Associative Behavior of Lignosulphonates in Moderately Concentrated Water, Water-Salt, and Water-Alcoholic Media.

Abstract

Industrial derivatives of lignin lignosulfonates are produced during sulfite delignification of wood. They are characterized by a wide molecular weight distribution, polyfunctionality, and lack of crystallinity. The presence of hydrophobic and hydrophilic domains in the lignosulfonate macromolecular system determines the amphiphilic and polyelectrolyte properties of this biopolymer. As a polyelectrolyte, lignosulfonates (LSs) show complex conformational and phase behavior, which can be controlled by a wide range of external factors (ionic strength, medium acidity, solvent polarity, etc.). Herein, we present the results of a study of the associative behavior of three lignosulfonate samples with different molecular weight distributions (Mw 9250-46 300) and structural and cationic (Na+, Ca2+) composition. The effects of the concentration of LS (0.2-200.0 g/dm3), temperature (293-353 K), ionic strength of the medium (KCl, 0.08-0.80 mol), and ethanol additives (0.6-73.0 vol %) on the bulk and surface properties of lignosulfonates have been revealed. It was assumed that the LS association in solutions is a consequence of the processes of counterionic condensation with the formation of ionic pairs and multiplets. The binding of counterions is facilitated by an increase in the ionic strength of the medium and ethyl alcohol additives.