Water permeability within polymeric

Figure 11.9 Water permeability within polymeric membranes and selectivity relative to CO2- Reprinted with permission from Separation Purification Reviews, Effects of minor components in carbon dioxide capture using polymeric gas separation membranes by Scholes, C. A., S. E. Kentish, and C. W. Stevens, 38 1-44, Copyright (2009) Taylor and Francis...

Geong and coworkers reported a new concept for the formation of zeolite/ polymer mixed-matrix reverse osmosis (RO) membranes by interfacial polymerization of mixed-matrix thin films in situ on porous polysulfone (PSF) supports [83]. The mixed-matrix films comprise NaA zeoHte nanoparticles dispersed within 50-200 nm polyamide films. It was found that the surface of the mixed-matrix films was smoother, more hydrophilic and more negatively charged than the surface of the neat polyamide RO membranes. These NaA/polyamide mixed-matrix membranes were tested for a water desalination application. It was demonstrated that the pure water permeability of the mixed-matrix membranes at the highest nanoparticle loadings was nearly doubled over that of the polyamide membranes with equivalent solute rejections. The authors also proved that the micropores of the NaA zeolites played an active role in water permeation and solute rejection. 

The water ingress properties of various polymers can be assessed by values of their permeability coefficient and the diffusion constant of water (Table 15.13). The permeability coefficient is defined as the amount of vapor at standard conditions permeating a sample that is 1 cm2 and 1-cm thickness within 1 s with a pressure difference of 1 cmHg across the polymer. The diffusion coefficient is a measure of the ease with which a water molecule can travel within a polymer. There is a wide variation in the maximum amount of water absorbed by polymeric materials. Certain systems have very low absorption at lower temperatures, but the rate of absorption increases significantly at higher temperatures. 

Profile modification is a process in which flooding water is diverted from highly permeable zones into less permeable oil-bearing layers within a subterranean reservoir. In recent years this has been achieved by the use of polymeric hydrogels in Y ich the water-soluble polymer is cross-linked by a multivalent metal ion". The latter may be generated in situ from a redox couple, e.g., sodium dichromate/sodium metabisulfite or as a complexed reagent, e.g., aluminum citrate. This enables the gelation process to be retarded until the aqueous polymer solution has been placed deep into the thief zone. 

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