at80℃for2h (the mass percentage of SiO2in the NiFe2O4powderwas10wt.%). Magnetic Yb-P-TiO2/SiO2/NiFe2O4composite photocatalyst wasprepared from TiCl4hydrolysis by a hydrothermal method, by which organic pollutioncould be degradated under simulated sunlight irradiation. At the same time, thephotocatalyst could be recovered for recycling use in water treatment.