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Title
Lignin separated from the hydrolyzate of the hydrothermal treatment of birch wood and its surface properties
Authors
GALIA SHULGA SANITA VITOLINA VADIMS SHAKELS LUBOVA BELKOVA GEORGETA CAZACU CORNELIA VASILE and LOREDANA NITA
Received
October 5, 2012
Published
Volume 46 Issue 5-6 June-July
Keywords
alkali lignin, globular structure, hydrolyzate, nanoparticles, oil-in-water emulsion, polyelectrolyte effect,
Abstract
The chemical composition, structural features and surface active properties of alkali lignin, separated from the hydrolyzate of the birch wood sawdust treatment in a moderately alkaline water solution at a temperature below 100 °C, were studied. The separated lignin was rich in p-oxyphenylpropane fragments and carbonyl groups, but contained a relatively low amount of aliphatic hydroxyl and methoxyl groups. The carboxyl groups were weaker than those in kraft lignins. The lignin aqueous solutions were structured, containing both nano- and micro-sized colloidal particles. The pronounced amphiphilic character of the lignin molecules governed their low critical micelle concentration (CMC) values and enhanced the surface activity at the water-air and liquid-liquid interfaces. When decreasing the pH and increasing ionic strength, the surface activity of lignin at the air-water interface grew, while that at the oil-water interface dropped. Scanning electron microscopy (SEM) images revealed that the microstructure of the lignin surface consisted of globules, forming extended clusters of the “grape-bunches” type.
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