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PubMedDate not supplied

A combination of ion exchange and electrochemical reduction for nitrate removal from drinking water. Part I: nitrate removal using a selective anion exchanger in the bicarbonate form with reuse of the regenerant solution.

The process of selective nitrate removal from drinking water by means of ion exchange was studied. A commercial strong base anion exchanger with triethylammonium (-N+Et3) functional groups was used in the bicarbonate (HCO3-) and carbonate (CO3(2-)) form. The aim of this study was to optimize ion-exchanger regeneration in view of the subsequent electrochemical reduction of nitrates in the spent regenerant solution. The effects of ion-exchanger form, concentration of regenerant solution, and presence of nitrates, chlorides, and sulphates in the regenerant solution were studied. The strong base anion exchanger in HCO3- form that was investigated was able to treat 270 bed volumes of model water solution containing 124 mg dm(-3) nitrates. To achieve adequate regeneration of the saturated anion exchanger, it is necessary to use approximately 30 bed volumes of fresh 1-M sodium bicarbonate (NaHCO3) regenerant solution. The presence of residual 50-mg dm(-3) nitrates in the regenerant solution, treated by electrolysis, resulted in an increase in the dose of regenerant solution to 35 bed volumes and a decrease in the subsequent sorption run of approximately 13%. The volume of applied regenerant solution was high, but the consumption of NaHCO3 for regeneration was low.

Anions↗
PubMed1990

Formulation parameters affecting the preparation and properties of microencapsulated ion-exchange resins containing theophylline.

A method of microencapsulating theophylline ion-exchange resins with ethylcellulose was developed to produce smooth and uniform coats which were predominantly mononucleated. This was achieved by controlling the amount of ethylcellulose and the particle size, and through the use of a protective colloid, polyisobutylene. The rate of release of theophylline was influenced by the ion-exchange resin crosslinking, the amount of ethylcellulose, and the smoothness of the coat. Mesh size and polyisobutylene did not appear to affect the rate in a regular manner. It was found that the release rate from coated resins with low crosslinking followed a logarithmic plot, indicating membrane-controlled release, whereas coated resins with high crosslinking fitted a t1/2 plot, suggesting particle diffusion control.

Capsules↗
PubMed1959

An enzymatic ion exchange model for active sodium transport.

An enzymatic ion exchange model for active sodium transport is described. Kinetic equations relating net flux to time, and to concentration difference across the actively transporting membrane are derived. The second of these equations is tested, using the isolated frog skin in the "short-circuit" apparatus of Ussing. Reasonable linearity, as predicted by this equation, is observed. The passive permeability coefficient for Na(+), is calculated as 5.3 x 10(-4) +/- 5.3 x 10(-4) cm./hr. If cholinesterase is assumed to be the enzyme responsible for transport, the activity required to account for the observations reported here is 17.7 x 10(-4) mmoles/cm.(2)/hr.

Biological Transport↗
PubMed1991

Enrichment of biologically active U1 small nuclear RNAs by ion-exchange high-performance liquid chromatography.

The use of ion-exchange high-performance liquid chromatography in conjunction with preparative electrophoresis to facilitate the purification of biologically active snRNAs is described. Separation of total nuclear RNA from a Bombyx mori cell line was done with a Bio-Rad MA7 plasmid column in a HRLC 500 system. Individual fractions were subjected to electrophoresis through 14% polyacrylamide gels for identification. High levels of U1 RNA were confirmed by Northern analysis with a human U1 probe. Biological activity of RNAs from the column was demonstrated by their ability to incorporate 32P-AMP at the 3' end. Ion-exchange chromatography provides a rapid, automated method for purifying large amounts of RNAs that can then be utilized in further studies.

Adenosine Monophosphate↗
PubMed2004

Ion exchange at a surface monolayer.

Total reflection total conversion electron yield X-ray absorption fine structure is applied to the evaluation of ion exchange occurring at the surface monolayer of two-tailed ammonium ions. X-ray absorption measurements at a Br K-edge allow us to detect ion-exchange equilibria between Br- and Cl- added in a subphase. The ion-exchange selectivity of Br- over Cl- basically increases as the monolayer is compressed, indicating that Cl- is selectively squeezed out by compression because of its larger hydrated ionic radius.

Absorption↗
PubMed2004

Development of new toxicity identification evaluation by assessing toxicity reduction on adsorption and ion-exchange treatments.

A new toxicity identification evaluation method for water exhibiting toxicity has been suggested by evaluating toxicity reduction resulting from adsorption and ion-exchange treatments. Adsorption using various adsorbents such as activated carbon, chitosan and zeolite, and ion-exchange using cationic and anionic ion-exchange resins were performed. In addition, toxicity was evaluated by a cell survival test using human liver cancer origin cells (HepG2), and the dose response data was applied to treatment characteristics. The amount of toxicity adsorbed by the various adsorbents was defined based on adsorption isotherm. Parameters of the toxicity adsorption isotherm provided information that allowed us to identify the toxicity-controlling chemicals in environmental water containing various chemicals. The method is promising for water quality management because it can be used to identify toxicity-controlling chemicals among various environmental pollutants.

Adsorption↗
PubMed2004

Carbon and SiC macroscopic beads from ion-exchange resin templates.

A method for preparing carbon and SiC macroscopic beads using ion-exchange resins as a macrotemplate that determines the macroshape and the pore structure of the product materials is reported. First, silicates are ion-exchanged into the resins to prevent the resin from collapsing during subsequent carbonization and allow them to be used as precursors for SiC formation. SiC is prepared via carbothermal reduction of carbon/silica composite beads obtained upon carbonization of the resin/silicate in an inert atmosphere. Finally, silica is removed by HF etching. Very high-surface area (1670-2026 m2 g-1) micro- or micro-/mesoporous carbon beads and relatively high-surface area (35-63 m2 g-1) macro- and meso-/macroporous SiC beads were prepared by the described method. The pore structure and the macroshape of the particles were controlled by the type of ion-exchange resins employed, gel or macroreticular.

Journal Article↗
PubMed2006

The delivery of ketoprofen from a system containing ion-exchange fibers.

A postulated model for transdermal delivery using ion-exchange fibers as controlling device was designed, and the main objective of this study was to assess the rationality of the model. The release rates of ketoprofen from the carbopol-based gel vehicles containing ion-exchange fibers to which the ketoprofen had been bound have been determined across 0.22 microm microporous membrane. The fluctuation of the release rate of ketoprofen from the vehicles was much lower compared with that of simple gels, though the cumulative amount of ketoprofen delivery was less. Additional ions could increase the rate and extent of ketoprofen delivery. The iontophoretically assisted transport of ketoprofen across rat skin was also studied and found to be favorable to ketoprofen permeation. According to the tested model, the ion-layer could enhance the ketoprofen delivery and satisfactory results were achieved.

Administration, Cutaneous↗
PubMed1976

Work-induced potassium changes in skeletal muscle and effluent venous blood assessed by liquid ion-exchanger microelectrodes.

Using liquid ion-exchanger semimicroelectrodes with a side pore, we measured changes of extracellular potassium concentration (Ke+) in adult rabbit and cat gastrocnemius muscles and in venous effluent blood flowing from the cat gastrocnemius muscle during various bouts of activity induced by sciatic nerve stimulation. 1. Isometric tetanic contractions (at 50 Hz) of various durations caused transient accumulation of Ke+ which was non-linearly related to the duration of muscle activity. The peak values of Ke+ in response to muscle stimulation were analogous in rabbits and cats, attaining values, e.g. after a 20-sisometric tetanus, between 8-9 mEq/1K+ in both species. 2. Potassium concentration in venous effleunt blood (K+ven) was transiently increased after isometric tetani. Since blood flow was measured at the same time, it was possible to calculate the amount of K+ lost by the muscle after tetani of various durations. A 32 g gastrocnemius muscle of the cat, for example, loses 9.36 +/- 1.52 muEqK+ after a 20-s isometric tetanus, which corresponds roughly to 0.5% of the total muscle potassium content. The loss of K+ in this muscle was 29.3 pEq K+ /impulse/100 g fresh muscle tissue. 3. There was no evident difference between the amount of K+ released during isometric tetani, or tetanic contractions performed under isotonic conditions. Single twitches evoked by indirect stimulation at 1 HZ for several minutes also induced a small rise in K+ven. 4. If the loss of K+ from the muscle into the blood stream is transiently prevented by arterio-venous occlusion installed immediately before a 10-s isometric tetanus, most K+ is released subsequently when blood flow is renewed, if the occlusion lasts for 20-25 s. It is not until blood flow is occuded for 40-60 s that most K+ is apparently resorbed and only a minor portion is released and is to be found in the venous blood. 5. The transient accumulation of muscle extra-cellular potassium may locally affect nerve endings, skeletal and smooth muscle cells.

Animals↗
PubMed2001

On-capillary ion-exchange preconcentration of inorganic anions in open-tubular capillary electrochromatogrpahy with elution using transient-isotachophoretic gradient. 2. Characterization of the isotachophoretic gradient.

Diffuse transient-isotachophoretic boundaries can be used as an elution gradient of increasing eluotropic strength to elute inorganic anions that have been preconcentrated on an open-tubular ion-exchange stationary phase prior to electrophoretic separation. The generation and characteristics of these gradients for elution after preconcentration have been investigated. The gradients are generated by placing a low-mobility, weak ion-exchange competing anion in the capillary (weak electrolyte, WE), and a high-mobility, strong ion-exchange competing anion in the electrolyte vials (strong electrolyte, SE). Application of voltage establishes a diffuse boundary with the composition changing from the weak anion to the strong anion. Comparison of elution gradients generated with different electrolyte systems was accomplished by comparing the eluotropic strength (a function of eluent concentration, ion-exchange selectivity coefficient, and charge) and the shape of the profile as it changes from WE to SE. The ion-exchange selectivity coefficient of the SE competing anion is important in establishing a sharp change in elution strength. A large difference in mobility between the WE and SE competing anions gives an SE with a higher final eluotropic strength, but the slope of the gradient is shallower. This results in a reduction in the efficiency of analyte focusing. To ensure maximum focusing efficiency, the WE and SE electrolytes should be selected such that the SE has the highest possible eluotropic strength for a given concentration of WE. The SE competing anion should also have a sufficiently low electrophoretic mobility to ensure focusing for the maximum number of analytes, and the mobility difference between the WE and SE competing anions should be as small as possible.

Journal Article↗
PubMed1966

The steady-state properties of an ion exchange membrane with mobile sites.

A study of the properties of the steady states of a system composed of two solutions separated by an ion exchange membrane having mobile sites is presented. It is assumed that the membrane is impermeable to coions; the solutions contain no more than two species of counterions, both of the same valence; and no flow of bulk solution occurs. Assuming that all ions are completely dissociated, behave ideally, and have constant mobilities throughout the membrane, explicit expressions are derived for the steady states of the electric current, individual fluxes, and concentration profiles as functions of the compositions of the solutions and of the difference of electric potential between them. The derived expressions are compared with those for an ion exchange membrane having fixed sites; and it is found that the expressions of certain quantities, such as the difference of electric potential between the two solutions for zero current or the ratio of the fluxes of the counterions as functions of the external parameters of the system, are the same for both types of membranes. On the other hand, differences in the behavior of the two types of membranes are found from other expressions-for example, the current-voltage relationship. In the mobile site ion exchanger the current asymptotically approaches finite limiting values for high positive and negative voltages while in the fixed site ion exchanger it is the conductance which approaches finite limiting values.

Biological Transport↗
PubMed2002

Lead removal from synthetic leachate matrices by a novel ion-exchange material.

This paper discusses the application of a novel polyacrylate-based ion-exchange material for the removal of Pb ions from water. Preliminary testing includes the establishment of the operating pH range, capacity information, and the effect of Ca2+ and anions in the matrix. Batch testing with powder indicates slightly different optimal operational conditions from those used for column testing. The ion-exchanger is excellent for removing Pb from aqueous solutions.

Acrylic Resins↗
PubMed2002

Influence of chloride ion exchange on the permeability and drug release of Eudragit RS 30 D films.

The objective of this study was to investigate the permeability of the cationic acrylic copolymer Eudragit RS 30 D as a function of the anionic buffer species of the dissolution media with special emphasis on the chloride ion exchange of the polymer. Indirect impedance measurement on isolated Eudragit RS films was used to investigate the mechanisms controlling membrane permeability. The chloride ion exchange was determined using capillary electrophoresis during dissolution testing of Eudragit RS 30 D-coated theophylline beads. The dissolution media investigated included various concentrations of sodium acetate, succinic acid and di-sodium succinate. The results of this study demonstrated that the degree of polymer swelling and related drug release was a function of the chloride counterion interaction with the polymer's quarternary ammonium groups. Chloride exchange during the dissolution test with other anions including acetate or succinate ions, resulted in significant changes in the polymer diffusion properties. The ion exchange proved to be the responsible mechanism of controlling polymer permeability as a function of anionic species and concentration. The order of anion permeability enhancing effect was acetate>mono-succinate>disuccinate. The ion exchange could be inhibited significantly by the addition of chloride ions to the dissolution medium.

Acrylic Resins↗
PubMed2007

Ion exchange chromatography of antibody fragments.

Effects of pH and conductivity on the ion exchange chromatographic purification of an antigen-binding antibody fragment (Fab) of pI 8.0 were investigated. Normal sulfopropyl (SP) group modified agarose particles (SP Sepharosetrade mark Fast Flow) and dextran modified particles (SP Sepharose XL) were studied. Chromatographic measurements including adsorption isotherms and dynamic breakthrough binding capacities, were complemented with laser scanning confocal microscopy. As expected static equilibrium and dynamic binding capacities were generally reduced by increasing mobile phase conductivity (1-25 mS/cm). However at pH 4 on SP Sepharose XL, Fab dynamic binding capacity increased from 130 to 160 (mg/mL media) as mobile phase conductivity changed from 1 to 5 mS/cm. Decreasing protein net charge by increasing pH from 4 to 5 at 1.3 mS/cm caused dynamic binding capacity to increase from 130 to 180 mg/mL. Confocal scanning laser microscopy studies indicate such increases were due to faster intra-particle mass transport and hence greater utilization of the media's available binding capacity. Such results are in agreement with recent studies related to ion exchange of whole antibody molecules under similar conditions.

Adsorption↗