Weak Acid Ion Research Articles

Deposition of coarse soil particles and ambient gaseous components dominating dew water chemistry

Dew water characteristics are not as acidic as those of rainwater and fog water, and they are abundant in weak acid components. The dew water components are dominated by the coarse‐mode aerosol rather than the fine‐mode aerosol, and calcium carbonate, the component of soil, is the important chemical species raising the pH of the dew water. Carbon dioxide is deposited as calcium carbonate into dew water and is the only major component released from dew water. The total concentration of carbon dioxide increased with an increase in the dew water pH, while the degassing rate increased with the decrease in dew water pH. In the low‐pH region, the pε values in dew water are lower than those in rainwater, and the dew water is in a reductive state. The concentration of the representative oxidant, hydrogen peroxide, was much lower in the dew water than in the rainwater in Yokohama (dew water, 0.4 μM; rainwater, 13.1 μM in 1998). The representative conjugate base ions of a weak acid, sulfite and hydrogen sulfite ions, are easily oxidized by hydrogen peroxide, and the lower concentration of hydrogen peroxide in dew water may cause the higher concentration of sulfite ion in dew water than in rainwater. The dew water pH is higher than the rainwater and fog water pH, and a weak acid is easily dissolved into the dew water. Therefore these weak acid ions are more abundant in dew water than in rainwater and fog water.

OXIDATIVE TREATMENT FOR THE PREVENTION OF CHROMIUM ACCUMULATION IN A POLYMERIC MATRIX

ABSTRACT Chromium (III) species tend to accumulate in the organic matrix with carboxylic groups like weak acid ion exchanger resins. Using conventional acidic solutions, chromium (III) can be partially eluted in some circumstances, while an oxidative stripping using hydrogen peroxide in alkaline media seems to be useful. Previously, Cr(III)–H2O2 reaction has been studied in aqueous solutions (homogeneous system) at 20°C, testing for 0.5, 1.0 and 2.0 mM of Cr(III) as total metal concentration. The effect of hydroxide ion on the rate of oxidation was also examined. Chromate was continuously monitored using an FIA system. The general mechanism of the homogeneous reactions has been postulated and the main kinetic parameters of the reactions have been calculated. Ageing of chromium (III) solutions has an important effect on the experimental results. Metal elution from cationic resin is usually carried out by strong acids, but here chromium loaded onto a cation-exchange resin is completely stripped after oxidation to chromate ion. The reaction rate is mainly controlled by intraparticular diffusion of the anionic species through the cationic resin. Surprisingly, these are not rejected from the resin phase by the Donnan exclusion. This apparently anomalous behaviour has been explained in terms of the reaction mechanism.

An analysis of partially film-controlled membrane potentials of weak cation exchange membranes using the space–charge model

Membrane potentials of weak acid ion exchange membranes separating almost neutral (pH = 5.7) solutions of NaCl, KCl and LiCl are studied both experimentally and theoretically. The space–charge model is applied in the theoretical description taking into account the proton flux, the variation of the effective fixed charge concentration in the transport direction and concentration polarization at the membrane/solution interfaces. For the case of perfectly stirred solutions, the validity of a general equation for the membrane potential similar to a well known relationship of non-equilibrium thermodynamics is discussed. Using the above model, the experimental results of membrane potentials of weak acid membranes are analyzed. These membranes were prepared by treating a cellulose acetate filter with a solution of a polyacid. Unstirred boundary layer effects are traced by comparing two types of potential measurements. Assuming free solution values of the diffusion coefficients and using a known value of the acid dissociation constant, respectively, the pore radius, the concentration of ionizable groups and a parameter related to the thickness of the unstirred layers are obtained. For the case of KCl solutions also, specific adsorption of K + to the fixed negative charges (counterion binding) is considered. Finally, the influence of the electrolyte concentration on the conformational state of the adsorbed polyacid is also discussed from the results of hydrodynamical permeability measurements.

Mass-transfer through ion exchange membranes: comparison between the diffusion and the diffusion-convection Stefan-Maxwell equations

We develop the mass transfer equations for a weak-acid ion exchange membrane in the dusty gas model using the generalised diffusion Stefan-Maxwell equation and the generalized convection-diffusion Stefan-Maxwell equation. Electrical conductivity, hydraulic permeability and water transport number are computed at variable ionization rates of the membrane. The viscous flux is computed from the Carman-Kozeni equation. It is shown that electrical conductivity and hydraulic permeability are the sum of a pure diffusive contribution and of a viscous flow term. The confrontation of experimental, equilibrium and mass transfer results published by Schaetzel and Auclair show that hydraulic permeability can be predicted from electrical conductivity and electroosmotical flux data in the simple diffusion model. For the analyzed experimental results, viscous flow can be neglected, suggesting that the ion exchanger investigated is a dense membrane. The same conclusion can be drawn from the early results published by Despic and Hills.

Zinc speciation in soil solutions of Vertisols

Soil solutions were obtained by a centrifugation method from 14 unfertilised and fertilised Vertisols. The soil solutions were analysed for all major cations and anions and organic carbon (C). Chemical speciation of zinc (Zn) in the soil solutions calculated with the aid of the computer program GEOCHEM showed that Zn in tile soil solution exists mainly as free Zn2+ ions in these soils. Complexation of total soluble Zn by organic and inorganic ligands constituted 40% and 50%, respectively, of total soluble Zn in fertilised and unfertilised soil solutions. The organo-Zn complexes constituted <10% of the total soluble Zn. The inorganic Zn complexes, ZnHCO3+ and ZnCO3, constituted 60–75% of the total inorganic Zn complexes. The Zn complexes with SO24- and OH- were less than or equal to 5% each of the total inorganic species in unfertilised soils; ZnSOo4 complexes were more common in fertilised soils. The activities of Zn were extremely low (0.01–0.1 µM) in unfertilised soils and were inversely related to soil solution pH. The experimentally determined solubility lines for Zn2+ in the soil solution were undersaturated with respect to the solubility of any known mineral form of Zn. Zn2+ activity was mainly determined by adsorption-desorption reactions. The weak acid ion exchangers, Chelex-100 and Bio Rex-70, retained smaller amounts of Zn front the soil solutions than the strong acid exchangers, AG 50W X2, AG 50W X4, and AG 50w X8. Soil solution pH strongly affected Zn concentrations in soil solutions. The amount of total soluble Zn present as Zn2+ ions as calculated by GEOCHEM was highly correlated with tile amount of soluble Zn retained by the cation exchange resins. In the case of Chelex-100, these amounts were equal, confirming the usefulness of Chelex-100 to estimate Zn2+ ions.

Application of the surface complex formation model to exchange equilibria on ion exchange resins Part III: Anion exchangers

The surface complexation theory considers the sorption of ions as a local equilibrium reaction, which is caused by the amphoteric behaviour of the surface. Application of this theory to exchange equilibria with ordinary and chelating weak-acid ion exchange resins which can release protons has opened the way for a comprehensive description. Binary equilibria are described by a logarithmic equilibrium parameter, which is a linear function of the composition of the resin phase. Multicomponent equilibria are considered as a superposition of several binary equilibria. The approach considers the pH-dependent dissociation of functional groups. Furthermore, chemical reactions in the liquid phase in which exchangeable species are involved, can readily be taken into account. In contrast to cation exchange resins, the behaviour of anion exchangers is characterized by the uptake of protons enabling them to also adsorb anions. As a consequence, anion exchange equilibria can be described in similar way. The evaluation of data demonstrates that similar relationships exist between a logarithmic equilibrium parameter and the resin phase composition. As for cation exchangers, multicomponent equilibria can be predicted with excellent accuracy from binary parameters.

A New Caustic Process for Softening Produced Water for Steam Generation

SummaryOilfield produced water containing a high concentration of total dissolved solids (TDS) and hardness can successfully be softened for use as oilfield steam-generator feedwater. At the Belridge field in Kern County, CA, the combination of caustic softening and weak-acid cation exchange has been used to soften produced water containing 11, 000 TDS and 550-ppm hardness to < 1-ppm hardness. The resultant sludge containing calcium carbonate and magnesium hydroxide is concentrated by centrifuging and is disposed of in a landfill. Compared to the use of conventional strong-acid ion exchange followed by weak acid or weak acid followed by weak-acid ion exchange systems, the process offers the benefits of lower capital and chemical costs, partial silica removal, and elimination of liquid waste discharge. This paper gives design parameters and operating conditions and discusses future applications in thermal recovery projects.

Application of the surface complex formation model to exchange equilibria on ion exchange resins. Part II. Chelating resins

Multicomponent equilibria on ordinary weak-acid ion exchange resins can be predicted accurately by means of the surface complex formation model, as demonstrated extensively in Part I of this series. In Part II this theoretical approach is extended to include chelating exchange resins with iminodiacetic functional groups. For systems with protons and divalent metal counterions, linear relationships have been found to exist between a logarithmic equilibrium parameter and the resin loading. The two parameters obtained from a graphical representation of this interdependence are valid for a broad spectrum of initial liquid phase compositions. Combination of several of these H +-metal ion equilibria allows multicomponent equilibria to be predicted in a simple way. Owing to the two steps of dissociation of the functional groups of chelating resins, not considered in the present approach, the agreement between experimental data and predicted multicomponent equilibria is not quite as good as for ordinary weak-acid resins.

Asymmetrische katalysen L. Heterogene enantioselektive hydrierungen mit immobilisierten rhodium(I)-komplexen

The supports BaSO 4, cellulose, silica gel, aluminum oxide, AgCl, and charcoal are impregnated with the complexes [Rh(COD)(−)-Diop]PF 6, [Rh(COD)(−)-Norphos]PF 6 and [Rh(COD)(+)-Norphos]PF 6, so that they are insoluble under the reaction conditions. These catalysts hydrogenate the substrate ( Z)-α- N-acetamidocinnamic acid (AAZ), dissolved in aqueous NaOH, with up to 79% ee to N-acetylphenylalanine (AcPhe). On repeated use of the [Rh(COD)(−)-Diop]PF 6 systems optical induction decreases, whereas it increases with the [Rh(COD)(−)-Norphous]PF 6 and [Rh(COD)(+)-Norphos]PF 6 systems in the first re-uses. The hydrogenation activity of all the catalysts declines on repeated use. The cations of the complexes [Rh(COD)(−)-Diop]PF 6, [Rh(COD)(−)-Norphos]PF 6, and [Rh(COD)(+)-Norphos]PF 6 are bound to the strongly acidic ion exchangers v DOWEX HCR-S and DOWEX MSC-1 and to the weakly acidic ion exchangers SERDOLIT CW-18 and SERVACEL CM-32. These catalysts hydrogenate the substrate ( Z)-α- N-acetamidocinnamic acid in aqueous or alcoholic solutions in optical yields of up to 87% ee. The results regarding the repeated use of the catalysts fixed on the ion exchange resins are similar to those obtained with the catalysts fixed on the other supports. N-Acetamidoacrylic acid (AAA) and methyl ( Z)-α- N-acetamidocinnamate (AAZM) are also hydrogenated enantioselectively by the heterogeneous catalysts.

Indirect evidence for the presence of non‐specific anion channels in rabbit mandibular salivary gland acinar cells.

1. Intracellular pH (pHi) was measured using the fluorescent pH-sensitive dye 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein in acini isolated from the rabbit mandibular salivary gland. 2. Stimulation of the acinar cells with acetylcholine (ACh) evoked an intracellular acidosis, the size of which was dependent on the HCO3-concentration in the bathing medium. A half-maximal acidosis was observed at approximately 10 mM-HCO3-. ACh also evoked an acidosis in HCO3(-)-free solutions containing acetate; a half-maximal acidosis was observed at about 10 mM-acetate. 3. Propionate, lactate and butyrate were also able to support the ACh-evoked acidosis to varying extents. In contrast, formate, pyruvate and salicylate did not support the ACh-induced acidosis to any great extent. 4. Acetazolamide greatly reduced the size of the acidosis in HCO3(-)-buffered medium, but had no effect in acetate-buffered medium, suggesting that the inhibitory effect of acetazolamide was due to a specific inhibition of carbonic anhydrase activity. 5. The Cl- channel blockers diphenylamine-2-carboxylic acid (DPC, 1 mM) and 5-nitro-2-(3-phenylpropylamino)-benzoic acid (0.5 mM) abolished the ACh-evoked acidosis in both HCO3(-) -and acetate-buffered media. 6. The data are consistent with the presence in the acinar cell of relatively non-specific anion channels sensitive to DPC and its derivatives. Such channels, activated on stimulation with ACh, would allow HCO3- and other weak acid ions to leave the cell, leading to the observed acidosis. The existence of such channels, located in the apical membrane, could explain why HCO3- or acetate can sustain fluid secretion in the intact perfused rabbit mandibular gland in the absence of Cl-.

Influence of counterion concentration on the ion-exchange equilibria of crosslinked weak-acid polyelectrolyte gels

The sensitive response of weak-acid ion exchangers to counterion concentrations in the aqueous phase has been attributed to a Donnan potential term. By correcting for this term a constant p Kina has, in a number of cases, been resolved for the repeating unit at each point of their titration with base. It has been suggested that this approach leads to the resolution of the intrinsic p Kina of the weak-acid functionality repeated in these ion exchangers. In other cases, however, this approach has not led to a constant p Kina. An error in the Donnan term introduced by macroporosity of these exchangers has been suggested as the source of this incongruity. A method based on the premise that the Donnan term is uniquely responsible for the variability of the uncorrected p Kina has been outlined and shown to give a satisfactory result.

A study on the crosslinking characteristics of Allyl itaconates

1-Allyl-2-methylene succinate (α-MAI) was synthesized by partial hydrolysis of diallyl itaconate (DAI) in the presence of hydrogen chloride. The three allyl itaconates (DAI, α-MAI and β-MAI) were polymerized or copolymerized separately with methyl acrylate (MA) in suspension, producing beads with varying resistance to hydrolysis. The beads containing DAI were hydrolyzed hardly at all. The beads made from 4-allyl-2-methylene succinate (β-MAI) were hydrolyzed relatively easily. Those made from α-MAI proved rather stable to alkaline hydrolysis; under general conditions for regenerating a weak-acid ion exchange resin they demonstrated strong stability against hydrolysis. The weak-acid ion exchange resin prepared from MA, DAI, α-MAI and a small amount of DVB had a high exchange capacity but did not produce sticky beads. α-MAI and DAI can be used as crosslinking agents to produce macroporous adsorbents of intermediate polarity.

Electrocoagulation of waterborne polymers in the presence of carbon black

AbstractElectrodeposition of paint is an electrochemical process, starting from water‐borne polymers. The electrode reactions are water decomposition, leading to diffusion layers of an extreme pH. Coagulation of polymers proceeds in these layers as an acid / base reaction rather than as a direct discharge of macroions at the electrodes. The electrodeposited film behaves like a weak acid or alkaline ion exchanger. Under polarization, high electric field strength leads to charge separation and the formation of a double space charge. Current / voltage‐behavior is nonlinear. The mechanism of charge transport is purely ionic. Resistivities are in the order of p = 108 Ohm·cm in the wet film. The stoved film is an insulator. Electrodeposition of a second film is impossible. However, electrodeposition of the primary film in the presence of dispersed carbon black, studied in detail for the first time, leads to an appreciable electronic conductivity in the stoved film. ρ is in the order of 105 ‐ 107 Ohm·cm even with a carbon black concentration of only a few wt.‐%. This has been explained in terms of a stick percolation model and the preferential formation of transversal carbon black chains in the film. The relatively high resistivities found along these chains is due to the need of electron tunneling through ultrathin polymer films around the polymer wetted individual carbon black particles. Temperature behavior of resistivities, field effect and other proofs are given for this model.For practical application, the most important findung is the possibility of an electrodeposition of a coherent second layer and even of multilayers in the presence of only 1 ‐ 5 wt.‐% of an appropriate carbon black filler.

Partial demineralization of water by ion exchange using carbon dioxide as regenerant part iii field tests for drinking water treatment

The combined application of a weak-acid ion exchange resin in the free-acid form and of an anion exchange resin in the bicarbonate form allows a partial demineralization of water. The particular advantage of this process is that CO 2 can be used for the simultaneous regeneration of both resins. As a consequence, the effluent contains only the amount of salt which has been eliminated in the service cycle. The present paper discusses results of field tests of the process with a mobile pilot plant in the case of drinking water demineralization.

EQUILIBRIUM SORPTION OF ON AM(III), CE(III) AND EU(III) BIO-REX 70 ION EXCHANGE RESIN

ABSTRACT The binding of Ce(III), Eu(III), and Am(III) to a weak carboxylic acid ion exchange resin was measured at several temperatures. The thermodynamic values correspond to contact ion-pair formation of the trivalent cations with the carboxyllc sites. The results of this study of binding of lanthanides and actinides to a weak carboxyllc acid resin are compared to analogous data for a strong sulfonic acid ion exchange resin.

Partial demineralization by ion exchange using carbon dioxide as regenerant part I: evaluation of the regeneration of weak acid ion exchange resins in the presence of anion exchanger material

Regeneration of weak acid ion exchange resins by carbonic acid can greatly be improved if anion exchanger material is added to the system. Theoretical and experimental evaluation of the regeneration equilibrium show the efficiency of this method. Furthermore this coupled application constitutes an effective way to reduce the neutral salt content of water. Only CO 2 is needed for the regeneration of both resins, so that additional amounts of salt have not to be discharged with the effluent.

Preparation of Magnetic Amine Resins by Polymer Modification

Abstract Weak acid ion exchangers prepared by graft polymerization of acrylic acid on cross-linked PVA microbeads containing magnetic iron oxide were converted to strong or weak base resins by reaction with glycidyltrimethylammonium chloride or with epichlorohydrin and diethylamine, respectively. Capacities up to 2.6 meq/g were obtained, but the products were susceptible to alkaline hydrolysis. Comparable resins prepared by grafting substituted methacrylic esters hydrolyzed more slowly, indicating that hydrolysis occurred at the ester linkage.

Tentative Hypothesis to Explain How Electrolytes Affect the Gelatinization Temperature of Starches in Water

AbstractAn hypothesis is proposed to explain some phenomena arising from the interactions between starch and electrolytes in water. The basis of this hypothesis is formed by the following claims: a) starch is a weak acid ion exchanger; b) cations tend to protect and to stabilize the granule structure; c) anions are the gelatinizing agents by rupturing hydrogen bonds. Arguments are put forward to sustain these claims.

Fission product behavior in UC xO y fissile particles made from weak-acid resins

High-Temperature Gas-Cooled Reactor fissile particles made from weak-acid ion exchange resins with compositions ranging from UO 2 plus excess carbon to UC 2 plus excess carbon were irradiated in test capsules. The fission product behavior in the particles was determined by electron microprobe analysis. The behavior of most fission products was dependent on the initial O/U ratio, and their overall chemical behavior is consistent with that for the phases calculated to be present.

Adsorption of streptomycin on ion exchange resins: Equilibrium and kinetic studies

AbstractEquilibrium and kinetic studies of streptomycin adsorption from aqueous solutions of streptomycin sulphate were carried out using four weakly acidic ion exchange resins: Indion 236 [Ion Exchange (India) Ltd], Amberlite IRC‐50 (Rohm and Haas Co, USA), KB‐2 and KB4‐P2 (both Russian resins), initially in the sodium form. The maximum amounts of streptomycin taken up by the exchangers were about 1640, 1560, 2050 1400 mg g−1 dry resin (sodium form), respectively. The rate of adsorption of the antibiotic was highest with the ion‐exchanger KB‐2, and lowest with KB4‐P2. The initial diffusivity values calculated for the four exchangers at a temperature of 9°C were 2.87 × 10−8, 1.87 × 10−8, 3.42 × 10−8 and 0.468 × 10−8 cm2 s−1, respectively.