Effective demulsification for oil–water separation through metal–organic frameworks with an amphipathic micro-domain

Abstract

Demulsification is highly important for both dehydration of crude oil and environmental remediation. The demulsification performance of conventional demulsifiers is limited by the condition and type of emulsion. Herein, we demonstrated the unique advantage of a metal–organic framework (MOF), MIL-100(Fe), for effective demulsification. The demulsification efficiency (DE) of MIL-100(Fe) for oil-in-water (O/W) model emulsion exceeds 99% within 30 min under optimal conditions. For the water-in-oil (W/O) crude oil emulsion, the DE was up to 79% within 5 min. MIL-100(Fe) also exhibited excellent demulsification performance against various  pH and salinity, which were supported by astable DE among the pH values of 2.0–10.0 and a positive relationship with salinity (1–1000 mmol L⁻¹ of NaCl solution). It was found that the amphipathicity of MIL-100(Fe) is crucial for demulsification, and the electrostatic interaction has an important role in regulating the demulsification. MIL-100(Fe) degraded sodium dodecyl sulfate by abstracting SO₃²⁻, destroying the function of the surfactant and eliminating the potential risk of emulsifying again. This study exhibited the potential of MOFs on demulsification for both O/W and W/O emulsion, and confirmed that enhancing the interaction between the demulsifier and emulsion is an effective strategy for universal demulsification against harsh conditions.