Superwettable Membranes for Highly Efficient Separation of Oil-in-Water Emulsions

Abstract

In this work, we report a facile and robust surface membrane modification method via a simple coating of PVDF membrane using tannic acid (TA) followed by oxidation with sodium periodate (NaIO4). The modified membranes were investigated by SEM, AFM, XPS, FTIR, and a water contact angle measurement. The Contact angle measurement shows that the TA modified membrane exhibits superhydrophilicity and underwater oleophobicity.

Results from FTIR and XPS indicate that the carboxylic groups were formed on the surface of the TA modified membrane due to the oxidation of quinone by NaIO4, which is the key to superhydrophilicity of the TA modified membrane surface. In addition, the modified membrane was tested for oil-in-water emulsion separation.

A high TOC rejection of 99% was achieved for different kinds of surfactant-stabilized oil-in-water emulsions as well as the surfactant-free oil/water mixture. The modified membrane not only showed a good water flux and oil/water separation performance but also exhibited excellent recyclability and chemical stability. Also, the developed method is versatile and can be applied to the different types of substrate material. This robust, simple, and green approach gives great potential to fabricate large-scale material surfaces for the industrial oily wastewater treatment.