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[Display omitted] • A CNT-CeO 2 electrode is fabricated to selectively remove F− in mixed ion solutions. • CNTs increase the conductivity of the electrode and hinder the aggregation of CeO 2. • Pseudo-capacitance behavior of F– entering CeO 2 was observed first time by EQCM. • The energy consumption for treating actual groundwater using scaled-up equipment is low at approximately 0.2 kWh/m3. Selective capacitive deionization (SCDI) is a promising process for preferentially removing specific ions from waters with complex compositions. The selectivity towards certain species in CDI is most frequently achieved through novel electrode materials with high affinities towards targeted species. In this study, we investigate the selective removal of fluoride ions from groundwater containing concentrated co-existing chloride ions. A carbon nanotube-CeO 2 (CNT-CeO 2) electrode is employed for the electro-sorption of fluoride ions. Our findings are compelling: when processing a mixed F−/Cl− solution comprising 10 mg/L F− and 100 mg/L Cl−, the CNT-CeO 2 electrode is seen to reduce the concentration of F− ions to 1.5 mg/L in just 150 min, amounting to an 85 % F− removal efficiency, while the Cl− removal efficiency remains below 2 %. Importantly, this translates to a F−/Cl− separation factor of up to 4.16 when using the CeO 2 -based electrodes, which is 40 times higher than that achieved with conventional activated carbon (AC) electrodes. Furthermore, the energy consumption for treating actual groundwater using scaled-up equipment is impressively low at approximately 0.2 kWh/m3. The high affinity of CNT-CeO 2 towards fluoride is attributed to the intercalation Faraday capacitance initiated by the reaction between F− with CeO 2 , as verified by the electrochemical quartz crystal microbalance (EQCM). Moreover, EQCM results show a substantial increase in both mass and current as the potential increased beyond 0.8 V vs Ag/AgCl, implying that the current surge is not a result of water splitting but rather the adsorption of F− onto the CNT-CeO 2 electrode. The addition of CNTs substantially increases the conductivity of CeO 2 electrodes and restricts the aggregation of CeO 2 , thereby accelerating ion diffusion and promoting selective adsorption characteristics. Importantly, our electro-driven approach demonstrates excellent adsorption–desorption over 20 cycles. This comprehensive study advances the technological development of selective CDI, while providing new insights for fluoride removal in groundwater. [ABSTRACT FROM AUTHOR]

• Comprehensive overview of common argentation separations is provided. • Selectivity mechanisms of argentation separations are described. • Optimization methods for liquid- and gas-phase argentation separations are discussed. • Recent advancements and novel innovations for argentation separations are highlighted. • Wide range of applications utilizing argentation separations are reviewed. The use of silver(I) ions in chemical separations, also known as argentation separations, is a powerful approach for the selective separation and analysis of many natural and synthetic organic compounds. In this review, a comprehensive discussion of the most common argentation separation techniques, including argentation-liquid chromatography (Ag-LC), argentation-gas chromatography (Ag-GC), argentation-facilitated transport membranes (Ag-FTMs), and argentation-solid phase extraction (Ag-SPE) is provided. For each of these techniques, notable advancements, optimized separations, and innovative applications are discussed. The review begins with an explanation of the fundamental chemistry underlying argentation separations, mainly the reversible π-complexation between silver(I) ions and carbon-carbon double bonds. Within Ag-LC, the use of silver(I) ions in thin-layer chromatography, high-performance liquid chromatography, as well as preparative LC are explored. This discussion focuses on how silver(I) ions are employed in the stationary and mobile phase to separate unsaturated compounds. For Ag-GC and Ag-FTMs, different silver compounds and supporting media are discussed, often with relation to olefin-paraffin separations. Ag-SPE has been widely employed for the selective extraction of unsaturated compounds from complex matrices in sample preparation. This comprehensive review of Ag-LC, Ag-GC, Ag-FTMs, and Ag-SPE techniques emphasizes the immense potential of argentation separations in separations science and serves as a valuable resource for researchers seeking to learn, optimize, and utilize argentation separations. [ABSTRACT FROM AUTHOR]

Ion-selective water treatment is needed to address emerging problems in an energy- and cost-efficient manner. Capacitive deionization (CDI) is a membraneless water treatment technology, which relies on storing ions in charged electric double layers (EDLs) of micropores. CDI has shown remarkable selectivity, with local density approximations (LDAs) showing some success in guiding selective separations. However, many underlying processes are represented by lumped fitting parameters in LDA models, hindering further progress. Atomistic models help unravel selectivity mechanisms, but are difficult to integrate with cell-level CDI theory. Here, we review and extend LDA models for CDI, highlight a knowledge gap in connecting between LDA and atomistic models for CDI, and emphasize and build upon analogies between micropore EDLs and nanofiltration membranes. [Display omitted] [ABSTRACT FROM AUTHOR]

Electrochemical methods are known to have attractive features and capabilities when used for ion separations and water purification. In this study, we developed a new process called shock ion extraction (shock IX) for selective and chemical-free removal of toxic heavy metals from water. Shock IX is a hybrid process that combines shock electrodialysis (shock ED) and ion exchange using an ion exchange resin wafer (IERW), and this method can be thought of functionally as an electrochemically assisted variation of traditional ion exchange. In particular, shock IX exhibits greater ion removal and selectivity for longer periods of time, compared to the use of ion exchange alone. The use of an IERW in shock ED also increases multivalent ion selectivity, reduces energy consumption, and improves the hydrodynamics and scalability of the system.

Micellar electrokinetic chromatography (MEKC) and ligand exchange-MEKC have been widely used for the separation of achiral and chiral compounds. For the separation of different compounds, one expects to obtain the desired different separation selectivity by choosing different surfactants as pseudo-stationary phases. This paper describes a comparative study on the separation selectivity in MEKC and LE-MEKC using different anionic surfactants such as sodium dodecyl sulfate (SDS), sodium alkyl polyoxyethylene sulfate (AES-Na) and sodium α-sulfonated fatty acid methyl esters (α-SF-Na). Different selectivities were observed with these anionic surfactants. For the separation of aromatic derivatives by MEKC, better selectivity was obtained by using AES-Na than SDS micellar phases. For the simultaneous separation, of positional enantiomers of o-, m- and p-fluoro-DL-phenylalanine by LE-MEKC, the SDS micellar phase provided the best selectivity among these anionic surfactants. Furthermore, the critical micelle concentrations (CMC) of these surfactants were also estimated by LE-MEKC. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fourteen Salen–M were screened to find the best one for the separation of C 2 H 2. • Salen–Mn (II) showed the largest adsorption energy difference of C 2 H 2 and C 2 H 4. • 3D–Salen–COF–Ni (II) showed an outstanding C 2 H 2 /C 2 H 4 selectivity. C 2 H 4 is an essential industrial organic chemical. Efficiently removing C 2 H 2 from C 2 H 2 /C 2 H 4 mixtures is a significant challenge. Introducing a Salen–metal unit into porous materials is a practical way to separate gas mixtures. In this work, we used density functional theory (DFT) and grand canonical Monte Carlo (GCMC) method investigated the performances of different Salen–metal complexes in separating C 2 H 2 from C 2 H 4. The gas adsorption energies of fourteen Salen–metal complexes were systemically studied. Two complexes, Salen–Mn (II) and Salen–Ni (II), exhibited superior adsorptive selectivity in capturing C 2 H 2 and C 2 H 4. This result will be helpful for developing porous materials for the efficient removal of C 2 H 2 from C 2 H 2 /C 2 H 4 mixtures. [ABSTRACT FROM AUTHOR]

Conventional desalination technologies such as distillation and reverse osmosis are well suited for the supply of fresh water at large scale. The expensive infrastructure and high capital, operating, and maintenance costs associated with these technologies, however, limit their application in remote or underdeveloped areas. Here, we show that shock electrodialysis, a recently developed electrokinetic process, can be used to continuously desalinate artificial seawater (3.5 wt. %) for small-scale (≤ 25 m3 day−1 as a long-term goal), decentralized applications. In two steps, 99.8% of the salt fed was rejected, with selectivity for magnesium ions of which > 99.99 % were removed (based on measurements of concentration by mass spectrometry). We also demonstrated for the first time the viability of using and continuously recycling solutions of sodium citrate buffer to simultaneously reduce waste and inhibit precipitation reactions in the electrode streams. As with conventional electrodialysis, the energy consumed by our technology can be significantly reduced by desalinating sources that are less saline than seawater, such as brackish water and various industrial or municipal process streams. Since the design of the system and choice of materials have yet to be optimized, there remain ample opportunities to further reduce the cost of desalination by shock electrodialysis. Unlabelled Image • Shock electrodialysis is used to desalinate artificial seawater, from which 99.8% of the salt fed is continuously rejected. • As a result of inherent ionic selectivity, more than 99.99% of magnesium ions are removed. • Sodium citrate buffer is used under closed-loop operation as a robust electrolyte for the electrode streams. [ABSTRACT FROM AUTHOR]