Its membrane emulsification performance
Membrane separation using hollow fiber membrane has become one of the emerging technologies which underwent rapid development for various applications during the past few decades. The large-scale membrane preparation processes are currently based on toxic solvents and diluents, which have negative impacts on the environment. To this end, researchers have developed several ways towards improving the sustainability of membrane fabrication, including using less toxic diluents and adopting solvent-free membrane fabrication processes. A simple, tunable, and less energy-consuming membrane emulsification technology is a tenable method that have exhibited potential application in numerous fields. However, its application is limited by the hydrophilic and alkali non-resistance properties of the commonly used Shirasu Porous Glass membrane.
To solve the above challenges, a team of researchers of the School of Material Science and Engineering at Tiangong University: Dr. Yan Huang, Professor Qinglin Huang, Professor Hailiang Liu, Professor Changfa Xiao, and Kaixuan Sun (Master Student) developed a new strategy for the fabrication of poly (tetrafluoroethylene-co-hexafluoropropylene (FEP) hollow fiber membranes using a melt-spinning technique. In this solvent/diluent-free process, water-soluble pore-forming agents such as polyethylene oxide and calcium chloride obtained by ball milling blending were used in place of toxic agents that are commonly used in traditional processes. A series of characterizations and tests that involved comparison with the commercially available poly(tetrafluoroethylene) (PTFE) and poly(vinylidene fluoride) (PVDF) membranes were carried out to validate the feasibility of the membrane fabrication strategy. Their work is currently published in the Chemical Engineering Journal.
Based on their findings, the presented hollow fiber membrane preparation method posed significantly reduced threats to the environment because no diluents or solvents were used in the entire preparation process. Alternatively, adopting completely water-soluble pore-forming agents also contributed greatly to keeping low the negative effects on the environment. Polyethylene oxide (PEO) and calcium chloride (CaCl2) pore-forming agents maximized the impact of the membrane on the pore formation to form multiple pore structure that helped in maintaining the inherent properties of the resulting membrane. Moreover, the obtained membrane exhibited excellent performance in terms of their morphologies, hydrophobicity, narrow pore size distribution, and high porosity that compared well with the commercially available membranes.
Due to its excellent properties that included inherent thermal and solvent resistance, a membrane emulsification test was carried out to validate the applicability of the FEP membrane. The authors observed a good performance for the FEP membrane with a mean of pore size of 0.461 µm. This was attributed to its suitable pore size distribution and relatively stable hydrophobic surfaces. The resulting emulsion, on the other hand, exhibited high stability with a narrow droplet size distribution suitable for emulsification applications.
In summary, the study presents a facile, environment friendly, and solvent-free approach for the fabrication of FEP hollow fiber membranes. The obtained membrane exhibited good properties and compared well with commercially available membranes such as PVDF. Importantly, it was successfully applied in the membrane emulsification process, which will highly contribute to avoiding problems and limitations caused by traditional methods. In a statement to Advances in Engineering, the authors pointed out that the FEP hollow fiber membranes have a huge potential of contributing towards the development of more sustainable membrane preparation technology as well as emulsification processes.
Huang, Y., Huang, Q., Liu, H., Xiao, C., & Sun, K. (2020). A facile and environmental-friendly strategy for preparation of poly (tetrafluoroethylene-co-hexafluoropropylene) hollow fiber membrane and its membrane emulsification performance. Chemical Engineering Journal, 384, 123345.