Fig.
8 Ion chromatogram (IC) of SDS
solution after interaction with MIL-100(Fe)
Above IC and LC-MS results confirmed that the SDS was degraded by
MIL-100(Fe). However, this reaction with SDS did not influence the
crystal structure of MIL-100(Fe) obviously, because XRD pattern of the
used MIL-100(Fe) was the same as that of the fresh MIL-100(Fe)
(Fig. S14 ).
Finally, the influence of electrostatic interaction on the
demulsification was studied by the zeta potentials and demulsification
efficiencies for different model emulsions. The negative charge
increased continuously because of hydroxylation 41when the pH was increased from 4.0 to 10.0 (Fig. 9a ). The zeta
potentials of MIL-100(Fe) and model emulsion at the condition of
demulsification were 19.8 mV and -67.2 mV, which suggested that there
was electrostatic attraction between MIL-100(Fe) and model emulsion
stabilized by SDS. And the electrostatic attraction
weakened along with an increased of
pH, which would decrease the adsorption capacity droved by the
electrostatic attraction for emulsion on MIL-100(Fe). Therefore, the DE
would decrease when the pH increased. But the results of demulsification
performance shown that the DE of MIL-100(Fe) maintained around 90% with
the range of pH (4~10) (Fig. 3b ). Additionally,
the DE for the model emulsion stabilized by Tween 80, a kind of nonionic
surfactant, was up to 91% using MIL-100(Fe) at the same conditions
(Fig. 9b ). It could conclude that the contribution of
adsorption droved by the electrostatic attraction on demulsification was
minor. However, the electrostatic repulsion hampered contact with
MIL-100(Fe) and emulsion, causing a low demulsification efficiency for
the model emulsion stabilized by
cetyl ammonium bromide (CTAB, a kind
of cationic surfactant) (Fig. 9b ).