Green Fractionation Of Sugar Beet Fiber And Preparation And Application Of Cellulose-based Composite Hydrogels

Sugar beet pulp?SBP?,a by-product of sugar production,has the characteristics of large yield,biodegradation,biocompatibility,complicated components,high dietary fiber content and high nutritional value.It can be processed in depth according to the specificity of each component in order to improve its added value.It aims at green fractionation of SBP fiber and modification of SBP cellulose to improve its adsorption framework structure stability and biological adsorption capacity,and has good antibacterial properties.In this paper,the depectinated SBP was used as a raw material,and dissolved by NaOH/Urea/H₂O and ionic liquid?IL?[C₄min]Cl,then the cellulose,hemicellulose and lignin components of depectinated SBP were regenerated.On the basis of cellulose,bacteriostatic cationic hydrogel,anionic hydrogel and bacteriostatic amphoteric hydrogel were prepared successively in combination with various functional materials.The mian conclusions of the study were presented:?1?The depectinated SBP was treated with 30%H₂SO₄ and successfully dissolved in NaOH/Urea/H₂O and[C₄min]Cl.The SBP cellulose,hemicellulose and lignin components were successfully regenerated.?The regenerated cellulose,hemicellulose and lignin from NaOH//Urea/H₂O system were recorded as UH-cellulose,UH-hemicellulose and UH-lignin respectively;the regenerated cellulose,hemicellulose and lignin from ionic liquid system were recorded as IL-cellulose,IL-hemicellulose and IL-lignin respectively.?IL-cellulose had a macroporous structure,while UH-cellulose had a smaller and denser surface structure.The surface of UH-hemicellulose was rough,loose and porous.The surface morphology of two lignin fractions showed irregular high-density clusters,which were composed of a large number of submicron particles.The crystal structure of UH-cellulose and IL-cellulose changed from cellulose I to cellulose II.The thermal stability of IL-cellulose and IL-lignin was slightly better than that of UH-cellose and UH-lignin,while that of UH-hemicellulose was better than that of IL-hemicellulose.Results of FTIR and ¹³C NMR showed that the chemical structures of SBP cellulose,hemicellulose and lignin regenerated from NaOH/urea/H₂O and[C₄min]Cl were similar.?2?The regenerated porous cellulose microparticles?RCM?were prepared,crosslinked after blending with chitosan.After grafting DMDAAC,the bacteriostatic cationic hydrogel beads were prepared?CCBG-g-PDMDAAC?.The physicochemical properties of hydrogels were characterized by FTIR,XRD,SEM and TG-DSC.Results showed that the crystallinity of the hydrogel bead CCBG10 decreased significantly after the grafting of DMDAAC by initiator.The surface of the hydrogel beads were smooth,porous,large,and the fracture surface were fluffy and porous.The chemical stability and acid resistance of hydrogel beads were obviously improved after the crosslinking.The RR195?Reactive Red 195?and MO?Methyl Orange?adsorption process was fitted well with pseudo-second-order kinetic model and Langmuir isotherm model.The maximum adsorption capacity of RR195 and MO was 1333.52 and 190.48mg/g,respectively.The separation and concentration of single dye in the mixed solution RR195/CV?Crystal Violet?or MO/MB?Methylene Blue?can be successfully realized by hydrogel beads.Antimicrobial tests indicated that composite hydrogel beads displayed good antibacterial properties on E.coli and S.aureus.?3?An anionic hydrogel?C/SA/Fe?was prepared by introducing sodium alginate?SA?and Fe?OH?₃ colloidal particles into the cellulose solution system.Compared to cellulose hydrogel and C/SA hydrogel,the hydrogel surface became rougher,wrinkle more compact,and pores disappeared after adding Fe?OH?₃ colloid particles.Results of FTIR and XRD showed that Fe?OH?₃ colloidal particles were successfully combined in the hydrogel system.The thermal stability of hydrogel decreased slightly after adding Fe?OH?₃ colloidal particles compared with C/SA hydrogel.Adding SA and appropriate Fe?OH?₃ colloid particles could significantly enhance the adsorption performance of cellulose hydrogels.The maximum adsorption capacity of hydrogel C/SA/Fe0.5 to MB was 93.99 mg/g.The MB adsorption process was fitted well with pseudo-second-order kinetic model and Langmuir isotherm model.The adsorption process of MB was mainly controlled by the mechanism of chemisorption,and monolayer coverage of adsorbate.The adsorption process was exothermic and spontaneous,and low temperature is more favorable for adsorption.Hydrogels had obvious salt sensitivity and good cationic dye selective adsorption.?4?Starch and activated carbon were added to the cellulose solution to synthesize the composite hydrogel?C/S/AC?.Then the nano ZnO was grafted under the NH₃·H₂O and ultrasonic system to prepare the bacteriostasis amphoteric hydrogel?C/S/AC-ZnO?.The surface of hydrogel with activated carbon and ZnO grafted showed different rough surface,while the surface of cellulose hydrogel was smooth.After grafting with ZnO,more porous structures appeared on the surface of the hydrogel.Results of FTIR,XRD and UV-vis spectra showed that ZnO particles were successfully grafted onto the surface of hydrogel.After ultrasonic treatment,the thermal stability of ZnO grafted hydrogel decreased slightly.Hydrogels have good adsorption properties for MB and MO.The maximum adsorption capacity of hydrogel C/S/AC3.0-ZnO to MB and MO was 142.70 and 72.63 mg/g,respectively,and the affinity for MB was stronger.The MB and MO adsorption process was fitted well with pseudo-second-order kinetic model and Langmuir isotherm model.The adsorption process was endothermic and high temperature was more favorable for the adsorption reaction.In addition,hydrogels had certain salt sensitivity and good adsorption regeneration.The grafted ZnO hydrogels had good antibacterial activity.Compared with S.aureus,it had better inhibition ability on E.coli.