Preparation and Performance of Online Chemically Foamed Polyurethane/Graphene Reinforced Membrane

Abstract

Polyurethane/graphene (PU/GE) hollow fiber membranes made of a chemically foamed PU/GE spongy layer and inner reinforced poly(ethylene terephthalate) (PET) tubular braids were prepared by a one-step online chemically foamed method. Online chemical foaming involved the simultaneous formation of membrane pores with reaction to form PU by controlling the reaction rate. The hydrophobicity and lipophilicity of the membrane were increased by the introduction of GE, which as a heterogeneous bubble nucleating agent increased the bubble density. The properties of PU/GE hollow fiber membranes were investigated by testing of the micro-morphology, contact angles of different liquids, oil/water separation and membrane reusability. The experimental results showed that when GE was introduced into the foaming solutions, the hydrophobicity of the prepared membrane was increased and the thermal stability of the membrane was improved. With the increase in GE content, the pore size, porosity and pure oil flux of the chemically foamed PU/GE hollow fiber membranes first decreased and then increased, and the inverse change was observed with the liquid osmotic pressure. When GE content was 1.8 wt%, PU/GE hollow fiber membranes exhibited superior membrane performance, with separation efficiency as high as 90% and high flux (143 L·m−2·h−1 at −0.5 bar). The PU/GE hollow fiber membrane could be applied to continuous oil/water separation experiments. In addition, PU/GE hollow fiber membranes showed durability and reusability, and the flux recovery rate was kept above 90%.