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Structural and electronic characteristics of molecular models of swollen polyacrylic and sulfostyrene-type cation exchangers in sodium and potassium ionic forms are calculated within the non-empirical HF/basis set method using the MINI Huzinaga basis set and the Firefly program. The obtained data are compared with those for water clusters of a comparable size. The molecular models include four and two monomeric units of corresponding polymers with ten water molecules per functional group; the water clusters contain 20 and 40 water molecules. The following characteristics of the model structure are obtained: the number and the types of the nearest neighbors of cations and water molecules; the distances between the interacting ions and the atoms; the orders of interionic and ion-molecular bonds; binding energy distribution of water molecules in the systems; number and length distributions of hydrogen bonds; the number and character of $$\text{RCO}_{2}^{-}\cdots {{\text{I}}^{+}},\ \text{RSO}_{3}^{-}\cdots {{\text{I}}^{+}}\ \text{and}\ {{\text{H}}_{\text{2}}}\text{O}\cdots {{\text{I}}^{+}}$$ bonds. The lengths of hydrogen bonds and the total number of intermolecular and ion-molecular bonds per water molecule in water clusters are established to be similar to those in Na+ and K+ molecular models of ion exchangers. The first coordination layer around both ions is filled with oxygen atoms of water molecules and fixed anions. The coordination numbers of Na+ and K+ are almost equal to those in aqueous solutions. The calculations indicate that direct interaction of Na+ and K+ with the anionic groups is responsible for the difference between their ion exchange selectivities on carboxylic and sulfostyrene ion exchangers. The Na+ ion forms direct largely covalent chemical bonds with the fixed carboxylate anion. The K+ ion forms long electrostatic bonds with the carboxylate group. This accounts for a higher selectivity of Na+ on carboxylic ion exchangers than that of K+. The K+ ion forms long direct electrostatic bonds with the fixed sulfonate anion. The Na+ ion does not form direct bonds with the sulfonate due to strong hydration of the former. This accounts for a higher selectivity of K+ on sulfonic acid resins that that of Na+.

A mathematical model for description of the sorption capacity of ion exchangers on alkaline compounds protonizable in aqueous solutions (exemplified by ammonia, mono-, diand triethylamine) was proposed. The Henry’s constants for these substances were experimentally determined. The model accounts for the concentration and acid-base properties of the sorbate, relative air humidity, acid-base properties and exchange capacity of the ion exchanger, as well as spatial availability of functional groups for interaction under conditions of limited permeability of polymeric ion exchanger. The applicability of the model is illustrated by processing the experimental results on the sorption of ammonia and ethylamines by fibrous carboxylic and sulfonic cation exchangers. Good agreement between the calculated and experimental data is observed.

New information on the state of water molecules and ions in the alkali ion forms of sulfostyrene resins have been obtained by joint application of thermodynamic and quantum chemistry methods to treatment of experimental water sorption isotherms taken from the literature. The theoretical water sorption isotherms have been computed from suggested earlier model of Predominant Hydrates. The model parameters were obtained with the help of quantum chemical calculations of structures of the swollen ion exchangers. Ab initio non-empirical SCF MO LCAO method has been used. The molecular models included fragments of the polystyrene chain with two sulfonic groups and the number of water molecules identical to that in the resins with 10% divinylbenzene. The theoretical water sorption isotherms for all alkali metal forms accurately describe the experimental data in the assumption of presence in the resin three (Li+ and Na+) or two (K+, Rb+ and Cs+) predominant hydrates. The calculations allowed obtaining the following characteristics of the molecular models: binding energy of the water molecules to the swollen ion exchanger, Gibbs' energy of the hydrates formation, distances between the water molecules and ions, lengths of the hydrogen bonds and some other parameters. These data allowed explaining physical reasons for the difference in properties of the alkali ions related to the water “structure forming” and “structure breaking” subgroups. The results of the quantum chemistry calculations clearly indicate separation of water molecules in the resin into several groups differing in the binding energy and the distances to the cations. The number of hydrogen bonds per water molecule in the ion exchanger is about 25% less than in the bulk water, but the total number of intermolecular bonds (hydrogen and ion-molecular) is approximately the same as in the bulk water. Intermolecular bonds in the ion exchanger form an integrated net in which the mobile and the fixed ions function as the knots.

The perspectives of using ion-exchange soils for growing plants in zero-gravity field are described. Standard methods for obtaining ion-exchange soils are not suitable for weakly dissociating ion-exchangers. Methods for obtaining ion-exchange soil based on weakly dissociating fibrous ion exchangers are proposed. The method using concentrated solutions made it possible to obtain ion-exchange soils with a larger content of deficient ions (K+ , NO3 – ). The suitability of the obtained ion-exchange soils was confirmed by a biological experiment.

Information on the state of proton and water molecules in sulfostyrene ion exchangers was obtained by joint application of thermodynamic and quantum chemistry methods to experimental water sorption isotherms from paper B.R. Sundheim , M.H. Waxman , H.P. Gregor , J. Phys. Chem. , 57 : 9 ( 1953 ) 974–978 . The model of Predominant Hydrates in combination with non-empirical quantum chemical calculation was used for calculation of theoretical water sorption isotherms. The experimental water sorption isotherms can be accurately described by the model accounting for the presence in the resins with different cross-linkages (0.4–23% DVB) of four hydrates (H 3 O + ; H 3 O + ·H 2 O; H 3 O + ·2H 2 O; H 3 O + ·6H 2 O) with practically the same Gibbs energy formation (stability constants). The IR and Raman spectra of dry and hydrated resins were interpreted by comparing theoretically calculated spectra of p-ethylbenzene sulfonic acid and experimental ones. Some corrections to their interpretation were suggested. The spectra show that complete dissociation of sulfonic groups occurs after sorption by the resin three water molecules per sulfonic group.

Valuable information on the state of water molecules in the ion exchanger can be obtained by joint application of thermodynamic and quantum chemistry methods to treatment of water sorption isotherms. An improved variant of the Predominant Hydrates model accounts for competitive process of formation in the resin of several hydrates forming an ideal mixture with the free water. The parameters of the model are number of hydrates, number of water molecules in each hydrate and Gibbs energies of the hydrates formation. The first two parameters can be obtained from quantum chemical calculation of structure of the molecular model of swollen ion exchanger and the energy state of the water molecules. The new approach was illustrated by its application to experimental data of Gregor H . P ., Sundheim B . R ., Held K . M ., Waxman M . H . Studies on ion-exchange resins . V . Water vapor sorption , J . of Coll . Sci ., 7 : 5 ( 1952 ) 511–534 on isopiestic data of water sorption by Li + and Na + forms of sulfostyrene resin with 10% DVB. The experimental water sorption isotherms can be accurately described by the model accounting for the presence in the resin of two hydrates with the same number of water molecules for Li + and Na + forms. The difference in the intensity of hydration reveals in the different Gibbs energy of the hydrates formation. The mole fraction of water in different hydrates and the free water was calculated. It appeared that more than a half of water molecules in both cases are free and enter the resin phase due to the entropy increase upon distribution of the free water between the solution and the resin.

The effect of 2% (v/v) addition of ion exchange substrate to a sandy soil on the growth of Dactylis glomerata L., used as a test species, was studied. Four different exchange additives having pH values in the range 4.45–7.14 were evaluated in pot experiments. These additives were prepared as mixtures of monoionic forms of a strong acid cation exchanger and a weak base anion exchanger, loaded with nutrient ions. The additions of the ion exchange substrates to the sand affected plant growth advantageously, increasing the total dry biomass 3.8– 8.5 times. The most efficient additive appeared to be the substrate with the lowest pH because it contained the largest stock of nutrient elements. The excessive acidity of the additive was spontaneously neutralized in the mixtures with sand due to reaction of the acid excess with carbonates present in the natural sandy soil.

Quantum-chemical calculations of vibrational spectra of the sulfonated ion-exchanger model p-ethylbenzenesulfonic acid hydrated by 1–10 water molecules and its dimer were calculated by the non-empirical SCF MO LCAO method with the 6-31G(d) basis set. The calculated results were compared with experimental IR and Raman spectra of sulfonated ion exchangers. The infl uence of hydration on the vibrational frequencies of functional groups in the ion exchangers was analyzed. It was shown that the sulfonic acid was completely dissociated if three and more water molecules per functional group were present. Bands near 1130 cm–1 were due to S–O–H bending vibrations in the absence of water molecules and C–S–O–H3O combination vibrations with 3–6 water molecules per sulfonic acid.

Comparative studies of the state of water molecules in carboxylic acid resins were carried out using classic thermodynamics and ab initio quantum chemical calculation of the structure of representative fragments of their polymeric matrix in the presence of different amounts of water molecules. Water sorption isotherms were obtained for H + , Li + , Na + , K + Mg 2+ , Ca 2+ and Ba 2+ forms of the carboxylic acid ion exchanger Lewatit S8227 using the isopiestic method. Quantum chemistry calculations were performed by the Firefly QC package, which is partially based on the GAMESS (US) source code, on the theory level RHF/MINI. Atomic structures of fragments of the resin interior containing 1–6 monomeric residues and 0–10 water molecules per functional group were computed. It has been shown that the water sorption isotherms are well described by the previously derived equation on the assumption of the presence in the swollen ion exchanger of one or two formal hydrates. Quantum chemistry calculations allow independent evaluation of the number of water molecules in the hydrates and in so doing reduce the number of fitting parameters needed for quantitative description of the water sorption isotherms. They also allow classifying the water molecules in the resin according to the type of interaction with fixed ion–counter-ion ion pair.

Acid–base properties, kinetics and equilibrium sorption of Ca 2+ , Cu 2+ , Pb 2+ , Cd 2+ , Ni 2+ and Mn 2+ ions on fibrous chelating ion exchanger FIBAN X-1 containing iminodiacetic group have been studied. The structural and electronic characteristics of ion-polymeric complexes have been obtained by non-empirical quantum chemical calculations. The rate of sorption processes was extremely high; the half-process time of the sorption process was equal to 24 s. The isotherms of ion sorption are described by the Langmuir equation what allowed deriving equation for dependence of the distribution coefficient on the ion concentration and accurate extrapolation of these value to zeros concentration. The concentration range the Henry’s law applicability was determined theoretically and proved experimentally. The sorption selectivity series in a neutral medium was Cu > Ni > Pb > Cd > Mn > Ca. The same series follows the pH at which the sorption begins. Complete extraction of all heavy metal ions occurs at pH > 4. The quantum chemical calculations have shown that the selectivity of sorption is determined by the number of coordination bonds between the cation and fixed anion, the length of the bonds and degree of their covalence. The way of combining of these factors is individual for each specific cation and can be revealed by quantum chemical calculations.

Hydrogen chloride sorption from the air in a wide range of relative humidity and the concentration of the absorbing component was examined under dynamic conditions with fibrous anion exchanger FIBAN distinguishing by basicity and type of functional groups.

The surface topography of silicon and germanium single crystals formed under 10-keV Ar+ and Ne+ irradiation was studied experimentally. A relief with typical nanometer-scale dimensions is detected using atomic-force microscopy. It is established that the average height of the nanorelief formed depends on the silicon doping levels. It is also shown that the average height is determined by the parameters of ion irradiation.

Ion exchange equilibria Cl−– NO 3 - , Cl−– SO 4 2 - , NO 3 - – SO 4 2 - on fibrous strong base anion exchangers on the basis of graft copolymer of styrene and divinylbenzene to polypropylene fibers with groups of benzyl trimethyl- (TMA), triethyl- (TEA), and tributyl- (TBA) ammonium have been studied and characterized by values of the equilibrium coefficients and separation factors. They were compared with the same equilibria on ion exchange resins Dowex1 with different cross-linkage. An equation allowing calculating the separation factor for different ionic concentrations and ratios of the ions in solutions of uni- and divalent ions from the equilibrium coefficient invariant to the concentration has been derived. The selectivity of nitrate and chloride sorption increases with increasing size of alkyl radicals in the functional group and with increasing percent of divinylbenzene in the resins. A quantity characterizing selectivity of ion exchanger to bivalent ion against the univalent ion named concentration of zeroth selectivity (CZS) has been suggested to describe the efficiency of ion exchangers in processes of water purification from univalent ions, specifically nitrates in waters containing sulfates. At concentrations above the CZS the univalent ion is absorbed selectively compared to the bivalent one; the “dumping effect” in frontal chromatograms of mixtures of such ions is not possible above the CZS point and this criterion can be used for choosing the ion exchanger for selective removal of univalent ions from mixtures with polyvalent ones. The CZS values for conventional strong base ion exchangers in ion exchange NO 3 - – SO 4 2 - is higher than typical total ionic concentrations in drinking waters (1–3 × 10−3 eq/L). For Dowex1 × 10 it was found equal 1.3 × 10−2 eq/L. For the fibrous ion exchanger with benzyltributylammonium groups CZS = 3.3 × 10−6 eq/L. This ion exchanger is suitable for selective removal of nitrates from the solutions with concentrations higher than this value and has exceedingly high selectivity to nitrates which makes the process of its regeneration difficult. The most suitable fibrous ion exchangers for application in drinking waters purification from nitrates with guarantied absence of the nitrate dumping appeared FIBAN A-1 TEA having the CZS values 4.3 × 10−4 eq/L.

For the hydration of isolated and adjacent functional groups of strongly basic anionites, ab initio quantum-chemical calculations have been performed via the molecular fragment method. As counterions, OH−, F−, Cl−, Br−, and I− ions have been tested. It has been shown that Cl−, Br−, and I− ions are strongly bonded to the functional groups. The hydration of the functional groups in all cases leads to the removal of anions from a cation at a distance that is markedly larger than the sum of their ionic radii. This effect makes itself evident even in the case of addition of two water molecules. During interaction of adjacent functional groups, no appreciable change in the mutual arrangement of ions takes place.

Sorption of hydrochloric and perchloric acids and their sodium salts was studied by Cl− and ClO4− forms of ion exchanger Dowex 1×8 in the concentration range of the external electrolyte 0.25–4 mol/l. Sorption of water and the total amount of the solution were also studied. Sorption of the acid appeared markedly higher than that of the respective salts. A mathematical modeling and computer simulation of the processes were performed. The overall sorption was represented as a superposition of the Donnan membrane distribution and formation associates type RAn · (AnKt)i · (H2O)n in the homogeneous resin phase. The model expresses non-ideality of the resin phase in explicit form as formation of the above associates characterized by the constants of their formation. A good agreement between the experimental and calculated sorption in the whole concentration range was obtained in the assumption of two associates with i=1, 2 and n=1–3. The same factors control sorption of the acids and the salts and the difference in their behavior has a quantitative character. The main introduction into the overall sorption of the salts makes the Donnan distribution up to concentration of the external electrolyte 4 M, while the main part of the absorbed acids is contained in the associates.

Treatment of drinking water to remove heavy metal ions Pb2+, Cu2+, Cd2+, Co2+, Ni2+, and Zn2+ with commercial fibrous carboxylic ion exchangers FIBAN Kh-1, K-3, K-4, and K-5 was studied. Features of metal ion sorption from two-component solutions were determined. A comparative evaluation of the sorption selectivity of FIBAN fibrous ion exchangers with respect to heavy metal ions was made.

A method for determination of the acidity parameters of ion exchangers with arbitrary functionality from potentiometric titration data was developed. Titration of ion exchanger RH (ROH) with alkali KtOH or acid HAn is considered as superposition of ion exchange H + –Kt + (OH − –An − ) and the reaction of neutralization. The method is based on the assumption of linear dependence of logarithm of the equilibrium coefficient of the ion exchange as a function of the neutralization degree. The acidity parameters are two constants of this dependence. They are thermodynamic equilibrium constant of ion exchange, p K and the difference between logarithm of the equilibrium coefficient at the complete and zeroth neutralization of the ion exchanger, Δp k . Specially developed computer program allows reconstruction of the potentiometric titration curve from the sets of the acidity parameters of each type of the functional groups in the resin. The theory was tested on a number of ion exchangers with different functionalities: sulfonic and carboxylic acid cation exchangers, polyfunctional weak base anion exchangers of different structures. The ion exchange capacity of each type of groups can be determined with precision higher than 0.1 meq/g. The p K i values of the groups present in macroamounts are determined with precision at least ±0.2 p K units.

A mathematical model establishing relations between the selectivity, degree of ion exchange and structure of spatial polyelectrolytes has been developed. The structure is expressed through two parameters: radius of interaction (that is a maximal distance at which the exchange sites influence each other) and the number of exchange sites situated in the sphere of interaction (neighbors). A larger number of neighbors should result in more complicated shape of property-composition dependencies of the ion exchange system. A computer model allowing estimation of the probability of the presence of different numbers of neighbors in different elements of the polymer network as a function of distance from the exchange site was suggested. The polymer network is represented as a body obtained by integration of fragments with eight to ten monomeric units of different shapes: linear chains, H and T shape units and small rings. The theory was applied to interpreting dependencies of selectivity of cation exchange on sulfonic styrene-divinylbenzene cation exchangers and strong base anion exchangers on the same matrix. Dependencies of selectivity on degree of ion exchange and cross-linkage of the resins are in good agreement with the prediction of the theory if the predominant number of neighbors in different particular cases is ranging between two and four. The non-equivalence of exchange sites of spatial polyelectrolytes is their inherent property because different exchange sites have different amounts of the neighbors. The difference in the selectivity dependence on the cross-linkage of cation and anion exchangers on styrene-divinylbenzene matrix finds a simple and natural explanation.

The effect of minor additions of ion exchange substrates Biona and mechanical mixtures of ion exchangers, saturated with a full set of biogenic elements, on the productivity of sand and garden soil was investigated. The addition of 2% of substrate Biona increased the crops by four to five times for soil and four to eight times for sand. The effect of the addition of the mixture of the monoionic forms was also very pronounced (two to three times) while less than that of the addition of the ion exchange substrate. Results of the experiments showed that ion exchanger substrates could be used for fertilization of depleted soils.

Comparative study of softening of model hard water with both strongly acidic fibrous FIBAN K-1 and granular KU-2 ion exchangers was carried out. The influence of the filter-bed height, packing density of fibrous ion exchangers, volume sorption capacity, and filtering rate on the efficiency of calcium removal from model hard water was analyzed.

A simple method for calculating acidity parameters, suggested in a previous publication (React. Funct. Polym. 38 (1998) 73), as well as constants for the modified Henderson–Hasselbach equation, is described. It follows from analysis of the shape of potentiometric titration curves of ion exchangers that along with the vertical inflection at the equivalence point, they have a horizontal inflection at half neutralization. The pH value and the tangent of the titration curve at that point are simply related to the acidity parameters of resins. The derived equations allow ready determination directly from the titration curve.

Fibrous ion exchangers (FIBAN) have been studied in a model process of water softening and removal from water simultaneously present heavy metal ions: Co2+, Ni2+, Zn2+, Cd2+, Cu2+, Pb2+. The effect of the following factors on the efficiency of Ca2+ removal from a model solution has been studied: the filtering bed height (7–40 mm); density of the column packing corresponding to the volume capacity, 0.17–0.83 meq/cm3; solution flow rate (4–37cm/min). A fibrous sulfonic-type ion exchanger in shallow beds has exhibited a high efficiency in removal Ca2+ from water, greatly exceeding efficiency of a conventional sulfostyrene resin studied in parallel. In all cases high breakthrough capacities corresponding to the degree of column utilization, 0.6–0.9, have been observed. In the processes of water purification from heavy metal ions the highest efficiency was observed for chelating fibrous ion exchanger with iminodiacetete groups. A granular resin of the same type had much lower efficiency. Fibrous ion exchangers can find a wide application in water treatment processes.

Equilibria of ion exchange of neutral aliphatic amino acid cations (A + =Gly + , Ala + , Val + , Leu + ) and H + have been studied on a liquid sulfonic type ion exchanger — dinonylnaphthalene sulphonic acid dissolved in heptane. It has been established that the difference in selectivity of extraction of these cations is much greater than on sulphostyrene resins, which is a favourable precondition for their selective extraction. The selectivity coefficients of the H + –A + exchange have a region of a low dependence on the degree of loading of liquid ion exchanger ( X =0 –0.5) and a region of a sharp decrease ( X >0.5) . This phenomenon is explained as a result of formation of very stable complexes of the amino acid cations and the anion of dinonylnaphthalene sulphonic acid containing one unsubstituted proton per 3–6 A + cations. The IR spectra confirm this assumption. The dependence of the selectivity coefficient on the degree of H + –A + exchange has been described using the previously developed mathematical model of ion-exchange processes. The model is consistent with the experimental data in an assumption that four nearest neighbours of an exchange centre in the associates of the liquid ion exchanger influence the energy of ion exchange on a given exchange site.

The effect of compression of a stearic acid Langmuir monolayer on the interaction of copper ions with the monolayer and on the formation of interface clusters has been studied as functions of pH and ionic content of the water subphase. Copper binding was estimated by direct electron paramagnetic resonance measurements of ion concentrations in the water subphase. A scanning tunnelling microscopy study of monolayer Langmuir-Blodgett films, deposited on graphite substrates, gave evidence for the formation of nanosized clusters on the monolayer surface. The data obtained showed that the interaction of the monolayer with copper ions and the accompaning cluster formation processes were determined by the arrangement, order and mobility of the stearic acid molecules in the monolayer and the electrostatics at the interface.

Parallel investigations with fertility were carried out in standard garden soil with ion exchange substrate BIONA 111 as well with mixtures in different proportions. The ion exchange substrate was a mixture of ion exchange resins saturated in certain proportions with a complete set of biogenic ions. Plant productivity in the ion exchange substrate in a 6-week vegetation period was 950 g/kg of the green biomass compared with 29 g/kg in soil. Productivity linearly depended on the mass fraction of the ion exchange substrate in the mixtures with the garden soil. Addition of 1% of the ion exchange substrate is sufficient for starting vegetation in completely depleted soil and barren sand. Addition of different ionic forms of ion exchange resins (K + , Ca 2+ +Mg 2+ +K + , NO 3 − , NO 3 − +H 2 PO 4 2− +SO 4 2− ) caused pronounced positive effects on soil productivity though these effects were less significant than those of ion exchange substrate. Addition of ion exchange substrates can be an efficient means for remediation of destroyed soils and fruitless rocks.

Neutralization of ion exchangers in H + or OH - forms by alkali M(OH) z or acid H z A was considered as a specific case of ion exchange H + -M z+ or OH - -A z- accompanied by the neutralization reaction. An equation connecting pH and the external electrolyte concentration with the ion exchanger neutralization degree was derived. It can be used for presentation of the potentiometric titration curves in mathematical form or their calculation at different (not necessarily constant) concentrations of external electrolyte. Applicability of the modified Henderson-Hasselbach equation as one of the possible means for description of potentiometric titration curves of ion exchangers was also discussed. The range of its applicability and limitations were established. The physical meaning of its constants was clarified, and the equations of their relations with the apparent ion exchange equilibrium constant have been obtained. The theoretical considerations are illustrated with the example of potentiometric titration curves of a carboxylic acid ion exchanger obtained in a wide range of degrees of neutralization and external electrolyte concentrations.

This chapter is a review of the authors’ works on the mathematical and computer modeling of ion exchangers on styrene–divinylbenzene matrix. A mathematical model based on the concept of influence of neighboring exchange sites on the properties of each other allowed explaining the dependence of selectivity and additive properties of the ion exchange system on the degree of ion exchange. The information of interaction between the nearest neighbors and water molecules in the vicinity of the functional groups as well of the structures on the fragments of the polymeric structure of the ion exchanger has been obtained using quantum chemistry nonempirical ab initio calculations. These data have been obtained for different degrees of hydration (0–10 water molecules per sulfonic group) and the following counter ions: H+, Li+, Na+, K+, Rb+, Cs+, Ag+, Be2+, Mg2+, Ca2+, Sr2+, Ba2+, Cd2+, Ni2+, and Pb2+. The mathematical modeling as well as molecular mechanic and quantum chemistry calculations is consistent with the main concepts used in interpreting of ion exchange equilibria: a concept of nonregularity of the exchange sites in polymeric ion exchangers and competitive interaction of the counter ions with the fixed ion and water molecules.

The chapter is a review covering the most important aspects of fibrous ion exchangers: syntheses, physical chemical properties, equilibria and kinetics of sorption processes, and possible and real fields of their applications. Their properties, methods of preparation, and applications are in many ways different from those of conventional ion exchange resins. Advantages and problems connected with fibrous ion exchangers are considered in the chapter. Sorption of different substances from air and applications of fibrous ion exchangers for air purification from substances of different natures (acid, base, neutral substances, water vapors) is a most important field for their practical use. Fibrous catalysts, color-changing sorbents, and hybrid fibrous sorbents impregnated with nanoparticles of inorganic substances are also described.

The possibilities and advantages of fibrous ion exchangers in different water treatment processes have been discussed in comparison with their granular analogues. The main advantage of fibrous ion exchangers is a unique combination of an extremely high rate of ion exchange process (like microspheric resins) and a low hydrodynamic resistance of the filtering layer (like conventional industrial resins). This allows using fibrous ion exchangers in shallow filtering beds (1–3 cm) at high flow rates of the purified water. A high efficiency of fibrous ion exchangers is demonstrated on several practically important examples: water softening, water purification from trace amounts of led, copper, cadmium and zinc and nitrates. Data on the properties of commercially available fibrous ion exchangers of FIBAN® type are presented. Alternative technologies of water treatment processes are discussed in comparison with the conventional fixed bed ion exchange technology. Fibrous ion exchangers can be a good supplement to traditional ion exchangers, especially in wastewater purification because they allow treatment of large volumes of water in a short period of time.

Ion exchange treatment of gases can be, in principle, as vast of a field for application of ion exchangers as liquid ion exchange technologies. Investigation of ion exchangers as sorbents from gaseous media began in the fifties, when the first patents, papers and monographs appeared[1–6]. Since then this research has developed in a number of countries, especially in USSR, Japan, Germany, USA and Poland[7–11].

Sorption of HCl, HF, SO2 and H2S from their mixtures with air have been studied in dynamic conditions on two types of novel fibrous ion exchangers: a strong base one of type 1 on polypropylene-styrene matrix and a weak base exchanger with amido-amino groups. Influence of the air flow rate, sorbate concentration and air flow humidity have been studied. Conditions for the ion exchangers regeneration with water or soda solutions are described. It has been found that side effects such as sorbate molecules association, water sorption and oxidation of the substances sorbed strongly influence their sorption — desorption behaviour. Characteristics of industrial air filtering plants with fibrous ion exchangers are presented.

A mathematical model for description of dependences of the ion exchange equilibria parameters on the composition of ion exchangers is suggested. It is assumed that ion exchange sites in the polymer network are different due to the difference in their micro-environment characterized by the number of the nearest neighbours and the local ionic composition. A “property-composition” equation was derived and proved to be adequate to describe the experimental data for some complicated ion exchange systems.

Donnees sur l'echange des ions ethylammonium primaires secondaires tertiaires et quaternaires en presence de l'acide dinonylnaphtalene-sulfonique (echangeur de cations liquide) dans de l'heptane, du nitrobenzene et de l'ethyl-2 hexanol. Donnees, aussi, sur l'echange en presence de l'echangeur de cations solide, le KRS-8

Ion exchange, water uptake and VPO studies have been performed on the two liquid cation exchangers, dinonylnaphthalene and didodecylnaphthalene sulfonic acids and some of their salts. It is found that didodecylnaphthalene sulfonic acid is slightly less aggregated than dinonylnaphthalene sulfonic acid, its water uptake is also less, but the selectivity is about the same. In heptane the presence of water increases the aggregate size, in benzene this increase is smaller and in chloroform no increase is observed. It is also demonstrated that in the concentration range used, the size of a certain aggregate is practically constant. It has been possible to follow the change in aggregate size during the ion exchange process for the system Al3+ - H+. The fact that the three parameter model applies suggests that the interactions at an exchange site are practically independent of aggregate size.

Physico-chemical properties, structure and possible application of the “Fiban” fibrous ion exchangers are reviewed. The materials described belong to strong-acid, strong-base and polyampholite types. They can be produced in the form of threads, cloths, non-woven materials, etc. Methods of their application as means for air purification from acid or base impurities are described. Examples of their use as chromatographic materials and absorbents are presented (separation of simple inorganic cations and anions, heavy cations, amino acids, removal of chromium(VI) from water).

Ion exchange and water sorption data for the systems (K,H)D and (Ca,H)D (D = dinonylnaphthalene sulfonic acid) in heptane-isooctanol mixtures can be described by a simple equilibrium model for formation of mixed micelles. This model gives the following relation between the experimental quantity Y and the corresponding quantities yi relating to the two pure micelles and the mixed micelle Y=y 1 X 2 +y 2 (1- X ) 2 +2y 3 (1- X ) X = equivalent fraction of metal ion in the organic phase. This equation can be identified with the relation Y=y 1 X +y 2 (1- X )+y′ 3 X (1- X ) used to fit experimental data Y( X ) . The quantity y3 is computed from y 3 = (y 1 +y 2 +y′ 3 2 Both extraction and IR data show that isooctanol forms complexes with the sulfonate partly blocking the ion exchange process.

A method for computing the ionic composition of an equilibrium phase, either solution or resin, at a given composition of the other has been suggested for multiionic systems. Application of the method requires a knowledge of selectivity coefficients as a function of exchanger phase composition for binary systems. The equivalent fractions of exchangeable ions in the resin or solution have been found by solving a set of equations composed of n−1 equations of selectivity coefficients of pseudobinary equilibria and an equation of mass balance. Knowledge of the dependence of selectivity coefficients of pseudobinary exchanges on resin ionic composition is required for the calculation. It has been found in an analytical form using the theoretical approach suggested in a previous paper [1]. The equations have been tested with five ternary systems exhibiting strong deviations from ideal behaviour (ion exchange equilibria of monovalent ions on highly cross-linked sulfonic resins). Three approximations have been used for theoretical calculations. In the first approximation, the system was treated as ideal (constant selectivity coefficient). In the second case, the function In k j i = f ( x j was approximated by straight lines (regular system) situated on the plane In k j i = f ( x i , x j ). In the third approximation, a second-power equation valid for irregular statistic systems was used for the function ln k j i = f( x i , x j ). The first approximation was shown to give results on highly cross-linked resins that are in disagreement with the experimental data. On the other hand, the third approximation gave results in excellent agreement with the experimental data.

The potassium-hydrogen exchange on dinonylnaphthalene sulfonic acid dissolved in heptane has been studied in the temperature range 1–80°C using batch techniques and titrimetric analysis. The data can be fitted with a simple model, where it is assumed that the system contains three kinds of micelles, HDNNS-micelles. KDNNS-micelles and a mixed micelle (K. H)DNNS each with a different ion exchange constant. The relation between the experimental value for the equilibrium quotient (κ) and the three parameters κ 1 , κ 2 and κ 3 is log κ= X log κ 1 +{l− X } log κ 2 + X (l− X ) log κ 3 where X is the mole fraction of potassium in the organic phase, i.e. the distribution of micelles is assumed to be statistical. From the curves log κ( 1 T ) x the function ΔH( X ) is obtained at each temperature. These data can be fitted with the same model i.e. δH ° =δH 1 ° X +δH 2 ° (1− X )+δH 3 ° X (1− X ) Together with the free energy data ( ΔG ° = − RT ln κ ) entropies are computed for the three kinds of micelles. It is found that while the two pure micelles have negative entropy changes, the mixed micelle has a positive entropy change, provided the assumptions inherent for the equation above are correct. The mixed micelle concept also explains the water extraction in the system HDNNS-KDNNS in heptane as shown for data at 25°C.

In previous papers in this series it was found[1,2] that ion exchange and water sorption data for dinonylnaphtalene sulfonic acid (HD) in various solvents could be fitted by the expression Y=y1X+y2(1-X)+y′2X(1-X) Y is the property studied and yi the same property related to three kinds of micelles, those corresponding to the pure salts (y1 and y2) and mixed micelles containing both ions (y′3). X is the equivalent fraction of metal ion in the organic phase the H+Me2+ exchange being studied. In the present paper it is shown that if it assumed that the distribution of ions over the three kinds of micelles is random the quantities in eqn (1) can be given a simple physical interpretation.

This article examines a family of ion-exchange fibers, FIBAN, containing primary and secondary amine groups. These ion exchangers have a fiber diameter of 20–40 Μm, high osmotic and mechanic stability, a high rate of adsorption and regeneration, and excellent dynamic characteristics as filtering media. Inparticular, this article discusses the use of FIBAN fibrous ion exchangers in the recovery of gold cyanide andbase-metal cyanides (copper and mercury) from mineral-leaching solutions. The influence of polymer structure and water content on their extraction ability is described, along with key parameters of gold hydrometallurgy such as extraction efficiency, selectivity, pH dependence, gold cyanide loading, kinetics, and stripping.