A Study For Photocatalytic Activity Of Self-assembly TiO₂-FeOOH Nano-films And Its "Photocatalysis Iron Cycling"

As an environmental mineral material,iron?oxygen?oxide is a semiconductor mineral that has been widely concerned in geocatalysis and photocatalysis.The high-efficiency photocatalytic oxidation of mineral materials is one of the main development directions of nanoscience in the future.Semiconductor photocatalysts such as TiO₂,are still the focus of research.In this paper,a multiphase mineral system was constructed by the highly active nano-FeOOH-TiO₂ composite membrane and modified clay mineral matrix.Their photocatalytic properties were discussed.The characteristics and influencing factors of photocatalysis iron cycling were studied.From a new perspective,the synergistic and cyclic promotion mechanism of the coupling of adsorption,catalysis and oxidation of pollutants was revealed.The results present herein:1.Modified montmorillonite?MdMMT?was prepared by physical modification method.The micromorphology and specific surface area of the samples were analyzed by TEM,BET.The results showed that the laminated layers in the MMT structure were peeled off to form ultrathin lamellar structure,after treatment with liquid nitrogen.The specific surface area of MMT was increased,and the adsorption performance of MMT was improved.The optimum preparation conditions of MMTGR composites were determined.When the mass ratio of montmorillonite to graphene was 10:2,the MMT and GR could be evenly mixed together.2.When FeOOH nanofilm was the outer layer,the composite had better photocatalytic activity.The results indicated that the photocatalytic performance was affected on composite sequence of material.Because the specific surface area of MMTGR was much higher than MdMMT.The enhancement of photocatalytic activity was found mainly due to the strong synergistic effect of the adsorption of thiamphenicol of MMTGR substrate.3.XPS characterization was applied to analyze relative content of Fe???on the solid surface.Ferrozine was used as a molecular probe to determine the relative concentration of Fe???in solution.We found that the periodic change of Fe???reduction and Fe???oxidation at the solid-liquid interface were determined by the relative content of Fe???.It proved that during the photocatalysis,iron cycling could be induced by photocatalysis and driven by the multiple redox reactions of iron in the solid and solution phases.We called it as photocatalysis iron cycling.4.Semiconductor recombination,substrate properties and target pollutants were taken as experimental factors.Their effects on the photocatalysis iron cycling were investigated.The result showed that the extent of photocatalysis iron cycling of FeOOH-TiO₂ was higher than FeOOH.FeOOH/MMTGR and FeOOH/TiO₂/MMTGR had higher the extent of photocatalysis iron cycling than FeOOH/MdMMT and FeOOH/TiO₂/MdMMT,respectively.There were significant differences in the degree,period and trend of the photocatalysis iron cycling when the pollutant changed from thiamphenicol to Cr???.