The Preparation And Performance Study Of TiO₂/PANI/Fe₃O₄ Photocatalytic Magnetic Fluid Synthesised Without Drying Process

The process of nano-TiO₂ photocatalytic degradation of pollutants has been widely concerning by scholars both at home and abroad,especially in dealing with complex composition of organic wastewater,because of its high catalytic activity,no selection,no secondary pollution,low price,etc.At present,the preparation of nano-TiO₂ powder（titanium dioxide） technology has been very mature and has formed production,and its preparation process is usually composed of raw materials after reaction in liquid phase by filtrating, washing, drying,grinding and a series of complicated operation process.Nanometer TiO₂ can not be directly use after liquid phase synthesis,mainly because in the synthesis of TiO₂ particle size is difficult to control,and the attached impurities must be completed separated by washing and heat treatment process.An important factor restricting nano-TiO₂ photocatalytic development is difficult recovery and magnetic photocatalyst research is dedicated to solving this problem. Small particles of composite catalyst need to be constantly ground in the process of preparation to control its growth,but the damage to the structure of catalyst is inevitable by grinding process.So the key point of this study is to directly control agglomeration of particle by chemical method and achieve the purpose that synthesizing a well-structured composite catalyst.According to the above the use of TiO₂ problem, the method of this paper taken tetrabutyl titanate as titanium source and butyl alcohol as dispersing agent,supplemented by low temperature hydrothermal method,preparing a well photocatalytic effect and directly put into used nano TiO₂ sol.In the aspect of magnetic carrier catalyst,microemulsion polymerization could be used to load polyaniline on Fe₃O₄ surface for synthesizing a great dispersibility water-based magnetic materials.Preparing of TiO₂/PANI/Fe₃O₄ photocatalytic magnetic depended on the principle of opposite charges attract each other as the TiO₂ sol prepared hydrothermal method combined with PANI/Fe₃O₄ composite materials.The whole preparation process without any drying,milling operation.Meanwhile butyl alcohol was used throughout the preparation process,and finally realized the part of the recycling.The phase composition,morphology,surface properties and magnetic properties of the composite particles were characterized by X-ray diffraction（XRD）,scanning electron microscope（TEM）,transmission electron microscope（TEM）, fourier transform infrared spectrometer（FT-IR） and vibrating sample magnetometer（VSM）. The photocatalytic activity and recovery of the magnetic fluid were evaluated by photocatalytic degradation of phenol. Through research this paper obtained the following conclusions:1. Tetrabutyl titanate was been used to synthesize nanometer TiO₂ sol by low temperature hydrothermal method. Dosage of butyl alcohol dispersant temperature and time of the hydrothermal reaction were designed of single factor experiments and investigated the effect of nanometer TiO₂ sol’s photocatalytic activity.The results illustrated that when the molar ratio of raw material was n（tetrabutyl titanate） : n（n-butanol） : n（H2O）=1 : 10 : 40、hydrothermal temperature was 170℃ and hydrothermal time was 18 h,synthesized TiO₂ sol has good properties.At the same time,the introduction of butyl alcohol as dispersing agent,which reduces the introduction of foreign material, suppressed butyl titanate drastic hydrolysis reaction and was advantaged to synthesis fine uniform TiO₂ particles.The average recovery rate of n-butanol reached 92.91% under these conditions.2.Using hexadecyl trimethyl ammonium bromide as emulsifier n-butyl alcohol as auxiliary emulsifier,the experiment had try to surface coating of Fe₃O₄ magnetic cores polyaniline in the microemulsion formated by water and aniline.The raw material ratio,pH of reaction liquid and demulsifier had been designed to be a 3×3 orthogonal experiment that each factor corresponded to the three levels.Orthogonal test standard judged by the uniformity of PANI/Fe₃O₄ size distribution and the growth of water-based magnetic Fe₃O₄.The conclusion was that in the raw material of Fe₃O₄ and aniline molar ratio of 1 : 2.1,reaction liquid pH of 4,n-butyl alcohol emulsion had the best particle size distribution.The introduction of n-butyl alcohol,on the one hand,reduced the introduction of the impurity,on the other hand ensured that the PANI/Fe₃O₄ in water-based magnetic further coated with stability.3.Combining the experiment in the first two parts of TiO₂ sol and PANI/Fe₃O₄ water-based magnetic synthesis methods with the condition that there were opposite electrode potential of TiO₂ and PANI/Fe₃O₄ under a neutral conditions,the paper had loaded TiO₂ on the surface of PANI/Fe₃O₄ to prepared TiO₂/PANI/Fe₃O₄ photocatalytic magnetic fluid. After investigating the effect of TiO₂ and PANI/Fe₃O₄ material ratio on the performance of magnetic liquidcatalytic activity and recycling,the material ratio that n（Fe₃O₄） : n（PANI） : n（TiO₂）=1 : 2.1 : 15 had been determined which made TiO₂/PANI/Fe₃O₄ photocatalytic magnetic fluids had the best photocatalytic activity and stability,and accorded with the requirement of the magnetic carrier recycling in this paper.4.Fe₃O₄ and TiO₂ in TiO₂/PANI/Fe₃O₄ photocatalytic magnetic fluid existed in the form of small nano-particles,but polyaniline（PANI） was present a large volume of amorphous state. Fe₃O₄ which had 10²0nm particle size embedded inside the polyaniline,and TiO₂ loaded on the surface of polyaniline by the adsorption effect of charge measured only 8 to 9 nm.They formed a structure composed of shell/shell/core.5.This paper exploratory researched the synthesis and performance of TiO₂/PANI/Fe₃O₄ photocatalytic magnetic fluid.Magnetic carrier structure got good results on the characterization,but its photocatalytic activity still had a gap from the pure TiO₂ catalyst.The key of the problem might be the stability of composite structure.All in all,the green, energy-saving and clean way of synthetic should become the new direction of the preparation of magnetic carrier catalyst.