Study On Extraction Of Gramineous Plants Cellulose And Preparation Of Biomass Membrane In Ionic Liquid Via Inversion Method

Nowadays,with the increasing energy crisis and the increasing awareness of environmental protection,cellulose has received high attention due to its excellent performance and huge potential.Gramineae plants are widespread in nature and have a high cellulose content.Therefore,the extraction of cellulose from it and the research of Cellulose-based Composites will have far-reaching significance and broad prospects.In this paper,the component and polymerization degree of the reed,bagasse and eulaliopsis binata were used to analyzed by copper ethylenediamine method.A new way of ultrasonic assisted alkaline and acid extraction of cellulose was opened up.Then select 1-propenyl-3-methylimidazolium chloride（[AMIM]Cl）/dimethyl sulfoxide（DMSO）ionic liquid composite solvent as the co-solvent of cellulose and chitosan,the regenerated cellulose membrane and cellulose/chitosan composite antibacterial membrane were prepared by phase transformation method.The composite solvent aqueous solution after membrane formation is recycled by means of rotary evaporation and vacuum drying.In the experiment,the orthogonal design was used to optimize the cellulose extraction process.The effects of mass fraction,compound solvent ratio,coagulation bath temperature,and the mass ratio of cellulose to chitosan in the composite membrane on the membrane production process and membrane performance were analyzed.The morphology,structure and properties of cellulose,cellulose membrane,chitosan,and cellulose/chitosan composite membrane were characterized by scanning electron microscope（SEM）,Fourier infrared spectroscopy（FTIR）,X-ray diffractometer（XRD）,rotational rheometer,thermogravimetric analyzer（TGA）,universal tensile machine,etc.The chemical stability of cellulose membrane is reflected by its solvent resistance and acid and alkali resistance.The bacteriostatic properties of the composite membrane were investigated by dilution coating plate method.The main research content and conclusions are as follows:（1）The components of reed,bagasse,and eulaliopsis binata are mainly cellulose,hemicellulose,and lignin,accounting for about 85%of all components,and the cellulose content is 36.72%,40.13%,and 45.1%,respectively.The copper ethylenediamine method measured the reed polymerization degree DP₁=227,the bagasse polymerization degree DP2=218,and the eulaliopsis binata polymerization degree DP₃=323.（2）Before chemical treatment of gramineous plants,brief ultrasonic radiation treatment is necessary.Under the optimal extraction process conditions,the reed cellulose has the highest purity of 93.5%,followed by bagasse cellulose with a purity of92.8%,and the eulaliopsis binata cellulose with the lowest purity of 90.4%.The purified cellulose has a clear fibrous structure inside,which still maintains the crystalline form of cellulose I,but the crystallinity is greatly improved.The crystallinity of reed cellulose increased from 44.05%to 71.52%,the crystallinity of bagasse cellulose increased from 43.3%to 68.7%,and the crystallinity of eulaliopsis binata cellulose increased from 49.04%to 70.9%.The thermal stability is effectively enhanced,the maximum pyrolysis peak of reed cellulose is increased from 349℃to 364℃,the maximum pyrolysis peak of bagasse cellulose is increased from 325℃to 353℃,and the maximum pyrolysis peak of eulaliopsis binata cellulose is increased from 334℃to359℃.（3）The[AMIM]Cl is a good solvent for cellulose and chitosan,and DMSO is a benign auxiliary.When the DMSO addition ratio is 1/3,the dissolving effect of the composite solvent is the best.Under the condition of 90℃,the solubility of reed cellulose is 11.3%,the solubility of bagasse cellulose is 13.4%,the solubility of eulaliopsis binata cellulose is 15.7%,the solubility of chitosan is 7.9%.The dissolution and regeneration of cellulose and chitosan in[AMIM]Cl/DMSO are not accompanied by derivatization reactions,and all belong to non-derivative direct dissolution,but the cellulose crystal form changes from typeⅠto typeⅡ.The sugar crystal form changes fromα-chitosan toβ-chitosan,and the apparent viscosity of the solution decreases with increasing temperature,increases with the increase of solute mass fraction,and increases with the shear rate The decrease is typical of pseudoplastic fluid rheological behavior.（4）When the mass ratio of[AMIM]Cl to DMSO in the composite solvent is 2:1,the membrane-forming property of regenerated cellulose is the best,and it is dense and uniform from the inside out.The breaking strength and breaking elongation of the regenerated cellulose membrane increase first and then decrease as the concentration of the casting solution increases.The breaking strength first strengthens and then decreases as the temperature of the solidification bath increases,and the elongation at break decreased with the increase of the temperature.When the cellulose mass fraction is 5%and the coagulation bath temperature is 25℃,the mechanical properties of the regenerated cellulose membrane are the best.The tensile strength of the reed cellulose membrane is 90.2 MPa and the breaking elongation is 13.6%.The tensile strength of the bagasse cellulose membrane 102.6 MPa,the breaking elongation is 10.6%.The tensile strength of the eulaliopsis binata cellulose membrane 96.2 MPa,the breaking elongation is 9.2%.The surface of the regenerated cellulose membrane is dense and smooth,with high uniformity and excellent resistance Organic solvents and acid and alkali resistance,thermal stability is slightly lower than the original cellulose.（5）The two components in the cellulose/chitosan composite membrane have good compatibility and can form hydrogen bonds,making the composite membrane have better thermal stability than cellulose membrane and regenerated chitosan.In the cellulose/chitosan composite membrane,cellulose is mainly subjected to external forces,and chitosan gives the composite membrane a broad-spectrum antibacterial property,and with the increase of chitosan content,the antibacterial properties of the composite membrane against escherichia coli and staphylococcus aureus were stronger,but the mechanical properties were worse.When the chitosan content in the composite membrane is 3/4,the tensile strength of the reed cellulose/chitosan composite membrane is 33.6MPa,the breaking elongation is 3.2%,the tensile strength of the bagasse cellulose/chitosan composite membrane is 35.8MPa,and the breaking elongation is 2.3%,the tensile strength of the eulaliopsis binata cellulose/chitosan composite membrane is 39.3MPa,and the elongation at break is 2.4%.（6）The recovery rate of the ionic liquid composite solvent recovered by rotary evaporation and vacuum drying reached 99.3%.The mechanical properties,surface morphology,structure and thermal performance of the regenerated cellulose membrane prepared by the original composite solvent and the recovered composite solvent are not very different.[AMIM]Cl/DMSO composite solvent has excellent recyclability.