Langmuir surface and interface films of lignosulfonates and Kraft lignins in the presence of electrolyte and asphaltenes: correlation to emulsion stability

The surface and interface properties of lignosulfonate (LS) and Kraft ligni n have been studied by means of the Langmuir technique. Surface films at di fferent bulk concentrations and varying pH, the effect of electrolytes and the interaction of LS and multivalent cations has been studied. The asphalt ene fraction from a bitumenous Venezuelan crude oil and LS-asphaltene inter face films is analyzed by the same method. The emulsifying properties of LS and aluminum-modified LS are also demonstrated. It was found that the surf ace activity of the lignin fractions varied as a function of pH and that th e surface activity of Kraft lignin were higher than LS. Film loss of LS dur ing film-compression was significant especially for the low molecular weigh t fraction. The formation of LS/cation complexes altered the surface and in terface properties of LS. This was utilized in the formation of stable crud e oil emulsions containing large amounts of asphaltenes. The polar nature o f the asphaltene fraction was demonstrated by varying pH in the aqueous sub -phase. (C) 2001 Elsevier Science B.V. All rights reserved.