Extraction Of Cellulose And Hemicellulose From Lignocellulose And Their Synergistic Enhancement In Calcium Alginate Membran

Lignocellulose is a kind of renewable resources with large abundance,which is considered as one of the ideal raw materials for environmental protection materials,alternative energy and green chemicals in the future.In this thesis,the effects of successive treatment by sodium hydroxide solution and deep eutectic solvent(DES)on the separation of lignocellulosic components were investigated.The extracted cellulose and hemicellulose were employed to modify calcium alginate film after further mechanical treatment.The influence of different dosages on the mechanical properties,thermal stability and gas barrier properties of calcium alginate film were studied systematically.The main contents are as follows:1.Hemicellulose in corn husk was extracted with sodium hydroxide solution.The extraction conditions was optimized,which are ultrasonication with 10 wt%NaOH solution at 20℃ for 1 h first,followed by stirring for 3 h.The yield of hemicellulose was 40.08%under the optimal condition.The extracted hemicellulose includes water-soluble and-insoluble hemicellulose.The number-average molar mass((?)n),the weight-average molar mass((?)w)and the z-average molar mass((?)z)of water-soluble hemicellulose are 2.521*10~4,3.984*10~4,6.501*10~4respectively,with the polydispersity index((?)w/(?)n)of 1.580.The water-insoluble hemicellulose is in the nano-particular form.There is almost no lignin in the hemicellulose.2.Deep eutectic solvent(DES)composed of lactic acid and choline chloride was used for the separation of cellulose and lignin.The influence of the molar ratio of lactic acid to choline chloride,the extraction temperature and time on the separation was explored and optimized.The optimal separation condition was determined as the mole ratio of lactic acid to choline chloride being 10:1 under 120℃ for 6 h,under which the yield of cellulose and lignin are 37.21 and 11.14%,respectively3.The extracted hemicellulose and cellulose were processed further through mechanical methods,yielding stable dispersion of cellulose and hemicellulose.The obtained cellulose and hemicellulose dispersion was used to reinforce calcium alginate film.Mechanical testing results indicate either cellulose or hemicellulose can strengthen calcium alginate film.In particular,their combination has a synergistic reinforcing effect.When the mass ratio of cellulose to hemicellulose is 9:1 and their total content is 2 wt%of the solid content,the tensile strength and elongation at break of composite membrane reach 98.49 MPa and 4.36%,increased by 2.2 and 1.7 times in comparison with pure calcium alginate film.Further characterization indicates the prepared composite films display good thermal stability and excellent gas barrier property,which is beneficial for potential application in packaging materials.