Robust PAAm-TA hydrogel coated PVDF membranes with excellent crude-oil antifouling ability for sustainable emulsion separation

Hydrogel coating was widely studied in the field of oil/water separation due to its underwater superoleophobic performance, which could avoid the blockage of the separation membrane by oil effectively, especially high viscosity crude oil. In this manuscript, a layer of ultra-thin Polyacrylamide-Tannic (PAAm-TA) hydrogel coating was coated on the surface of PVDF microfiltration membrane by a simple immersion process, which could endow it with superhydrophilic and underwater superoleophobic performance. Due to the outstanding superhydrophilic and ultrathin hydrogel coating, the obtained sample showed an ideal emulsion separation efficiency and flux, 99.47% and 1184.3 L/(m2 h bar) for toluene-in-water emulsion. Additionally, the residual crude oil on the membrane surface can be easily and quickly removed by rinsing with water. Attributed to a variety of chemical and hydrogen bonding and negatively charged groups on the tannic acid molecules, the membranes possess good mechanical stability and electrostatic adsorption properties. The obtained PVDF/PAAm-TA membrane could maintain its special wettability in a wide range of chemical environments, enabling it great potential to be used in complex water treatment. In summary, this study will provide new insights into a new idea and method for the preparation of hydrogel coated porous materials for oil/water separation.