Durable superwetting materials through layer-by-layer assembly: Multiple separations towards water/oil mixtures, water-in-oil and oil-in-water emulsions

Abstract

Separation of oily waste water and emulsified water/oil mixtures has gained much social attention due to the increasing emission of industrial waste water and sanitary sewage. However, endowing a material with the capacity of separating multiple immiscible water/oil mixtures and emulsified water-in-oil/oil-in-water mixtures is still challengeable but urgently desirable. Herein, a universal layer-by-layer assembly method utilizing the electrostatic attraction between polyethyleneimine (PEI) and SiO2 nanoparticles has been adopted in fabricating superwetting materials regardless of the substrates. The as-prepared materials which possess both superhydrophilicity/underwater superoleophobicity and superoleophilicity/underoil superhydrophobicity present high separation capability without any pre-wetting treatment towards various water/oil mixtures, including water/heavy oil mixtures, water/light oil mixtures, water-in-oil emulsions and oil-in-water emulsions. Significantly, the addition of (3-Glycidyloxypropyl) trimethoxysilane (KH-560) acting as a crosslinking agent with PEI endues as-prepared materials excellent durability and chemical stability in cyclic separations and extreme environments, respectively. Benefitting from the universality and substrate-independency of LbL-assembly, the method adopted in this paper could satisfy multiple demands of industry by applying on desirable substrates.