Janus ZnO-cellulose/MnO2 hybrid membranes with asymmetric wettability for highly-efficient emulsion separations

Efficient and rapid-separation of various surfactant-stabilized oil-in-water and water-in-oil emulsions is urgently needed and still remains a worldwide challenge. In this work, a Janus membrane via in situ assembly of well-dispersed superhydrophilic MnO2 nanowires on the surfaces of the superhydrophobic ZnO nanorods array-coated cellulose membrane was prepared. To attain this aim, the superhydrophobic ZnO nanorods array-coated cellulose membrane was fabricated by combining with in situ growth technology and subsequent hydrophobic modification, and the MnO2 nanowires were prepared via a hydrothermal route. The assembly mechanism of MnO2 nanowires layer on the superhydrophobic ZnO/cellulose membrane proves the excellent interfacial compatibility between them. Given their asymmetric wettability, highly porosity and extreme interfacial compatibility of the Janus membrane, both surfactant-stabilized water-in-oil emulsions and oil-in-water emulsions can be efficiently separated with promising flux (more than 1590 L m(-2) h(-1) bar(-1) for water-in-oil emulsions and 8380 L m(-2) h(-1) bar(-1) for oil-in-water emulsions) and high separation efficiency (as high as 99.8% for oil-in-water emulsions and 99.4% for water-in-oil emulsions) in one superwetting Janus membrane. These features make the Janus membrane preferentially suitable for treatment of complex oily wastewater. Moreover, this work could be beneficial for the design and development of materials with special wettability and the practical application in industrial applications and environmental protection. [GRAPHICS] .