Construction of tannic acid-Fe complex coated PVDF membrane via simple spraying method for oil/water emulsion separation

Here, a polyvinylidene difluoride composite membrane (PVDF@TA–Fe membrane) was prepared via the repeated spraying of tannic acid (TA) and Fe3+ to form a TA–Fe complex on the hydrophobic PVDF membrane, which endows the membrane surface superhydrophilicity. The effects of the number of sprays on the surface wettability and emulsion separation capacity of membrane were systematically investigated. It was found that the TA-Fe(III)-complex network formed on the membrane significantly increased the hydrophilicity of the membrane, and the PVDF@TA–Fe membrane was found to exhibit superhydrophilicity/underwater superoleophobicity. The PVDF@TA–Fe membrane was found to exhibit good separation efficiencies (above 99%) and high fluxes (1189.1–2310.0 L m−2 h −1 bar−1) when used to separate oil and water in various oil/water emulsions. The repeated separation experiments show that the membrane has a good antifouling performance and maintains a good oil/water separation performance after more than 10 cycles. The present work is of great importance to the large-scale preparation of superhydrophilic membranes and treatment of oily wastewater.