The conversion of industrial wastewater, salt-lakes and seawater into the valuable ionic resources is a critical challenge for sustainable global development. Electro-driven membranes are a remarkable class of separation materials established as a viable solution for this challenge. In the past few years, the design and development of ionic transfer materials in electro-driven membranes with target ion selectivity for diverse resources and environment-related applications has attracted a huge surge of interest in material science and engineering disciplines. This tutorial review aims to analyses and summarize the latest advances in the key principles and experimental procedures for designing target ion-selective separation in electro-driven membranes. Particular attention is given to the fabrication process of target ion-selective electro-driven membranes, in view of obtaining a controllable membrane structure, cross-linking and assembly. Moreover, the current evaluation metrics for the selective separation efficiency of electro-driven membranes are critically analyzed. In addition, the state-of-the-art applications of the membranes are summarized, including the selective separation of lithium, fluoride, heavy metal ions, and nutrient ions (e.g., NH4+, PO43-). Overall, this tutorial review suggests promising potential approaches for designing, fabricating, testing, and applying electro-driven membranes in target ion-selective separation for resource sustainability.

Kevlar aramid nanofibers (KANF) are formed by the nanoscale structure of poly (paraphenylene terephthalamide) chains and are the emerging candidate for organic solvent permeation. However, the KANF membranes have a highly ordered and compact structure with few nanofluidic channels, resulting in low-efficiency solvent transport and undesirable membrane filtration. Here, the aligned composite membranes were fabricated by assembling the amino-polystyrene nanospheres (APN) into the KANF matrix and finally obtained a series of the APN@KANF membranes. These APN disrupted the KANF chain packing and increased the fractional free volume (from 27.7 to 35.6%). The ethanol permeance of the APN@KANF membrane was six times higher than the KANF membrane and maintained its rejection performance. Experiments and molecular simulations indicated that these APN increased the pore interconnectivity, which enhanced solvent permeability and molecular sieving. In addition, these highly stable and rigid resulting APN@KANF composite membranes could be used in extreme polar aprotic and nonpolar environmental conditions. This work highlights a promising application of the APN@KANF membranes in organic solvent nanofiltration.

Discharged hospital wastewater contains various pathogenic microorganisms, antibiotic groups, toxic organic compounds, radioactive elements, and ionic pollutants. These contaminants harm the environment and human health causing the spread of disease. Thus, effective treatment of hospital wastewater is an urgent task for sustainable development. Membranes, with controllable porous and nonporous structures, have been rapidly developed for molecular separations. In particular, membrane bioreactor (MBR) technology demonstrated high removal efficiency toward organic compounds and low waste sludge production. To further enhance the separation efficiency and achieve material recovery from hospital waste streams, novel concepts of MBRs and their applications are rapidly evolved through hybridizing novel membranes (non hydrophilic ultrafiltration/microfiltration) into the MBR units (hybrid MBRs) or the MBR as a pretreatment step and integrating other membrane processes as subsequent secondary purification step (integrated MBR-membrane systems). However, there is a lack of reviews on the latest advancement in MBR technologies for hospital wastewater treatment, and analysis on its major challenges and future trends. This review started with an overview of main pollutants in common hospital waste-water, followed by an understanding on the key performance indicators/criteria in MBR membranes (i.e., solute selectivity) and processes (e.g., fouling). Then, an in-depth analysis was provided into the recent development of hybrid MBR and integrated MBR-membrane system concepts, and applications correlated with wastewater sources, with a particular focus on hospital wastewaters. It is anticipated that this review will shed light on the knowledge gaps in the field, highlighting the potential contribution of hybrid MBRs and integrated MBR-membrane systems toward global epidemic prevention.

The development of fluoride selective separation technology is essential for water purification and simultaneous ion capture. In this paper, a novel Kevlar amide nanofiber (KANF) based anion exchange membrane for fluoride capture was reported. The incorporation of positively charge groups into the KNAF's framework was enabled through a novel yet facile method, i.e., through the embedding and subsequent self-assembly of hydroxypropyltrimethyl ammonium chloride chitosan (HACC) into the KANF-based hydrogel framework. The membrane surface was further sulfonated to enhance the fluoride selectivity. Dissipative particle dynamics simulation revealed that the highly hydrophilic and positively charged HACC was homogeneously embedded into the KANFbased hydrogel framework. Membranes with varying HACC content showed up to 3.7 mmol g(-1) ion exchange capacity and 17% water content. Compared to a commercial anion exchange membrane (AMX membrane), the HACC#KNAF membranes exhibited a much lower surface electrical resistance (e.g., ~1.23 omega cm(2)) and exceptional desalination/concentration efficiency with NaF solution in electrodialysis. The sulphonated membrane S-HACC#KNAF achieved a permselectivity of 2.75 and selective efficiency of 17% favoring the F- cross-membrane transport over SO42-, outperforming its commercial counterpart. The resulting membranes were significantly less prone to foulant deposition and exhibited superior stability over semi long-term tests. The design principles developed will greatly broaden the possibilities of KANF-based membranes' fabrication for achieving efficient ion separation towards sustainable ion capture.

Metal-organic frameworks (MOFs) are an increasingly popular class of porous materials due to their tailorable structure comprised of ordered porous cavities, high specific surface areas, and versatile functional organic ligands. Implementation of these porous materials into membrane separation technologies can create an energyefficient alternative for ion-selective separation. However, their low stability in aqueous environments and other challenges has limited their industrial breakthrough. In the past five years, many developments have improved MOF-based membranes for the selective separation of target ions. Novel insight into MOF-based membranes' structure-property relationships improves dispersibility, stability, size-sieving, electrostatic repulsion, and ionic conductivity for ideal membrane performance. The latest design principles for MOF-based membrane use advanced confinement conversion, in situ self-assembly, layer-by-layer assembly, and interfacial polymerization methods for enhanced separation performance. Analysis of separation mechanisms in MOF-based membranes now extends applications to desalination, lithium extraction, removal of heavy metal ions, and separation of ions from organic solvents. Overall, further development of MOF-based membranes presents numerous opportunities and challenges in target ion separation.

Membrane technology is a green and highly efficient separation method rapidly developed for gas and water treatments. As the core part of this technology, the functional membranes are used to selectively separate molecules or ions from an initial feed stream into a purified permeate stream and a rejected retentate stream. In this chapter, the functional membranes, including gas, liquid, and pervaporation separation membranes, are discussed. Moreover, the challenges and limitations of current membrane processes are critically analyzed. In addition, the state-of-the-art applications of the membranes, including gas separation fields, pervaporation fields, aqueous treatment, petroleum industrial treatment, and organic solvent separation fields, are summarized.

The selective separation and extraction of lithium from salt lakes is compromised by the high salt concentration and the presence of competing ions. In this study, a class of novel cation exchange membranes based on Kevlar aramid nanofibers (KANFs) was designed via interpenetrating networks of poly(4-styrenesulfonic acid-co-maleic acid) sodium salt (PSSMA) and amide reaction of 4-amino-2,2,6,6-tetramethylpiperidine-1-oxyl (ATTO). Membranes with different PSSMA content were fabricated, and the final membrane denoted as A#PSSMA@KANF-2 achieved a similar to 1.2 mmol g(-1) ion exchange capacity, similar to 28% water content, similar to 4.5% swelling rate and similar to 1.8 Omega cm(2) surface electrical resistance. The thin A#PSSMA@KANF-2 membrane (similar to 8 mu m thickness) also exhibited a high membrane limiting current density of 32.0 mA cm(-2) (in 0.1 M NaCl solution) and an exceptional desalination efficiency (99.9% for NaCl) in electrodialysis. Moreover, compared to some commercial monovalent selectivity cation exchange membranes (CSO and CIMS membranes, which are two commercial monovalent cation selective membranes), the A#PSSMA@KANF-2 membrane was found functional for the separation of Li+/Mg2+ and to have an excellent anti-scaling performance. As the selectivity has potential to be as high or higher as that of commercial membranes, this work provides a promising method to develop membranes with anti-scaling performance for the extraction of lithium from high salt concentrations in salt lakes.

This study demonstrates the application of a hydrogel as the aqueous phase in interfacial polymerization for the synthesis of a thin film composite membrane with ultrahigh permeability.