Preparation And Characterization Of Hydrogels Based On Tea Residue Cellulose And Its Application

Abundance of tea residue is produced in the recent years as tea is further processed into beverages and instant tea,.To make full use of the tea residue and its cellulose(10.0%-16.0%),in this study,tea cellulose(TC)was extracted from tea residue and prepared into tea cellulose hydrogels in the solvent of 1-allyl-3-methyl-imidazolium chloride([AMIm]Cl),meanwhile,?-carrageenan(CA),chitosan(CH),guar gum(GG),soluble starch(SS),single-walled carbon nanotube oxide(SWNTs),graphene oxide(GO)and ferriferous oxide(Fe3O4)were used as additives to modify the prepared hydrogels.The prepared hydrogels were characterized to compare their structures,thermal properties,texture profile surface topography and so on.In the aspect of application,swelling kinetics,eviromental response properties,mode molecule adsoption and release,biological compatibility.The results are as follow:1.Yield of TC was about 4.2% by the method of extraction with petroleum ether to degrease,followed acetone to decolorize,NaClO2 to delignify,KOH to remove semi-cellulose and H2O2 to bleach respectively.The purity of TC was demonstrated by ion chromatography(IC),Fourier transform infrared spectroscopy(FTIR),X-ray diffraction(XRD)and thermogravimetric analysis(TGA).2.Tea cellulose hydrogels were prepared via the method of heating-cooling-washing process.The prepared TC was stir-treated in [AMIm]Cl solvent at 100 °C for 5 h.Tea cellulose hydrogels were obtained after the reacted mixtures were cooled to ambient temperature.FTIR suggested that no derivatives was generated during the dissolving process.XRD indicated that the partial amorphous component of TC was changed to cellulose crystal during dissolutionregeneration.The texture profiles(hardness,springiness,cohesiveness and resilience),swelling ratio and drug loading ratio were increased due to the addition amount of TC.3.Several types of hydrogel conmposites such as ?-carrageenan / tea cellulose hydrogel(TCH-CA),chitosan / tea cellulose hydrogel(TCH-CH),guar gum / tea cellulose hydrogel(TCH-GG)and soluble starch / tea cellulose hydrogel(TCH-SS)were prepared by the addition of CA,CH,GG and SS respectively.By scanning electron microscopy(SEM),the structures of TCH-CH and TCH-GG were observed more compact than TCH-CA and TCH-SS.The differences in these structures were found related to the differences in texture,swelling,adsorption and release release properties of the prepared hydrogels.By additions of CA and SS,the prepared hydrogels had better thermal stability,swelling ratio and drug loading ratio,whereas by additions of GG and CH,the prepared hydrogels had better drug releasing ratio.Cell toxicity experiments proved that all of the tea cellulose composite hydrogels had good cell compatibility and low toxicity.4.single-walled carbon nanotube oxide / tea cellulose hydrogel(TCH-SWNTs)and graphene oxide / tea cellulose hydrogel(TCH-GO)were prepared by addition of SWNTs and GO.Except springiness,all the texture profiles of the prepared hydrogels were increased due to additions of SWNTs and GO.In addition,the thermostability of the prepared hydrogels was enhanced with the fastest degradation temperature from 280 °C to 320 °C.The kinetic adsorption behaviors of TCH-SWNTs and TCH-GO were found to fit well the pseudo secondorder model,indicating the domination of chemical adsorption.Both TCH-SWNTs and TCHGO showed perfect adsorption on methylene blue because of the their oxygen groups(-COOand-O-)on the skeleton.While due to high area of adsorptive surface,TCH-GO showed 46.4 mg/g adsorption capacity and 92.7% adsorption ratio,great higher than TCH-SWNTs.5.Tea cellulose hydrogels showed paramagnetic and good thermal stability and favourable texture profiles(hardness,fracturability,springiness,gumminess and resilience)when Fe3O4 magnetic particles were introduced,but showed the deteriorated swelling ratio and drug loading ratio.