Extraction And Modification Of Lignin From Poplar Hydrolysate

Agroforestry is a rich plant resource on earth,which can be chemically or biologically transformed into materials,energy and chemicals for human use.In pulp and paper industry,the extraction of hemicellulose from lignocellulose is realized by prehydrolysis process and then converted into high added value products.Therefore,the combination of prehydrolysis technology and traditional pulping technology has greatly improved the degree of refining biomass in pulp and paper industry,and gradually attracted the attention of the industry.In this paper,the production and chemical characteristics of lignin induced by poplar hydrolysate cooling were studied.Samples of treated wood and hydrolysate were taken out from digester at various temperatures during the cooling process for characterization.SEM images evidenced a progressive deposition of cooling-induced pseudo-lignin?CIPL?on the surface of the treated wood during cooling process.However,the treated wood which was collected isothermally at reaction temperature showed no pseudo-lignin.Variation of organic compounds in hydrolysate from lignocellulose degradation during cooling process revealed that depolymerized lignin and furfural accounted for 80.4 and 10.6%of CIPL,respectively,while soluble saccharides from carbohydrate hydrolysis were independent from CIPL formation.In this paper,the flocculation method was used to treat the poplar hydrolysate to improve the velocity of microporous filtration.The results showed that flocculation by polyaluminium chloride?PAC?at 500 mg/L prior to microfiltration improved the flux over 102 times for a volume reduction factor of 10.The flux was further increased by 81.2%by addition of anionic polyacrylamide?APAM?at 50 mg/L.However,combination of PAC and cationic polyacrylamide?CPAM?aggravated membrane fouling due to the adhesion of CPAM on membranes.Variation of chemical compositions revealed that lipophilic substances and lignin were key foulants for regenerated cellulose?RC?membranes.In this paper,the lignin extracted from the hydrolyzate was analyzed by FT-IR,UV spectrophotometer,gel permeation chromatography?GPC?.The lignin extracted from the hydrolyzate was sulfonated by two different modification methods.GPC,FT-IR,UV spectrophotometer,energy spectrum analysis and dispersion properties were determined.The FT-IR spectra showed that S=O and S-O had strong absorption peaks at 1043 cm^-1 and 1185 cm^–11 respectively,indicating that the sulfonate was attached to lignin.The wavelength of lignosulfonate shifted at 210 nm,mainly due to the conjugated carbonyl and sulfonic acid groups attached to the aromatic side chain of lignin.The relative molecular weight of lignosulfonate prepared by formaldehyde-sodium sulfite method was obviously increased,and the dye dispersibility was excellent.