Fluorine-free and hydrophobic/oleophilic PMMA/PDMS electrospun nanofibrous membranes for gravity-driven removal of water from oil-rich emulsions

Emulsions are very challenging to separate due to their small droplet size. Recent attention has been drawn to gravity-driven filtration using membranes due to their simple, easy and yet efficient way of separating emulsions. To achieve this, membranes with high porosity and high selectivity must be prepared. Nanofibrous membranes prepared through electrospinning are recently being explored for their excellent bulk properties such as high porosity and tunable wettability. In this study, a fluorine-free hydrophobic/oleophilic matrix was fabricated through electrospinning of the blend poly(methyl methacrylate)/ polydimethylsiloxane (PMMA/PDMS) to form highly porous nanofibrous membranes for gravity-driven separation of oil-rich emulsions is first investigated. The combination of high porosity (77.6%), large pore size (5.8 µm), and high hydrophobicity (154°) of the composite membranes (PMMA blended with 60 wt% PDMS) allowed it to breakdown and separate a variety of oil-rich emulsions such as water-in-hexane, water-in-hexadecane, water-in-diesel, and water-in-soybean with separation efficiency of 99.0%, 99.5%, 99.25% and 97.75%, respectively. The presence of methyl groups endowed the membrane with the ability to efficiently repel water droplets from passing through the membrane thus, allowing the successful breakdown of complex oils (although at a slower permeation rate). All aspects considered, PMMA/PDMS nanofibrous membrane appear to be a promising material for effective and fast gravity-driven filtration of oil-rich emulsions.