Ion-exchange Media Research Articles

Time- and pH-dependent leaching of ions from deciduous and coniferous foliage

Leaching of ions from foliage of black gum (Nyssasylvatica Marsh.), chestnut oak (Quercusprinus L.), and white pine (Pinusstrobus L.) in response to increasing exposure time to and concentration of H+ was examined in a laboratory study. Ten individual leaves and needle bundles were exposed to H+ solutions at pH 3.0, 4.0, and 5.6 for periods of 5, 50, 500, and 1000 min. Increases in the removal of Ca2+ and Mg2+ from all species tested were strongly related to increases in experiment duration and H+ concentration, confirming the role of ion exchange in the removal of these ions from the forest canopy. Removal of Na+ and K+ did not appear to be strongly influenced by ion exchange. Positive relations between SO42− and H+ (and presumably Cl−) for the deciduous species suggest that anion exchange may be involved in the removal process. Given the relatively small number of anion exchange sites on cuticles, and because SO42− is the primary anion in both rain and throughfall, anion exchange is not likely to contribute significant amounts of anions under natural conditions. It is difficult to extrapolate results from an experiment of this type to what might be expected under natural conditions. However, the response of whole leaves and needles fits that expected based on the ion selectivity of the cuticle as a carboxylic acid ion-exchange medium and holds promise for understanding the processes involved in ion leaching from forest canopies.

Evidence that yeast cell wall debris can separate proteins by ion‐exchange during cell lysis

In this communication, data are presented suggesting that cell wall debris produced by enzymatic lysis can aid in the recovery of intracellular proteins. Specifically, cell wall debris produced by the enzymatic lysis of the yeast Saccharomyces cerevisiae is shown to exhibit characteristics of an ion-exchange medium, and that judicious pH control of the lysis buffer can yield some degree of protein separation based upon the isoelectric pH of the proteins

Aquaculture water treatment by ion exchange: Continuous ammonium ion removal with clinoptilolite

The performance of Hector Clinoptilolite as an ion exchange medium during uptake and regeneration in small continuous fixed bed columns is examined. The model system used was the multi ion system Na + NH 4 + K +Mg 2+Ca 2+ in the presence of Cl − as the co-ion. The objective of the work was to examine the suitability of clinoptilolite as an exchange medium for fish farm water treatment in fresh water recycle systems. Ammonia uptake, the most important criterion used to assess performance, was strongly influenced by ammonium ion concentration in the feed and in the concentration range studied (1–5 mg NH 4N litre −1) the exchange capacity for ammonium varied linearly with feed concentration. The presence of calcium ion appeared to depress the capacity of the clinoptilolite after the first uptake/regeneration cycle. The multi cycle use of clinoptilolite may be inhibited by this loss of capacity and the relatively inefficient rinsing characteristics which were exhibited.

Separation of cis and trans isomers of unsaturated fatty acids by high-performance liquid chromatography in the silver ion mode

High-performance liquid chromatography in the silver ion mode has been adapted for the analysis of positional and geometrical isomers of fatty acids, and especially for the determination of trans unsaturation in fats and oils. The stationary phase consisted of an ion-exchange medium, which was a silica gel matrix with bonded sulphonic acid moieties, loaded with silver ions. Fatty acids were converted into phenacyl esters so that UV detection at 242 nm could be used. The mobile phase for the separation of rans- and cis-monoenoic isomers was 1,2-dichloroethane—dichloromethane (1:1, v/v), and 0.5% of acetonitrile was added in order to elute geometrical isomers of linoleic and linolenic acids. Gradient elution was employed for mixtures containing a full range of components. Provided that the column temperature was kept constant, the retention times were reproducible over long periods of time, and the response of the detector was related in a rectilinear manner to the molar proportion of each fatty acid, irrespective of the structure. Monoenoic isomers from commercially hydrogenated soybean oil were identified by gas chromatography—mass spectrometry of picolinyl ester derivatives. The method was applied to natural fats containing trans double bonds, i.e., sheep adipose tissues from three sites, to commercial margarines' and cooking fats, and to soybean oil, rapeseed oil and a fish oil at various times during hydrogenation.

Absorption, magnetic circular dichroism and magnetic circular polarization of luminescence studies of Ru(bpy)2+3 and complexes with a Di(ethoxycarbonyl)-substituted bipyridine ligand as a probe of rigid environments

The ruthenium tris(bipyridine)(RBY) chromophore and mono di(ethoxycarbonyl) derivatives have been studied by low temperature absorption, magnetic circular dichroism (MCD) and magnetic circular polarization of luminescence (MCPL) spectroscopy in a range of rigid systems of varying character. These include 4:1 ethanol–methanol glass (EM), poly-(methylmethacrylate)(PMMA), poly(vinyl alcohol)(PVA) and Nafion, a transparent ion exchange medium based on poly(tetrafluoroethane). Absorption and MCD spectra of RBY show some variation in spectral width with medium, but the luminescence and MCPL spectra show more significant variations in position, magnitude and profile as a function of environment. The reduction in MCPL and profile changes in luminescence for RBY in Nafion are taken as evidence for a strong (environmentally induced) distortion in the excited state, giving some degree of localization in this environment. This is matched with the markedly increased photo-chemical activity of RBY in the Nafion environment. MCD spectra of the substituted complexes are markedly different to those of the parent RBY, indicative of a dominant low symmetry potential influencing the metal t52 core in the excited state. Luminescent states are less (but significantly) affected, indicative of their largely spin-derived magnetic moments.

Separation of molecular species of triacylglycerols by high-performance liquid chromatography with a silver ion column

Molecular species representative of the wide range of triacylglycerols occurring in nature, ranging from relatively saturated fats such as that from sheep adipose tissue through polyunsaturated seed oils, including sunflower and linseed oils, to an oligounsaturated fish oil, have been resolved by high-performance liquid chromatography in the silver ion mode. The stationary phase consisted of an ion-exchange medium, which was a silica gel matrix with bonded sulphonic acid moieties, loaded with silver ions. The mobile phase for the more saturated fractions was a gradient of acetone into 1,2-dichloroethane-dichloromethane, then acetonitrile was introduced to elute polyunsaturated fractions. A mass detector was employed to monitor separations. Fractions were collected via a stream-splitter for identification and quantification by gas chromatography as methyl esters. Excellent resolution was obtained on the silver ion column with no contamination of fractions with silver ions, while the column was stable and retained its activity in prolonged use.

Properties of Novel Selective Ion Exchangers for Nuclear Plant Applications

A new family of ion exchange and sorption media has been developed and applied for the removal of radioactive contaminants from aqueous streams in nuclear power plant operations. The general principle in the development of these materials is optimization of their selectivity for species that significantly contribute to the radioactivity of these streams (e.g., cesium, iodine, and cobalt) in the presence of a large excess of other ions (e.g., sodium, potassium, magnesium, calcium, chlorine, and SO4). This results in improved effective capacity and service lifetime of these new materials compared with the performance of conventional broad-spectrum ion exchange resins. Other advantages include higher decontamination factors, shorter contact times, greater stability, and convenience of disposals. Examples of the new materials include Durasil™ 10, a high-capacity ion exchange medium for cesium and strontium, and Durasil™ 60 and 70, which are highly effective in the removal of iodine and cobalt, respectively. The performance of these new media has been characterized in laboratory studies, engineering-scale demonstration tests, and 1 to 2 yr of experience with the Durasil™ media in routine waste-water treatment in several nuclear power plants.

A method for quick estimation of129I by low energy photon spectrometry

Methods have been developed for the routine analysis of129I in effluents of fuel reprocessing plants using 29.4 keV xenon X-rays. Direct counting methods have been standardized in liquid medium as well as in ion-exchange resin medium. A low energy photon spectrometry Ge detector system and a well-type NaI/Tl/ detector are used for direct counting. Attenuation of xenon X-rays in liquid medium as well as in ion-exchange resin medium have been studied. Sample size is optimized by studying the self attenuation of xenon X-rays in the sample. Activity as low as 1 Bq could be detected with an accuracy of 11% and 30% using LEPS and NaI/Tl/counting systems, respectively.

The Preparation and Properties of Acrylic and Methacrylic Acid Grafted Cellulose Prepared by Ceric Ion Initiation. Part I. Preparation of the Grafted Cellulose

Abstract The ceric ion method has been used to graft acrylic acid directly onto cellulose with a minimum amount of homopolymer. The method utilizes the pretreatment of the cellulose with ceric ammonium nitrate followed by washing out any excess of the catalyst. Oxygen can be present with the pretreatment step, but must be excluded during the grafting reaction itself. The process, which is entirely aqueous in nature, would appear to be quite practical on a large scale. Wet strengthened papers which are essential for the use of the grafted products as ion-exchange media can also be grafted but with adequate but lower yields than with the untreated paper. Apart from ion exchange, the products are of considerable potential value as water sorbing agents. Methacrylic acid gave lower grafting yields than acrylic acid, but these were much improved at higher temperatures.

Evaluation of a porous silica-based ion-exchange medium for the production of protein fractions from rennet- and acid-whey

SUMMARYThe use of a silica-based ion-exchange medium for the recovery of protein from wheys prepared by treatment with rennet or with acid has been investigated. The protein capacity of the medium whilst maintaining an adsorption greater than 75% during the passage of rennet-and acid-whey was 0·079 and 0·053 g/g respectively. Bovine serum albumin (BSA), α-lactalbumin (α-la) and β-lactoglobulin (β-lg) adsorbed from acid-whey were mostly recovered in yields greater than 93% in an undenatured form essentially free of lactose and milk salts by elution using 0·1 M-HC1. With rennet-whey, BSA and part of the α-la were not recovered in the native form, probably because of proteolysis during elution by enzymes originating in the rennet used in the manufacture of the whey. There was, however, no effect on the recovery of native β-lg adsorbed by the medium. An unidentified proteinaceous fraction, thought to be of casein origin, was also adsorbed and recovered from rennet-whey. Fractions of the adsorbed proteins could not be obtained by eluting with a gradient increase in NaCl concentration. Nevertheless, purified β-lg was obtained by passing a large quantity of whey through the medium. This protein had a high affinity for the functional groups of the medium, to the extent that other proteins initially adsorbed were subsequently displaced. Unidentified proteinaceous material in rennet-whey also had a high affinity for the functional groups of the ion exchanger but most of this fraction could be removed by a pretreatment procedure which involved passing the whey through the medium at pH 5·0; unidentified material was selectively adsorbed at this pH. The medium could also be used to produce a fraction containing a mixture of BSA and α-la but it was not possible to separate these proteins.

A convenient equilibrium separation method for competitive protein-binding assay of corticosterone in rat serum

Competitive protein-binding assays for corticosterone have typically employed adsorption methods for separation of free and bound ligand. Such methods often impose inconveniently strict limits upon incubation time and temperature, due to the necessity of minimizing the progressive loss of bound ligand to the adsorbent. This paper describes a convenient equilibrium assay method in which a centrifugable ion-exchange medium, DEAE-cellulose , is used to separate the corticosteroid binding globulin of rat serum and ligand bound to it, from free ligand. This method allows great latitude in incubation time and temperature, and is therefore very convenient for processing large numbers of samples. An assay optimized for use over the 50–1000 pg range showed midrange precision averaging 12% c.v., an interassay variation of 15%, and high specificity.

Radiolytic Gas Generation and Oxygen Depletion in Ion Exchange Materials

ABSTRACTThe process of ion exchange is used extensively throughout numerous industries where water of extremely high purity is required. Government and commercial nuclear power facilities are typical of this, and have applied ion exchange processes for the removal of radioactive ions from aqueous solutions. When water is decontaminated in this fashion the ion exchange medium becomes saturated with the radioactive ions from solutions, and is then stored as radioactive waste in standard burial facilities. During this indefinite storage period, the chemical changes which occur in the ion exchange medium may result in oxygen depletion and gas generation within the storage vessel, and subsequent loss of integrity. It is the object of this work to investigate the early phases of radiolytic oxygen depletion and gas evolution through experimental procedure and observation. The results of this work will then be analyzed with respect to applications for the storage of radioactive ion exchange waste.

Removing metals from waste solutions with low rank coals and related materials

Ion exchange media were produced by contacting brown coal, peat or wood sawdust with a solution of calcium hydroxide, preferably as an aqueous slurry of lime. The resultant calcium loading on the media, which ranged up to 8% for sawdust, 12% for peat and to 19% for brown coal, was exchanged for many metals in solution. Preliminary work showed the method to be amenable to extraction of copper, nickel, chromium, cadmium, lead, zinc, mercury, cobalt, silver, iron, manganese, vanadium, germanium, gallium, aluminium, antimony and uranium. For most of the metals more than 99% was removed from I g 1 −1 solutions. In more detailed work, confined to calcium loaded brown coal and solutions having metal concentrations more typical of industrial operations, minimum residual metal concentrations of 0.0005 mg l −1 mercury; 0.02 mg 1 −1 copper; 0.02 mg 1 −1 zinc; <0.05 mg l −1 cadmium; 0.1 mg 1 −1 lead and 0.2 mg l −1 manganese were obtained. These results compare favourably with those reported for other relevant processes and there might be operational advantages in the method. The method can be applied either by agitating the calcium loaded media in the solution and then filtering, or by passing the solution through packed beds of the media. Where appropriate, dilute solutions can be up-graded for re-use by stripping the metals from the media which can also be re-used. Alternatively, the loaded media can be combusted and the metals recovered from the residues. The method might be applicable to mine drainage and to effluents from metallurgical processing and electroplating, but more work is required to assess costs. It is suggested that the method is environmentally preferable to other common effluent treatment procedures because it enables collection and recycling of heavy metal pollutants.

Supernatant Treatment Considerations for the Neutralized Waste at West Valley

ABSTRACTThe neutralized high-level waste, stored at the Western New York Nuclear Service Center in West Valley, New York, was produced during the operation of the Nuclear Fuel Service, Inc. commercial nuclear fuel reprocessing plant. The supernatant is a highly concentrated salt solution (NaNO3 , NaOH, Na2SO4 and NaCl) containing essentially all of the dissolved cesium as the primary radioactive component. The sludge is primarily iron and aluminum hydroxides and contains strontium and the bulk of the long-lived isotopes. The supernatant will be treated to remove essentially all of the radioactivity and then be concentrated and disposed of as low level nuclear waste. The following supernatant treatment considerations have been evaluated on a laboratory scale using simulated West Valley waste: 1) Organic ion exchange resins; 2) Inorganic ion exchange media; 3) In-tank processing. These processes will be described and preliminary laboratory data will be presented.

Human cathepsin D.

Cathepsin D was purified from human liver by a procedure involving autolysis, acetone fractionation, and chromatography on ion-exchange media and organomercurial-sepharose. Multiple forms of the enzyme were then separated by preparative isoelectric focusing. The molecular weight of the protein was found to be 43,000. Its amino acid composition was determined and it was shown to be a glycoprotein. When treated with sodium dodecyl sulphate or chaotropic agents (without reduction) all forms of the enzyme tested gave components of about 28,000 and 14,000 molecular weight. Specific antisera were raised against the enzyme, and the characteristics of immunoinhibition were investigated. Immuno-inhibition of rabbit cathepsin D within living macrophages was shown to interfere with degradation of some proteins endocytosed by the cells. The antisera against human and rabbit cathepsin D were used in immunofluorescent localization of the enzyme in sites of tissue damage in which cathepsin D might be implicated. The characteristics of inhibition of human cathepsin D by pepstatin were established. At pH values below 5, KD values of 5 x 10(-10)M were determined and pepstatin was shown to be an excellent titrant for cathepsin D. In the range pH 5-6.4 DK increased steeply and it was concluded that the binding site for substrate and inhibitor was abolished by a conformational change in the enzyme molecule in which three protons are lost.

Some ion exchange properties of exfoliated vermiculite

Exfoliated vermiculite was used as an ion exchange medium for the removal of transition metal ions from dilute aqueous solutions. Two different grades of a commercial exfoliated vermiculite were employed. Ion exchange was effected by continuous flow through a packed column. A simple favourable-equilibrium model for the breakthrough curve was found to fit the data provided the flow rate was less than 1.5 ml/cm 2 min. Diffusion coefficients for the ions in the vermiculite were estimated from the model to be of the order of 10 −9 cm 2 sec −1. The times taken to breakthrough were in the order Ni 2+ > Cu 2+ > Zn 2+ > Cr 3+. It was found that the breakthrough time of the smaller vermiculite particles was considerably greater than that of the larger particle size. Total cation exchange capacities were determined by batch equilibration. Those of nickel and zinc were of the order of 1 meq/g, whilst those of copper and chromium were of the order of 2 meq/g. These values are of the same magnitude as those found in the literature for similar ions.

Chromatography of hemoglobins on cm-cellulose with bis-tris and sodium chloride developers

CM-Cellulose as an ion-exchange medium with Bis-tris as buffer and a gradient of sodium chloride provides a versatile system for the chromatography of hemoglobins. Changes in pH, Bis-tris concentration, and slope of the sodium chloride gradient provide means for markedly altering chromatographic behavior for special separations. Examples are given of the application of the method to normal samples and to those with hemoglobinopathies.

12] Methods for isolation and characterization of chromosomal nonhistone proteins: Fractionation of chromatin on hydroxyapatite and characterization of the nonhistone proteins by ion exchange chromatography and polyacrylamide gel electrophoresis

Publisher Summary This chapter provides methods for isolation and characterization of chromosomal nonhistone proteins. The methodology is based on the ability of hydroxyapatite to act as an ion exchange medium for macromolecules in the presence of high ionic strength and urea and consists of a single column procedure, yielding high recoveries of chromatin constituents. The methodology utilizes combination of salt and urea, which has been used as a solvent both for the dissociation and solubilization of chromatin and its specific reconstruction from previously isolated components. The complexity of nonhistone proteins is demonstrated by the presence of polypeptides of differing isoelectric points in sodium dodecyl sulfate–protein complexes that appear as individual components in the one–dimensional sodium dodecyl sulfate system. In addition, the two-dimensional separation procedure indicates that there is a considerable range of rapidly phosphorylated proteins in chromatin. The proteins comprising fractions H2 and H3 are markedly different because the latter possess more acidic isoelectric points. However, some overlap probably does occur between these two fractions because the proteins designated as P1 and P2 appear common to both, the more phosphorylated forms in the liver being present in fraction H3.

Role of Gravity, Temperature Gradients, and Ion-Exchange Media in Formation of Fossil Brines

Calculations show that gravitational settling of ions in an isothermal sediment column could produce increases of equilibrium concentrations in pore waters ranging from 1 percent per 100 m depth for chloride to 4 percent per 100 m depth for strontium. The migration of ions in a thermal gradient (Soret effect) would cause minor salt enrichment upward toward the colder pole, but the presence of cation-exchanging particles such as clays would reverse this tendency and cause pumping of salt downward. A model calculation using literature data for the thermal potentials suggests that about 5-percent enrichment in Cl per 100 m depth may occur under steady-state conditions. These mechanisms do not explain the greater enrichments commonly found in subsurface brines, but may modify salt distributions due to other phenomena.

A method for the estimation of 45Ca in biological samples using a specific adsorbant

Ca 45 may be specifically absorbed from solutions by the ion exchange medium “Chelex 100.” A procedure has been developed which takes advantage of this and enables Ca 45 to be simply and conveniently estimated with effeciencies in the region of 50%. The method is primarily useful where the isotope is present in dilute solution at moderate (0·1 Hc/g) specific activities as was designed for the radioassay of plasma or urine samples. A method for the routine assay of such samples is presented, and some further experiments are described indicating where the scope of the method may be extended to meet other problems of radiocalcium estimation. The technique may be further exploited by using other specific adsorbants where these are available; for example S 35O 4 is specifically taken up by zirconium hydroxide. The possibilities of counting S 35 in this way are briefly indicated.