Study On Preparation Of TiO₂ Janus Particles And Degradation Of High Concentration Organic Wastewater

With the development of chemical industry,the problem of water pollution is becoming more and more serious,especially the accidents of chemical raw materials and products in the process of production,storage and transportation,which cause a large amount of organic matter to enter the water body.Most organic compounds can be recovered by simple physical separation,but there are still high concentration of water-insoluble pollutions in the form of oil droplets,which are difficult to further removed.Titanium dioxide photocatalytic technology has the advantages of mild conditions,green and high efficiency and no secondary pollution in the treatment of high concentration and refractory wastewater.However,due to its strong hydrophilicity,the contact area with organic matter is limited and the degradation efficiency is relatively low.Pickering emulsion is a new technology of interfacial catalysis.It is an oil-water dispersing system formed by amphiphilic colloidal particles instead of traditional surfactants.Solid particles adsorbed at the oil/water interface and enhanced the solid-liquid contact area,thus forming numerous microreactors with enhanced reaction.In this paper,the photocatalytic technology combined with the advantages of Pickering emulsion to maximize the interfacial area between catalyst and organic matter,thereby improving the degradation efficiency.Firstly,stearic acid modified titanium dioxide particles?STA-TiO₂?were prepared by impregnation method.Then,TiO₂ Janus particles were prepared using STA-TiO₂ as raw material and solid paraffin as protective agent by topological selective surface modification method.Then,the photocatalytic degradation system of Pickering emulsion was constructed by using TiO₂ Janus particles and organic wastewater,and the degradation efficiency of organic wastewater was studied.With purchased Deggusa P25 TiO₂ as the main raw material and stearic acid?STA?as the modifier,random modified titanium dioxide particles?STA-TiO₂?were prepared by impregnation method.FT-IR,UV-Vis,TG and contact angle were used to characterize the structure.The results showed that STA reacted with TiO₂ to form a stable structure.Compared with pure TiO₂,the contact angle of STA-TiO₂ particles increased from 18^oto 95^o,and the hydrophobicity was greatly improved.TG analysis results showed that no thermal decomposition of STA-TiO₂ particles occurred below 200?,indicating that the modified particles had good thermal stability.Based on the preparation of STA-TiO₂,TiO₂ Janus particles were prepared by topological selective surface modification with solid paraffin as the protective agent and deionized water as the solvent.It was characterized by FT-IR,XPS,FM,HRTEM and EIS.The results showed that COOTi structure still existed in TiO₂ Janus particles.Meanwhile,XPS results also showed that the TiO₂ Janus particles contained carboxyl oxygen?COO-?and O=C-O signal peaks.Stearic acid was uniformly distributed on one side of TiO₂,which was consistent with the structural characteristics of Janus particles.This indicated that the TiO₂ Janus particles were successfully prepared by topological selective surface modification.The interface dispersion behavior analysis results showed that the prepared particles were adsorbed stably at the interface of kerosene and water,which further confirmed the amphiphilicity of the particles.The possibility of charge recombination of TiO₂ Janus particles is small,which is beneficial to improve the efficiency of subsequent photocatalytic degradation of organic compounds.Using TiO₂ Janus particle as emulsifier,kerosene as oil phase,deionized water as water phase and high-speed disperser as emulsifying device,Pickering emulsion was prepared,and the effect of various factors on emulsion stability was studied.The results showed that TiO₂Janus particles could effectively stabilize Pickering emulsion.The droplet size was small and uniform,and the average size was only 81 nm.When the kerosene,nitrobenzene and chlorobenzene were used as oil phase,the Pickering emulsion was stable.Pickering emulsion was prepared from high concentrations of kerosene and nitrobenzene using 254 nm UV lamp as the light source and TiO₂ Janus particle as the catalyst,and the Pickering emulsion photocatalytic degradation system was constructed.The degradation of nitrobenzene and kerosene by pure TiO₂,STA-TiO₂,TiO₂ Janus particles was compared.The results showed that the photocatalytic degradation effect of TiO₂ Janus particles was significantly better than that of pure TiO₂ and STA-TiO₂,TiO₂ Janus particles were stable and recyclable.In addition,the degradation mechanism of nitrobenzene by TiO₂ Janus particles was studied by adding different scavengers into the nitrobenzene degradation system.The results showed that the degradation mechanism of this experiment was basically consistent with that of pure TiO₂.