Figure 8. The fitting results of H2SO4 and MixC4 mass density for the calculation of interfacial thickness in the DES-aiding systems with different concentrations. (a), (b), and (c) ChCl-Pho (1:2) at 1.0 wt%, 3.0 wt%, and 5.0 wt%, respectively. The obtained interfacial thickness for different DESs as a function of concentrations (d).