Rapid Ion Exchange Research Articles

Li/Na exchange and Li active transport in human lymphoid cells U937 cultured in lithium media

Lithium transport across the cell membrane is interesting in the light of general cell physiology and becau- se of its alteration during numerous human diseases. The mechanism of Li4 transfer has been studied mainly in erythrocytes with a slow kinetics of ion exchange and therefore under the unbalanced ion distribution. Prolife- rating cultured cells with a rapid ion exchange have not been used practically in study of Li4 transport. In pre- sent paper, the kinetics of Li4 uptake and exit as well as its balanced distribution across the plasma membrane of U937 cells were studied at minimal external Li+ concentrations and after the whole replacement of external Na+ for Li+. It has been found that a steady state Li+ distribution is attained at a high rate similar to that for Na+ and Cl- and that Li+/Na+ discrimination under the balanced ion distribution at 1-10 mM external Li+ keeps on 3 and drops to 1 following blocking of the Na,K-ATPase pump by ouabain. About of 80% of the total Li+ flux across the plasma membrane under the balanced Li+ distribution at 5 mM external Li+ accounts for the equiva- lent Li+/Li+ exchange. The most part of the Li+ flux into the cell down the electrochemical gradient is a flux through channels and its small part may account for the NC and NKCC cotransport influxes. The downhill Li+ influxes are balanced by the uphill Li+ efflux involved in Li+/Na+ exchange. The Na+ flux involved in the countertransport with the Li+ accounts for about 0.5% of the total Na+ flux across the plasma membrane. The study of Li+ transport is an important approach to understand the mechanism of the equivalent Li+/Li+/Na+/Na+ exchange because no blockers of this mode of ion transfer are known and it cannot be revealed by electrophysiological methods. Cells treated with the medium where Na+ is replaced for Li+ are recommended as an object for studying cells without the Na,K-ATPase pump and with very low intracellular Na+ and K+ concentration.

Mesoscopic photosystems for solar light harvesting and conversion: facile and reversible transformation of metal-halide perovskites.

Recently, hybrid organic-inorganic metal halide perovskites have gained prominence as potent light harvesters in thin film solid-state photovoltaics. In particular the solar-to-electric power conversion efficiency (PCE) of devices using CH(3)NH(3)PbI(3) as sensitizer has increased from 3 to 20.1% within only a few years. This key material can be prepared by solution processing from PbI(2) and CH(3)NH(3)I in one step or by sequential deposition. In the latter case an electron capturing support such as TiO(2) is first covered with PbI(2), which upon exposure to a CH(3)NH(3)I solution is converted to the perovskite. Here we apply for the first time quartz crystal microbalance (QCMD) measurements in conjunction with X-ray diffraction and scanning electron microscopy to analyse the dynamics of the conversion of PbI(2) to CH(3)NH(3)PbI(3). Employing 200 nm thick PbI(2) films as substrates we discover that the CH(3)NH(3)I insertion in the PbI(2) is reversible, with the extraction into the solvent isopropanol occurring on the same time scale of seconds as the intercalation process. This offers an explanation for the strikingly rapid and facile exchange of halide ions in CH(3)NH(3)PbX(3) by solution processing at room temperature.

Na2FePO4F cathode utilized in hybrid-ion batteries: a mechanistic exploration of ion migration and diffusion capability

Layered Na2FePO4F is utilized as a cathode in hybrid-ion batteries in order to explore the ion migration and diffusion capability. It is the first time that the ion migration mechanism and capability in a hybrid-ion battery is investigated by considering the activation energies of different migration ways. It is proposed that a rapid ion exchange of Na+ ions on the Na(2) site of the crystal structure with Li+ ions can take place to produce the NaLiFePO4F phase and is firstly confirmed by first principle calculations. Li+ ion conduction in NaLiFePO4F is prone to be two-dimensional (2D) in the interlayer plane with an essentially restricted migration along the [010] direction for interlayer transport due to the much higher energy value (4.53 eV for sodium ion and 1.63 eV for lithium ion). Additionally, the 2D ways which need lower activation energies along [100] and [001] directions and the small volume variation during redox cycling are responsible for the large diffusion capability with a maximum magnitude of 10−10 cm2 s−1.

Fabrication and supercapacitive behavior of tetramethylammonium ion-intercalated MnO2 prepared by an exfoliation and self-assembly process

Layered birnessite-type manganese oxide is exfoliated into single-layer manganese oxide nanosheets. Then, the exfoliated manganese oxide nanosheets are spontaneously restacked by a self-assembly process, which is driven mainly by electrostatic interactions between the negatively charged manganese oxide nanosheets and the positively charged tetramethylammonium (TMA+) ions, yielding a new ordered layered structure of MnO2 (self-assembled MnO2) with a large interlayer spacing of 0.67nm, suggesting the formation of a layered hybrid form, intercalated with TMA+ ions in residence between the manganese oxide nanosheets. The large interlayer spacing facilitates rapid ion exchange and the intercalation and deintercalation of electrolyte cations. The supercapacitive behavior of the as-prepared self-assembled MnO2 is evaluated by cyclic voltammetry (CV), galvanostatic charge–discharge (CD) experiments and electrochemical impedance spectroscopy (EIS). The specific capacitance value is 180Fg−1 at a current density of 0.5Ag−1. After 10,000 cycles, the specific capacitance is still approximately 90% of the maximum specific capacitance. In addition, the intercalation of TMA+ ions between the manganese oxide nanosheets leads to a low charge-transfer resistance. These experimental results demonstrate that this self-assembled MnO2 is a promising candidate for use as electrode material in supercapacitor applications.

An efficient and green approach to prepare hydrophilic imidazolium ionic liquids free of halide and its effect on oxygen reduction reaction of Pt/C catalyst

An efficient process to prepare basic imidazolium ionic liquids (ILs) solution free of halide has been developed based on the rapid ion exchange between alkyl sulfate anion (ROSO3−, R=alkyl) and OH− in ethanol. Eight halide-free ILs with a flexible range of cations and anions were prepared by neutralizing the basic IL solution with corresponding acids. The viscosity, ionic conductivity or melting points of the ILs obtained by present method were examined and discussed. The results implied that the whole process is green since only ethanol and water were used as solvents and by-products were only solid KROSO3 and KY (Y=desired anion). Furthermore, a typical imidazolium ionic liquid, [Emim]HSO4, was synthesized by different precursors with various amounts of Br impurity, and its effect oxygen reduction reaction (ORR) of Pt/C catalyst was systematically investigated.

PROPERTIES OF PHILLIPSITE DERIVED FROM FLY ASH

The physico-chemical properties of the phillipsite derived from fly ash were investigated to evaluate the utility of the product in the various fields of industry and agriculture. CEC of the product was little affected by the suspension pH, and varied with the exchange cations in the following sequence : NH 4 + > K + > Ca 2+ . A rapid ion exchange reaction took place on the surface of the product. The synthesized phillipsite was stable below 250°C or above pH 3. The hypothetical chemical formula of the synthesized phillipsite would be suggested as follows : K 0.14 Na 0.86 (Al Si 1.84 O 5.68 ).nH 2 O. The proportion of the synthesized phillipsite in the product was estimated to be about 33.6%. It was considered that the product can be used for treating the poultry wastewater.

Nonlinear dynamics of capacitive charging and desalination by porous electrodes

The rapid and efficient exchange of ions between porous electrodes and aqueous solutions is important in many applications, such as electrical energy storage by supercapacitors, water desalination and purification by capacitive deionization, and capacitive extraction of renewable energy from a salinity difference. Here, we present a unified mean-field theory for capacitive charging and desalination by ideally polarizable porous electrodes (without Faradaic reactions or specific adsorption of ions) valid in the limit of thin double layers (compared to typical pore dimensions). We illustrate the theory for the case of a dilute, symmetric, binary electrolyte using the Gouy-Chapman-Stern (GCS) model of the double layer, for which simple formulae are available for salt adsorption and capacitive charging of the diffuse part of the double layer. We solve the full GCS mean-field theory numerically for realistic parameters in capacitive deionization, and we derive reduced models for two limiting regimes with different time scales: (i) in the "supercapacitor regime" of small voltages and/or early times, the porous electrode acts like a transmission line, governed by a linear diffusion equation for the electrostatic potential, scaled to the RC time of a single pore, and (ii) in the "desalination regime" of large voltages and long times, the porous electrode slowly absorbs counterions, governed by coupled, nonlinear diffusion equations for the pore-averaged potential and salt concentration.

Crystal Structure of the Light-Driven Chloride Pump Halorhodopsin from Natronomonas pharaonis

The light-driven chloride pump halorhodopsin from Natronomonas pharaonis (phR) crystallised into the monoclinic space group C2, with a phR trimer per the asymmetric unit. Diffraction data at 2.0-Å resolution showed that the carotenoid bacterioruberin binds to crevices between adjacent protein subunits in the trimeric assembly. Besides seven transmembrane helices (A to G) that characterise archaeal rhodopsins, the phR protomer possesses an amphipathic α-helix (A′) at the N-terminus. This helix, together with a long loop between helices B and C, forms a hydrophobic cap that covers the extracellular surface and prevents a rapid ion exchange between the active centre and the extracellular medium. The retinal bound to Lys256 in helix G takes on an all-trans configuration with the Schiff base being hydrogen-bonded to a water molecule. The Schiff base also interacts with Asp252 and a chloride ion, the latter being fixed by two polar groups (Thr126 and Ser130) in helix C. In the anion uptake pathway, four ionisable residues (Arg123, Glu234, Arg176 and His100) and seven water molecules are aligned to form a long hydrogen-bonding network. Conversely, the cytoplasmic half is filled mostly by hydrophobic residues, forming a large energetic barrier against the transport of anion. The height of this barrier would be lowered substantially if the cytoplasmic half functions as a proton/HCl antiporter. Interestingly, there is a long cavity extending from the main-chain carbonyl of Lys256 to Thr71 in helix B. This cavity, which is commonly seen in halobacterial light-driven proton pumps, is one possible pathway that is utilised for a water-mediated proton transfer from the cytoplasmic medium to the anion, which is relocated to the cytoplasmic channel during the photocycle.

Incorporation of Nanoparticles into Polyelectrolyte Multilayers via Counterion Exchange and in situ Reduction

We report a general method for incorporation of nanoparticles into polyelectrolyte multilayer (PEM) thin films by utilizing the excess charges and associated counterions present in the PEMs. Silver ions were introduced directly into multilayers assembled from poly(diallyldimethylammonium chloride) (PDDA) and poly(styrene sulfonate) (PSS), (PDDA/PSS)(n), by a rapid ion exchange process, which were then converted into silver nanoparticles via in situ reduction to create composite thin films. The size and the content of the nanoparticles in the film can be tuned by adjusting the ionic strength in the polyelectrolyte solutions used for the assembly. Spatial control over the distribution of the nanoparticles in the PEM was achieved via the use of multilayer heterostructure containing PDDA/PSS bilayer blocks assembled at different salt concentrations. Because excess charges and counterions are always present in any PEM, this approach can be applied to fabricate a wide variety of composite thin films based on electrostatic self-assembly.

Ion exchange behavior of plutonium(IV) on imidazolium nitrate immobilized resin

Imidazolium nitrate anchored on poly(styrene-divinylbenzene) co-polymer, Im-NO3, has been synthesized and evaluated for plutonium purification. The results are compared with those obtained using Dowex 1 × 4 anion exchange resin. The distribution coefficient (Kd) of Pu(IV) increased with increase in concentration of nitric acid, reached a maximum at 8 M, followed by decrease in Kd values. Rapid ion exchange of Pu(IV) followed by the establishment of equilibrium occurred within 100 min of equilibration and the data was fitted in to first order rate equation. Variation of distribution coefficient of Pu(IV) as a function of exchange capacity and nitrate ion concentration suggest the involvement of anion exchange mechanism is responsible for extraction. The apparent ion exchange capacity was 310 mg/g at 8 M nitric acid. The performance of the Im-NO3 under dynamic condition was assessed by column breakthrough experiments. Radiolytic degradation of Im-NO3 resin in presence and absence of nitric acid (8 M) was studied and the results are reported in this paper.

H2xMnxSn3‐xS6 (x = 0.11–0.25): A Novel Reusable Sorbent for Highly Specific Mercury Capture Under Extreme pH Conditions

AbstractThe H2xMnxSn3‐xS6 (x = 0.11–0.25) is a new solid acid with a layered hydrogen metal sulfide (LHMS). It derives from K2xMnxSn3–xS6 (x = 0.5–0.95) (KMS‐1) upon treating it with highly acidic solutions. We demonstrate that LHMS‐1 has enormous affinity for the very soft metal ions such as Hg2+ and Ag+ which occurs via a rapid ion exchange process. The tremendous affinity of LHMS‐1 for Hg2+ is reflected in very high distribution coefficient KdHg values (>106 mL g−1). The large affinity and selectivity of LHMS‐1 for Hg2+ persists in a very wide pH range (from less than zero to nine) and even in the presence of highly concentrated HCl and HNO3 acids. LHMS‐1 is significantly more selective for Hg2+ and Ag+ than for the less soft cations Pb2+ and Cd2+. The Hg2+ ions are immobilized in octahedral sites between the sulfide layers of the materials via Hg–S bonds as suggested by pair distribution function (PDF) analysis. LHMS‐1 could decrease trace concentrations of Hg2+ (e.g. <100 ppb) to well below the acceptable limits for the drinking water in less than two min. Hg‐laden LHMS‐1 shows a remarkable hydrothermal stability and resistance in 6 M HCl solutions. LHMS‐1 could be regenerated by treating Hg‐loaded samples with 12 M HCl and re‐used without loss of its initial exchange capacity.

A rapid ion exchange procedure that facilitates spectrophotometric assays of phosphorylated metabolites in potato extracts

A variety of metabolites are routinely assayed after perchloric acid extraction of plant tissues. A common technique uses coupled enzyme assays that produce or consume pyridine nucleotides together with spectrophotometric detection at 340 nm. Because of the presence of pigments in plant tissues, the high absorbance of such extracts usually limits the amount of extract that can be assayed spectrophotometrically. Here, we show that after batch adsorption with AG50WX8 (H+ form), the absorbance of potato root perchloric acid extracts at 340 nm is significantly reduced. This clean up procedure does not interfere with the assay or the recovery of anionic metabolites such as hexose phosphates. It therefore facilitates spectrophotometric assays of metabolites in plant extracts with high absorbance.

Rapid microwave-enhanced ion exchange process for the synthesis of LiNi0.5Mn0.5O2 and its characterization as the cathode material for lithium batteries

Download options Please wait... Article information DOI https://doi.org/10.1039/B822854J Article type Paper Submitted 19 Dec 2008 Accepted 08 Apr 2009 First published 18 May 2009 Download Citation J. Mater. Chem., 2009,19, 4536-4544 BibTex EndNote MEDLINE ProCite ReferenceManager RefWorks RIS Permissions Request permissions Rapid microwave-enhanced ion exchange process for the synthesis of LiNi0.5Mn0.5O2 and its characterization as the cathode material for lithium batteries B. Hwang, T. Yu, M. Cheng and R. Santhanam, J. Mater. Chem., 2009, 19, 4536 DOI: 10.1039/B822854J To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page. If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given. If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page. Read more about how to correctly acknowledge RSC content. Search articles by author Bing-Joe Hwang Tzu-Hung Yu Ming-Yao Cheng Raman Santhanam

A Mutation in Telethonin Alters Nav1.5 Function

Excitable cells express a variety of ion channels that allow rapid exchange of ions with the extracellular space. Opening of Na(+) channels in excitable cells results in influx of Na(+) and cellular depolarization. The function of Na(v)1.5, an Na(+) channel expressed in the heart, brain, and gastrointestinal tract, is altered by interacting proteins. The pore-forming alpha-subunit of this channel is encoded by SCN5A. Genetic perturbations in SCN5A cause type 3 long QT syndrome and type 1 Brugada syndrome, two distinct heritable arrhythmia syndromes. Mutations in SCN5A are also associated with increased prevalence of gastrointestinal symptoms, suggesting that the Na(+) channel plays a role in normal gastrointestinal physiology and that alterations in its function may cause disease. We collected blood from patients with intestinal pseudo-obstruction (a disease associated with abnormal motility in the gut) and screened for mutations in SCN5A and ion channel-interacting proteins. A 42-year-old male patient was found to have a mutation in the gene TCAP, encoding for the small protein telethonin. Telethonin was found to be expressed in the human gastrointestinal smooth muscle, co-localized with Na(v)1.5, and co-immunoprecipitated with sodium channels. Expression of mutated telethonin, when co-expressed with SCN5A in HEK 293 cells, altered steady state activation kinetics of SCN5A, resulting in a doubling of the window current. These results suggest a new role for telethonin, namely that telethonin is a sodium channel-interacting protein. Also, mutations in telethonin can alter Na(v)1.5 kinetics and may play a role in intestinal pseudo-obstruction.

Connexin 32 and 43 gap junctions differentially modulate tenocyte response to cyclic mechanical load

Gap junctions allow rapid exchange of ions and small metabolites between cells. They can occur between connective tissue cells, and in tendons there are two prominent types, composed of connexin 32 or 43. These form distinct networks – tenocyte rows are linked by both longitudinally, but only by connexin 43 laterally. We hypothesised that the junctions had different roles in cell response to mechanical loading, and measured the effects of inhibitors of gap junction function on secretion of collagen by tenocyte cultures exposed to mechanical strain. Chicken tendon fibroblasts were exposed to cyclic tensile loading in the presence or absence of general gap junction inhibitors (halothane or the biomimetic peptide gap27), or antisense oligonucleotides to chicken connexin 32 or 43. Untreated cultures increased collagen secretion by around 25% under load. Halothane eliminated this response but caused cell damage. Gap27 peptide reduced secretion but maintained loading effects – strained cultures secreting more collagen than unstrained. Antisense downregulation showed major differences between connexins: antisense 32 reduced, and antisense 43 increased, collagen secretion. In both cases loading effects were maintained. This shows that (i) gap junctional integration of signals is important in load response of tenocyte populations – mechanotransduction occurs in individual cells but integration of signals markedly enhances it and (ii) communication via connexin 32 and 43 have differential effects on the load response, with connexin 32 being stimulatory and connexin 43 being inhibitory. Cells coordinate and control their response to mechanical signals at least in part by differential actions of these two types of gap junction.

Ion exchanger using electrospun polystyrene nanofibers

Polymer nanofiber ion exchangers (PNIE) are produced by electrospinning from solutions of dissolved polystyrene followed by sulfonation processes. A polystyrene nanofiber cation exchanger was developed for high ion exchange capacity, and rapid ion exchange velocity. In this paper, new experimental results investigating the performance of PNIE are presented in relation to the relevant parameters (ion exchange capacity (IEC), water uptake, and surface morphology). The ion exchange capacity (IEC) and water uptake of the PNIE depend upon the sulfonation time. The PNIE sample with 30 min sulfonation time showed the maximum IEC of 3.74 mmol/g and maximum water uptake of 0.77 g H 2O/g-dry-PNIE at 40 min sulfonation time.

Preparation of Cation Exchanger Using Electrospun Polystyrene Nanofiber

We studied a new ion exchanger for high ion exchange capacity (IEC) and rapid ion exchange. Polystyrene nanofiber ion exchangers (PSNIEs) were prepared by electrospinning from solutions of dissolved polystyrene followed by sulfonation. Coating and sulfonation were used to modify the glass fiber surface with polystyrene to produce cation exchanger fiber (CEF). We present new experimental results on the performance of PSNIE and CEF related to parameters of IEC, water uptake, and surface morpoholgy. IEC and water uptake of PSNIE depend on sulfonation time. IEC reached 3.74 mmol/g at relatively high water uptake of 0.6 to 0.77g H2O/g-dry-PNIE. IEC and water uptake of CEF reached 3.61mmol/g-CEF and 0.25g H2O/g-dry-CEF.

Selected Papers from HNICEM 2005

HNICEM is a biennial international conference of experts in the fields of Robotics, Nanotechnology, Information Technology, Control and Communication, Environment, and Management. This special issue presents 11 articles selected from HNICEM 2005 that will provide valuable references for researchers and practitioners. The first article presents new content-based image retrieval based on the visual keys concept. Visual keys are defined as representative regions extracted from an image database and are constructed using image feature clustering. The second article presents interactive video recording and playback technique originally developed for biomedical multimedia training. The third article proposes techniques for determining motion parameters based on complex number expression of the rotation matrix. The fourth article studies the learning behavior of Genetic Algorithm and its potential in real time non-linear control. The effects of different parameters used in the GA for its learning are analyzed. The fifth article presents a Coordinated Hybrid Agent (CHA) framework for the control of Multi-Agent Systems (MASs) applied to a heterogeneous multi-agent such as a mobile robot, an overhead crane, and a robot manipulator. The sixth article presents an algorithm that emulates human inference in deducing root causes, avoiding intermediary causes and anticipating subsequent moves. The seventh article proposes a technique to create Intelligent Distributed Robotic Systems (IDRS) that show smart behavior using a wrapper-components approach. The eighth article presents an autonomous mobile robot with neural network (NN) vision that searches for and collects golf balls in an open or indoor golf driving range. The ninth article demonstrates the technological benefits of miniaturizing machine tools in the context of machine stiffness and accuracy. It also presents the design philosophy and configuration of a 4-axis miniaturized vertical machining center with a positioning accuracy of 4 to 10nm. The tenth article investigates a new type of ion exchanger for high ion exchange capacity (IEC) and rapid ion exchange velocity. Experimental results demonstrate the performance of polystyrene nanofiber ion exchangers (PSNIE) and cation exchanger fiber (CEF). The eleventh and last article presents the architectural design of a Multiservice Provisioning Platform (MSPP) for WiMAX over SONET/SDH. It involves networking existing technologies to deliver a solution that caters to a unique situation favoring wireless access networks to a fully cabled system. We extend our warmest thanks and deepest gratitude to the distinguished authors and reviewers who have contributed to this special issue for their outstanding contributions and cooperation. We are also grateful to Prof. Toshio Fukuda and Prof. Kaoru Hirota, chief editors of JACIII, for inviting me to serve as Guest Editor of this Journal.

Drug release properties of polyethylene-glycol-treated ciprofloxacin-Indion 234 complexes

The polyethylene glycol (PEG) treatment of ciprofloxacin-Indion 234 complex was aimed to retard rapid ion exchange drug release at gastric pH. Ciprofloxacin loading on Indion 234 was performed in a batch process, and the amount of K(+) in Indion 234 displaced by drug with time was studied as equilibrium constant K(DM). Drug-resin complex (DRC) was treated with aqueous PEG solution (0.5%-2% wt/vol) of different molecular weights (MWs) for 2 to 30 minutes. The PEG-treated ciprofloxacin-Indion 234 complex was evaluated for particle size, water absorption time, and drug release at gastric pH. During drug loading on Indion 234, the equilibrium constant (K(DM)) increased rapidly up to 20 minutes with efficient drug loading. Increased time of immersion of the drug resinate in PEG solutions significantly retained higher size particles upon dehydration. The larger DRC particles showed longer water absorption times owing to compromised hydrating power. The untreated DRC showed insignificant drug release in deionized water; while at gastric pH, ciprofloxacin release was complete in 90 minutes. A trend of increased residual particle size, proportionate increase in water absorption time, and hence the retardation of release with time of immersion was evident in PEG-treated DRC. The time of immersion of DRC in PEG solution had predominant release retardant effect, while the effect of molecular weight of PEG was insignificant. Thus, PEG treatment of DRC successfully retards ciprofloxacin ion exchange release in acidic pH.

Ion Exchange Studies of Cerium (III) on Uranium Antimonate

Ion exchange of cerium on uranium antimonate (USb) from nitric acid medium was studied. The distribution coefficient of ~19,000 mL/g was obtained for ion exchange of cerium in 0.1 M nitric acid and it decreased with increase in the concentration of nitric acid. Rapid ion exchange of cerium in the initial stages of equilibration followed by the establishment of equilibrium occurs after one hour. Ion exchange data were fitted into both Langmuir and Freundlich adsorption models using non-linear regression. The enthalpy change accompanied by ion exchange of cerium was determined by the temperature variation method. The performance of the ion exchanger under dynamic condition was assessed by following a breakthrough (BT) curve and the BT curve was fitted using Thomas equation.