| Summary: | 碩士 === 中原大學 === 化學工程研究所 === 90 ===
The sorption of gas in the polymeric membrane is governed by the condensability of penetrating gas, the gas-polymer interactions, and the free volume of the polymeric membrane. To study the effect of free volume on gas sorption and membrane transport, we produced polysulfone membranes of different free volume by casting PSF from different solvents. It was found that both the solubility coefficient and permeability of CO2 increased with the increase in free volume. Analyzed by the dual sorption mode, it was found the increase of CO2 solubility was largely due to the higher Langmuir sorption. Further analyzed by the dual mobility model, it was found that the higher gas permeability was not due to the higher gas sorption, but due to the higher Henry’s diffusivity ( DD ).
Membranes of similar free volume but different chemical structures were made of three bisphenol-A polymers: polycarbonate ( PC ), polysulfone ( PSF ) and Polyetherimide ( PEI ). It was found that the membrane of higher Langmuir gas sorption had the lower gas diffusivity. PEI had the highest gas solubility. The high gas solubility of PEI membrane was resulted from its highest C′H. But both the Langmuir’s and the Henry’s diffusivities ( DH and DD ) of the PEI membrane were the lowest. Comparing the CO2 sorption in PSF with that in the PC membrane, it was found that the PSF membrane had a higher C′H but the lower DH. It indicated that the higher Langmuir sorption was not beneficial to the gas transport. It was the higher Henry’s sorption and the higher Henry’s diffusivity DD that benefited gas transport.
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