ABSTRACT
Membrane processes have received growing attention due to their low energy consumption and ease of operation. Thin-film composite reverse osmosis membranes based on polyamides are the most widely applied commercial membranes, because of their high flux and selectivity. However, their application for gas separation processes is still limited. This is the due to the presence of defects in the membrane when in the dry state. Traditionally, thin-film composite membranes are made by interfacial polymerization between a polar (aqueous) phase and a non-polar (organic) phase. The most commonly applied thin-film composite membranes are made by dissolving m-phenylene diamine in the aqueous phase and trimesoyl chloride in the organic phase. This work investigated the possibility of fabricating thin-film composite membranes when an aliphatic alcohol (methanol, ethanol or isopropanol) is used as the polar phase. This is further extended to examining the ability of a PDMS coating to plug the defects in such layers. The effects of temperature and support type on the membrane performance were also studied. Solubility tests were conducted to determine the solubility limit of commercial and in-house fabricated amine monomers in water, methanol, ethanol and isopropanol. Water-insoluble monomers were found to be soluble in ethanol and methanol. Gas permeation tests were conducted on membranes made using water, methanol, ethanol and isopropanol as the polar phase. The results showed that the membranes produced by aliphatic alcohols had higher selectivities. The highest H2/CO2 selectivity of ~ 26 was observed in the ethanol-based membranes when they were coated with PDMS and tested at 80 C. It was confirmed that PDMS is able to plug the defects in the membrane. Membranes made on the polysulfone support were found to have higher permeance and comparable selectivity relative to the membranes made on the polyacrylonitrile supports. It was also found that a change in the polar phase solvent is able to alter the morphology of the membranes. SEM micrographs showed clear differences in the surface structure of each membrane. The average thickness values obtained from ellipsometry measurements showed a correlation with the interface miscibility. The thickest membrane corresponded to the most miscible interface (IPA/Isopar).
Mark Your Calendar:
June 27th | 10:00 am |Auditorium 0215 between building 4&5
Please support M.S. candidate Praise Eromosele’s final defense supervised by Prof. Ingo Pinnau. Join in person or on zoom:
https://kaust.zoom.us/j/99057317592
Meeting ID: 990 5731 7592