The Preparation Of Cellulose Nanocrystal From Carex Meyeriana And Its Application In Dye Adsorption

Carex meyeriana,mainly distributing in the northeast area in China,have obtained growing attention with their distinguish advantages in abundant source,renewability,and biodegradability.Carex meyeriana have sililar chemical composition with hemp,mainly containing cellulose,lignin and hemicellulose,pectin and other components.Meanwhile,carex meyeriana have high yield annually.Therefore,the reaserch on extraction of cellulose from carex meyeriana have important significance.In this paper,we choose carex meyeriana as raw material,and extract fibers from them by aqueous biphasic system,which can lay the theoretical foundation for degumming technology of carex meyeriana;then the fibers were treated by mechanical crush,dimethyl sulfoxide(DMSO)and 2,2,6,6-tetramethyl-piperidin-1-oxyl(TEMPO)oxidation system to prepare cellulose nanowhisker.We also preliminarily explored the application of cellulose nanocrystal in dye adsorption to provide new solutions for printing and dyeing waste water pollution problems.In this paper,the main research contents include:(1)The basic structure and performance characterization of carex meyeriana.The chemical composition,Fourier transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD),Scanning Electron Microscope(SEM)testing,etc.were analyzed.The result shows that: carex meyeriana mainly contain the compositions such as cellulose,lignin,hemicellulose,and pectin.The content of cellulose is 19.98%,which is quite lower;while the contents of lignin and hemicellulose are relative higher.Its crystallinity is 24.12%.The SEM observations show that carex meyeriana has uneven surface along longitudinal direction and waves along transverse.The peak parts along transverse have porous structure,and valley parts are composed of solid material.(2)The optimization on extraction process and characterization of carex meyeriana fiber.In this work,carex meyeriana fibers were obtained by aqueous biphasic system(polyethylene glycol-2000)/inorganic salt solution).In the degumming process,lignin was dissolved in organic phase,while cellulose stayed in inorganic salt solution.Through single factor control variable method and the orthogonal test analysis,the influence of various chemical reagents,treating time and temperature on the weight loss rate of fiber were discussed,and the optimal processing parameters were determined.Besides,chemical composition analysis,fourier transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD),Scanning Electron Microscope(SEM),etc.were used to characterize the fibers’ structure and performance.On the base of test results,we can get the following conclusions: the fibers contain more cellulose and less hemicellulose,lignin,water soluble matter,et al.The crystallinity increases significantly,which is nearly twice higher than that of carex meyeriana,up to 42%.The surface of carex meyeriana fiber is smoother than that of raw material due to the remove of large amounts of impurities.(3)Comparison between traditional alkali boiling method and aqueous biphasic system.In order to compare the performance of the fibers prepared by different ways,the tensile strength,length,moisture regain,linear density of the corresponding fibers were tested.The results show that the fiber treated with aqueous biphasic system is better in length,fineness and tensile strength than the fiber with traditional alkali boiling.Therefore,aqueous biphasic system has potential application prospect in fiber degumming.(4)Preparation and characterization of cellulose nanocrystal from carex meyeriana.Carex meyeriana fiber as raw material was treated by TEMPO oxidation to obtain cellulose nanocrystal,then the nanocrystal was characterized by transmission electron microscopy(TEM),SEM,FT-IR,XRD,thermogravimetric analysis(TGA),etc.The results show that: carex meyeriana cellulose nanocrystal is short-rod shaped,with diameter of 20-60 nm and length of 100-300 nm;dried cellulose nanocrystals is thin flatshaped and polyporous,indicating it has potential application in acoustics and biomedical field;compared with carex meyeriana,cellulose nanocrystals have higher content of cellulose;the cellulose nanocrystal has the same crystal structure as the fibers,i.e.cellulose Ⅰ type,and its crystallinity is 51.01%;the cellulose nanocrystals start to degrade at 220 ℃,and reach to stability at 320 ℃.(5)Preliminary exploration on the application of carex meyeriana cellulose nanocrystal in the adsorption of methylene blue dye.The blend of cellulose nanowhisker deposit and hydrogen peroxide was used as adsorption system,and the processing parameters,including cellulose nanocrystal dosage,hydrogen peroxide concentration,reaction temperature and time,were optimized.The experimental results show that the absorption rate can reach to maxium value of 98.76% with cellulose nanocrystal dosage of 0.06g/ml and hydrogen peroxide concentration of 2.4mol/L at 30 ℃ for 180 min.Therefore,cellulose nanowhisker is one of the ideal adsorbent of methylene blue dye.