Highly Efficient Isolation Of Lignocellulose Components By Deep Eutectic Solvents And Cellulose Utilization

Lignin and cellulose were separated from eucalyptus wood powder by partial liquefaction using four different deep eutectic solvents(Choline chloride-lactic acid,Choline chloride-glycerol,Choline chloride-PEG200,Choline chloride-glycerol-PEG200)as the liquefying reagent.Then using the choline chloride-oxalic acid dihydrate eutectic solvent to treat the separated cellulose under different conditions to prepare cellulose nanocrystal.A composite film was prepared by blending polyvinyl alcohol with prepared nanocrystalline cellulose,and the mechanical and thermodynamic properties of the composite film were studied.The effects of solvent,reaction temperature and reaction time on the separation of the components of eucalyptus wood powder were discussed.The separated cellulose and lignin were analyzed and characterized.The results showed that a relatively high yield of lignin,i.e.,approximately 95%(w/w)of total lignin,was separated from eucalyptus wood with choline chloride-PEG200 system at 140 ~oC for 1.5 h.The purity of the lignin reached 99%.The purity of the cellulose obtained by choline chloride-PEG200-glycerin system was above 92%under the oprimal reaction condition,i.e.,reaction time 90min,reaction temperature 140 ~oC.The maximum degree of crystallinity was up to 73%.Cellulose was separated from eucalyptus wood powder by partial liquefaction using choline chloride-PEG200-glycerin solvent as the liquefying reagent.Then using the choline chloride-oxalic acid dihydrate eutectic solvent to treat the separated cellulose under different conditions to prepare cellulose nanocrystal.The effect of different reaction conditions on the yield of cellulose nanocrystal was discussed.And the obtained cellulose nanocrystals were characterized by scanning electron microscopy,transmission electron microscopy,Fourier transform infrared spectroscopy,X-ray diffraction,Zeta potential and UV-vis spectra.The results showed that the yield of CNC gradually increases with the increase of solid-liquid ratio,reaction time and reaction temperature.The optimal reaction conditions are solid-liquid ratio1:100 at 100 ~oC for 4h,the yield of cellulose nanocrystal can reach 90.06%.The cellulose nanocrystals were rod-shaped,between 100 and 300 nm long,with a diameter ranging from 3to 13 nm.The molecular cellulose type I crystalline structure remained intact while the crystallinity decrease slightly during the preparation of cellulose nanocrystals.In addition,the light transmittance of the CNC solution is good,and the effect of different reaction conditions on the light transmittance is not obvious.Even at a wavelength of 300 nm,the light transmittance can reach about 70%.The PVA and CNC were blended to prepare a CNC/PVA composite film.The influence of the addition amount of CNC on the morphology,mechanical properties and thermodynamic properties of the composite membrane was discussed.The results showed that with the increase of the amount of CNC,the tensile strength of the composite film was gradually increased,and the maximum tensile strength was 59.61 MPa when the addition amount was3%,which was 58.75%higher than that of the pure PVA film.The elongation at break of the composite membrane gradually decreases as the amount of CNC increases.The results of light transmittance show that the light transmittance of the composite film is hardly affected when the amount of the CNC is 1%or less,and the transmittance of the composite film tends to decrease as the amount of the CNC continues to increase.FTIR results show that the connection between CNC and PVA is through hydrogen bonding,and there is no other chem9ical connection between physical properties.The results of TG analysis show that the addition of CNC can slightly improve the thermal stability of the composite film.