Preparation Of Fe₃O₄-TiO₂（P25） Composite Photocatalyst And Photocatalytic Degradation Of Dye Waste Water Under Solar Radiation

Firstly, a comparative study of degradation of alizarin red S (ARS) was carried out ina solar photo-Fenton-like system using, respectively, a natural ironsand, home-madeFe3O4powder and commercial one as heterogeneous catalysts. X-ray powder diffraction(XRD) and X-ray fluorescence spectroscopy (XRF) jointly revealed that the most mainchemical composition of the natural ironsand is Fe3O4(82.6%), SiO2(8.6%) and TiO2(2.3%). It was found that the natural ironsand exhibited higher photocatalytic activity fordegradation and mineralization of ARS than the home-made Fe3O4powder andcommercial one. The possible reason was that TiO2semiconductor components achievedthe efficient separation of electron-hole pairs to improve the photocatalytic activity,moreover the natural ironsand utilized SiO2components to make Fe3O4bond together toimprove the stability. Since this natural ironsand as heterogeneous catalyst shows manyadvantages, such as high photocatalytic activity for the degradation of dye pollutants inthe sunlight, low cost, low consumption, facile recovery and recycles, a compositephotocatalyst whice utilized SiO2to make Fe3O4bond together was prepared, itsuccessfully simulated the natural ironsand whice showed high catalytic activity in thewastewater treatment.Secondly, a new Fe3O4-TiO2(P25) composite photocatalyst FT0.75was prepared byco-precipitation method in the presence of TiO2(P25) and characterized by XRD, SEM,TEM and UV-vis diffuse reflectance spectra. The photocatalytic activity of FT0.75wasevaluated by removing model pollutant alizarin red S (ARS) under solar radiation. Theeffects of major factors including mass ratio of Fe3O4to P25, FT0.75dosage and initial pHon the removal of ARS were investigated. Reuse and stability of FT0.75were also tested.FT0.75not only had a higher photocatalytic activity than the mixture of Fe3O4and P25, butalso was magneticlly recoverable from treated wastewater. The high photocatalyticactivity of FT0.75could be kept from pH3to5.5(natural pH of ARS solution) undersunlight. An important virtue of FT0.75was that it utilized the photodisslution of Fe3O4component to achieve the efficient separation ofelectron-hole pairs to improve the photocatalytic activity. FT0.75did not almost lose itsphotocatalytic activity after5times of uses, indicating its superior stability and reusability.Calcination of FT0.75in the temperature range of200-500℃resulted in the change of ironoxide species from Fe3O4to Fe2O3and the decrease in the photocatalytic activity.