Polyacrylonitrile Nanofibers Coated with Covalent Organic Frameworks for Oil/Water Separation

Abstract

The demand for oil cleanup is one of the most urgent issues and has been involved in global sustainable and green economic development. Existing industrial separation techniques are inefficient and time-consuming, and flexible membranes with selective wettability are currently advantageous for oil/water separation. Here, we report an effectual strategy to prepare composite membranes by combining covalent organic frameworks (COFs) with electrospun nanofibers for oil/water separation. A dip-coating strategy was developed to prepare two different Schiff base COFs [2,4,6-triformylphloroglucinol−4,4′diaminobiphenyl (Tp-BD) and 3,5-tris(4-aminophenyl)benzene−terephthalaldehyde (TAPB-TPA)] on polyacrylonitrile (PAN) nanofibers at room temperature, in which Tp-BD and TAPB-TPA COFs could grow in situ on the surface of single-lined PAN nanofibers, structurally forming rough structures on the nanoscale. The thickness of the COF layer could be controlled by the concentration and volume of the ligand solution. Furthermore, on the basis of the rough structure, lauryl groups were linked to COF nanofibers to simultaneously obtain excellent hydrophobic COF nanofibers and maintain oleophilicity. Finally, superhydrophobic PAN/COF nanofibers with a water contact angle of 167°were applied to separate water-in-oil mixtures. The separation efficiencies of different samples with different oil and water concentrations were all greater than 95%, and the recycling performances of the materials were also satisfactory. The results show that the as-prepared nanofiber membranes have great potential for separating water-in-oil mixtures.

Superhydrophilic Modification of Polyvinylidene Fluoride Membrane via a Highly Compatible Covalent Organic Framework–COOH/Dopamine-Integrated Hierarchical Assembly Strategy for Oil–Water Separation

“…The current research on the application of COFs in oil–water separation mainly focuses on superhydrophobic modification, which display the advantages of high surface roughness, outstanding stability, and excellent separation efficiency. However, the superhydrophobic modification of COFs by fluorinated chemicals greatly increases the cost, − and the preparation of most hydrophobic COFs is complicated, time-consuming, and under harsh reaction conditions. , Thus, the development of inexpensive raw materials, simple preparation processes, as well as hydrophilic modification methods might be the focus of COFs applied in oil–water separation in future research. To the best of our knowledge, hydrophilic modification using COFs for oil–water separation needs to be studied.…”

Facile and Green Fabrication of Superhydrophobic Polyacrylonitrile Nonwoven Fabric with Iron Hydroxide Nanoparticles for Efficient Oil/Water Separation

“…Nonwoven fabrics (NWFs) are considered as random sheets/webs of fibers, which are held together by bonding or interlocking of the fibers through chemical, mechanical, thermal, or solvent methods along with their combinations . NWFs have been proposed for water–oil separation in harsh environments due to their low cost, flexibility, high porosity, high permeability, and good mechanical durability. − Therefore, different approaches have been adopted for fabricating superwetting NWFs with selective oil/water separation performance. For example, Zhu et al utilized the non-solvent-induced phase separation method for the fabrication of superhydrophobic poly­(lactic acid) (PLA) NWF modified with stereocomplex crystals.…”

Janus Nanofiber Antibacterial Membrane for Switchable Separation of Oil/Water Emulsions

“…Treatment and recycling reuse of oily wastewater caused by offshore oil spill accidents and the discharge of food industry have become an urgent hot issue and promote the development of oil/water separation materials. − Conventional commercial separating technologies including floatation, skimming, centrifugation, and gravity separation suffer from low separation efficiency, high energy cost, as well as secondary environmental pollution, which restrict their widespread use.…”