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 coniferous wood species in cellulose production, which represents an important source of long-chain fatty and resinic acids. Static and dynamic light scattering techniques were used to study the self-aggregation of the sodium salts of such carboxylic acids from Portuguese CTO in aqueous solutions. In static light scattering measurements, the apparent critical micelle concentration of CTO sodium salts aqueous solutions was calculated (2 g dm(-3)), as well 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 be 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 mixtures). Dynamic light scattering measurements were used to estimate the hydrodynamic radius of the CTO self-aggregates ([R-h] = 64 nm). The ratio between the gyration and hydrodynamic radius (rho = 1.5) was used to access the geometry of the self-aggregates (closer to coils than homogenous spheres). (C) 2001 Elsevier Science B.V. All rights reserved.