Green synthesis of environmentally benign collagen fibers-derived hierarchically structured amphiphilic composite fibers for high-flux dual separation of emulsion

Developing dual separation materials that exhibit high-flux separation capabilities towards oil-in-water (O/W) and water-in-oil (W/O) emulsions provides a promising and facile remediation strategy for the contamination caused by emulsified oily wastewater. Herein, environmentally benign amphiphilic composite fibers (ACFs) were facilely prepared by a green synthesis approach that relied on the non-covalent decoration of tannic acid (TA), the natural amphiphilic phenolic compound, onto collagen fibers (CFs) with inherent amphiphilicity and structural hierarchy. Hydrophobic interactions and multi-hydrogen bonding interactions between the amphiphilic TA and CFs brought the enhancement of amphiphilicity-enabled wetting behaviors as well as the structural stability of CFs. The green synthesized ACFs exhibited hydrophilicity, underwater superoleophobicity and underoil hydrophilicity. The as-prepared ACFs were directly utilized for the dual separation of O/W and W/O emulsions with high separation efficiency (> 99.99%) and high flux (e.g. 2471 L m−2 h−1) by selectively permeating the continuous water phase of O/W emulsions and the continuous oil phase of W/O emulsions, respectively. Compared with CFs, the structural stability of ACFs was improved significantly, which therefore provided appreciable reusability and long-term separation stability. Our findings demonstrated the essential role of amphiphilicity played in the dual separation of O/W and W/O emulsions, which also provided a new solution for the remediation of emulsified oily wastewater by developing biomaterials-based amphiphilic separation materials.