ADSORPTION-KINETICS OF ASPHALTENES AT TOLUENE ACID-SOLUTION INTERFACE

The adsorption kinetics of asphaltenes at the asphaltene-in-toluene/acid solution interface was studied using dynamic interfacial tension measurements. The pH of the aqueous phase was varied from 0.5 to 7 to study the effect of pH. Three asphaltene concentrations were used, one below the critical micelle concentration (CMC), one near the CMC and one above it. The results showed that for asphaltene concentrations below or near the CMC, at pH between 3 and 7, the dynamic interfacial tension (DIFT) decays monotonically. The decay rate followed a diffusion-controlled process closely. At a concentration above the CMC, the DIFT behaved differently. It exhibited similar behaviour initially, but reached a minimum at similar to 40-70min, depending on the pH, and slowly increased thereafter. A physical and a chemical process were used to rationalize this phenomenon.