Artificial membranes for investigation of the human absorption (oral, dermal or respiratory) of target organic compounds are aimed at mimicking the interactions occurring at and within the cell lipid ...membrane. Biomolecules such as proteins are also integral components of the lipid membranes and play a pivotal role towards understanding the complex mechanisms of human absorption. In this review, we will differentiate biomimetic platforms based on static (batchwise) and dynamic modes. In the former, a synthetic membrane placed between two phases (donor and acceptor) mimics a given biological system to study permeability. Parallel artificial membrane permeation assays are the most common approaches for static mode. As to dynamic modes, there is a plethora of bioanalytical techniques such as immobilized artificial membrane chromatography, biopartitioning micellar chromatography or immobilized plasma protein chromatography. In any case, all of the dynamic approaches capitalize upon analytical separation techniques such as liquid chromatography and the use of the chromatographic factors to predict permeability and other bioparameters. However, improvements in the fabrication of novel sorptive materials or the development of innovative techniques/approaches to enhance the prediction capability of permeability by simulated membranes has been left in the background. For this reason, this review covers the current state-of-the-art of immobilized artificial membranes in bioanalytical science with particular focus on new materials and techniques reported from 2015 to mid-2021. Future perspectives related to the fabrication of innovative artificial membranes for in vitro intestinal absorption studies have been highlighted so as to encourage fundamental studies in this research area.
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•Membrane surrogates in analytical science.•Role of static and dynamic systems in human absorption assays.•Overview of parallel artificial membrane permeability assays.•Overview of immobilized artificial membrane chromatography (LC), biopartitioning micellar LC and biomimetic LC.•Trends and selected applications reported in the literature since 2015.
Background: The medium cutoff (MCO) dialyzer increases the removal of several middle molecules more effectively than high-flux hemodialysis (HD). However, comparative data addressing the efficacy and ...safety of MCO dialyzers vs. postdilution hemodiafiltration (HDF) in Korean patients are lacking.
Methods: Nine patients with chronic HD were included in this pre-post study. Patients underwent HD with an MCO dialyzer for 4 weeks, followed by a 2-week washout period using a high-flux dialyzer to minimize carryover effects, and then turned over to postdilution HDF for 4 weeks. Reduction ratios and differences in the uremic toxins before and after dialysis were calculated from the MCO dialysis, postdilution HDF, and high-flux HD. In the in vitro study, EA.hy926 cells were incubated with dialyzed serum.
Results: Compared to postdilution HDF, the MCO dialyzer achieved significantly higher reduction ratios for larger middle molecules (myoglobin, kappa free light chain κFLC, and lambda FLC λFLC). Similarly, the differences in myoglobin, κFLC, and λFLC concentrations before and after the last dialysis session were significantly greater in MCO dialysis than in postdilution HDF. The expression of Bax and nuclear factor κB was decreased in the serum after dialysis with the MCO dialyzer than with HDF.
Conclusion: Compared with high-volume postdilution HDF, MCO dialysis did not provide greater removal of molecules below 12,000 Da, whereas it was superior in the removal of larger uremic middle molecule toxins in patients with kidney failure. Moreover, these results may be expected to have an anti-apoptotic effect on the human endothelium.
A CO2-tolerant dual phase membrane with composition of 60wt% Ce0.9Gd0.1O2−δ–40wt% Ba0.5Sr0.5Co0.8Fe0.2O3−δ (60CGO–40BSCF) was successfully developed. The 60CGO–40BSCF dual phase membrane showed good ...reversibility of the oxygen permeation fluxes and good stability in CO2 atmosphere. A stable oxygen permeation flux of 0.67mL/mincm2 was obtained with pure CO2 as the sweep gas during a 250h oxygen permeation at 950°C. The electronic conductivity results confirmed the concept that the electronic conductivity of the BSCF perovskite oxide could be partly reserved in CO2 atmosphere. Due to the high oxygen permeation fluxes and the good stability in CO2-containing atmosphere, the 60CGO–40BSCF dual phase membrane has great potential application in oxyfuel techniques for CO2 capture and storage.
•A concept for designing CO2-stable oxygen permeable membranes was proposed.•60CGO–40BSCF dual phase membrane was prepared.•Electrical conductivities in different atmospheres were performed.•Effects of CO2 on oxygen permeation of 60CGO–40BSCF were investigated.•60CGO–40BSCF showed good stability against CO2.
► Modern opportunities of FO are intensively reviewed. ► Five key challenges faced by FO are systematically reviewed and discussed. ► The intrinsic relationships between the five challenges are ...explored. ► This paper provides a clear outline for researchers on the recent developments of FO.
Recently, forward osmosis (FO) has attracted growing attention in many potential applications such as power generation, desalination, wastewater treatment and food processing. However, there are still several critical challenges, including concentration polarization, membrane fouling, reverse solute diffusion and the need for new membrane development and draw solute design in FO. These challenges are also the current research focus on FO. This paper aims to review the recent developments in FO, focusing on the opportunities and challenges. It begins with discussing the advantages of the FO process over pressure-driven membrane processes. These potential advantages lie in FO's low energy consumption, low fouling propensity, reduced or easy cleaning, low costs, high salt rejection and high water flux. Next, the recent applications of FO, as the outcomes of the above advantages, are described. The key part of this review is a detailed discussion of five critical challenges faced by FO and their relationships. Finally, the future of FO is viewed. This review provides a clear outline for FO-concerned researchers on the recent developments in FO.
► Overview of recent progress on the production and modification of poly(vinylidene fluoride) (PVDF) membranes. ► Crystalline properties, thermal stability and chemical resistance were firstly ...introduced. ► Production methods of PVDF membranes via phase inversion were reviewed. ► Various hydrophilic modification approaches such as surface modification and blending modification were investigated.
This article provides a comprehensive overview of recent progress on the production and modification of poly(vinylidene fluoride) (PVDF) membranes for liquid–liquid or liquid–solid separation. The crystalline properties, thermal stability and chemical resistance were firstly considered in this review, followed by the production methods of PVDF membranes via phase inversion including immersion precipitation and thermally induced phase separation. Various hydrophilic modification approaches such as surface modification and blending modification for improving the fouling resistance of PVDF membranes were subsequently reviewed. Finally, in the light of the anticipated role of PVDF as a superior membrane material, future prospects on the production and modification of PVDF membranes were suggested.
This paper describes the formation of a new generation of organic solvent nanofiltration (OSN) membranes: high flux thin film composite (TFC) membranes prepared via interfacial polymerization (IP) ...and solvent activation. These are the first reported TFC membranes which are stable in DMF. They exhibit significantly higher permeabilities for polar aprotic solvents, including DMF, acetone and THF, than commercial integrally skinned asymmetric OSN membranes; and yet have comparable rejections. Solvent stable crosslinked polyimide (PI) ultrafiltration (UF) membranes were used as supports for the formation of these TFC membranes. To increase solvent flux we employed two approaches. In the first approach, the UF support was impregnated with polyethylene glycol (PEG). Comparison of membranes formed using UF supports with and without PEG suggests that PEG impregnated in the support plays an important role in thin film formation and, consequently, in solvent permeation, resulting in increased fluxes. The second approach we employed was to treat the TFC membranes with an “activating solvent” after the IP reaction. This resulted in dramatically improved solvent fluxes without compromising rejection; for some solvents, there was a flux only after activation. Such TFC membranes prepared by interfacial polymerization and treated with an activating solvent may lead to the next generation of high performance OSN membranes.
► A new generation of OSN membranes: high flux thin film composite membranes via interfacial polymerization have been developed. ► These are the first TFC membranes prepared by IP to be stable in DMF. ► Flux was increased by impregnating the UF crosslinked support with polyethylene glycol. ► Flux activation and dramatic flux enhancement are achieved through DMF and DMSO treatment without compromising rejection. ► Able to manipulate MWCOs by using different amines in the aqueous phase.
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► The first report of zeolite-polyamide TFN membrane for forward osmosis. ► Enhanced performance of TFN membranes compared with TFC FO membrane. ► Rejection layer of TFN membranes ...optimized in terms of zeolite loading. ► Substrate of TFN membranes tailored for a relative small structural parameter.
Zeolite-polyamide thin film nanocomposite (TFN) membranes were prepared on a polysulfone (PSf) porous substrate tailored for forward osmosis (thin thickness, high porosity, and straight needle-like pores). The TFN membranes were characterized and evaluated in comparison with a thin film composite (TFC) membrane. The incorporation of NaY zeolite nanoparticles in the polyamide rejection layer significantly changed its separation properties. In the range of 0.02–0.1wt./v% zeolite loading, the incorporation of zeolite-polyamide exhibited enhanced water permeability of membrane likely due to the porous nature of zeolite. However, further increase in zeolite loading led to a reduction in water permeability, possibly as a result of the formation of a thicker polyamide layer. The most permeable TFN membrane (TFN0.1, with 0.1wt./v% zeolite loading) had a water permeability approximately 80% higher compared to the baseline TFC membrane. The FO water flux followed a similar trend to that of the membrane water permeability. Under all cases evaluated in the current study (0.5–2.0 NaCl draw solution, DI water and 10mM NaCl feed solution, and both membrane orientations), the membrane TFN0.1 exhibited highest water flux (up to 50% improvement over the TFC membrane). To the best knowledge of the authors, this is the first report on zeolite-polyamide based TFN membranes for FO applications.
A novel composite membrane of sulfonated graphene oxide (s-GO) and SPEEK with various sulfonated graphene oxide contents was prepared and investigated. The sulfonation of graphene oxide and PEEK ...induces an increase in the number of sulfonic groups (SO3H), which significantly increases the proton conductivity of sulfonated graphene oxide/SPEEK membrane. The introduction of sulfonated graphene oxide in membranes not only improved proton conductivity, but also positively affected the mechanical properties and the blocking of methanol and water molecules passing through the membrane. Consequently, incorporation of sulfonated graphene oxide into SPEEK membrane has considerably increased the selectivity of the membrane. Therefore, this sulfonated graphene oxide/SPEEK membrane is a good candidate for usage in direct methanol fuel cells.
► The sulfonic acid groups are introduced into graphene oxide(GO) and PEEK matrix. ► The sulfonated GO lead to enhance the proton conductivity of SPEEK membrane. ► The sulfonated GO act as barriers against water swelling and methanol crossover.
A commercial polyamide reverse osmosis (RO) membrane was surface-modified with polydopamine deposited from buffered, aqueous dopamine solution at ambient conditions. The influence of various ...modification conditions (i.e., dopamine solution concentration, polydopamine deposition time, and initial pH of Tris–HCl buffer) on pure water flux, flux during filtration of an oil/water emulsion, and NaCl rejection was investigated. Dead-end filtration results showed decreased pure water flux with increasing dopamine solution concentration and polydopamine deposition time. Membranes modified at a pH of 5 exhibited no change in pure water flux or flux during fouling experiments compared to the native membranes, suggesting that polydopamine was not deposited under such acidic coating conditions. All polydopamine-modified membranes, except those coated at a pH of 5, had higher fluxes when filtering an oil/water emulsion than that of unmodified membranes. NaCl rejection values in all membranes were within the manufacturer's specification. The increased flux when filtering an oil/water emulsion was not sensitive to dopamine concentration, coating time greater than 60min, or alkaline buffer pH value. Short deposition times slightly reduced the fouling resistance of coated membranes, and membranes modified at acidic pH values showed no improvement in fouling.
► Polydopamine was deposited on polyamide reverse osmosis membrane to improve fouling resistance. ► Effect of dopamine concentration, deposition time, and pH on membrane properties was studied. ► Polydopamine coating could improve membrane fouling resistance.
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