Effect of Low-Saline Aqueous Solutions and pH on the Desorption of Crude Oil Fractions from Silica Surfaces

摘要

Desorption of interfacially active crude oil components was studied by exposing coated silica surfaces to aqueous solutions with different composition. The measurements were carried out for two North Sea crude oils as well as for fractions where the acidic and basic components were removed, respectively. One crude oil was acidic in nature, while the other was basic. Initially, the amount of adsorption onto the silica crystals was determined by a quartz crystal microbalance (QCM). Contact angle measurements showed small changes in wettability when the silica surfaces coated with components from the acidic oil were exposed to high-salinity solutions. On the other hand, considerable changes in wettability were seen when the surfaces coated with components from the basic crude oil were exposed to similar solutions. Consequently, significant desorption occurred in the latter case. Subsequent desorption was followed by QCM for both cases upon exposing the surfaces to low-salinity solutions. Generally, the acidic components desorbed more readily for the acidic oil, while basic components desorbed more readily for the basic oil. Ln both cases, the amount of desorption depended upon the pH and the composition of the aqueous solutions.