Surface characteristics of fibers in high-yield pulping with ethanol

The surface properties of pulps obtained from high-yield pulping with ethanol are examined in this study. Chemical changes on the fiber surface were determined by ESCA measurements, accessibility of pulps was identified by enzymatic hydrolysis and the physical modifications of the fiber surface were characterized by nitrogen adsorption and Hg porosimetry. Samples were prepared using different ethanol concentrations and cooking temperature. There was a significant effect of ethanol on the surface characteristics of fibers. Pretreatment with ethanol (up to 30%) increased the polysaccharides and decreased the lignin content on the fiber surface, improved the accessibility to cellulase and xylanase enzymes, and spread the specific surface area of fibers. The presence of higher ethanol concentrations in the process had a negative effect on surface properties. Because of lower pH, lignin remained stuck on the fiber surface and restrained the access of enzymes. Results from the ESCA measurement and specific surface determination correlated well with the enzymatic hydrolysability of the samples. The access of enzymes on the fiber surface is facilitaded by the high cellulose and hemicellulose content on the fiber surface and high specific surface area.