| Plant polysaccharide aerogels are safe and non-toxic,and can be widely used in food packaging materials and food-grade adsorbents,and so on.The raw materials of polysaccharide aerogels are derived from plant polysaccharides,which are harmless to humans,and will not cause pollution to the environment.And they can be recycled and degraded after use,they belong to green materials.Carrageenan extracted from red algae is non-toxic and harmless,and is widely used in industries such as biomedicine,medical supplies and food additives.In this thesis,carrageenan and carrageenan/carbon nanofibers aerogels were prepared with carrageenan extraction from Chondrus by freeze-drying technology and potassium chloride as cross-linking agent.The physical and chemical properties,mechanical properties,swelling,oils/organics adsorption properties of the aerogels were invested in this study.The results are as follows:1.The Chondrus extraction was obtained after cleaning,pretreatment,heating,stirring and filtration of Chondrus.The Chondrus extraction is then freeze-dried to obtain carrageenan powder.The types of carrageenan are detected by means of infrared detection,X-ray diffraction,zeta potential,and gel permeation chromatography(GPC)testing.The results showed that the carrageenan extracted directly from Chondrus was iota-carrageenan,and the molecular weight of single carrageenan extracted in the laboratory was higher than that of commercial carrageenan we bought from Chondrus.2.Carrageenan aerogels were prepared directly from the Chondrus extraction using freeze-drying technology with potassium chloride as cross-linker.The effect of carrageenan concentration on the performance of the carrageenan aerogel was explored.SEM showed that with the concentration of carrageenan increases,the internal structure of carrageenan aerogel began to change,and the pore volume and porosity also changed.FTIR and XRD showed that adding potassium chloride didn't change the basic structure and crystal structure of carrageenan.When the concentration of carrageenan was increased from 1wt% to 4wt%,the water absorption rate of carrageenan decreased from21.5g/g to 11.5g/g.When the concentration of carrageenan was 2.5wt%,the adsorption ability of carrageenan aerogel to oil and organic solvent was the best,the ability to adsorb oils can reach up to 25 times of its own weight,and the adsorption capacity of organic solvents was more than 14g/g.3.The carbon nanofibers with different concentrations were added to the carrageenan solution,and potassium chloride was used as cross-linking agent,and the carrageenan/carbon nanofiber composite aerogels were prepared by freeze-drying technology.The effects of carbon nanofiber concentration on the performance of composite aerogels were characterized by mechanical performance test,flame retardancy test,hydrophile-hydrophobic test,adsorption oil and organic solvent test.The results showed that after adding carbon nanofibers,the properties of the composite aerogel are superior to pure carrageenan aerogel.FTIR and XRD showed that there was no chemical bonding between carbon nanofibers and carrageenan.With the concentration of carbon nanofibers increased from 0.5% to 2%,the breaking strength of the composite aerogel increased and the elongation at break decreased,which may be because the carbon nanofibers play a supporting role in the aerogels.The limit oxygen index value of the composite aerogel increased from 45% to 54%,indicated that the flame retardancy of carrageenan/carbon nanofiber composite aerogels gradually improved with the increasing of the concentration of carbon nanofibers.The water absorption of the aerogel decreased from 26g/g to 18 g/g,and the adsorption of oils and organic solvents was generally better than that of pure carrageenan aerogels for oils and organic solvent. |
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