MULTT-COMPONENT ADSORPTION OF ASPHALT FUNCTIONALITIES ON SILICA

Single- and multi-component adsorption of compounds representing highly polar functional groups in asphalt onto SI-1000 silica has been performed at 25 °C using cyclohexane as a solvent. The asphalt functionalities used are benzoic acid (strong acid), 1-naphthol (weak acid), phenanthridine (strong base), and phenyisulfoxide (weak base). The bi-, tri-, and quadh-component adsorption behaviors demonstrated that the competitive adsorptive affinities of the asphalt functionalities for the silica are ranked as 1-naphthol < benzoic acid » phenanthridine < phenyisulfoxide. The prediction of multi-component adsorption equilibria has been made by applying the Langmuir Competitive Model (LCM) and the Ideal Adsorbed Solution Theory (LAST) to single-component adsorption data. Both the LCM and the LAST provided a good prediction for benzoic acid/1-naphthol and phenanthridine/phenyisulfoxide combinations. In the cases that involved acid-base combinations, however, both the LCM and the LAST yielded predictions that deviated from actual behavior. This deviation was most likely caused by the nonideal behavior of strong adsorbate-adsorbate interaction in the adsorbed phase