A greener approach to design Janus PVDF membrane with polyphenols using one-pot fabrication for emulsion separation

In contrast to the traditional coating of tannic acid (TA), the deposition of mussel-inspired TA on hydrophobic PVDF surfaces is realized using a one-pot fabrication method, thus forming a multi-functional Janus membrane. In this study, a facile TA modification using vacuum filtration is demonstrated to modulate the wettability of PVDF on a single side. With the introduction of sodium periodate, rapid chemical oxidation of TA occurs, which results in the design of a thin hydrophilic coverage over one side of the PVDF membrane. This multi-functional Janus membrane demonstrates a higher separation efficiency of ∼ 99% and ∼ 97% for both oil-in-water and water-in-oil emulsions. The hydrophilic coating of the Janus PVDF-TA membrane remains stable in harsh environments. Moreover, the recyclability of the as-prepared membrane evidenced an oil rejection performance of 99% for three repeating cycles. This nature-inspired Janus membrane using a green modification method is new insights for integrating the area of bionics into oily wastewater treatment.