Influences of Alkaline and Salinity on Adsorption Capacity of Anionic Sodium Dodecyl Sulfate Surfactant

Abstract

Chemical losses in surfactant flooding could substantially degrade the efficiency of the process. This study aims to analyze the prospect of alkaline in minimizing surfactant adsorption. Static adsorption tests were conducted to investigate the adsorption of anionic sodium dodecyl sulfate (SDS) surfactant on local sand and kaolinite surfaces. Alkaline (sodium carbonate) ranging from 1wt% to 3wt% were added into the surfactant formulation with local sand or kaolinite at fixed volume to mass ratio of 5:1. Brine (sodium chloride) concentrations were varied from 1wt% to 3wt%. Equilibrium adsorption test was conducted by shaking the suspension for 24 hours, centrifuged and the supernatant sample was analyzed using UV-Vis spectrophotometer. The kinetics of surfactant adsorption was also analyzed by taking the suspension samples at every 30-60 minutes interval during the shaking process. Adsorption kinetics of SDS surfactant showed a nonlinear increase of the adsorption followed by a plateau. Adsorption on the kaolinite was found higher than the local sand. Increasing SDS concentration resulted in increase of adsorption on both local sand and kaolinite surfaces until reaching its micelle concentration. The increase in brine concentration also led to higher adsorption capacity, but alkaline addition has potentially reduced the adsorption due to higher repulsion force.