Electro-enhanced rapid separation of nanosized oil droplets from emulsions via the superhydrophilic micro-sized pore membrane

Abstract

Waste oil-in-water emulsion is a special and unmanageable oily wastewater produced by several industries. Based on the sieving effect, the use of a membrane is a promising method to separate emulsion, whereas low flux remains a fundamental challenge. In this study, the coupling of an electric field with superhydrophilic fibrous membranes helped separate micro-/nano- paraffin in water emulsions (247–1887 nm) stabilized by SDS (100–500 mg/L) with a general applicability. The micro-sized pore membrane (0.634 μm) achieved outstanding rejection of nano-sized oil droplets (247 nm) using an electric field. It promoted flux from 1,202 to 18,388 LMH/bar by 1,429 % which was more than that in other literature by 1–2 orders of magnitude and improved oil removal from 97.61 % to 99.88 %. The reduction of equivalent pore size of membrane by the double layer force and the promotion of coalescence of oil droplets driven by the Laplace force rooted in the fibrous spindle of the membrane achieved enhanced selectivity. Electrophoretic force and double layer force mitigated the formation of the filter cake and irreversible fouling, respectively, to promote permeability and antifouling. This research provides a method for the simultaneous promotion of flux and improvement in effluent quality using an electric field, which breaks the limit of the trade-off effect.