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#3.4. Results and discussion 41 #C ! " # $ %J E A D Fig. 3.5: Interfacial tension, measured at room temperature with the ring tensiometer, as afunction of time. The initial volume fraction of TMOS was 0.40.shows an increasing IFT during the reactive mass transfer, although the increase appearsto be delayed and smaller compared to the MRI experiments.3.4.3 DiscussionThe IFT between the oleic phase and aqueous phase is always lower than the IFT betweenpure water and n-hexadecane. The effect of TMOS in the oleic phase on the IFT withrespect to pure water can be inferred from the first data point of each experiment. TheIFT appears to decrease with increasing TMOS concentration in the oleic phase. However,when the mixture of TMOS and n-hexadecane is brought in contact with water, the watercomposition changes in the course of time due to the reactive transfer of TMOS. The effectof methanol in the aqueous phase is to lower the IFT significantly. It is known that thepresence of alcohol in aqueous solutions lowers both the surface tension with respect tothe vapor or the interfacial tension with respect to organic liquids [90, 91]. In general,upon solving additional compounds in either the oleic or aqueous phase the IFT willdecrease with respect to pure water against the pure organic liquid, provided that thesolutes exhibit an excess surface concentration with respect to the bulk phases [92]. Inthe two-phase systems described above both TMOS and methanol adsorb to a certainextent at the interface. The effect of decreasing concentration of TMOS in the oleic phaseon the IFT during the mass transfer is dominant compared to the increasing concentrationof methanol and other reaction products in the aqueous phase.