AN INVESTIGATION OF THE EFFECT OF ANTISTRIPPINGAGENTS ON SILICA ADSORPTION OF ASPHALT FUNCTIONALITIES

ABSTRACT

The effect of precoating antistripping (AS) agents onto silica on the adsorption behavior of model asphalt functionalities has been examined. Two commercially available polyamine AS agents were used. Their adsorption onto silica showed a strong surface interaction. One of the AS agents followed the Langmuir adsorption model; the other did not. After removing the weakly adsorbed AS fraction by washing with dichloromethane, seven asphalt functionalities In cyclohexane solution were adsorbed onto the precoated silica. The functionalities used represented those present in asphalt and were carboxylic acids, phenolics, nitrogen bases, sulfoxides, ketones, esters, and polynuclear aromatics. The adsorption of benzoic acid and phenol was increased by precoating with AS agents, whereas the other functionalities showed large decreases in their adsorption due to the precoated AS agents. The enhanced adsorption shown by benzoic acid and phenol is likely due to an acid-base interaction between the basic AS agents and the acidic model compounds.