Crude tall-oil sodium salts micellization in aqueous solutions studied by static and dynamic light scattering

Crude tall-oil (CTO) is the major by-product in Kraft pulp mills from conif erous wood species in cellulose production, which represents an important s ource of long-chain fatty and resinic acids. Static and dynamic light scatt ering techniques were used to study the self-aggregation of the sodium salt s of such carboxylic acids from Portuguese CTO in aqueous solutions. In sta tic light scattering measurements, the apparent critical micelle concentrat ion of CTO sodium salts aqueous solutions was calculated (2 g dm(-3)), as w ell as the ones of sodium oleate (0.5 mM) and sodium resinate (20 mM), the main acidic components of CTO. Mixtures of both latest compounds seems to b e not good molecular acidic models for CTO sodium salts, as the aggregation behavior is quite complex (1:1 mixtures) or is not detected (2:1 and 1:2 m ixtures). Dynamic light scattering measurements were used to estimate the h ydrodynamic radius of the CTO self-aggregates ([R-h] = 64 nm). The ratio be tween the gyration and hydrodynamic radius (rho = 1.5) was used to access t he geometry of the self-aggregates (closer to coils than homogenous spheres ). (C) 2001 Elsevier Science B.V. All rights reserved.