Ethanol-Enhanced Alkaline Pulping of Arundo donax L. Reed: Influence of Solvent on Pulp Yield and Quality
Summary The effect of solvent on yield and properties of ethanol-alkali pulps from Arundo donax L. was studied. Selectivity of pulping was significantly improved with increase in solvent proportion in the cooking liquor. A rise in ethanol concentration from 20 to 60% (by vol.) increased pulp yield from 44.0 to 48.9%, while decreasing residual lignin from 5.0 to 3.0%. Ethanol addition had a positive effect on preservation of carbohydrate complex against degradation in alkaline medium. Intrinsic viscosity of cellulose was improved up to 35% and xylan content increased from 8.6 to 12.1% with increase in ethanol concentration from 20 to 60%. The preservation of minor non-cellulosic polysaccharides with solvent addition was also observed. The papermaking properties of ethanol-alkali pulps were best for 20% ethanol content. An increase in solvent charge led to a drop in burst, tear and tensile pulp strength. Solvent addition assisted the conversion of glucuronic to hexenuronic acids, whereas the content of HexA in ethanol-alkali pulps of Arundo donax (about 10 μmol/g) was substantially lower than reported for kraft pulps from wood.