Dynamic Adsorption of Organic Compounds Dissolved in Synthetic Produced Water at Air Bubbles: The Influence of the Ionic Composition of Aqueous Solutions

A detailed analysis of the dynamic adsorption of crude oil components dissolved in produced water onto air bubble surfaces is presented. Synthetic produced water was prepared using three crude oils and aqueous solutions with varying ionic composition. The total organic carbon content, molecular mass, and dynamic surface tension was determined for the samples. A modified version of the Ward-Tordai model was used to evaluate the experimental data. This allowed for determination of the characteristic diffusion coefficients and investigation of the adsorption mechanisms. The adsorption process was diffusion-controlled on short time scales, while adsorption barriers occurred on longer time scales. The presence of salts in the aqueous solutions had a strong influence on the time at which deviations from diffusion-controlled kinetics took place. This was explained in terms of salting-out of larger hydrocarbons. The presence of divalent cations did not have a major influence on the salting-out effect nor the time where the adsorption barrier appeared.