| Biomass is the most abundant renewable resources in nature,and human beings have been exploring how to make full use of biomass resources.As one of the main agricultural wastes in China,wheat straw is an important part of biomass resources,accounting for a high proportion of agricultural wastes.At the same time,the country has banned the import of waste paper and other solid waste,so it is of great significance to transform wheat straw into new biological products.Wheat straw is used as raw material,because of the high cost and poor pulping quality in the biological pulping process.At the same time,a wheat straw pulping method under normal temperature and pressure was extended by combining biological pulping with other pulping methods.The equations related to pulp indexes were established to realize on-line control of biological pulping.In view of the above problems,this research has carried out the following work:1.Through the comparative analysis of the main components of five different areas of wheat straw,wheat straw from Dezhou City,Shandong Province was selected as the raw material for pulping process.At the same time,the enzyme activities of xylanase,pectinase,β-mannanase,cellulase and laccase were determined.When p H is 7.0,xylanase,pectinase,β-mannanase and cellulase had the highest activity at 50 ℃,and the enzyme activity was 644.58 U/m L,60.78 U/m L,0.85 U/m L and 7.05 U/m L,respectively.After that,the technological process was determined preliminarily,and the content of reducing sugar(RS)and soluble solids(SS)were determined as the detection indexes,reflecting the separation effect of enzyme preparation on wheat straw during pulping.2.The reaction time of enzyme,reaction temperature of enzyme,addition amount of enzyme,swelling time,swelling temperature,liquid-solid ratio,revolutions and KOH dosage were selected as the investigation factors.Through single-factor experiment,it was found that beating degree first increased and then decreased with the increase of enzyme temperature.The optimal temperature of enzyme was 50 ℃,while beating degree increased with the increase of other variables.The factors and levels of Plackett-Burman test were determined by single-factor experiment.The results showed that the dosage of KOH,revolutions and liquid-solid ratio were the significant factors affecting beating degree.According to Box-Behnken response surface test,the process can be determined according to the target beating degree.For example,the target beating degree is 43 °SR,and the optimal process conditions are as follows: the concentration of KOH is 1.75%,the ratio of wheat straw to water is 1:7.56,and the number of revolutions is 2850.At the same time,the fitting equation was determined according to beating degree,reducing sugar content and soluble solid content.By comparing the two equations,it can be found that the fitting degree of beating degree and soluble solid content is relatively high,which is suitable for practical production.3.The pulping effect of wheat straw was characterized by SEM,FT-IR,XRD and HPLC.Among them,through the analysis of the surface morphology and fiber changes reflected by SEM,it is found that the fiber surface has changed significantly after enzyme treatment;through the FT-IR analysis of pulp,the changes of specific functional groups of fibrous substances were judged.XRD analysis showed that the crystallinity index of wheat straw after chemical mechanical treatment decreased by about 17.5%,and the crystallinity index of pulp treated with different enzymes increased in varying degrees,among which pectinase increased by 14.69%.Through HPLC analysis,it was found that the addition of different enzyme preparations had a significant effect on the content of D-(+)-glucose,D-(+)-xylose,D-arabinose,and other soluble sugars. |
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