Modification Of Hemicellulose Based On Polyxylose And Its Utilization

As the second major components of plants in nature,hemicellulose has been widely concerned in recent years due to its rich resource and renewability.With the continuous improvement of people’s research level,more and more hemicellulose and its derivatives have been developed and utilized to meet different demands.Cinnamic anhydride with carbon-carbon double bond,phenyl,and carboxyl groups wassynthesizedthroughhomogeneousesterificationofxylanin1-allyl-3-methylimidazolium chloride（[AMIM]Cl）ionic liquid,and different catalysts（NaOH,KOH and LiOH）were used to promote the acylation synthesis of xylan derivatives.The biopolymers with different degrees of substitution（DS,between 0.11and 0.57）were feasible in a completely homogeneous system by changing different catalysts,time,temperatures,and cinnamic anhydride/xylan molar ratios.The chemical structure of xylan derivatives were characterized by FT-IR,¹³C NMR spectroscopy,and the results confirmed the structure of xylan derivatives and their functional groups.The thermogravimetry indicated that the thermal stability of the derivatives was lower than that of the original xylan.The cinnamoylated xylan（CX）with different degrees of substitution（DS）were added to the alkaline peroxide mechanical pulp（APMP）and chemical pulp respectively.The results showed that the physical strength properties and optical properties of APMP were significangtly improved by using CX as an additive.When the optimal DS of CX was 0.18,and the optimal conditions of adding CX were 15 min of mixing time and 1.0%of CX dosage,the physical strength properties and optical properties of APMP were better.Compared with the control APMP without any additive,the breaking lengthen,burst index,tear index,brightness and opacity of the APMP with CX addition increased by 37.4%,47.5%,19.0%,3.7%and 5.6%,respectively.The APMP with CX addition could promote physical strength properties of paper at the same proportion of the APMP to KP pulp.The addition of CX can significantly reduce the proportion of KP pulp.The SEM and FT-IR spectra indicated that CX was adsorbed on the surface of the pulp fibers,which decreased the porosity between the fibers and improved the uniformity of paper surface.Composite films were prepared by adding montmorillonite（MMT）and polyvinyl alcohol（PVA）into the xylan derivatives with different DS.The thermal properties of the films were investigated by thermogravimetric analysis（TGA and DSC）.The morphology,structure and absorption properties of the films were analyzed by SEM,AFM,FT-IR and XRD.The results showed that the film performance improved with the addition of xylans derivatives.The performance of film was ideal when the DS of xylan derivatives was 0.57,and the composite films can be used for food packaging materials.The chemical structure and surface porous structure of the xylan derivatives（cinnamoylated xylan）-based hydrogel was observed and analyzed by FTIR and SEM,the optimal preparation conditions of MBA/xylan and AA/xylan were 0.1 and 8respectively.And the optimal adsorption conditions of CX-g-AA hydrogel were the MBA/CX ratio of 0.1,the AA/CX ratio of 8,the DS of 0.57,the pH of 5.5 for Cr³⁺,the pH of 6.5 for Cd²⁺,the pH of 6.5 for Zn²⁺,the time of 120 min and the metal ion concentration of 800 mg/g.Under these conditions,the maximum adsorption capacities of hydrogel for Cd²⁺,Cr³⁺,and Zn²⁺were 787.3,612.5,and 556.8 mg/g,respectively.CX-g-AA hydrogel adsorption of heavy metal ions was a pseudo two stage kinetic adsorption process,and it was a chemical process.In addition,CX-g-AA hydrogel can be reused and there was no obvious loss in the amount of adsorption and recovery efficiency.