Preparation And Performance Evaluation Of Sunflower Straw Cellulose-based Sand-fixing Material

Sunflowers,as a kind of commercial crop,are widely planted in Inner Mongolia Autonomous Region in our country,accounting for more than half of the total planted area of the country.They are the dominant crops in Hetao irrigation area of Bayannur City.With the accompanying agricultural waste of sunflower straw,the majority of sunflower culms are directly discarded and specially burned in the applied condition due to incomplete resource transformation technology.Due to the influence of the edge of desertification in Hetao irrigation area,a small part of sunflower straw was used to construct the physical sand barrier of sunflower straw for windbreak and sand fixation.Under the background of this application,the utilization rate and application efficiency of sunflower straw wood resources were relatively low.Therefore,in this thesis,sunflower culm,the main agricultural waste in Denkou County,Hetao Irrigation District,was used as raw material to synthesize a kind of sunflower culm cellulose-based sand fixing material.The sand fixing material can promote the formation of effective adhesion between sand grains,reduce the porosity of loose sand grains,and inhibit the movement of sand grains.At the same time,the material has good water solubility,salt resistance and acid resistance,and has certain environmental adaptability,degradability and ecological friendliness.The main contents and results of this study are as follows:（1）Sunflower culm cellulose extraction:The apparent effects of HNO₃,HCl and H₂SO₄on sunflower culm cellulose extraction were analyzed,and the reaction reagents for sunflower culm pretreatment were determined.On this basis,the law ofα-cellulose content in sunflower stem raw materials changing with liquid-solid ratio of reaction system,acid reagent concentration,reaction temperature and reaction time was investigated.Withα-cellulose content as evaluation index,orthogonal optimization experiment was designed to obtain the optimal extraction conditions:The liquid-solid ratio was 14,the concentration of HNO₃was 8%,the reaction temperature was 95℃,and the reaction time was 100 min.The purity of cellulose was high and the content ofα-cellulose was 87.3%.（2）Preparation of sodium carboxymethyl cellulose from sunflower culm cellulose:the proportion of ethanol in the fixed reaction system was 80%.The effects of the amount of alkali,alkalization time,amount of sodium chloroacetate,etherification temperature and etherification time on the viscosity of 2%aqueous solution of the product were explored.The viscosity value of aqueous solution at 25℃was used as the evaluation index to obtain the optimal preparation conditions of sodium carboxymethyl cellulose from sunflower culm:The amount of alkali was 5 g,the alkalization time was 60 min,the amount of sodium chloroacetic acid was 4 g,the etherification temperature was 45℃,the etherification time was 180 min.The degree of carboxymethylation of sodium carboxymethyl cellulose in sunflower culms was higher and the viscosity was 477 m Pa·s.（3）Using SEM,FTIR,XRD,TG and characterization methods of sunflower stalk fiber and sunflower stalk the properties of sodium carboxymethyl cellulose were analyzed,and the results show that after the pretreatment of lignin and hemicellulose was basic,after treated with sodium chloroacetate modified sunflower stalk cellulose crystal structure change,fromⅠcellulose intoⅡtype of cellulose,The internal structure was changed and the product showed typical characteristics of sodium carboxymethyl cellulose,indicating that the modification of sunflower straw cellulose was successful and the raw material cost of sodium carboxymethyl cellulose was effectively reduced.（4）Scanning electron microscopy was used to characterize the binding morphology between sand grains,analyze the changes of binding morphology between sand grains,and evaluate the compressive strength,water retention,aging resistance,water saline-alkali resistance,degradability and ecological friendliness of the sand samples.The results showed that the sand consolidation material could meet the requirements of international standards on the mechanical properties of sand consolidation materials,and the sand grains changed from loose unconnected state to chemical bond adsorption state.The results showed that the application of sunflower culm in the solidification and improvement of sandy soil had broad application prospects.It could not only reduce the production cost,but also realize the local conversion of sunflower culm resources,which could not only reduce the economic cost,but also improve the utilization and conversion efficiency of waste resources,which had broad application prospects.