The role of skin layer defects in organic solvent reverse osmosis membranes

Jang, Hye Youn; Lively, Ryan P.

doi:10.1016/j.memlet.2021.100004

Cited by 4 publications

(3 citation statements)

References 18 publications

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“…Competitive sorption alone is also not likely to be the cause of this transport behavior, as the magnitudes of the sorption selectivity are completely mismatched with those of the diffusion selectivity (i.e.,

). Indeed, classical sorption–diffusion analyses suggest highly selective water permeation based on the water and DMF sorption/diffusion coefficients alone ( 38 ).…”

Section: Resultsmentioning

confidence: 99%

Selective permeation up a chemical potential gradient to enable an unusual solvent purification modality

White

Yoon

Ren

et al. 2023

Proc. Natl. Acad. Sci. U.S.A.

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The need for energy-efficient recovery of organic solutes from aqueous streams is becoming more urgent as chemical manufacturing transitions toward nonconventional and bio-based feedstocks and processes. In addition to this, many aqueous waste streams contain recalcitrant organic contaminants, such as pharmaceuticals, industrial solvents, and personal care products, that must be removed prior to reuse. We observe that rigid carbon membrane materials can remove and concentrate organic contaminants via an unusual liquid-phase membrane permeation modality. Surprisingly, detailed thermodynamic calculations on the chemical potential of the organic contaminant reveal that the organic species has a higher chemical potential on the permeate side of the membrane than on the feed side of the membrane. This unusual observation challenges conventional membrane transport theory that posits that all permeating species move from high chemical potential states to lower chemical potential states. Based on experimental measurements, we hypothesize that the organic is concentrated in the membrane relative to water via favorable binding interactions between the organic and the carbon membrane. The concentrated organic is then swept through the membrane via the bulk flow of water in a modality known as “sorp-vection.” We highlight via simplified nonequilibrium thermodynamic models that this “uphill” chemical potential permeation of the organic does not result in second-law violations and can be deduced via measurements of the organic and water sorption and diffusion rates into the carbon membrane. Moreover, this work identifies the need to consider such nonidealities when incorporating unique, rigid materials for the separations of aqueous waste streams.

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). Indeed, classical sorption–diffusion analyses suggest highly selective water permeation based on the water and DMF sorption/diffusion coefficients alone ( 38 ).…”

Section: Resultsmentioning

confidence: 99%

Selective permeation up a chemical potential gradient to enable an unusual solvent purification modality

White

Yoon

Ren

et al. 2023

Proc. Natl. Acad. Sci. U.S.A.

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“…Since He and N 2 are commonly used gases to gauge membrane quality, we performed preliminary permeation tests using these gases for each set of membranes by applying a reliable and rapid method before performing the mass-transport studies for syngas components. We used an isobaric permeation system with temperature controlled at 35 °C, using reported methods .…”

Section: Methodsmentioning

confidence: 99%

Evaluation of the Permeation of Syngas and Its Components through a Synthesized Matrimid Asymmetric Hollow-Fiber Membrane

Calvo

Jang

Ren

et al. 2023

Environ. Sci. Technol. Lett.

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Bioconversion of syngas (H2–CO–CO2) to organics is an excellent means of carbon recycling. Membrane-based gas-delivery systems can overcome the challenge of syngas’s low solubility in water. However, to maintain syngas conversion stoichiometry, it is crucial to have a membrane that delivers gases at high rates without selectivity toward any component. We synthesized an asymmetric, high-flux, low-selectivity hollow-fiber membrane, “small-defect-engineered”, to prevent bubble formation in future bioreactors. We created six sets of Matrimid membranes and screened their He/N2 selectivity and permeances. We compared the pressure-normalized flux of the set with the highest He/N2 permeance against a commercial symmetric membrane for a syngas mixture and its individual purified components. Under equal pressure, the asymmetric membrane exhibited 300-fold higher H2-flux, 80-fold higher CO-flux, and 100-fold higher CO2-flux than the symmetric membrane for pure gases. For the mixture, the asymmetric membrane had a 45-fold greater H2-flux, 100-fold greater CO-flux, and 400-fold greater CO2-flux than those of the symmetric membrane. Although the asymmetric membrane’s selectivity (H2:CO:CO2, 1:5.2:12) exceeded that of the commercial membranes (1:3:1.7), the asymmetric membrane possesses highly desirable traits for bioconversion of syngas, as its gas fluxes greatly exceed those of commercial membranes.

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“…Membranes can only tolerate a small number of skin layer defects, as defects can quickly eliminate membrane selectivity for small organic solvent molecules. 51 It is critical to properly balance multiple spinning variables with the dope composition to fabricate high-quality hollow fibers. The spinning parameters used to create the hollow fibers in this work are shown in Table 2.…”

Section: Methodsmentioning

confidence: 99%

Matching Analysis of Mixed Matrix Membranes for Organic Solvent Reverse Osmosis

Roos

Weber

Jang

et al. 2022

Ind. Eng. Chem. Res.

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Existing polymeric membranes struggle to separate small molecule solvents in the liquid phase due to low selectivity from solvent-induced plasticization and dilation. Mixed matrix membranes (MMMs) can potentially alleviate this issue via diffusion-based separations within rigid framework materials. Previous work from our lab and others has shown that organic solvent reverse osmosis membranes have different responses to transmembrane pressure depending on whether the material is a rigid structure (e.g., a carbon, zeolite, or metal-organic framework) or a swollen polymer. This work combines two Maxwell−Stefan transport models, representing the flexible polymer phase and a rigid microporous filler, with the Maxwell model to predict mixed matrix membrane solvent separation performance as a function of pressure and membrane material properties. The model demonstrates that for every filler perm-selectivity, there is a filler permeability that provides the largest separation factor in the final MMM. This optimum permeability increases with the filler's perm-selectivity. Dual-layer UiO-66/Matrimid hollow fiber MMMs were created to evaluate the model's prediction on the influence of transmembrane pressure on the separation of toluene and mesitylene as a test case. The UiO-66/Matrimid membrane demonstrated a predicted decline in permeance as pressure was increased. The separation factors increased as higher pressures increased the driving force for separation, consistent with the model. UiO-66 was shown to have superior selectivity to Matrimid in toluene/mesitylene; however, we conclude that ultraselective materials are ultimately needed to enable the mixed matrix membrane concept for the most challenging solvent− solvent separations, and open questions remain about polymer−filler pairings for organic solvent reverse osmosis.

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The role of skin layer defects in organic solvent reverse osmosis membranes

Cited by 4 publications

References 18 publications

Selective permeation up a chemical potential gradient to enable an unusual solvent purification modality

Selective permeation up a chemical potential gradient to enable an unusual solvent purification modality

Evaluation of the Permeation of Syngas and Its Components through a Synthesized Matrimid Asymmetric Hollow-Fiber Membrane

Matching Analysis of Mixed Matrix Membranes for Organic Solvent Reverse Osmosis

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