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Selective extraction of Li + ions from highly saline solutions is challenging due to the presence of competing ions like Mg2+ and Na+. This study employed a straightforward interfacial polymerization technique to modify cation exchange membranes (CEM, CR671) to enhance Li+ transport selectivity and capacities. The modification involved a two-layer coating, with polydopamine (PDA) as the initial layer facilitating subsequent coating with polyethyleneimine (PEI). The second layer, comprising PEI and 2-OH-15-crown-5 ether (15CE), created the channels for selective Li transport through crosslinking with 1,3,5-benzenetricarbonyl trichloride. Fourier transform infrared spectroscopy confirmed the presence of 15CE coating on the modified membranes (15CE-PEI-PDA-CR671), while zeta-potential analysis indicated a positive surface charge attributed to PEI to increase the electrostatic repulsion of divalent cations. Electrochemical impedance spectroscopy demonstrated a reduced impedance of 15CE/PEI-PDA-CR671 for Li transport, indicating its high transport potential and selectivity for Li. Bench-scale electrodialysis experiments simulating high Mg2+ and Na + brine conditions demonstrated promising results that 15CE/PEI-PDA-CR671 membrane achieved up to 80% and 90% Li+ recovery efficiency in Mg2+/Li+ and Na+/Li+ mixtures, respectively. The modified membranes exhibited enhanced selectivity, as evidenced by reduced relative transfer numbers (t Mg/Li and t Na/Li). Specifically, 15CE/PEI-PDA-CR671 demonstrated significant improvements in Li+ permselectivity and flux compared to CR671 and PEI-PDA-CR671, highlighting its potential for enhancing Li+ recovery effectively from brine water sources. [Display omitted] • Innovative membrane modifications facilitated effective Li extraction from brine. • Two-layer coating strategy enhanced Li transport in modified CR671 membranes. • Incorporation of 15-crown-5 ether played a pivotal role in enhancing Li selectivity. • 15CE-PEI-PDA-CR671 membranes significantly enhanced Li permselectivity and flux. • Li recovery efficiency was demonstrated at 80% in Mg2+/Li+ and 90% in Na+/Li+ brines. [ABSTRACT FROM AUTHOR]

Abstract: A series of poly (arylene ether sulfone) block copolymers with hydrophilic segments containing fluorene groups were successfully synthesized as confirmed by 1H NMR. The molecular weights were measured in the range 115–140kDa by gel permeation chromatography (GPC). The hydrophilic segment showed a helical structure due to fluorene with butterfly-shaped framework in the main chain. With incorporating imidazolium groups, the microphase separation can also be achieved between the hydrophilic and the hydrophobic moieties. The membrane structure was characterized by positron annihilation lifetime spectroscopy (PALS) and small angle X-ray scattering (SAXS). The block copolymers were used to prepare membranes successfully for pervaporation separation of methanol (MeOH)/methyl tert-butyl ether (MTBE) mixture. The correlation between the membrane microstructure and the separation performance was discussed thoroughly. By increasing the hydrophilic segment proportion, the permeation flux increased while the separation factor declined. The membranes have the highest permeation flux (0.334kgm−2h−1) and the lowest separation factor (287) for a 15wt% MeOH feed mixture at 40°C, and the mass fraction of MeOH in the permeate is higher than 98wt%. [Copyright &y& Elsevier]

A series of novel quaternized fluorene-containing poly(arylene ether sulfone)s (APESs) were synthesized. Bromination rather than chloromethylation was used for the conversion of –CH3 to reactive –CH2Br. N,N,N׳,N׳-tetramethyl-1,6-diaminohexane (TMHDA) dissolved in isopropanol (IPA) was used as a quaternization reagent for the preparation of target anion exchange membranes (AEMs). Fourier transform infrared spectroscopy (FT-IR), 1H NMR spectroscopy and gel permeation chromatography (GPC) were used to characterize the as-synthesized copolymers. The ratio of hydrophilic to hydrophobic monomers was varied to study the structure property of the AEMs. The obtained AEMs were characterized by scanning electron microscopy (SEM) and thermogravimetric analysis (TGA). Water uptake (WU), swelling ratio, ionic exchange capacity (IEC), ionic conductivity, methanol permeability and alkaline stability were also studied. These AEMs have good properties as polymer electrolyte materials with high ionic conductivity (under hydrated conditions) in the range 2.89–8.85×10−2 Scm−1 and 5.60–15.64×10−2 Scm−1 at 30 and 80°C, respectively. The methanol permeability of the AEMs in the range 5.99–14.51×10−8 cms−1 is lower than that of Nafion® 117 (1.82×10−6 cms−1). The AEMs show excellent alkaline stability in 1M KOH solution at 60°C for a long time. Single cell testing using APES-0.8 showed an open circuit voltage of 0.89V. A maximum power density of 146mWcm−2 at a current density of 423mAcm−2 can be achieved at 60°C. In summary the AEMs are good candidates for evaluation in fuel cell applications. [ABSTRACT FROM AUTHOR]

Abstract: In this study we evaluated the performance of forward osmosis (FO) at the pilot scale to achieve simultaneous seawater desalination and wastewater reclamation. The investigation was performed with a commercial spiral wound FO membrane element for approximately 1300h of continuous operation, processing 900,000L of wastewater effluent and producing 10,000L of purified water through a hybrid FO-RO process. Water and solute fluxes were monitored during the study. Reversible and irreversible membrane fouling was observed; however, water flux was maintained at a relatively constant rate of 5.7±0.2Lm−2 h−1 with MBR permeate feed and seawater draw solution. Subsequent increase of total suspended solids (TSS) concentration in the FO feed (secondary treated effluent with 5 to 16mgL−1 TSS) resulted in incremental flux decline; however, the membrane typically achieved stable water flux after the initial exposure to foulants. Additional analysis focused on bi-directional transport of inorganic species and a detailed evaluation of dissolved organic matter permeation through the membranes in the hybrid process. Evaluation of sample fluorescence revealed that the FO membrane and the hybrid process provide a strong barrier to protein-like fluorophores associated with wastewater effluent. Results also demonstrated the robust nature of dual barrier membrane systems to achieve greater than 99.9% removal of orthophosphate and dissolved organic carbon and more than 96% rejection of nitrate. Upon completion of the study a comprehensive membrane autopsy was performed on the FO and RO membranes. Organic fouling on the FO membrane was observed to have low adhesion to the membrane surface, but did result in some modification to membrane active layer properties. [Copyright &y& Elsevier]

Abstract: Microbial desalination cell (MDC) offers a new and sustainable approach to desalinate saltwater by directly utilizing the electrical power generated by bacteria during organic matter oxidation. The successful MDC development relies on the fundamental understanding of the interactions and removal mechanisms of different ion species present in saline water or wastewater, but there is limited understanding of ion transport mechanisms in MDCs and potential membrane fouling/scaling during treatment of wastewater and saline water. In this study, we investigated the transport behavior of multiple ions in MDCs and the effects of ionic composition on system performance and membrane scaling and fouling. The results showed that the presence of sparingly soluble cations in saltwater negatively affected MDC power generation and desalination. Membrane characterization revealed that the majority of such ions precipitated on the ion exchange membrane surface and caused membrane scaling. Anions such as Br− and SO4 2− with Na+ as counter-ion did not show significant effects on system performance. Sharp pH changes were observed during MDC operation, which resulted in the inhibited MDC anode microbial activity and the accelerated formation of alkaline precipitations on both sides of the cation exchange membrane. An anode–cathode recirculation approach was proved to be effective to solve such problems and improved the desalination rate by 152% and the electron harvest rate by 98%. [Copyright &y& Elsevier]

Abstract: This study investigated membrane fouling during wastewater reclamation by collecting operational performance data and employing state-of-the-art techniques for characterization of membrane foulants. Utilizing a pilot-scale membrane unit, two nanofiltration membranes (NF-90 and NF-4040, Dow/Filmtec) and one low-pressure reverse osmosis membrane (TMG10, Toray America) were tested at two wastewater reclamation facilities treating microfiltered non-nitrified secondary effluent and nitrified/denitrified tertiary effluent. The membranes and foulants were characterized by environmental scanning electron microscopy coupled with energy dispersive spectroscopy, attenuated total reflection-Fourier transform infrared spectrometry, zeta-potential measurement, atomic force microscopy, phospholipids analysis, and contact angle measurement. During treatment of the nitrified/denitrified effluent, membrane fouling was dominated by biofouling in combination with organic fouling, colloidal fouling, and inorganic scaling. Sufficient chloramines residual was identified as being critical in controlling biofouling during wastewater desalination. During filtration of the non-nitrified effluent, fouling of the membrane lead-elements was mainly caused by adsorption and deposition of effluent organic matter while biofouling still observed in tail-elements despite the formation of chloramines. Rough and hydrophobic membrane with high permeability (e.g., NF-90) displayed more severe initial specific flux decline during filtration, while smooth and hydrophilic membrane (e.g., NF-4040) exhibited high and constant specific flux when biofouling was under control. [Copyright &y& Elsevier]

Abstract: Commercial polyamide nanofiltration (NF), reverse osmosis (RO), and ultra-low pressure RO (ULPRO) membranes (NF-90, NF-200, TFC-HR, and XLE) as well as a cellulose triacetate RO membrane (CTA) were employed to investigate the effect of fouling on transport of organic micropollutants. Due to foulant precipitation and cake-layer formation, membrane surface characteristics changed considerably in terms of contact angle (an index of hydrophobicity), zeta-potential, functionality, and surface morphology, which potentially affected transport of contaminants as compared to unfouled (virgin) membranes. The transport of ionic organic micropollutants was hindered as a result of improved Donnan exclusion (electrostatic repulsion) likely due to a more negative surface charge as quantified by zeta-potential measurements. Membrane fouling also resulted in an increased adsorption capacity and reduced mass transport through partitioning and diffusion of solutes across the membrane. These effects led to an increase in rejection of hydrophobic non-ionic solutes (e.g., disinfection byproducts and chlorinated solvents) by fouled membranes. However, the increasing surface charge has the potential to result in a larger molecular weight cut-off of a fouled membrane due to membrane swelling, which can lead to lower rejection for hydrophilic non-ionic solutes, especially where nanofiltration membranes with a larger molecular weight cut-off are employed. Membrane fouling facilitated the transport of hydrophobic and hydrophilic organic contaminants through CTA membranes resulting in elevated concentrations of target solutes in the permeate. Findings of the study indicate that membrane fouling significantly affects the rejection of organic solute by CTA, NF, and ULPRO membranes while it is less important for thin film composite RO membranes. [Copyright &y& Elsevier]

A series of composite gel polymer electrolytes (GPEs) based on poly (vinylidene fluoride- co -hexafluoropropylene) (PVDF-HFP), 1-ethtyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([EMIM][TFSI]), lithium bis(trifluoromethane) sulfonimide (LiTFSI) and covalent linked 2,2''-(ethylenedioxy) bis (ethylamine) to reduced graphene oxide (rGO-PEG-NH 2) have been successfully prepared by solution casting method. With the increase of [EMIM][TFSI] and rGO-PEG-NH 2 content, the crystallinity of the GPE decreased, and the thermal decomposition temperature increased significantly. A high-speed lithium ion transport network was formed in the 3P5E2LG-10 GPE, with rGO as the connection site and PEG as the bridge. 3P5E2LG-10 GPE exhibited a conductivity of 2.1 × 10−3 S cm−1 at 30 °C, a lithium ion transference number of 0.45, and a electrochemical window of 5.0 V. The 3P5E2LG-10 based cell exhibited more than 99% columbic efficiency and the initial discharge capacity reached the maximum of 163.7 mAh/g, and capacity retention was about 88% after 80 cycles at 0.1C. 3P5E2LG-10 GPE will have great potential for lithium ion battery with high safety and long cycle life. Image 1 • [EMIM][TFSI] and rGO-PEG-NH 2 decrease the crystallinity of PVDF-HFP and promote transmission of lithium ion. • 3P5E2LG-10 exhibits 2.1 × 10−3 S cm−1, a lithium ion transference number of 0.45, and a electrochemical window of 5.0 V. • The electrolyte has excellent cycle performance and good inhibitory effect on the growth of lithium dendrites. [ABSTRACT FROM AUTHOR]

Abstract Monovalent permselective cation-exchange membrane (CEM) CR671 was developed by coating polyethyleneimine onto the normal grade CEM CR67. Pilot-scale electrodialysis of brackish groundwater demonstrated excellent monovalent permselectivity of the modified CR671 as compared to the normal grade CR67. Advanced analytical approaches were employed to characterize the physicochemical and electrochemical properties of the CEMs to elucidate the mechanisms of permselectivity. Ion-exchange capacities of the CR671 and CR67 were measured to be 2.0 and 2.1 meq/g dry membrane, respectively. Zeta-potential analysis revealed that the CR671 surface was positively charged as a result of polyethyleneimine coating. Electrochemical impedance spectroscopy (EIS) data indicated larger impedance for the CR671 and fitted well to the Maxwell-Wagner model, which provided an equivalent electric circuit for the CEMs, as well as indication of the existence of polyethyleneimine layer. The time constants of different ions transporting through polyethyleneimine modification layer were calculated based on the EIS responses. The results revealed the polyethyleneimine modification layer led to longer transport time for Ca2+ ions through the CR671 than for Na+ ions, supporting the pilot-scale testing results that the CR671 improved the Na+ removal by selectively rejecting Ca2+ ions. However, the difference in ion transport time became less significant with increasing ionic strength of the feed water. The EIS results suggest the monovalent permselectivity decreased during treatment of higher salinity water, supporting the finding that the CR671 exhibited higher monovalent permselectivity during electrodialysis of brackish groundwater than reverse osmosis concentrate in which the salt concentration was 5.7 times higher than the brackish groundwater. This study demonstrates that ion transport time constant is a better indicator for permselectivity of modified ion-exchange membranes than electrical resistance measured by EIS. Graphical abstract fx1 Highlights • Monovalent permselective CR671 was developed by coating a polyethyleneimine layer. • CR671 presented excellent monovalent permselectivity in pilot-scale electrodialysis. • EIS indicated a different electrical performance for CR671 than normal grade CR67. • The modification layer resulted in longer time for Ca2+ to transport than for Na+. • Ion transport time constant is a better indicator to permselectivity than resistance. [ABSTRACT FROM AUTHOR]

The understanding of membrane charge neutralization and diffuse layer compression at environmentally relevant ionic strengths is becoming increasingly important. In this work, the impact of high ionic strengths on membrane zeta potential was determined using a combination of streaming potential measurements and theoretical modeling. Streaming potential measurements were conducted on cellulose triacetate (CTA) and polyamide thin-film composite (TFC) membranes at ionic strengths within the operating limits of an electrokinetic analyzer. Zeta potential calculated from streaming potential was then extrapolated to environmentally relevant ionic strengths (0.05 to 1 M 1:1 electrolyte) using the Debye–Hückel and Helmholtz-Smoluchowski models. Extrapolated zeta potential values revealed that membrane charge neutralization and compression of the diffuse layer are limited by the size of the hydrated counter-ions, and full membrane charge neutralization, or even charge reversal, can not be achieved. The expected zeta potential of CTA membranes was similar to that of TFC membranes at high ionic strength, which has considerable implications in the comparison of membrane performance when treating brackish and saline feed waters. The methodologies developed in this work can help to better understand the contribution of electrostatic forces resulting from zeta potential to the sum of interfacial forces present at the membrane surface. [ABSTRACT FROM AUTHOR]

Membrane fouling, in particular biofouling is a major problem in membrane applications for water and wastewater treatment. In this study, cation-exchange membranes were modified with conductive polymer polyethyleneimine and nanomaterials such as titanium dioxide (TiO 2) and graphene oxide (GO) to improve membrane anti-microbial properties and energy efficiency during electrodialysis. The anti-fouling potential was evaluated by quantitative measurement of biomass and biofilm accumulation on membrane surface with Escherichia coli (E. coli) as model microbes. Experimental results showed polyethyleneimine and nanomaterials coating changed membrane surface hydrophilicity and significantly improved anti-biofouling properties with an optimal nanomaterial dosage of 37.5 μg/mL of coating solution. Polyethyleneimine had limited effect on preventing microbial cell attachment, but demonstrated remarkable anti-biofilm growth by its cytotoxicity. Overall desalination performance of polyethyleneimine coated membrane was similar to unmodified membrane. GO coating significantly improved desalination efficiency because of its high conductivity and negative charge, while TiO 2 coated membrane showed decreased overall desalination performance due to its reduced electrical conductivity. Image 1 • Anti-biofouling and energy-efficient cation exchange membranes were developed. • Polyethyleneimine (PEI) reduced biofilm by 67% but not cell attachment. • PEI-TiO 2 coating reduced cell attachment and biofilm coverage by 60% and 78%. • PEI-GO coating reduced cell attachment and biofilm coverage by 96% and 98%. • PEI-GO coating significantly enhanced energy efficiency during electrodialysis. [ABSTRACT FROM AUTHOR]