Energy & Fuels, Vol.25, No.10, 4430-4437, 2011
Adsorption Behavior of Betaine-Type Surfactant on Quartz Sand
The betaine-type amphoteric surfactant exhibits excellent ability in reducing oil water interfacial tension for many kinds of crude oil, but less attention is paid to its adsorption behavior on oil reservoir rock. In this paper, a high-performance liquid chromatography (HPLC) method is established to measure the adsorption of betaine on quartz sand. The mobile phase consists of methanol and water (methanol/water = 90:10 or 85:15 by volume). The column temperature is 40 degrees C; the flow rate is 1 mL/min; and the sample volume is 20 mL. On the basis of this method, the adsorption of the betaine-type surfactant and sodium dodecyl benzene sulfonate (SDBS) in different conditions was measured and compared. The results indicate that the adsorption of the carboxybetaine-type surfactant and sulfobetaine-type surfactant decreases first and then increases with the increase of the NaCl concentration and reaches relatively low points when the concentration of NaCl is 5 and 10-20 wt %, respectively. The adsorption of SDBS increases with the NaCl concentration monotonically, which is at least 50% higher than that of the betaine surfactant when the concentration of NaCl is over 5 wt %. After Ca2+ was added to the solution, the adsorption of the betaine-type surfactant on the quartz sand surface, as the opposite case of SDBS, decreases. Moreover, it is found that the adsorption of betaine on the surface of quartz correspondingly decreases with the increase of pH. These behaviors can be explained by the charges of the betaine-type surfactant molecule and the quartz surface. The investigation is instructive for surfactant selection for enhanced oil recovery (EOR).