Ultrahigh pressure compaction-resistant thin film crosslinked composite reverse osmosis membranes.

In this study, we present a class of thin-film crosslinked (TFX) composite reverse osmosis (RO) membranes that resist physical compaction at ultrahigh pressures (up to 200 bar). Since RO membranes experience compaction at virtually all pressure ranges, the ability to resist compaction has widespread implications for RO membrane technology. The process described herein involves crosslinking a phase inverted porous polyimide (PI) support membrane followed by interfacial polymerization of a polyamide layer, thereby forming a fully thermoset composite membrane structure.

Kinetics of Silica Polymerization on Functionalized Surfaces: Implications for Reverse Osmosis Membranes.

The general mechanisms of silica scaling through the polymerization of silicic acid at supersaturation have been predominantly studied in solutions. However, the pathway of silica polymerization occurring directly on surfaces, leading to silica precipitation, remains largely unexplored despite its wide-ranging implications for biomineralization processes, green material synthesis, and scaling in various engineered systems. In this study, we analyze the kinetics of silica polymerization from oversaturated solutions onto surfaces functionalized with various types of self-assembled monolayers (SAMs) or reverse osmosis (RO) membranes using a quartz crystal microbalance with dissipation.

Toward Continuous, Oriented Covalent Organic Framework Membranes for Precise Molecular Separations.

The goal of achieving energy-efficient, precise molecular separations has motivated interest in developing and employing porous crystalline frameworks as membrane materials. Covalent organic frameworks (COFs) are ordered crystalline matrices composed of covalently bonded organic monomers and are synthesized via reversible reticular chemistry. COFs possess high porosity, structural tunability, and chemical and thermal stability, making them ideally suited for emerging, high-value membrane separation processes, such as ion separations, organic solvent nanofiltration, and gas separations.

Solvent Transport in Disordered and Dynamic Membrane Pores: Implications for Reverse Osmosis and Nanofiltration Membranes.

Pressure-driven separations with nanoporous membranes, such as reverse osmosis and nanofiltration, play a vital role in addressing water scarcity and enabling resource recovery. Understanding water or solvent transport in membrane pores is essential for advancing membrane separation technologies. A key question in transport modeling is to establish a relationship between solvent permeability and membrane porous structure properties, such as porosity or pore size.

A covalent organic framework membrane with highly selective and permeable artificial sodium channels via ion recognition.

Biological sodium channels efficiently discriminate between same-charge ions with similar hydration shells. However, achieving precise ion selectivity and high throughput in artificial ion channel fabrication remains challenging. Here, we investigate angstrom-scale channels in 15-crown-5 (15C5) functionalized COF membranes for fast, selective ion transport.

Intensified atomic utilization efficiency of single-atom catalysts for nitrate conversion via electrified nanoporous membrane.

Conventional electrochemical reactors for nitrate reduction typically suffer from limited reaction efficiency when applied for real-world water treatment due to poor utilization of electrocatalytic active sites. Here, we applied nanoporous electrofiltration to intensify atomic utilization by incorporating single-atom catalysts into an electrified membrane for reducing low-concentration nitrate to ammonia under realistic water conditions. We enhance the exposure of single atoms in nanopores by coating the catalysts on a carbon nanotube-interwoven membrane framework.

Compaction of Pressure-Driven Polymer Membranes: Measurements, Theory, and Mechanisms.

Membrane compaction is inherent in pressure-driven membrane processes, resulting in a decrease in porosity and pore size of polymeric membranes as solvent flow compresses the porous structure of the polymer. The compaction of pores reduces solvent permeability and significantly impacts separation performance. Despite the importance of membrane compaction, its fundamental mechanisms have not been well studied.

Nanonet trapping for effective removal of nanoplastics by iron coagulation.

Nanoplastics (NPs) are emerging aqueous pollutants, posing risks to drinking water safety and human health. However, conventional coagulants, widely employed in water treatment plants globally, are ineffective at removing NPs. Here, we present an in-situ Fe(III) method based on the simultaneous use of Fe(II) coagulant and an oxidant to enhance conventional coagulation by altering the nanostructure of Fe-based precipitates in flocs for efficient NP removal.

Deciphering co-ion and counterion transport in polyamide desalination membranes reveals ion selectivity mechanisms.

Membrane-based processes, such as reverse osmosis (RO) and nanofiltration (NF), are widely used for water purification and desalination due to their high energy efficiency and exceptional solute-water selectivity. Nevertheless, the fundamental, molecular-level mechanisms governing ion selectivity are still not fully understood. This study explores ion selectivity in polyamide desalination membranes, focusing on the partitioning and diffusion mechanisms of co-ions and counterions.

Ionophore-Based Molecular Layer-by-Layer Polyamide Membranes for Facilitated Single-Ion Transport.

Single-ion-selective membranes are indispensable for efficient ion separations in environmental, energy, and biomedical technologies. Inspired by biological ion channels, this work harnessed the selective and reversible ion binding features of ionophores to fabricate an ultrathin, ionophore-based K-selective polyamide membrane through molecular layer-by-layer (m-LbL) polymerization with 18-crown-6-functionalized monomers. Compared with Cs, Li, and Mg, K exhibited the highest binding energy to 18-crown-6, facilitating its transport over the competing cations across the sub-10 nm polyamide film in a binary salt mixture.

Nodular networks in hydrated polyamide desalination membranes enhance water transport.

For nearly half a century, thin-film composite reverse osmosis membranes have served as key separation materials for desalination. However, the precise structure of their polyamide selective layer under hydrated conditions and its relationship to membrane transport remain poorly understood. Using cryo-electron tomography, we successfully reconstructed the three-dimensional structure of six commercial polyamide membranes under hydrated conditions, revealing a fully swollen nodular network.

Role of Transmembrane Pressure and Water Flux in Reverse Osmosis Composite Membrane Compaction and Performance.

This study explores the compaction behavior of thin-film composite reverse osmosis (TFC RO) membranes for different combinations of transmembrane pressure (TMP) and transmembrane water flux. Operating a crossflow system at constant feed pressure (60 bar) but different feed solution osmotic pressures enabled adjusting the TMP─the difference between hydraulic and osmotic pressure─and water flux. The extent of membrane compaction increases as TMP (and flux) increases.

Ceramic-carbon Janus membrane for robust solar-thermal desalination.

The desalination performance of conventional distillation membranes is limited by insufficient stability and energy efficiency, impeding their application in sustainable water production. Herein, we report a ceramic-carbon Janus membrane with solar-thermal functionality for enhanced desalination performance, energy efficiency, and stability for hypersaline water treatment. The feed and permeate sides of this Janus membrane are designed with different properties such as wettability, conductivity, and solar-thermal conversion to enhance performance.

Relating Solute-Membrane Electrostatic Interactions to Solute Permeability in Reverse Osmosis Membranes.

Despite the widespread use of reverse osmosis (RO) membranes in water desalination, the role of solute-membrane interactions in solute transport remains complex and relatively not well understood. This study elucidates the relationship between solute-membrane electrostatic interactions and solute permeability in RO membranes. The transport of salt and neutral molecules through charged polyamide (PA) and uncharged cellulose triacetate (CTA) RO membranes was examined.

Approaching infinite selectivity in membrane-based aqueous lithium extraction via solid-state ion transport.

As the gap between lithium supply and demand continues to widen, the need to develop ion-selective technologies, which can efficiently extract lithium from unconventional water sources, grows increasingly crucial. In this study, we investigated the fundamentals of applying a solid-state electrolyte (SSE), typically used in battery technologies, as a membrane material for aqueous lithium extraction. We find that the anhydrous hopping of lithium ions through the ordered and confined SSE lattice is highly distinct from ion migration through the hydrated free volumes of conventional nanoporous membranes, thus culminating in unique membrane transport properties.

Gypsum heterogenous nucleation pathways regulated by surface functional groups and hydrophobicity.

Gypsum (CaSO·2HO) plays a critical role in numerous natural and industrial processes. Nevertheless, the underlying mechanisms governing the formation of gypsum crystals on surfaces with diverse chemical properties remain poorly understood due to a lack of sufficient temporal-spatial resolution. Herein, we use in situ microscopy to investigate the real-time gypsum nucleation on self-assembled monolayers (SAMs) terminated with -CH, -hybrid (a combination of NH and COOH), -COOH, -SO, -NH, and -OH functional groups.

Tuning Metal-Organic Framework Linker Chemistry for Transition Metal Ion Separations.

The pressing demand for critical metals necessitates the development of advanced ion separation technologies for circular resource economies. To separate transition metal ions, which exhibit near-identical chemical properties, adsorbents and membranes must be designed with ultraselective chemistries. We leverage the customizability of metal-organic frameworks (MOFs) to systematically study the role of material chemistry in sorption and selectivity of Co, Ni, and Cu.

Depolymerization mechanisms and closed-loop assessment in polyester waste recycling.

Alcoholysis of poly(ethylene terephthalate) (PET) waste to produce monomers, including methanolysis to yield dimethyl terephthalate (DMT) and glycolysis to generate bis-2-hydroxyethyl terephthalate (BHET), is a promising strategy in PET waste management. Here, we introduce an efficient PET-alcoholysis approach utilizing an oxygen-vacancy (V)-rich catalyst under air, achieving space time yield (STY) of 505.2 g·g·h and 957.

The physical basis for solvent flow in organic solvent nanofiltration.

Organic solvent nanofiltration (OSN) is an emerging membrane technology that could revolutionize chemical separations in numerous vital industries. Despite its significance, there remains a lack of fundamental understanding of solvent transport mechanisms in OSN membranes. Here, we use an extended Flory-Rehner theory, nonequilibrium molecular dynamic simulations, and organic solvent transport experiments to demonstrate that solvent flow in OSN membranes is driven by a pressure gradient.

Inhibition of silica scaling with functional polymers: Role of ionic strength, divalent ions, and temperature.

High concentrations of dissolved silica in saline industrial wastewaters and brines cause silica scale formation, significantly hampering the efficacy of diverse engineered systems. Applying functional polymers as scale inhibitors in process feedwater is a common strategy to mitigate silica scaling. However, feedwater characteristics often vary widely, depending on the specific processes, making the inhibition of silica scaling challenging and complex.

More resilient polyester membranes for high-performance reverse osmosis desalination.

Thin-film composite reverse osmosis membranes have remained the gold standard technology for desalination and water purification for nearly half a century. Polyamide films offer excellent water permeability and salt rejection but also suffer from poor chlorine resistance, high fouling propensity, and low boron rejection. We addressed these issues by molecularly designing a polyester thin-film composite reverse osmosis membrane using co-solvent-assisted interfacial polymerization to react 3,5-dihydroxy-4-methylbenzoic acid with trimesoyl chloride.

Revolutionizing Airborne Virus Defense: Electromagnetic MXene-Coated Air Filtration for Superior Aerosol Viral Removal.

The COVID-19 pandemic sparked public health concerns about the transmission of airborne viruses. Current methods mainly capture pathogens without inactivation, leading to potential secondary pollution. Herein, we evaluated the inactivation performance of a model viral species (MS2) in simulated bioaerosol by an electromagnetically enhanced air filtration system under a 300 kHz electromagnetic induction field.