Studies On Separation, Cationic Modification And Application Properties Of Straw Components

Straw is one of the most abundant and cheapest renewable resources in the world. It is mainly composed of cellulose, hemicellulose and lignin. Separation and utilization of the three components are key research subjects in development and comprehensive utilization of biomass resources.In this paper, cellulose was obtained by treatment of straw with dilute sodium hydroxide solution containing hydrogen peroxide, hemicellulose was got by ethanol precipitation of the above filtrate and lignin was precipitated by adjusting pH of the remaining filtrate below 1.5. Separation of the three components was thus realized with 58% of cellulose,16.6% of hemicellulose and 8.1% of lignin.Cationic cellulose was synthesized by using the separated cellulose as raw materials, isopropanol and water as solvents and 3-chloro-2-hydroxypropyl trimethyl ammonium chloride (CTA) as cationic agent. The optimal synthesis conditions were as follows, reaction time was 3h, n(NaOH):n(CTA) was 2:l,n(CTA):n(Cellulose) was 1:6 and m(isopropanol): m(water) was 84%.Under the above conditions, the reaction efficiency could reach 46.2% and cationization degree was 0.12. The cationic cellulose was applied to flocculation of C.I.Acid Blue 324. The results showed when pH was 6, flocculation time was 30min and dosage of cationic cellulose was 0.8g/L, the decolorization rate could reach 96%.Cationic lignin was synthesized by using lignin as raw materials, water as solvent, sodium hydroxide as catalyst and 3-chloro-2-hydroxypropyl trimethyl ammonium chloride as cationic agent. When 5g of lignin was used, reaction time was 5h, n(NaOH):n(CTA) was 1.5 and dosage of CTA was 3 mol/kg, the grafting yield could reach 0.31g GTA per 1.Og lignin and the utilization ratio of CTA was 51.5%. The synthesized cationic lignin was applied to flocculation of reactive dyes. When the concentration of the dyes was all 0.1g/L, decolorization rate higher than 91% could be obtained with addition of cationic lignin of 0.3g/L,0.2g/L and O.lg/L for solutions of C.I Reactive Red 24, Reactive light yellow 6G and C.I. Reactive Blue 19, respectively.