Fig. 2 Photographs of the demulsification phenomenon (a ) (the dosage of MIL-100(Fe) and concentration of model emulsion were 1% (w·w-1) and 1:250 (v·v-1)), microscope photographs of the demulsified liquid (b ) and model emulsion (c )
To investigate the influence of time, pH and salinity on the demulsification performance of MIL-100(Fe), the rest demulsification was carried out with a 0.5% (w·w-1) of MIL-100(Fe) and 1:250 (v·v-1) of model emulsion. As showed inFig. 3a , the DE exceeded 86% of maximum demulsification capacity within 1 min, and the saturated demulsification time was no more than 30 min. When the pH was 2.0, the DE was 97%. As increasing for pH from 4.0 to 10.0, the DE maintained around 90% (Fig. 3b ). Besides, the DE increased from 92% to 98%, following a rise of the salinity (1 mmol·L-1 ~ 1000 mmol·L-1) (Fig. 3c ). What’s more, a DE of 95% indicated that the demulsification performance of MIL-100(Fe) was not inhibited by the 10 mmol·L-1 of Mg2+ solution. Generally, the concentrated electrolyte could weaken the electrostatic attraction by shrinking the double electric layer and supramolecular interaction by increasing the hydration, thus decreasing the demulsification performance of demulsifier 17. But this was contrary to the results in this work, which implied that the interaction between MIL-100(Fe) and emulsion was more powerful than that of the conventional demulsifiers. Afterwards, the regenerability of MIL-100(Fe) was studied. The DE of the used MIL-100(Fe) decreased by 14% and 36% after 2th and 3th cycles (Fig. 3d ). The reason of decrease for the demulsification performance might be related to the change of wettability for the used MIL-100(Fe), which was illuminated by the following study.