Preparation And Application Of Modified Cellulose/Graphene Oxide Composites

Cellulose is the most abundant natural polymer in the world,which has the advantages of low price,good biocompatibility,easy to be chemical modification and degradability.Graphene oxide（GO）is an ideal two-dimensional carbon material with large specific surface area,rich oxygen-containing functional groups,good dispersion,excellent mechanical strength and thermal stability.Therefore,they have attracted much attention in the application of water absorption and ion adsorption.Nevertheless,it is difficult for cellulose to be dissolved in water and organic solvents due to the large number of intermolecular and intramolecular hydrogen bonds in cellulose,which greatly limits the application range of cellulose.Compared with traditional cellulose solvents,lithium chloride/N,N-Dimethylacetamide（LiCl/DMAc）is used to dissolve cellulose,which has the advantages of simple process and easy recovery of solvent.The graft copolymerization of cellulose in LiCl/DMAc system will give new functions to cellulose materials.Moreover,the composite of modified cellulose and GO will further expand their scope of application.The research contents and test results of this paper are as follows:（1）An environment-friendly superabsorbent resin（cellulose-g-PAMPS）was prepared by grafting 2-acrylamido-2-methyl-1-propane sulfonic acid（AMPS）monomer onto cellulose substrate in LiCl/DMAc system.The structure,morphology and thermal stability of the synthesized resin was characterized by Fourier-transform infrared spectroscopy（FTIR）,scanning electron microscopy（SEM）,Carbon-13 nuclear magnetic resonance spectrum(¹³C NMR),thermogravimetric analysis（TGA）and X-ray diffraction（XRD）.The effects of water absorption time,temperature and different salt concentration on the water absorption capacity of cellulose-g-PAMPS were studied systematically.The results in this thesis indicated that the water absorption equilibrium of cellulose-g-PAMPS could be achieved within 10 min in distilled water.The water absorption behavior of cellulose-g-PAMPS was interpreted by the pseudo-second-order model.The maximum water absorption capacity of cellulose-g-PAMPS in distilled water and 0.9 wt%NaCl solution were 648.9 g·g^-1and 298.4 g·g^-1,respectively.In addition,the water retention rate of cellulose-g-PAMPS could be maintained above 90%at room temperature after 6 h.Therefore,the synthesized cellulose-g-PAMPS can be used as water retaining materials to increase plant growth and survival time under drought conditions or even saline alkali conditions.（2）A novel composite adsorbent（cellulose-g-PAMPS/GO）for effectively removing rare earth ion pollutant Ce（Ⅲ）was successfully prepared in LiCl/DMAc system.In this thesis,the effects of adsorption time,Ce（Ⅲ）concentration,adsorbent dosage,pH value and NaCl concentration on the adsorption of Ce（Ⅲ）by cellulose-g-PAMPS/GO were systematically studied.The results indicate that the adsorption equilibrium could be achieved within 25 min.The adsorption behavior was explained by pseudo-second-order model and Langmuir adsorption isothermal equation,which belonged to chemical adsorption.The X-ray photoelectron spectroscopy（XPS）analysis of adsorbed and desorbed adsorbents indicated that the adsorption of Ce（Ⅲ）on cellulose-g-PAMPS/GO was the ion exchange mechanism.Furthermore,the maximum adsorption capacity of cellulose-g-PAMPS/GO for Ce（Ⅲ）was271.8 mg·g^-1at the pH value of 4.23.The results in this thesis show that cellulose-g-PAMPS/GO has broad application prospects in the treatment of rare earth ions pollutions from wastewater.