Preparation And Properties Of Aerogels Based On Cyclodextrin And Chitosan

With the continuous development of economy,more and more waste water from printing,dyeing and food industries is being discharged in large quantities.It contains insoluble oils and organic dyes,which are hard to degrade,highly toxic and have caused serious threat to ecological balance and human health.Therefore,how to efficiently remove pollutants from wastewater is an urgent problem to be solved.β-Cyclodextrin-based（β-CD）adsorption materials have been one of the research hotspots in wastewater treatment in recent years.But traditional modifiedβ-CD materials still have some problems such as complex preparation processes,low yields and so on,which have limited its application.Chitosan（CS）,as a kind of green,easily degradable and highly active particles,is an excellent polymer carrier.Due to the rich network adsorption structure and simple recycling performance,aerogels have broad application prospects in the treatment of hydrophobic organic matters and dyes in wastewater.Therefore,this paper usedβ-cyclodextrin and chitosan as raw materials to prepare cyclodextrin-chitosan-based aerogels,which could be used in dye adsorption,water-oil and water-organic reagents separation after modification.It had the advantages of no secondary pollution,large adsorption capacity and so on.The specific results are as follows:Firstly,β-CD and CS were used as raw materials,sodium phytate were as cross-linking agent to prepared aminoethyl-β-cyclodextrin-sodium phytate-chitosan aerogel（CTCS aerogel）.Andβ-CD grafting rate was measured as optimization index.The optimum material ratio of m_CS∶m_EA-CD,reaction temperature,reaction time and concentration of acetic acid（HAc）were1∶1,50℃,4 h and 2%.The highest amount of graftedβ-CD in CTCS aerogel could be up to237.28μmol/g.The spectrum of fourier transform infrared spectroscopy（FT-IR）showed that CTCS aerogel had new absorption bonds at 2929 cm^-1 and 1095 cm^-1.The characteristic peak of X-ray diffraction（XRD）shifted and the intensity became weak.The content of P element increased greatly by the measurement of energy dispersive spectroscopy（EDS）.All above could prove thatβ-CD were successfully bound to the surface of CS by sodium phytate（STP）.Thermogravimetric analysis（TGA）also showed that CTCS aerogel had good thermal stability.Secondly,CTCS aerogel was modified with citronellaldehyde to prepare citronellaldehyde modified aminoethyl-β-cyclodextrin-sodium phytate-chitosan aerogel（CCTCS aerogel）in ord-er to improve its physical and chemical stability.FT-IR,XRD,TGA,SEM and EDS were all used to characterize the structure and properties of CCTCS aerogel.A new C=N bond vibratio-nal absorption peak appeared at 1645 cm^-1 in the FT-IR spectrum.In the XRD spectrum,a new diffraction peak appeared at 12.18°.And the content of N and P elements in the EDS spectrum decreased.All of these had proved that citronellaldehyde was successfully modified to CCTCS aerogel.The test of TGA showed that the aerogel had little mass loss before 250℃,which meant it had good thermal stability.SEM also characterized that CCTCS aerogel had rich network adsorption structure,which laid the theoretical basis for its application in dye adsorption.Thirdly,the adsorption characteristics of CCTCS aerogel for the industrial wastewater with acid magenta（AM）,methylene blue（MB）and indigo（IN）as pollutants were explored.The effect of amount of CCTCS aerogel,adsorption time,dye concentration and pH were studied.The maximum adsorption capacity of CCTCS aerogel for AM,MB and IN could be up to 165.22,94.60 and 76.55 mg/g.The adsorption process of these three types of dyes were in accordance with Freundlich model（R²>0.9843）,quasi-second kinetics order（R²>0.9924）and W-M intra particle diffusion model（R²>0.9668）,which indicated that the adsorption process was a multi-layer site combination and chemical,electrostatic and hydrogen bonding forces were the main driving forces for adsorption.All above proved that CCTCS aerogel could effectively remove three types of dyes in wastewater and had good practical application value.Finally,in order to improve the hydrophobicity of aerogel,CCTCS aerogel was modified with organic acid to get palmitic acid and citronellaldehyde modified aminoethyl-β-cyclodextrin-sodium phytate-chitosan aerogel（ACCTCS aerogel）.The optimum organic acid type,reaction time,reaction temperature and organic acid concentration were determined to be palmitic acid,50℃,4 h and 80 mmol/L.The maximum water contact angle was 147.83°.Using FT-IR,XRD,TGA,EDS and SEM to characterize the aerogel.The modified ACCTCS aerogel had more loose and rough micro-network structure,which could be better used in oil adsorption filed.The industrial wastewater with hydrophobic pollutants adsorption experiments showed that the maximum adsorption capacity of oils and organic reagents could reach to 16.9～32.6times of its own mass,and nearly more than 80%of its own volume could be used to adsorb.After 10 times of adsorption-extrusion-absorption experiments,it could still maintain more than80%of the original absorption capacity.At the same time,it could quickly separate water-oil and water-organic reagents.All above research results indicate that the prepared series of cyclodextrin aerogels have good application prospects in the fields of organic wastewater treatment and are potentially good adsorption separation materials.