Study On The Extraction And Mechanism Of Xylan From Corn Stalk By Mechanically Assisted Alkali Method

Corn stalk,as one of the agricultural wastes with the largest annual output,contains abundant hemicellulose,which made it had a very high utilization value.As the main component of hemicellulose,xylose has been widely used in functional food and pharmaceutical fields due to its unique physical and chemical properties.However,the high production cost and low purity of xylooligosaccharide in China seriously restrict the application of xylooligosaccharide.Therefore,in this study,we extracted xylan by alkali method from corn stalk so as to protect its main chain and structure well,which provides a wide space for the subsequent application of xylose.Firstly,the dissolution rule of xylan by alkali method was investigated by single factor tests,such as alkali concentration,temperature,time and liquid ratio,and the optimal extraction conditions were obtained by orthogonal experiment:10%Na OH,120°C,100min and liquid-ratio of 1:4,the dissolution rate of xylan reached 89.34%.On this basis,the purity of the target product was improved by p H classification of alcohol-submerged xylan.It was found that the purity of xylan could be increased by 12.32%,up to 65.81%,which proved that this method had obvious effect.Based on the extraction of xylan by single alkali method,the mechanical assisted alkali method was used to extract xylan from corn stalks.The effects of three different mechanical treatment methods on the structure of the raw materials were investigated.It was found that78.60%of xylan could be extracted by HC refiner assisted alkaline method under the condition of low alkali concentration,and the purity of xylose was as high as 77.79%.It is proved that the amount of alkali can be greatly reduced by mechanically assisted alkaline method under the condition of high yield of xylan.The influence of mechanical treatment on the internal structure of raw material fiber was analyzed by SEM and XRD.The results of thermal analysis and molecular weight distribution showed that the product had good thermal stability and higher molecular weight,which provided basic properties for the later application of xylan in various aspects.The results of FTIR,~1H and 2D HSQC showed that the xylan had a backbone of D-xylp with a?-(1?4)-linkage attached with?-L-Araf and4-O-Me-?-D-Glcp A.In the process of extracting xylan by mechanical treatment assisted alkali method,the 90%of lignin was dissolved due to the effect of alkali,and then the fiber structure was retained by the mechanical action of disk grinding.Therefore,the remaining fiber could be reused in paper-making process under the condition of ensuring a higher extraction rate of xylan.Besides,the lignin obtained in the process of p H fractionation can be used in the study of adsorption.It is found that the fibers obtained have a good fiber morphology.Secondly,the lignin has a good adsorption potency,and can be used as adsorbent for wastewater treatment in the dye industry.So that the by-products in the process of extracting xylan can also be fully utilized,which meet the requirements of sustainable development.