Figure 5. The relationship between interfacial tension and
concentration of two phases.
We have shown that the DIFT varies with the column height in the above
text. However, it is still an important issue to analyze the intrinsic
influencing factors of DIFT. Comparing to the blank experiments, AC is
introduced into the system under mass transfer conditions and the
concentration of AC will affect the interfacial tension. In addition,
due to the interphase mass transfer, the interface between the two
phases will be disturbed (partially attributed to the well-known
Marangoni effect), resulting in change of interfacial tension.
Preliminary analysis shows that the above two factors are responsible
for the dynamic change of interfacial tension under mass transfer
conditions. To analyze the contribution of these two factors, the AC
concentration profile in the column needs to be measured.
Because of the low fraction of dispersed phase in this experiment, only
continuous phase can be led off from the sampling port of the column.
The AC concentrations in the continuous phase from different sampling
points are measured by titration and the results are shown in Table 3.
Though the AC concentration profile of dispersed phase cannot be
directly measured, it can be calculated based on the concentration
profile of continuous phase through the
axial
diffusion model 38. The calculation AC concentration
profile in dispersed phase is shown in Table 3. The calculated process
is described in the Appendix. We can see that the calculated AC
concentration in the dispersed phase at the bottom of the column is 1.04
mol/L, which is almost equal to the measured AC concentration at the
aqueous phase outlet (1.05±0.03 mol/L). This result proves that the
calculated AC concentration in the dispersed phase by axial diffusion
model is trustable.