Polyurethane Foam Supported Titanium Oxide Photocatalytic Material And Its Application In The Degradation Of Antibiotics

With the large-scale application of antibiotics,the pollution of antibiotics in the environment is becoming more and more serious.Therefore,it is urgent to control the pollution of antibiotics.Compared with other antibiotic treatment methods,photocatalytic technology with the advantages of environmental friendliness,energy saving and mild reaction conditions,and has a broad prospect in treating antibiotic pollution in water environment.Among all kinds of photocatalysts,the floating photocatalyst has better performances in treating water pollution in the environment due to its outstanding characteristics of stronger light utilization and easy recovery and reuse.Based on the above considerations,polyurethane foam（PUF）,as a new type of floating photocatalyst substrate,with rich pore structure,high specific surface area,low density and high stability,could be used as an excellent photocatalyst carrier material,which has gradually aroused more and more research interests.The research content of this dissertation is mainly divided into the following two parts:（1）The PUF/GO composite carrier was prepared by dipping graphene oxide（GO）in PUF take advantage of the characteristics of swelling reaction between PUF and anhydrous ethanol without destroying the structural integrity,which finally improved the hydrophilicity and stability of polyurethane foam.PUF/GO/TiO₂composite catalytic material（PGT）was synthesized by loading TiO₂（Degusser P25）on PUF/GO surface using anhydrous ethanol solution of GO as binder.The PGT was then irradiated under xenon lamp.After curing under high light,the smooth GO part was reduced to reduced graphene oxide（r GO）,forming a two-sided structure with one hydrophilic side and hydrophobic side,and finally obtaining the PUF/r GO/TiO₂composite catalytic material（PRT）.In PRT photocatalyst,r GO film not only effectively protected PUF foam from photocorrosion by TiO₂,but also can firmly attach TiO₂to the surface of PUF.In addition,r GO also improved the photoabsorption capacity and electron transport capacity of the catalyst,and enhanced the activity of TiO₂.The optimized PRT photocatalyst achieved 99.6%degradation rate and 83.4%mineralization rate for oxytetracycline hydrochloride OTC.The experiment of free radical trapping agent confirmed that the main active substance in OTC photocatalytic degradation is photogenerated hole,which can degrade OTC to small molecular groups,CO₂and H₂O with molecular weight lower than 100.This kind of catalyst has a simple recovery operation,and its performance still preserved after six times of reuse.It also has a good removal effect on OTC in Yellow River water under natural light conditions.Meanwhile,PRT photocatalyst also had good degradation performance for ciprofloxacin,norfloxacin and aureomycin（93.8%,80.0%,83.7%）.（2）In order to improve the surface adsorption capacity and light absorption capacity of PRT photocatalyst,and thus further improve the photocatalytic efficiency,g-C₃N₄nanosheets were coated on the P25 particles to prepare.TiO₂@g-C₃N₄composites（TCN）were formed under the action of high power ultrasound.The TiO₂@g-C₃N₄（PGTCN）composite catalyst was then loaded on PUFF/GO by impregnation method.After maturation under xenon lamp,PUF/RGO/TiO₂@g-C₃N₄（PRTCN）composite photocatalyst was obtained.Among them,the GO film in the intermediate layer not only effectively protected PUF foam from photodegradation,but also realized the solid combination of the catalyst and the catalytic substrate.PRTCN photocatalyst can remove norfloxacin,oxytetracycline hydrochloride,ciprofloxacin,aureomycin with high efficencies 95.4%,98.9%,86.1%,79.0%.In the dark state,the adsorption rate of norfloxacin was 57.5%,which was 39.8%higher than that of adding g-C₃N₄,and the final removal rate was 24.79%higher than that of adding g-C₃N₄.In addition,after illumination curing,PRTCN’s GO towards the smooth surface is reduced to r GO,forming a Janus sutures with a hydrophilic structure on one side and hydrophobic on the other.This structure is not only conducive to better floating on the surface of the PRTCN photocatalyst to receive illumination,but also can improve the mass diffusion inside the catalyst.In addition,r GO also improved the electron transfer ability of photocatalyst and promoted the separation of photogenerated carriers.According to the active radicals trapping agent experiment,in the degradation process of norfloxacin by PRTCN,the main active substance is photogenerated hole（h⁺）,which can effectively degrade norfloxacin into small molecular groups,reaching a mineralization rate of 70.6%.The recovery of the catalyst is simple and stable.After repeated use for 6times,the adsorption and catalytic performance of the catalyst still do not decline.Under natural conditions the catalyst showed good,Norfloxacin removal effect in the Yellow River water.