Phase inversion (chemistry)
Phase inversion is a chemical phenomenon exploited in the fabrication of artificial membranes. It is performed by removing the solvent from a liquid-polymer solution, leaving a porous, solid membrane.
Process
Phase inversion is a common method to form filtration membranes, which are typically formed using artificial polymers. The method of phase inversion is highly dependent on the type of polymer used and the solvent used to dissolve the polymer.
Phase inversion can be carried out through one of four typical methods:[1]
- Reducing the temperature of the solution
- Immersing the polymer solution into anti-solvent
- Exposing the polymer solution to a vapor of anti-solvent
- Evaporating the solvent in atmospheric air or at high temperature
The rate at which phase inversion occurs and the characteristics of the resulting membrane are dependent on several factors, including:[2]
- Solubility of solvent in the anti-solvent
- Insolubility of the polymer in the anti-solvent
- Temperature of the anti-solvent
Characterization
Phase inversion membranes are typically characterized according pore size and pore distribution. This can be measured using evapoporometry, where the membrane is immersed in 2-propanol and measured for change in mass due to evaporation of the 2-propanol. The rate of evaporation of 2-propanol from the pores of the membrane can be used to calculate the pore size using the Kelvin equation.[3][4] A Scanning electron microscope (SEM) can be used to characterize membranes with larger pore sizes, such as microfiltration and ultrafiltration membranes, while Transmission electron microscopy (TEM) can be used for all membrane types, including small pore membranes such as nanofiltration and reverse osmosis.
See also
- Membrane
- List of synthetic polymers
- Microfiltration
- Ultrafiltration
- Nanofiltration
- Reverse Osmosis
- Hollow fiber membrane
References
- ↑ Strathmann, H.; Kock, K. (May 1996). "Recent advances in the formation of phase inversion membranes made from amorphous or semi-crystalline polymers". Journal of Membrane Science. 113: 361–371. doi:10.1016/0376-7388(95)00256-1.
- ↑ Krantz, William.B.; Greenberg, Alan.R. (September 1977). "The formation mechanism of phase inversion membranes". Desalination. 21: 241–255. doi:10.1016/s0011-9164(00)88244-2.
- ↑ Krantz, William.B.; Greenberg, Alan.R.; Kujundzic, Elmira; Yeo, Adrian; Hosseini, Seyed S. (July 2013). "Evapoporometry: A novel technique for determining the pore-size distribution of membranes". Journal of Membrane Science. 438: 153–166. doi:10.1016/j.memsci.2013.03.045.
- ↑ Merriman, Lauren; Moix, Alex; Beitle, Robert; Hestekin, Jamie (October 2014). "Carbon dioxide gas delivery to thin-film aqueous systems via hollow fiber membranes". Chemical Engineering Journal. 253: 165–173. doi:10.1016/j.cej.2014.04.075.