Efficient separation of nanoemulsion and simultaneous membrane cleaning by electroflotation coupled membrane filtration process

Abstract

The unique stability and complexity of oil-in-water (O/W) nanoemulsions originating from various fields of life and production pose significant challenges for their separation. In this work, a novel oil/water separation membrane (MFC/PPy/Ni–Co–P) is constructed by loading polypyrrole (PPy) particles on cellulose (MFC) membranes to provide growth sites for Ni–Co–P alloys, so as to endow the membrane with in situ bubble-generating capability. Under the external electric field, the MFC/PPy/Ni–Co–P membrane is integrated into the electroflotation filtration system as a cathode, and the effective membrane cleaning and demulsification of nanoemulsions can be realized through the micro-aeration environment constructed in situ. The MFC/PPy/Ni–Co–P membrane demonstrates outstanding performance in gravity-driven separation of various oil/water mixtures, with a rejection rate of >99.99 % and a flux of >3000 L∙m⁻²∙h⁻¹. The interaction energy between oils with different viscosities and membranes is quantified by the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theory, revealing the dominant role of acid-base interactions in the anti-fouling process. Notably, the integration of MFC/PPy/Ni–Co–P membrane into an electroflotation separation system enables the coalescence and separation of small-sized, highly stable nanoemulsions with separation efficiencies of >99.86 %. This study provides a novel approach for simultaneous and efficient nanoemulsion separation and membrane fouling remediation, showing a great potential in the development of efficient and sustainable oil/water separation technologies.