Nonlinear Flux–Pressure Behavior of Solvent Permeation through a Hydrophobic Nanofiltration Membrane

Abstract

Nonpolar solvents have been reported to exhibit a nonlinear flux–pressure behavior in hydrophobic membranes. This study explored the flux–pressure relationship of six nonpolar solvents in a lab-cast hydrophobic poly­(dimethylsiloxane) (PDMS) membrane and integrated the permeance behavior in the evaluation of the proposed transport model. The solvents exhibited a nonlinear relationship with the applied pressure, along with the point of permeance transition (1.5–2.5 MPa), identified as the critical pressure corresponding to membrane compaction. Two classical transport models, the pore-flow model and solution-diffusion model, were evaluated for the prediction of permeance. The solution-diffusion model indicated a high correlation with the experimental results before the point of transition (R 2 = 0.97). After the point of transition, the compaction factor (due to membrane compaction after the critical pressure) derived from the permeance characteristics was included, which significantly improved the predictability of the solution-diffusion model (R 2 = 0.91). A nonlinear flux–pressure behavior was also observed in hexane–oil miscella (a two-component system), confirming the existence of a similar phenomenon. The study revealed that a solution-diffusion model with appropriate inclusion of compaction factor could be used as a prediction tool for solvent permeance over a wide range of applied transmembrane pressures (0–4 MPa) in solvent-resistant nanofiltration (SRNF) membranes.

From Trace to Pure: Pilot-Scale Scandium Recovery from TiO2 Acid Waste

“…One explanation might be the five times larger membrane area in the pilot trials, which would have required a longer swelling time initially. 34 During the bench-scale tests, membranes were only used once for the concentration experiments. As shown in this process, reusing was beneficial in terms of permeate flux and Sc selectivity over several impurities, such as Fe, V, or U (Figure 3).…”

“…This “parabolic” behavior was not previously observed in bench-scale tests. One explanation might be the five times larger membrane area in the pilot trials, which would have required a longer swelling time initially …”

“…One explanation might be the five times larger membrane area in the pilot trials, which would have required a longer swelling time initially. 34 …”

Simulation of Nanofiltration Mass Transfer for Magnesium and Lithium Separation in Salt Lakes

“…However, the traditional DSPM, a semiempirical model, necessitates membrane characterization through a complex fitting process. Furthermore, the Donnan equilibrium alone fails to elucidate the high rejection rate of multivalent cations, favoring their distribution within the negatively charged membrane . Dielectric exclusion (DE), serving as an additional distribution effect at the interface between the membrane and the external solution, offers a more comprehensive explanation of mass transfer mechanisms in porous media .…”

“…Furthermore, the Donnan equilibrium alone fails to elucidate the high rejection rate of multivalent cations, favoring their distribution within the negatively charged membrane. 13 Dielectric exclusion (DE), serving as an additional distribution effect at the interface between the membrane and the external solution, offers a more comprehensive explanation of mass transfer mechanisms in porous media. 14 Consequently, the Donnan Steric Pore and Dielectric Exclusion model (DSPM-DE) was proposed by Schaep et al 15 to effectively delineate the ion transfer process in NF.…”