Donnan Dialysis Desalination with a Thermally Recoverable Solute

This study presents a novel desalination technology that couples Donnan dialysis (DD) with thermally-recoverable solutes and utilizes low-grade heat as energy input. In the proposed process, saline feed streams and receiver solutions of concentrated NH4HCO3(aq) flow stepwise across cation- and anion-exchange membranes. The large transmembrane concentration differences of NH4+ and HCO3– set up electrochemical potential gradients to drive the uphill transport of Na+ and Cl– ions, respectively, from the saline feed into the receiver stream. Warming the two outlet streams using low-temperature thermal sources volatilizes NH3 and CO2, thus removing NH4HCO3 to yield desalinated product water and concentrated brine. The separated NH3(g) and CO2(g) are then recycled to reconstitute the receiver solution. The concept was first experimentally validated by desalinating brackish water simulated with 100 mM NaCl solutions to freshwater salinities (<17 mM). DD desalination was then demonstrated for larger ranges of feed and receiver concentrations of 100–1000 mM, and the experimental salt removals showed good agreement with theoretical Donnan equilibria (within 5%). The experimental results revealed that the unavoidable permeation of receiver solute co-ions due to imperfect membrane permselectivities is the main factor that prevents the theoretical thermodynamic potential from being reached. Nonetheless, current commercial ion-exchange membranes are sufficient to suppress the undesired co-ion leakage, yielding salt removals adequate for practical desalination. Module-scale analysis quantitatively showed that countercurrent DD operation can obtain higher desalination performance compared to co-current flows, achieving salt removals and water recovery yields as high as 95.5 and 87.5%, respectively. The utilization of low-grade thermal sources, such as waste heat and low-temperature geothermal reservoirs, as the primary energy input to drive the innovative approach opens up opportunities to lower the carbon intensity of desalination

Elucidating conductivity-permselectivity tradeoffs in electrodialysis and reverse electrodialysis by structure-property analysis of ion-exchange membranes

Ion-exchange membranes (IEMs) are used in environmental and energy technologies of electrodialysis (ED) desalination and reverse electrodialysis (RED) power generation, respectively. Recent studies reported empirical evidence that the conductivity and permselectivity of IEMs are bound by a tradeoff relationship, where an increase in ionic conductivity is accompanied by a decrease in counterion selectivity over co-ion. A fundamental understanding of this conductivity-permselectivity tradeoff is principal to inform membrane development. This study presents an IEM transport model to analytically relate conductivity and permselectivity to intrinsic membrane chemical and structural properties. The model employs the Nernst-Planck transport framework and incorporates counterion condensation theory to simulate the performance of IEMs in a range of ED and RED operations. The analysis revealed the mechanism for the tradeoff induced by bulk solution concentration: a higher salinity suppresses IEM charge-exclusion, thus lowering permselectivity, but elevates mobile ion concentration within the membrane matrix to improve conductivity. As such, IEM applications are practically confined to sub-seawater salinities, i.e., RED using hypersaline streams will not be efficient. In another tradeoff driven by IEM water sorption, increasing membrane swelling enhances effective ion diffusivity to raise conductivity, but diminishes permselectivity due to dilution of fixed charges. The transport model indicates that increasing membrane ion-exchange capacity and reducing thickness can yield highly selective and conductive IEMs

Virosome, a hybrid vehicle for efficient and safe drug delivery and its emerging application in cancer treatment

A virosome is an innovative hybrid drug delivery system with advantages of both viral and non-viral vectors. Studies have shown that a virosome can carry various biologically active molecules, such as nucleic acids, peptides, proteins and small organic molecules. Targeted drug delivery using virosome-based systems can be achieved through surface modifications of virosomes. A number of virosome-based prophylactic and therapeutic products with high safety profiles are currently available in the market. Cancer treatment is a big battlefield for virosome-based drug delivery systems. This review provides an overview of the general concept, preparation procedures, working mechanisms, preclinical studies and clinical applications of virosomes in cancer treatment

Influence of electrolyte on concentration-induced conductivity-permselectivity tradeoff of ion-exchange membranes

In ion-exchange membranes (IEMs), the concentration-induced tradeoff between conductivity and permselectivity constrains process performance. This study investigates the impacts of different electrolytes on the conductivity-permselectivity tradeoff of commercial cation and anion exchange membranes. Nine different electrolyte solutions containing mono-, di-, and trivalent ions, and spanning 1.5 orders of magnitude in concentration were examined. Effective conductivity is found to be determined by valency and mobility of the counterion and is insensitive to the co-ion identity. Apparent permselectivity declines with higher valency of the counterion and with lower valency of the co-ion. Overall, the IEMs exhibited different conductivity-permselectivity tradeoff behaviors across the electrolyte solutions investigated. The disparate tradeoff trends are shown to be governed by counter- and co-ion valencies, and counterion diffusivity. The study sheds light on the principal factors underpinning the tradeoff and advances the understanding of attainable conductivity-permselectivity performance in more complex water chemistries that are pertinent for practical IEM applications

Advancing ion-exchange membranes to ion-selective membranes: principles, status, and opportunities

Ion-exchange membranes (IEMs) are utilized in numerous established, emergent, and emerging applications for water, energy, and the environment. This article reviews the five different types of IEM selectivity, namely charge, valence, specific ion, ion/solvent, and ion/uncharged solute selectivities. Technological pathways to advance the selectivities through the sorption and migration mechanisms of transport in IEM are critically analyzed. Because of the underlying principles governing transport, efforts to enhance selectivity by tuning the membrane structural and chemical properties are almost always accompanied by a concomitant decline in permeability of the desired ion. Suppressing the undesired crossover of solvent and neutral species is crucial to realize the practical implementation of several technologies, including bioelectrochemical systems, hypersaline electrodialysis desalination, fuel cells, and redox flow batteries, but the ion/solvent and ion/uncharged solute selectivities are relatively understudied, compared to the ion/ion selectivities. Deepening fundamental understanding of the transport phenomena, specifically the factors underpinning structure-property-performance relationships, will be vital to guide the informed development of more selective IEMs. Innovations in material and membrane design offer opportunities to utilize ion discrimination mechanisms that are radically different from conventional IEMs and potentially depart from the putative permeability-selectivity tradeoff. Advancements in IEM selectivity can contribute to meeting the aqueous separation needs of water, energy, and environmental challenges

Advancing the conductivity-permselectivity tradeoff of electrodialysis ion-exchange membranes with sulfonated CNT nanocomposites

Ion exchange membranes, IEMs, are widely applied in water and energy technologies, such as, electrodialysis for desalination and reverse electrodialysis for sustainable power generation. However, a tradeoff between conductivity and permselectivity constrains the efficiency of IEM-based technologies. The incorporation of rationally functionalized 1-dimensional nanomaterials as fillers into the polymer matrix offers opportunities to depart from this tradeoff. In this study, we develop nanocomposite cation exchange membranes by incorporating sulfonic acid-functionalized carbon nanotubes, sCNTs, in sulfonated poly(2,6-dimethyl-1,4-phenyleneoxide) polymer matrix. The fabricated nanocomposite IEMs exhibit improved conductivity while maintaining permselectivity. Intrinsic resistivity, the reciprocal of conductivity, is lowered with greater blending of sCNTs fillers, decreasing by approximately 25% with 20 w/w% incorporation of sCNTs, while permselectivity is effectively unchanged across the different degrees of sCNT incorporation (within 2% variation). Compared with pristine membranes, the conductivity-permselectivity tradeoff line of the fabricated nanocomposite membranes is advantageously advanced, thus improving overall performance. Further characterization and analysis show a percolating network of carbon nanotubes is achieved in the polymer matrix with 10 w/w% sCNTs. We posit that the improved effective ionic conductivity is attributed to the interconnected sCNT network reducing the tortuosity of the ion transport path. This study demonstrates the promise of percolating 1D nanomaterial networks to potentially advance the conductivity-permselectivity tradeoff governing conventional IEMs

Mobility of Condensed Counterions in Ion-Exchange Membranes: Application of Screening Length Scaling Relationship in Highly Charged Environments

Ion-exchange membranes (IEMs) are widely used in water, energy, and environmental applications, but transport models to accurately simulate ion permeation are currently lacking. This study presents a theoretical framework to predict ionic conductivity of IEMs by introducing an analytical model for condensed counterion mobility to the Donnan-Manning model. Modeling of condensed counterion mobility is enabled by the novel utilization of a scaling relationship to describe screening lengths in the densely charged IEM matrices, which overcame the obstacle of traditional electrolyte chemistry theories breaking down at very high ionic strength environments. Ionic conductivities of commercial IEMs were experimentally characterized in different electrolyte solutions containing a range of mono-, di-, and trivalent counterions. Because the current Donnan-Manning model neglects the mobility of condensed counterions, it is inadequate for modeling ion transport and significantly underestimated membrane conductivities (by up to ≈5× difference between observed and modeled values). Using the new model to account for condensed counterion mobilities substantially improved the accuracy of predicting IEM conductivities in monovalent counterions (to as small as within 7% of experimental values), without any adjustable parameters. Further adjusting the power law exponent of the screen length scaling relationship yielded reasonable precision for membrane conductivities in multivalent counterions. Analysis reveals that counterions are significantly more mobile in the condensed phase than in the uncondensed phase because electrostatic interactions accelerate condensed counterions but retard uncondensed counterions. Condensed counterions still have lower mobilities than ions in bulk solutions due to impedance from spatial effects. The transport framework presented here can model ion migration a priori with adequate accuracy. The findings provide insights into the underlying phenomena governing ion transport in IEMs to facilitate the rational development of more selective membranes. Keywords: Charge transport, Counterions, Electrical conductivity, Ions, Membrane

Inversion for Refractivity Parameters Using a Dynamic Adaptive Cuckoo Search with Crossover Operator Algorithm

Using the RFC technique to estimate refractivity parameters is a complex nonlinear optimization problem. In this paper, an improved cuckoo search (CS) algorithm is proposed to deal with this problem. To enhance the performance of the CS algorithm, a parameter dynamic adaptive operation and crossover operation were integrated into the standard CS (DACS-CO). Rechenberg’s 1/5 criteria combined with learning factor were used to control the parameter dynamic adaptive adjusting process. The crossover operation of genetic algorithm was utilized to guarantee the population diversity. The new hybrid algorithm has better local search ability and contributes to superior performance. To verify the ability of the DACS-CO algorithm to estimate atmospheric refractivity parameters, the simulation data and real radar clutter data are both implemented. The numerical experiments demonstrate that the DACS-CO algorithm can provide an effective method for near-real-time estimation of the atmospheric refractivity profile from radar clutter

PACT/RAX Regulates the Migration of Cerebellar Granule Neurons in the Developing Cerebellum

PACT and its murine ortholog RAX were originally identified as a protein activator for the dsRNA-dependent, interferon-inducible protein kinase PKR. Recent studies indicated that RAX played a role in embryogenesis and neuronal development. In this study, we investigated the expression of RAX during the postnatal development of the mouse cerebellum and its role in the migration of cerebellar granule neurons (CGNs). High expression of RAX was observed in the cerebellum from postnatal day (PD) 4 to PD9, a period when the CGNs migrate from the external granule layer (EGL) to the internal granule layer (IGL). The migration of the EGL progenitor cells in vivo was inhibited by RAX knockdown on PD4. This finding was confirmed by in vitro studies showing that RAX knockdown impaired the migration of CGNs in cerebellar microexplants. PACT/RAX-regulated migration required its third motif and was independent of PKR. PACT/RAX interacted with focal adhesion kinase (FAK) and PACT/RAX knockdown disturbed the FAK phosphorylation in CGNs. These findings demonstrated a novel function of PACT/RAX in the regulation of neuronal migration