Ion-exchange Constants Research Articles

Оценка предельно допустимых концентраций тяжелых металлов в почвах с учетом взаимосвязей свойств почв

It has been proved in the work that admissible concentration limits of mobile fraction of heavy metals in the soils have to be additionally rated for the water- soluble fractions taking into consideration the rate of the ion transition into solution and soil deposit capacity, with respect to environment pH, as pH = 4,8 in the CH3COONH4 exudate basically does not appear in the soils. The admissible concentration limits have to be assessed due to the soil characteristics combination which determines heavily the concentration of heavy metal water-soluble fractions (efficient solubility of their deposits, effective constants of the ion exchange and effective constants of the complex instability). The correlation of water-soluble fractions of heavy metals depending on pH in the common black soils was: for Pb = -0,40; for Cd = -0,32; for Co = -0,39; for Ni = -0,47. The proportion of positively charged species not linked into complexes increases under the pollution augment in the soil. This way, PbL7PbL+ ratio was 0,33±0,01 in the check, under the pollution it was Pb - 0,08±0,01. The feedback systems on photosynthesis activity, sprout development, microbial flora change, genetic tests on drosophila are offered for the assessment of the heavy metal influence over the biotests. Keywords: HEAVY METALS, ADMISSIBLE CONCENTRATION LIMITS, BIOTESTS

In Ukrainian

The adsorption and direct calorimetric studies of the binary exchange of Ca2+ and Sr2+ cations on the Na-form of low-silica type natural clinoptilolite (Sokyrnytsya, Ukraine) were performed. The ion exchange of Ca2+ and Sr2+ cations on the Na-form of natural clinoptilolite was studied under static conditions at a solid to liquid phase ratio of 1 : 100 and a constant ionic strength of the solution of 0.1. The integral heats of ion exchange for these systems were measured using a highly sensitive Tian-Calve microcalorimeter in a special lab-made cell. Also, the ion exchange isotherms and Kielland curves were plotted, and the corrected selectivity coefficients and ion exchange constants were calculated. Changes in the integrated Gibbs free energies, enthalpies, and entropies of the ion exchange of Ca2+ and Sr2+ cations on the Na-form of clinoptilolite were calculated in entire range of the substitutions of the exchange complex. The thermodynamic parameters of incomplete ion exchange were analyzed in terms of the crystal structure of the zeolite. In addition, the state of exchangeable cations in the channels of clinoptilolite was described in detail. It is shown that structural heterogeneities of cation-substituted forms of clinoptilolite are clearly reflected in the dependence of thermodynamic functions on the degree of exchange, and significant differences are observed between the exchange of Ca2+ and Sr2+ cations that could not be described by standard thermodynamic values. Although the isotherms of ion exchange have a convex shape, the Na-form of clinoptilolite does not show any thermodynamic affinity to Ca2+ cations. This ion exchange reaction is accompanied by positive enthalpy changes in all range of substitutions of the exchange complex. At the same time, thermodynamic selectivity toward Sr2+ cations was observed for 40 % of the zeolite exchange centers, and the exchange is accompanied by minor exothermic effects in the range of small substitutions, and the ion exchange isotherm has σ-like form. In general, the thermodynamic affinity of the Na-form of clinoptilolite to the studied metal ions under conditions of incomplete exchange is ordered as following hydration energy trends in the case of the lyotropic properties among alkaline earth metals. Thus, the experimental thermodynamic characteristics of ion exchange equilibria could be a reliable support for the practical using of natural clinoptilolite.

The effect of sonication on the ion exchange constant, [formula omitted] of CTABr/chlorobenzoates micellar systems

The ion exchange constant, KXBr (for the case of cetyltrimethylammonium bromide, CTABr, in this study) is a method dependant characterization of ion exchange process by counterions, X and Br with different relative binding ratios. In this report, the ion exchange constant, KXBr values for micelle systems irradiated under 2 min of sonication at 120 W power using a probe sonicator with 1 cm tip were determined to be 85.2, 125.6 and 122.4 when X = o-, m- and p-chlorobenzoates, respectively. The values were quantified using a semiempirical kinetic method coupled with Pseudophase Micellar model, and later compared to the same system in the absence of sonication. The sonication was found to amplify the KXBr values by ~ 13-fold for X = o-chlorobenzoate and ~ 2.5-fold for X = m- and p-chlorobenzoates. This is due to the improvement of ion exchange process by the oscillation of bubbles generated by acoustic cavitation. An active ion exchange process indicates better stabilization of the micelle aggregational structure by the penetration of the introduced counterions, X into the micelle Stern layer leading to the growth of the micelle. This is supported by the remarkable increase in the viscosity of the micelle system by > 7-fold for X = o-chlorobenzoate and by > 2-folds for X = m- and p-chlorobenzoates. Sonication was also found to induce maximum viscoelasticity at lower concentration ratio of [CTABr]:[X]. The ability of ultrasound to induce micelle growth and exhibiting viscoelasticity at lower concentration of counterionic additive will be very useful in technologies where viscoelastic solution is desired such as in oil drilling and centralized heating and cooling system.

Terbium extraction by functionalized surface: experimental and DFT approach

The rare earth elements including terbium are highly important in high-tech applications. Considering the commercial aspects of terbium metal, we report its sequestration from their solutions by 1-(2-pyridylazo)-2-naphthol (PAN) doped hybrid silica. This material can adsorb about 97% of Tb(III) ions (2.01 × 10−6 M) at pH 8 within 30 min, using 50 mg of the adsorbent. The adsorption process is modeled with Freundlich, D-R and Langmuir isotherms. The ion-exchange constants such as Q (0.43 ± 0.1μmol g−1, b (0.37 ± 0.04 × 104 dm3 mol−1), l/n (0.42 ± 0.1), Cm (37.9 ± 4.2 mmol g−1), Xm (2.8 ± 0.8 mmol g−1), β (− 0.0025 ± 0.00012 kJ2 mol−2) and energy E (14 ± 0.3 kJ mol−1) were computed from these models. Thermodynamic parameters like ΔH (39.6 ± 0.2 J mol−1 K−1), ΔS (148 ± 0.3 J mol−1 K−1) and ΔG (− 42.10 ± 0.2 J mol−1(298 K)) reflected that Tb+3 adsorption is spontaneous and endothermic. EDTA, Fe(III),oxalate and citrate reduced the adsorption significantly. Density functional theory simulations show that adsorption of PAN over SiO2 takes place due to strong intermolecular hydrogen bonding. The energy gap of the SiO2 surface was significantly decreased and favored the orbital interactions and charge transfer effects of the metal adsorption over the PAN/SiO2 surface.

Phosphorus recovery by ion exchange in a solid carbonate: modeling of the process.

Phosphorus (P) is a nutrient for plant growth but also a pollutant in water bodies causing eutrophication. The source of P is mainly human and animal wastewater and runoffs from different land uses. The objective of the present study is to evaluate P removal and recovery processes by ion exchange (IE) with solid carbonate (SC) in biodigestor-treated swine effluent (BTSE) using hydrogeochemical modeling. For this, BTSE compositions were obtained by literature review. A synthetized and characterized SC was used and the ion exchange site concentration ([SC-IE]) and the IE constants (Kie) were obtained experimentally and applied to model P and major anion removal and recovery processes. P recovery was evaluated for different BTSE compositions and several concentrations of SC, dissolved P (HPO42-), competing anions such as SO42-, and CO32-. The simulations suggest that a [SC-IE]:[HPO4] of 1.4 molar ratio would allow the recovery of 90% of HPO4 in BTSE, and at average alkalinity concentrations in BTSE, CO32- would compete with HPO4 for the SC-IE. The P recovery by the SC-IE process was compared with two other methods commonly used in P removal from BTSE: removal with aluminum sulfate and precipitation of struvite as a function of pH. The results suggest that SC-IE is the most efficient method in the pH range of BTSE. Besides, HPO42- was readily recovered as inorganic P that may be reused in agriculture and industrial processes.

Kinetics and Mechanism of Alkaline Hydrolysis of N-(o-Aminophenyl)Phthalimide in the Presence and Absence of Cationic Micelles and Sodium Salts of Aliphatic Acids

Pseudo first-order rate constants, k obs, for the alkaline hydrolysis of N-( o-aminophenyl) phthalimide, obtained at constant [CTABr]T (total concentration of cetyltrimethylammonium bromide) and varying concentrations of inert salt MX (MX = sodium formate, sodium acetate, sodium propanoate, sodium butyrate, sodium valerate and sodium hexanoate) follow the relationship: [Formula: see text], where θ and KX/S are empirical constants and S = HO-. The values of KX/S for each aliphatic acid decrease with an increase in [CTABr]T. This relationship gives an empirical constant whose magnitude is the measure of the ability of an ion, X-, to expel another counterion S-, from the cationic micellar surface to the bulk aqueous phase. The values of the empirical constant, KX/S, are used to derive the ion exchange constant, KBrX.

Kinetics and Mechanism of Cationic Micelle/Flexible Nanoparticle Catalysis: A Review

The aqueous surfactant (Surf) solution at [Surf] > cmc (critical micelle concentration) contains flexible micelles/nanoparticles. These particles form a pseudophase of different shapes and sizes where the medium polarity decreases as the distance increases from the exterior region of the interface of the Surf/H2O particle towards its furthest interior region. Flexible nanoparticles (FNs) catalyse a variety of chemical and biochemical reactions. FN catalysis involves both positive catalysis ( i.e. rate increase) and negative catalysis ( i.e. rate decrease). This article describes the mechanistic details of these catalyses at the molecular level, which reveals the molecular origin of these catalyses. Effects of inert counterionic salts (MX) on the rates of bimolecular reactions (with one of the reactants as reactive counterion) in the presence of ionic FNs/micelles may result in either positive or negative catalysis. The kinetics of cationic FN (Surf/MX/H2O)-catalysed bimolecular reactions (with nonionic and anionic reactants) provide kinetic parameters which can be used to determine an ion exchange constant or the ratio of the binding constants of counterions.

Study of Cationic and Nonionic Mixed Micelles with NaBr and 3,5-Cl2C6H3CO2Na by Use of Probe Nucleophilic Reaction of Piperidine with Ionized Phenyl Salicylate.

Behaviors of cationic and nonionic mixed micelles in the form of hexadecyltrimethylammonium bromide (HDABr) and hexadecyltrimethylammonium bromide-Polyethylene glycol hexadecyl ether (C16E20), in the presence of inert salts (NaBr and 3,5-dichlorosodium benzoate), by the use of reaction probe between Pp and ionized PhSH (Pp = piperidine and PhSH = phenyl salicylate), has been reported in this work. The values of RXBr (RXBr denotes ion exchange constants obtained in the presence of micelles of different structural features) or KXBr (KXBr denotes ion exchange constants obtained in the presence of micelles of the same structural features) for 3,5-Cl2C6H3CO2- were almost the same at three different [HDABr]T (0.006, 0.010 and 0.015 M). The average value of RXBr or KXBr determined, in the presence of pure HDABr micelles, using semi empirical kinetic (SEK) method appeared to be almost 2½-fold larger (RXBr or KXBr = 198) than that in the presence of mixed HDABr-C16E20 micelles (RXBr or KXBr = 78). Rheological measurements indicated the existence of wormlike/twisted micelles and vesicle at 0.015 M pure HDABr, various [3,5-Cl2C6H3CO2Na], and 25 and 35℃ whereas there were evidence of only spherical micelles in the presence of mixed HDABr-C16E20 ([HDABr]T = 0.015 M and [C16E20]T = 0.006 M) at both temperatures.

Counterion‐Induced Cationic Flexible Nanoparticle Catalytic of Piperidinolysis of Phenyl Salicylate

AbstractThe removal of PSa− from bulk aqueous phase to the pseudo‐micellar phase by halobenzoate counterion X is responsible for the monotonic increase in kobs (pseudo first‐order rate constants) with the increase in the values of [MX] where MX = sodium salts of 2‐, and 4‐halobenzoic acids. The values of ion exchange constants, or for X = 2‐ and 4‐halobenzoate ions in the presence of tetradecyltrimethylammonium bromide (TTABr) were calculated from the apparent catalytic rate constants, Xkcat which represent the catalytic effect of CFN. Larger values of or were observed for X = 4‐halobenzoate ions than that for X = 2‐halobenzoate ions due to isomeric factors. The values of or determined in the presence of TTABr were compared with previously determined or values in the presence of cetyltrimethylammonium bromide (CTABr). The values of or are nearly 8 ~ 9‐fold larger for 4‐IBz−, 4‐BrBz− and 4‐ClBz− compared to the respective values of X = 2‐IBz−, 2‐BrBz− and 2‐ClBz−. The values of or for X = 4‐FBz− is nearly 3‐fold larger than that for X = 2‐FBz−. The values of or for X = 2‐ and 4‐halobenzoates are significantly smaller in the presence of TTABr than these in the presence of CTABr nanoparticles.

Determination of Relative Counterion Binding Constant to Cationic Micelles.

The efficiency of counterion affinity towards ionic micelles is often described in terms of the degree of counterion binding (β X ) to ionic micelles or the conventional ion-exchange constant ([Formula: see text]) or relative binding constant ([Formula: see text]) of X - and Br- counterions. This review describes the use of ionized phenyl salicylate ions, PSa-, as a new probe to determine [Formula: see text] values using a semiempirical spectrophotometric method. The value of [Formula: see text] is found to be comparable to reported values obtained using different probes by the semiempirical kinetic method as well as different physical methods. Application of semiempirical methods for calculation of [Formula: see text] or [Formula: see text] values involves an inherent assumption that these values are independent of the physicochemical characteristics of the probe molecule.

Determination of ion exchange constants for pairs of metal ions to lignocellulosic materials by column chromatography

Abstract A method based on column chromatography has been developed for determination of ion exchange (IE) constants for pairs of metal ions for different types of wood, pulp, and bark samples. Bark was found to have higher selectivity than wood and pulp for the metal ions studied. Of the 14 different metal ions studied, the toxic transition metal ions Pb, Cu, and Cd were most strongly bound to all the materials used in this work. The validity of the column method was tested by means of different mixtures of metal ions as the loading solution. The IE constants obtained by the column method showed a good agreement with those obtained by the batch method reported earlier by our group. The IE constants were also determined for synthetic cation exchanger (CE) based on weak and strong acid groups. The IE constants of most pairs of metal ions are highest for the weakly acidic CE followed by bark, wood, pulp, and strongly acidic CE.

Ultrafast spin dynamics in magnetic wide‐bandgap semiconductors

Magnetic wide‐bandgap semiconductors based on ZnO and GaN are promising for spintronics applications and interesting for studying the interaction of charge carriers with magnetic ions. We use time‐resolved Faraday rotation spectroscopy to investigate the ultrafast spin dynamics in Zn1−xMnxO and Ga1−xMnxN. The mean field electron–magnetic ion exchange constant is determined by measuring the transient effective g‐factor (g*) for these materials. The relevant scattering processes are revealed by analyzing the ensemble spin dephasing time .

Quantitative and Qualitative Counterion Exchange in Cationic Metallocene Polyelectrolytes

Metallocene-containing polyelectrolytes show many unique properties in a variety of electrochemical, optoelectronic, medicinal, and magnetic applications. The utilization of counterions plays crucial roles in many aspects of these polyelectrolytes. This paper reports the first quantitative analysis of counterion exchange in metallocene-containing polyelectrolytes. Particularly counterion exchange of cationic cobaltocenium-containing polyelectrolytes was analyzed by diffusion NMR, which determined molar fractions of dissociated and associated ions as well as ion-exchange constant. Qualitative impact of counterion exchange on macromolecular conformation was directly observed from cobaltocenium-containing molecular brushes. This study may provide valuable guidance on applications such as layer-by-layer assembly and ion-triggered drug delivery that are involved with ion exchange of polyelectrolytes.

Thermodynamic study of cerium sorption onto anionite from sulfate media

Isotherms of the sorption of cerium in the form of a sulfate complex onto D-403 anionite at a temperature of 298 K and pH values from 2 to 4 in the presence of magnesium sulfate of different concentrations are obtained. The thermodynamic description of the sorption isotherm of cerium sulfate complexes is verified by linearization of the mass action law, modified for ion exchange reactions. The values of the apparent ion exchange constant and differential Gibbs energy for Ce(SO4)2− ions are calculated.

A Semi-Empirical Spectrophotometric (SESp) Method for the Indirect Determination of the Ratio of Cationic Micellar Binding Constants of Counterions X^|^ndash; and Br^|^ndash; (KX/KBr)

The semi-empirical spectrophotometric (SESp) method, for the indirect determination of ion exchange constants (K(X)(Br)) of ion exchange processes occurring between counterions (X⁻ and Br⁻) at the cationic micellar surface, is described in this article. The method uses an anionic spectrophotometric probe molecule, N-(2-methoxyphenyl)phthalamate ion (1⁻), which measures the effects of varying concentrations of inert inorganic or organic salt (Na(v)X, v = 1, 2) on absorbance, (A(ob)) at 310 nm, of samples containing constant concentrations of 1⁻, NaOH and cationic micelles. The observed data fit satisfactorily to an empirical equation which gives the values of two empirical constants. These empirical constants lead to the determination of K(X)(Br) (= K(X)/K(Br) with K(X) and K(Br) representing cationic micellar binding constants of counterions X and Br⁻). This method gives values of K(X)(Br) for both moderately hydrophobic and hydrophilic X⁻. The values of K(X)(Br), obtained by using this method, are comparable with the corresponding values of K(X)(Br), obtained by the use of semi-empirical kinetic (SEK) method, for different moderately hydrophobic X. The values of K(X)(Br) for X = Cl⁻ and 2,6-Cl₂C6H₃CO₂⁻, obtained by the use of SESp and SEK methods, are similar to those obtained by the use of other different conventional methods.

Diffusion and sorption of Cs +, I − and HTO in samples of the argillaceous Wakkanai Formation from the Horonobe URL, Japan: Clay-based modeling approach

Diffusion and sorption behaviors of cationic Cs +, anionic I − and neutral HTO in samples of the Wakkanai Formation from the Horonobe underground research laboratory (URL), Japan, were investigated as a function of ionic strength ( I) of synthetic groundwater by through-diffusion and batch sorption experiments and mechanistic modeling. The effective diffusivities ( D e) measured by through-diffusion experiments showed cation excess and anion exclusion effects, which were strongly dependent on I; D e for Cs + decreased as I increased, D e for I − showed the opposite dependency and D e for HTO showed no dependence. The sorption of Cs + measured by through-diffusion and batch sorption experiments were described by Freundlich isotherms with consistent parameters and decreased with I as a result of competitive ion exchange. Diffusion and sorption behaviors were interpreted by assuming the clay components of illite and smectite control diffusion and sorption mechanisms. The component additive (CA) sorption model, which includes illite and smectite contents and their ion exchange constants, provided a reasonable account of the Cs + sorption trends measured as functions of I and Cs concentration. The diffusion model was developed by coupling the electrical double layer (EDL) model, describing the change of ionic concentrations (cation excess and anion deficit) and viscoelectric effects caused by electrostatic interaction at negatively charged clay surfaces, and a simplified pore model assuming one type of pore shape and includes their size distribution. When averaging the electrostatic effects by using the pore surface area distribution, the model could predict the cation excess and anion exclusion effects, and its dependence on I reasonably well. This result implies the nanoscale pores dominating the pore surface area can strongly impact on ionic diffusion in argillaceous rocks. The clay-based modeling approach described here provides a useful tool to predict ionic diffusion and sorption in argillaceous rocks.

Biosorption of Heavy Metal Ions: Ion-Exchange versus Adsorption and the Heterogeneity of Binding Sites

Surface heterogeneity-related effects have been studied in the context of biosorption systems designed for the removal of bivalent heavy metal ions from aqueous systems. The research was focused on incorporating these effects into the concept of the ion-exchange (IE) constant. Cases of both correlated and uncorrelated values of the affinity constants towards metal ions and protons were considered. When strong correlations were assumed, the dispersion of the IE constant was smaller (or, in the limiting case, the same) in comparison to the dispersions of the affinity constants. In contrast, when no correlation was assumed, the dispersion of the IE constant was greater than those corresponding to any of the affinity constants. The dispersion of the IE constant could be additionally enhanced by the existence of multi-dentate binding modes related to the metal ions.

Diffusion characteristics of surface-modified MK-40 mixed-cation ion-exchange membranes

Previously proposed approaches to determining diffusion parameters of mixed-cation membranes have been tested to describe ionic conductance and H+/M+ (M = Li, Na, K) interdiffusion data for asymmetric MK-40-based membranes modified with a thin layer of MF-4SK perfluorinated membrane material containing silica and zirconia additions. The diffusion coefficients, effective ion exchange constants, and asymmetry effects in the membranes are evaluated. The conclusion is made that there is an additional barrier to ion transport across the surface of MK-40 membranes.

An Empirical Kinetic Approach for the Determination of the Ion Exchange Constants for Counterions of Cationic Micelles: The Rate of pH-Independent Hydrolysis of Phthalimide as the Kinetic Probe: Effects of (CH3)4N+ on (X=Br− and Y=Cl−)

Pseudo-first-order rate constants (k obs ) for pH-independent hydrolysis of phthalimide (1), obtained at constant total concentration of cetyltrimethylammonium bromide (CTABr]T), 2.0 × 10−4 M 1, 0.02 M KOH and varying concentration of inert salt MX (=(CH3)4NCl and (CH3)4NBr), follow a kinetic equation derived in terms of pseudophase micellar (PM) model coupled with an empirical equation. This derived equation gives empirical constants. F X/S and K X/S where S represents anionic 1. The magnitude of F X/S is the measure of the fraction of micellized anionic 1 transferred to the aqueous phase by the limiting concentration of X − and the magnitude of K X/S is the measure of the ability of the ion X −, to expel another counterion ion S − from the cationic micellar surface to the aqueous phase through ion exchange process X −/S −. The values of the empirical constants, F X/S and K X/S , are used to determine the usual ion exchange constant . The values of F X/S are ∼1 for MBr and in the range 0.97–0.78 for MCl within [CTABr]T range 0.006 −≤0.016 M. The mean value of is 2.4 ± 0.1 and it is comparable with those obtained by other kinetic probes (with M+ = Na+) as well as physicochemical techniques.

A new semiempirical kinetic method for the determination of ion exchange constants for counterions of cationic micelles: Study of the rate of pH‐independent hydrolysis of phthalimide as the kinetic probe

AbstractPseudo‐first‐order rate constants (kobs) for pH‐independent hydrolysis of phthalimide (1), obtained at a constant total concentration of cetyltrimethylammonium bromide and hydroxide ([CTABr]T), 2.0 × 10−4 M 1, 0.02 M MOH (M+ = Li+, Na+ and K+) and various concentrations of inert salt MX (= LiCl, LiBr, NaCl, NaBr, KCl and KBr), follow a relationship derived from the pseudophase micellar (PM) model coupled with an empirical equation. This relationship gives empirical constants, FX/S and KX /S, with S representing anionic 1. The magnitude of FX/S is the measure of the fraction of micellized anionic 1 (S−M) transferred to the aqueous phase by the limiting concentration of X−. The value of KX/S is the measure of the ability of the counterions (X−) to expel the reactive counterions (S−) from the cationic micellar surface to the aqueous phase. The values of FX/ S are ∼ 1 for MBr (M+ = Li+, Na+ and K+) and in the range ⩽ 0.7 to ⩾ 0.5 for MCl (M+ = Na+ and K+) at 0.006, 0.010 and 0.016 M CTABr. For LiCl, the values of FX/S become ∼1 at 0.006 and 0.010 M CTABr and 0.8 at 0.016 M CTABr. The values of the empirical constants, FX/S and KX/S, have been used to determine the usual ion exchange constant (KClBr). The mean values of KClBr are 3.9 ± 0.5, 2.7 ± 0.1, and 2.6 ± 0.3 for LiX, NaX, and KX, respectively. These values of KClBr are comparable with those obtained directly by other physicochemical techniques. Thus, this new method for the determination of ion exchange constants for various counterions of cationic micelles may be considered as a reliable one. © 2010 Wiley Periodicals, Inc. Int J Chem Kinet 43: 9–20, 2011