Weak Acid Cation Exchange Resin Research Articles

Polyfunctionality of carboxyl sites on IRC-50, an MR-type ion-exchange resin, evaluated by modeling with the Frumkin isotherm

For efficient and adequate recovery or removal of ions by ion exchange, it is important to know the properties of ion-exchange resins quantitatively. The exchange properties of Amberlite IRC-50, a macroreticular-type weak acid cation-exchange resin, were measured by titration. The properties were modeled by considering ion-exchange sites with different reactivities (polyfunctionality) and suppression of ion exchange with the progress of the reaction due to repulsive lateral interactions between adsorbed ions. It was found that there are two types of sites with similar ion-exchange intensities but different lateral interactions. The different properties of the ion-exchange sites were ascribed to the micro- and macropore environments of the resin. The adsorption affinity of alkali metal ions for the two types of sites is discussed in terms of the hydrated ion sizes and the complex formation with carboxyl group sites.

Ion-exchange chromatography of mono- and divalent cations in natural waters on a weak-acid anion-exclusion column

Ion-exchange chromatography with indirect conductimetric detection for the simultaneous determination of mono- and divalent cations is investigated using an anion-exclusion chromatographic column packed with polymethacrylate-based weakly acidic cation-exchange resin in the H + form (Tosoh TSKgel OA-PAK-A, 300 mm×7.8 mm I.D.). An eluent comprising a strong acid, a weak organic acid, methanol and water is used. Using 0.75 m M sulfuric acid, 2 m M tartaric acid, 7.5% (v/v) methanol in water as eluent, the monovalent cations (Na +, NH 4 +, and K +) and divalent cations (Mg 2+ and Ca 2+) were separated simultaneously by a cation-exchange mechanism in about 25 min. The application of this method to the analysis of several natural waters including rain, river, lake, underground and forest soil waters for estimating acid rain effects on the natural and urban environments is presented.

Potentiometric titration in studies of ion exchangers

The methods for the determinations of dissociation or protonation constant and ion exchange equilibrium constant for weakly dissociating ion exchange resin and hydrous oxide by means of potentiometric titration are presented in this paper. The weakly acidic cation exchange resin and basic anion exchange resin, the chelating exchange resin in which the iminodiacetic acid groups are covalently bound to the matrix, and the chromatographic grade finely divided alumina are concerned.

Sorption of metal ions on a weak acid cation-exchange resin containing carboxylic groups

The sorption properties of a commercial resin containing a carboxylic active group, Amberlite® CG-50, for magnesium, calcium, copper and zinc were investigated on the basis of the Donnan model. It is assumed that the main driving force for the sorption of divalent metal ions is the complexation by the carboxylic groups inside the resin. Under typical batch conditions (large excess of ligand) only the 1:2 complexes are formed for all metal ioas considered, whereas in aqueous solution only 1:1 complexes are reported for calcium and magnesium and the monomeric analogues of the active group of Amberlite® CG-50. The intrinsic complexation constants obtained from the batch experiments agree well with those in aqueous solution. The same holds for the intrinsic complexation constant evaluated from Chromatographic experiments. This confirms some previous results obtained with a chelatteg resin containing an iminodiacetic group, Chelex 100. The values of the complexation constants for the carboxylic groups found with Chelex 100 are in agreement with those found with Amberlite® CG-50.

DETERMINATION OF ION EXCHANGE EQUILIBRIUM CONSTANTS FOR WEAKLY DISSOCIATING ION EXCHANGE RESINS

ABSTRACT In this paper the general progressive neutralization technique has been developled to evaluate the ion exchange equilibrium constant for weakly dissociating ion exchange resin. In substance, this technique is the potentiometric titration procedure of the weak acid resin weak base resin ) with the mixture solutions containing various ratios of base and salt, M(OH)n — MpXn( acid and salt, HpX—MpXn), where Mn+is metal cation, Xp−anion. According this technique, the rational equilibrium constants of the ion exchange reactions for the weak acid cation exchange resin D725 and for the weak base anion exchange resin D705 have been determined. This technique has proved useful in the determination of rational equilibrium constant of ion exchange reaction for weakly dissociating ion exchange resin.

DETERMINATION OF ION EXCHANGE EQUILIBRIUM CONSTANTS FOR WEAKLY DISSOCIATING ION EXCHANGE RESINS

ABSTRACT In this paper the general progressive neutralization technique has been developled to evaluate the ion exchange equilibrium constant for weakly dissociating ion exchange resin. In substance, this technique is the potentiometric titration procedure of the weak acid resin (weak base resin ) with the mixture solutions containing various ratios of base and salt, M(OH)n—MpXB(( acid and salt, HpX-MpX^), where M°+is metal cation, X^anion. According this technique, the rational equilibrium constants of the ion exchange reactions for the weak acid cation exchange resin D725 and for the weak base anion exchange resin D705 have been determined. This technique has proved useful in the determination of rational equilibrium constant of ion exchange reaction for weakly dissociating ion exchange resin.

Effects of ionic and complexed metal concentrations on plant uptake of cadmium and micronutrient metals from solution

Uptake of Cd and micronutrient metals by intact tomato plants (Lycopersicon esculentum, cv. Wisconsin-55) from solution cultures was investigated by establishing four levels of Cd-ion activity in the presence or absence of a metal-complexing agent (±EDTA). Activity ratios of Cd, Cu, Mn, Ni, and Zn were controlled with chelating resin while activity ratios of K, Ca, and Mg were controlled with a strong-acid cation-exchange resin. Hydrogen ion activity was controlled with a weak-acid cation-exchange resin and P activity by a cation-exchange resin containing adsorbed polynuclear hydroxy-Al. The concentrations of all nutrients and Cd were maintained at concentrations similar to those occuring in solutions of sludge-amended soils. The EDTA treatments increased the concentrations of Cu and Ni in hydroponic solution by approximately four orders of magnitude, Zn by two orders of magnitude, Cd by a factor of 50, Mn by a factor of 2.4, and Fe by a factor of 1.6 Neither the Cd nor the EDTA treatments affected plant yield, and Cd treatments did not significantly affect uptake of other elements. EDTA treatments inhibited Fe uptake, enhanced Cu uptake, and had little effect on the uptake of Cd, Zn, and Mn. Accumulation of Cd, Zn, Mn, and Cu in plant shoots appears to be related to their respective ionic activities rather than their concentrations in hydroponic solution.

Recovery of uranium from carbonate leach liquors using weak-acid cation exchange resins

Uranium is currently recovered from both sulfuric acid and carbonate leach liquors using anion exchange resins. This technology is based upon the facts that uranium exists as anionic complexes in these liquors and that the anion exchange resins have a high selectivity for these complexes. Whereas this technology is most effective in most situations, in the case of in situ solution mining with dilute alkaline solutions, the anion exchange technique is faced with such problems as ground water contamination and poor yellow cake product purity. Unexpectedly, the use of a carboxylic cation exchange resin has been found to be quite effective for recovering the uranium from the in situ solution mining alkaline liquor, thereby overcoming the problems associated with the anion exchange process. Not only is the cation exchange process more effective, the carboxylic acid cation exchange resins are considerably more stable and lower in cost than the anion exchange resins.

Ammonia Volatilization from Surface‐Applied Urea: Effect of Hydrogen Ion Buffering Capacity

AbstractThe influence of soil pH and soil cation exchange capacity on ammonia volatilization from surface applied ammoniacal nitrogen has been reported in previous studies. Since the hydrolysis of ureacontaining N fertilizers causes an increase in alkalinity, a soil's inherent H+ buffering capacity (defined as the soil's total acidity, comprised of exchangeable acidity plus non‐exchangeable, titratable acidity), should exert a dominant influence on the maximum soil pH at the site of urea fertilizer application. The objective of this study was to demonstrate the importance of a soil's H+ buffering capacity in affecting NH3 volatilization from surface‐applied urea. The H+ buffering capacity of two soils was increased by adding hydroxy‐Al polymers to one soil, and weak and strong acid cation exchange resins to the other soil. Care was taken to keep cation exchange capacity and initial pH close to the same on amended and unamended (control) soils. Urea was surface‐applied to amended and unamended soils and ammonia volatilization and soil surface pH were measured. The increase of H+ buffering capacity of soils was found to reduce soil surface pH and NH3 volatilization after application of urea. It is concluded from this work that H+ buffering capacity of a soil is a better indicator of NH3 loss potential than a soil's initial pH.

Use of cation-exchange resin for the detection of alkyl- pyridines in beer

A method has been devised whereby trace amounts of certain basic compounds such as pyridines, may be detected and semi-quantified in beer in the presence of an excess of other flavour constituents including pyrazines. The method involves steam distillation of beer under reduced pressure and subsequent passage of the distillate through a column of weakly acidic Zerolit cation-exchange resin. The resin is eluted with aqueous sodium chloride, the eluate extracted with organic solvent and the concerntrated extract analysed by gas chromatography coupled with mass spectrometry. Using this technique with multiple ion detection, a series of alkylpyridines was readily detectable in beers and worts at level below 1 ppb.

Recovery of Cytokinins from Cation Exchange Resins

AbstractCytokinins exhibit great affinity for the polystyrene matrix of Dowex‐50 cation exchange resins. Model experiments showed that only c. 20% of the applied 2‐methylthio‐trans‐zeatin and c. 70% of the trans‐zeatin are eluted from AG 50W columns with six bed volumes of 1 N NH4 OH. Inclusion of 70% (v/v) ethanol in the eluant increases the recovery to c. 55 and 85% respectively. No additional recovery was obtained upon continued elution to 14 bed volumes. Similar experiments with Duolite CS‐101, a weak acid cation exchange resin with acrylic matrix, showed that c. 95% of the applied 2‐methylthio derivatives of isopentenyladenine and zeatin are recovered from the resin with six bed volumes of 70% (v/v) ethanol (pH 10) or 1 N NH4OH in 70% (v/v) ethanol. The less modified cytokinins, isopentenyladenosine and ribosylzeatin, are recovered completely under these conditions. Recovery of cytokinins was determined by means of high‐pressure liquid chromatography of the column eluates.