Hydraulic permeation of liquids through swollen polymeric networks. II. Liquid mixtures

Abstract

synopsisThe hydraulic permeation of toluene-cyclohexanone and isooctane-CCl4 mixtures through a membrane, a rubber network, was studied. No separation of components occurred in this mode. The mixture flux data were successfully analyzed using a solution-diffusion theory by treating the mixture as if it were a single component with properties of the mixture. Diffusion coefficients determined in this way appear to be governed by frictional forces having a hydrodynamic origin. Slight separation of the components did occur when the pervaporation mode of operation was used. The significance of this is discussed.

Solvent flux through dense polymeric nanofiltration membranes

“…These results could be inferred to support a hydraulic transport mechanism as identified in Figure 7. The non-separation of solvent mixtures is in agreement with the data of Paul et al [26] and Machado et al [7].…”

“…Since the chemistry of the cyclic compounds is quite different the effect is likely to be influenced by their cyclic shape. Bowen and Welfoot [26], working with aqueous NF systems, have suggested that straight chain molecules are able to become more ordered when permeating through a confined space (such as the transport region within PDMS) and increase their viscosity, particularly close to pore walls. In MF and UF the membrane pore size is much greater than the molecular dimensions of the permeating solvent.…”

Solvent permeation behavior of PDMS grafted γ-alumina membranes

“…2, a linear relationship of flux versus TMP was observed for both types of membranes for all solvents, suggesting no effect of compaction. This behavior is in contrast with what is mostly found for pure PDMS polymeric membranes where a non-linear behavior in flux versus TMP is observed due to compaction [16,27]. The linear relationship between the flux and TMP, as observed in our work, also indicates the absence of any shear rate flow-induced behavior as described by Castro et al [11], who studied the permeability for PVP-grafted porous silica membranes with a native pore diameter of 410 nm.…”

Water purification by membranes: The role of polymer science

“…Water permeates through filtration membranes by pressure gradients within the pores of the membrane. A great deal of evidence has shown that the selective layer of reverse osmosis membranes has no pores (except possibly for a very small number of defects) and should be regarded as a homogeneous structure through which water and salts are transported by molecular diffusion through the polymeric matrix 1, 12, 35–40, 144–147, 287–295. As shown below, the role of the pressure differential Δ p is to induce a concentration gradient of water within the membrane that causes a flux of water by molecular diffusion.…”

“…26). The procedure for handling this thermodynamic analysis in reverse osmosis or hydraulic permeation begins from the fact that mechanical equilibrium requires the pressure in a homogeneous, supported membrane to be constant throughout its thickness at the value imposed upstream, p 0 , as schematically illustrated in Figure 26 10, 36, 38, 39, 287–295. As also illustrated in Figure 26, the chemical potentials of water in the phases on each side of either membrane‐solution interface are equal as stipulated by thermodynamics.…”