Bioinspired MOF-Based PVA/TA Hybrid Membrane with Superior Mechanical Durability and Antifouling Properties for Emulsion Separation

Separation of emulsified oily wastewater poses a significant challenge due to ongoing problems such as severe membrane fouling and low separation efficiency. Metal-organic frameworks (MOFs) are widely regarded as viable candidates for separation applications due to their high surface area and tunable properties. However, forming a stable and uniform MOF-based separation layer on membrane supports remains a significant challenge. The complex synthesis procedures and limited mechanical flexibility of conventional MOF membranes have hindered their adoption for oil-in-water separation. In this research work, MIL-101(Fe) was prepared and successfully used to construct a barrier layer on membrane surfaces via a simple vacuum-assisted filtration method. Notably, tannic acid (TA) exhibited excellent compatibility with MIL-101(Fe), acting as a natural binder that reinforced the MOF layer. This interaction yielded a highly stable and flexible separation layer, addressing the key limitations of traditional MOF membranes in treating complex oily wastewater. The MIL-101(Fe) based membranes have shown excellent stability against tape peeling, continuous water flushing, bending, and sonication tests. Furthermore, the PTM membrane exhibited superior antifouling properties, with UWOCA of 162.6°, indicating strong oil repellency. Its hydrophilic surface facilitated rapid water transport, leading to a separation efficiency exceeding 98% when treating oil-in-water emulsions with a concentration of 1000 ppm. The membrane performance is not compromised under several cycles of reusability, and an unprecedented 99.1% flux recovery was observed. This work has demonstrated that, with the appropriate engineering, a stable and effective MIL-101(Fe) coating can be developed on the surface of the support membrane, offering outstanding separation efficiency, durability, and abrasion resistance. This makes it an effective solution for addressing complex oily wastewater streams.