Influence of carboxylic group content on the solution behavior of carboxymethylated lignin (CML) in water

Abstract

Carboxymethylated lignin (CML) is well suited as a dispersant or natural adsorbent applied in ceramics, gypsum paste, graphite suspension, and water treatment. In this paper, the effects of COOH content in CML on its behavior in water and the dispersion stability of aqueous graphite suspension has been investigated by means of viscosimetry, surface tension measurement, fluorescence spectrometry, dynamic light scattering (DLS), Turbiscan Lab Expert (TLE) stability analysis, and ζ potential measurement. Viscosimetry clearly revealed the polyelectrolyte effect in diluted aqueous solution of CML. With a higher COOH content of CML, the surface tension of water is reduced. Moreover, the aggregation behavior of CML was strengthened with increasing COOH content, leading to a more compact molecular structure of the aggregates. Based on the results, an aggregation model was proposed to illustrate the variations in the solution behavior of CML with different COOH contents at various concentrations. The dispersion stability of aqueous graphite suspension was improved by adding CML with high COOH content.

From lignin association to nano-/micro-particle preparation: extracting higher value of lignin

“…Both kraft lignin and lignosulfonate present surface active 45 and amphiphilic properties and they share a polyelectrolyte character. 3,46 In 1979, Lindström studied the association and precipitation of kraft lignin (Indulin ATR, 11037-2, Westvaco Co., Charleston, SC., USA) in aqueous solutions varying in pH from 8.6 to 3.7. 47 It was found that the degree of association between lignin molecules increased with decreasing ionization of the carboxylic group in the lignin.…”