NaOH concentration, electrophoretic

Electrophoretic Mobility. The electrophoretic mobility of the crude oil droplets as a function of caustic concentration has been determined in relation to enhanced oil recovery (52). It was observed that a maximum in electrophoretic mobility corresponds to a minimum in interfacial tension at the crude oil/caustic interface (Figure 11). The maximum electrophoretic mobility at minimum interfacial tension can be attributed to the ionization of carboxyl groups present in the crude oil, which in turn determine the charge density at the crude oil/caustic interface, depending on NaOH concentration. 

Figure 8 shows the values of electrophoretic mobility and interfacial tension as a function of the NaOH concentration for the Long Beach crude oil which has been equilibrated with the alkaline solution. This figure shows that the electrophoretic mobility increases and then decreases with increasing caustic concentration. It should be noted that the maximum in electrophoretic mobility appears to correspond to a minimum in interfacial tension. This finding is consistent with our recent results for surfactant systems (6) and those of Shah and Walker (21). 

Figures 10 and 11 display both the interfacial tension and electrophoretic mobility data for Huntington Beach crude as a function of NaOH concentration in aqueous solutions containing 1% NaCl. It is to be noted that as in the case of the Long Beach crude, the minimum in interfacial tension corresponds to the maximum in electrophoretic mobility and hence interfacial charge. It should be further stated that this behavior is the same for both the equilibrated system (Figure 10) and for the non-equilibrated system (Figure 11). In the latter case, the interfacial tension reported here is the initial value at a given NaOH concentration. It is observed that the minimum interfacial tension for the pre-equilibrated system lies at about 0.06% NaOH whereas the minimum for the non-equilibrated sample is between 0.003% and 0.005% NaOH concentration. Furthermore, the minimum interfacial tension in this case is below 0.001 dynes/cm.

Figure 5. Electrophoretic mobility of the hydroxyl form 357-nm PS latex as a function of the concentration of electrolytes ((A) in NaOH ( A ) in NaCl (O) in...

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