Extraction Of Cellulose From Wheat Stalk And Preparation Of Nanocellulose

As a renewable and environmental friendly resource with large quantity,biomass resource has great potential to be explored nowadays.Stalk is a large category of biomass with cellulose as its main component.Cellulose is the most widely distributed and richest natural polymer in the nature.Using wheat straw as raw material,after the analysis of main components of it,cellulose was extracted.Nanocellulose was further prepared by the sulfuric acid method and phosphotungstic acid method.The processes were optimized.(1)Analysis of main compositions of wheat straw and extraction of celluloseThe main components of wheat stalk were determined by Van Soest method.There were 42.19%cellulose,21.64%hemicellulose,24.21%lignin and 11.14%other substances in wheat straw.Cellulose was extracted by nitric acid-ethanol method.After treated with nitric acid-ethanol for 5 times,the obtained solid substance was white,and the content of cellulose was 91%.FTIR showed that there were characteristic peaks of cellulose,while no characteristic peak of either hemicellulose or lignin.SEM was employed which showed that the fascicular fiber structure of extracted cellulose was more obvious compared with the original wheat straw.(2)Preparation of nanocellulose by sulfuric acid methodBased on the results of single-factor experiments,response surface method was used for the optimization of the process.Effects of the three main factors(sulfuric acid concentration,temperature and reaction time)on the yield of nanocellulose were discussed.The structure and crystallinity of the resulting nanocellulose were also analyzed.The results showed that 57.40%sulfuric acid at 63.7 C for 123.90 min was the best option,the predicted yield of nanocellulose from the model was 38.45%,and the actual yield from test experiments was 38.23%.FTIR,XRD and SEM results showed that the nanocellulose had a typical type I crystal structure with crystallinity of 64.70%,150 nm length and 30 nm diameter.(3)Preparation of nanocellulose by phosphotungstic acid methodBased on the results of single-factor experiments,response surface method was used for the optimization of the process.Effects of the three main factors(phosphotungstic acid concentration,temperature and reaction time)on the yield of nanocellulose were discussed.The structure and crystallinity of the resulting nanocellulose were also analyzed.The recovery and recycling use of phosphotungstic acid were also studied.It was shown that the optimum condition was 55.65%phosphotungstic acid,at 94.6 C for 7.60 h.The predicted yield of nanocellulose from the model was 42.44%,the actual yield from test experiments was 42.18%.FTIR,XRD and SEM showed that the nanocellulose had a typical type I crystal structure with crystallinity of 72.40%,800 nm length and 100 nm diameter.The recovery yield of phosphotungstic acid was about 90%?After 5 times of recycling,phosphotungstic acid was used for preparation fo nanocellulose,the yield showed no obvious decrease compared with the original phosphotungstic acid.