Enhanced oil-fouling resistance of micro-nano structured membranes through ovalbumin-mediated layer deposition for efficient oil-in-water emulsion separation

This study presents a novel, eco-friendly method for enhancing the oil-fouling resistance of polyvinylidene fluoride (PVDF) membranes, employing ovalbumin (OVA) and tannic acid (TA) for surface modification. The modification process imparts superhydrophilic and underwater superoleophobic properties to the membranes, significantly improving their performance in oil–water emulsion separation. Traditional separation techniques often fall short in effectively handling complex and stable oil-in-water emulsions produced by various industrial sectors. Membrane technology, while promising, is frequently hampered by fouling issues that reduce permeance and increase operational costs. Our method leverages the unique molecular structure of TA, known for its hydrophilic hydroxyl and carboxyl groups and hydrophobic phenolic ester groups, to achieve robust membrane modifications through simple immersion techniques. The interaction between OVA and TA forms a micro-nano rough structure on the membrane surface, enhancing its superhydrophilic and underwater superoleophobic characteristics. The modified PVDF@OVA–TA membranes exhibit a sliding contact angle of 2.6°, indicating extremely low oil adhesion. These membranes achieve high permeance values for various oil-in-water emulsions of 4812.2 L m⁻² h⁻¹ bar⁻¹ for hexane-in-water, 3720.1 L m⁻² h⁻¹ bar⁻¹ for petroleum ether–water, 3127.4 L m⁻² h⁻¹ bar⁻¹ for dichloromethane–water, and 5587.4 L m⁻² h⁻¹ bar⁻¹ for soybean oil-in-water with separation efficiencies exceeding 99%. Moreover, the membranes demonstrate exceptional stability and reusability, maintaining high separation efficiency and permeance after multiple cycles. This study underscores the importance of developing sustainable membrane technologies that align with green chemistry principles, utilizing non-toxic, naturally derived materials. The findings highlight the potential of OVA and TA in advancing oil–water separation technology, offering a practical solution to industrial wastewater challenges and contributing to more sustainable environmental practices.