Preparation Of ZnFe₂O₄、CDs-modified TiO₂ Composites And Study On The Photocatalytic Mechanism By The Degradation Of Water Pollutants

We utilize Carbon dots and zinc ferrite（ZnFe₂O₄）modified TiO₂ photocatalytic materials and study the degradation of pollutants in water under simulated sunlight.The mechanism of pollutants is proposed.It may play an important role in treating water pollutants as scientific basis and theoretical basis in the future.In first study,stable ZnFe₂O₄/TiO₂ catalysts were successfully prepared by coupling TiO₂ with ZnFe₂O₄.The morphology,structure and spectrum of ZnFe₂O₄/TiO₂ Composites were characterized by X-ray diffraction（XRD）,ultraviolet-visible absorption spectrum（UV-vis）and transmission electron microscope（TEM）.The modified ZnFe₂O₄ contents of3wt%resulted in 2.15 folds higher reaction rate than of pristine TiO₂ due to the heterojunction.The photocatalytic activity of IDM was highest under the condition（pH=5,T=25°）.The photodegradation of IDM followed pseudo-first-order kinetics and IDM was removed 95%under 15 mins under simulated sunlight exposure.With the increase of the photocatalyst concentration,the photocatalytic efficiency is correspondingly strengthened.The catalysts significantly can retain a stable photodegradation efficiency of>90%for at least 5 cycles.The quenching experiment revealed that the contribution rate of photogenerated holes（h⁺）which is the main active species in photocatalytic degradation of IDM was 78.2%.In second study,a novel and highly efficient ternary photocatalytic ZnFe₂O₄/TiO₂/CDs nanocomposite was successfully synthesized by a hydrothermal method.The properties and structures of the samples were characterized by X-ray diffraction（XRD）,photoluminescence spectrum（PL）,Fourier transform infrared spectrometry（FT-IR）and X-ray Photoelectron Spectroscopy（XPS）.The UV-vis diffuse reflectance spectrum was used to demonstrate that carbon quantum dots could increase the absorption of visible light wavelengths.When compared with TiO₂/3.00wt%CDs and Zn Fe₂O₄/TiO₂ nanocomposites,the ternary photocatalysts exhibited the enhanced photocatalytic activity under solar-spectrum irradiation.A low CDs content of 3.00wt%in the ternary photocatalysts possessed excellent performance in the decomposition of Rhodamine B（RhB）.Act as donator and receiver,CDs can efficiently improve the ability of electron transfer and separate the electron-hole pairs..OH and O₂^·-were confirmed to be involved in the photocatalytic degradation of Rh B base on the Electron spin resonance（ESR）tests,and the photocatalytic mechanism of the Zn Fe₂O₄/TiO₂/3.00wt%CDs was proposed.After four sequential operational cycles,the Zn Fe₂O₄/TiO₂/CDs maintained its photocatalytic efficiency,indicating its high photocatalytic stability.Therefore,our results provide a high efficient photocatalytic nanocomposite that synthetized by a facile method,and have implications in the removal of environmental persistent pollutants under ternary photocatalysts mediated solar degradation.