The description of multicomponent equilibria for the sorption of ions onto charged surfaces by means of the Surface Complexation Theory (“SCT_model”) has been elaborated by German researchers. Such approach is included into the solution of the problem of multicomponent nonlinear dynamics in ion exchange column with using the equilibria on the basis of the SCT_model extended to the description of the competitive adsorption of heavy metal salts and strong acids onto weakly basic anion exchanger such as Purolite A109 and PEI-CS-07. Unique properties of these resins are due to the LEWIS-base properties of amino groups. As a consequence, they are able to undergo coordination bonding with LEWIS acids such as heavy metals.

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The ability to accurately predict ion exchange equilibria is vital if efficient ion exchange processes and equipment are to be designed. This is particularly true when three or more ionic species are competing with one another for sites on the exchanger. Many models to predict ion exchange equilibrium behaviour have been developed over recent years. The complexity of the models have increased from simple ones which assume ideal behaviour in both phases to ones which can predict behaviour in fourcomponent systems based upon binary equilibrium data. This paper will critically review the models developed in recent years and propose a series of requirements that any proposed ion exchange equilibrium model should meet.

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The interaction of an ionic solute with a charged surface has been interpreted with an appropriate model derived on the basis of electrostatic theories. The electrostatic effects should play important roles in ion-exchange chromatography, but have not been well involved in the derivation of a retention model. The model proposed in this paper, which is derived based on an electrostatic theory, is capable of reasonable explanation of the retention of ionic solutes having different molecular sizes.

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Although ion-exchange phenomena are usually studied using bulk materials, such as resins, membranes etc, ion-exchange occurs even at solution surfaces (or solution/air interface) . Efficient approaches to ion-exchange occurring at this slightly unusual domain have been severely limited because of the restricted reaction volume (in turn small amounts of solutes involved m the reaction) . We have developed a special approach to the reaction occurring at solution surfaces on the basis of X-ray absorption fine structure. In the present paper, we briefly mention the effectiveness of this approach, and discuss surface ion-exchange equilibria and the structures of conterions electrostatically attracted by surface monolayers.

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To study the energetic and structural characteristics of the systems involved in the Ca²⁺ ↔ Mg²⁺ ion exchange at clinoptilolite, the quantum chemical modelling was performed of several clusters representing the portion of the heulandite lattice which involve one 10-member (10M) ring containing the isomorphic substitution, one 8-member (8M) ring also containing the isomorphic substitution, and adjacent 4- and 5-member rings. It was shown that, while for dehydrated systems the localisation of Mg²⁺ ion in the 10M ring and Ca²⁺ ion in the 8M ring is preferable, for the partially hydrated systems the localisation of Ca²⁺ ion in the 10M ring and Mg²⁺ ion in the 8M ring is favourable, with the energetic yield of corresponding ion exchange reaction of the order of 100 kJ/mol.

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Adsorption of mono, di-, tri- and tetra-gly by FSM-16 was attempted and isotherms for adsorption of them was drawn. The isotherms for adsorption were arranged from high to low that of tetra-, tri-, di- and mono-gly in order. The arrangement of the isotherms was dependent on the solubility of glycine and its oligomers. On the other hand, FSM-16 can function as the molecular sieve because FSM-16 has a mesopore. The effect of the molecular sieve showed very little in extend of the adsorption.

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Although the structures of ions in ion-exchange resins are of fundamental importance, very few studies have been reported because of the lack of efficient approaches. X-ray absorption fine structure is one of the most efficient tools for studying structural aspects involved in ion-exchange processes because it is highly selective to an element of interest and is applicable to any materials and phases. The structures of Cl^- and Br^- an anion-exchange resin are discussed by this approach; the structures both in dry resins and in resins soaked in solvents are compared to reveal the effects of ion-exchange groups and solvents.

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The ³¹P NMR chemical shift of phosphinate ion (PH₂O₂^-) is highly sensitive to the concentration of tetramethylammonium cation. Phosphinate ion was therefore taken as a generic probe species to explore the invasion of the non-exchange electrolyte (tetramethylammonium phosphinate) into tertamethylaznmonium form resin (AG 50W-X1, 50W-X2 and 50W-X4) and gel (SP Sephadex C-25) type cation exchangers. By making use of the mass balance and the Donnan equations the ionic composition of the exchanger phases was calculated as a function of concentration of the non-exchange electrolyte (0.025-1 M) .

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Boron species adsorbed onto polysaccharide gels, cellulose (Cellulofme GC), cellulose cross-linked with epichlorohydrin (Cellulofme GCL) and dextran cross-linked with epichlarohydrin (Sephadex G), were characterized by ¹¹B NMR spectroscopy. Borate ion reacts with Cellulofine GCL-25 to form both (α, β) -monochelate and (α, β) (α, β) -bischelate complexes. In the case of Cellulofine GC-100, however, hydrogen bonds among the cellulose chains to hold the gel structure prevent the completion with borate. For Sephadex G-25 the formation of (α, β) (α, γ) -bischelate complex was revealed in addition to (α, β) -monochelate, (α, β) (α, β) -bischelate and (α, γ) -monochelate complexes similarly to the borate-dextran system. Formation constants of borate complexes with Cellulofine GCL and Sephadex G are reported.

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An elastomeric protein called elastin is fully responsible for sophisticated biological elasticity in mammalian tissues such as the aortal wall, ligament, lung, and skin. A key step in elastogenesis to establish the structural basis of elastomeric function, a self assembly of the precursor protein in extracellular space, can be mimicked by the temperature-dependent coacervation of an elastin-related polypeptide-water system. Characteristics of the two types of metal cation binding sites, carboxy oxygens of side ammo acid residues and peptide backbone carbonyl oxygens, were examined in relation to the multiple biofunctionality as an extracellular matrix using biologically derived α-elastin and synthetic elastin model polypeptide. Nonspecific metal cation bibdings to the carboxy groups of side amino acid residues cause simple salting-in and -out effects. Peptide backbone carbonyl oxygens of particular repeating peptide sequence, -Val-Pro-Gly-Val-Gly-, are specifically selective to Ca²⁺ ions and substantially rejective of other metal cations including alkali metal cations, Mg²⁺, and Cu²⁺ ions. Ca²⁺ ion binding to peptide carbonyl groups of elastomeric protein induces destruction of a key structure for coacervate characteristics and elastomeric functions.

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New functionalized graft polymers (fCMS-Br₃, fCMS-BH₄) were synthesized from an anion-exchange fiber, which was prepared using radiation-induced graft polymerization. The abilities of these polymers as polymer-supported reagents are discussed. After bromination of p-cresol and reduction of benzaldehyde with these polymers in a column-mode, the relationship between flow rate and product yield was examined, and compared with the results of the polymer-supported reagents prepared from a porous resin. In both cases, the present graft polymers provided the desired compounds more efficiently even at a high flow rate.

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Ion exchange resins are used to extract nickel from the waste liquor at lab scale. The adsorption and stripped characteristic are studied. Suitable resins, which are commercially available, were evaluated in order to recover nickel from ammoniacal sulphate waste liquor with 0.164-0.235g/dm³ Ni and 0.038-0.040g/dm³ Mg, for substitute the sodium or ammonium hydrosuiphide used. The nickel concentration after the waste liquor has been flowing through the dynamic ion exchange column until the breakthrough point was 0.2mg/dm³, the maximum permitted nickel concentration in the effluent waste liquor according to exigent European Standard, the adsorption efficiency exceed 98%.

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In condensate polishing system, the reduction of sulfate ion concentration is very important to prevent corrosion of the steam generator. The sulfate ion is derived from cation exchange resin (CER) leachables such as polystyrene sulfonic acid (PSS) . On the other hand, anion exchange resin (AER) with high capability to capture sulfate ion derivatives is also required. It has become clear that highly crosslinked CER is effective to reduce its leachables under oxidative conditions. And, thermally stable AER with porous structure was found to have higher capacity to remove the leachables from CER. The combination of highly crosslinked CER and thermally stable porous AER are recommended for condensate polishing system.

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Ion-exchange equilibria of Fe (II), Mn (II) and Co (II) complexes of chloride on Amberlite IRA 400 Anion-exchanger have been studied by determining distribution number (D) of each complex between aqueous and resin phases as a function of metal ion and ligand (HCl) concentrations. Result of the study shows that increasing the concentration of metal ion (at a constant concentration of ligand) or vice versa resulted in the increase of D values. Analysis of ion exchange process using isotherm Langmuir and stoichiometric equilibria has suggested that the exchange is a complete monolayer adsorption and that the charge of the complex, in this case, does not significantly affect the ion-exchange process.

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To evaluate the effectiveness of anion exchange resin in the binding of dietary phosphate in the digestive system, we carried out in vitro and in vivo studies of phosphate binding by comparing the anion exchange resin PAA-B, which has the same chemical structure as Sevelaner HCl (Reriagel R), with CaCO₃. In in vitro phosphate-binding experiments, the anion exchange resin bound less phosphate at pH 7 than did CaCO₃. In vivo phosphate-binding experiments demonstrated that the levels of phosphorus excretion in the feces of rats treated with PAA-B increased to the same degree as those of rats treated with CaCO₃; however, PAA-B treatment resulted in gastrointestinal transport delay. These data suggest that anion exchange resin has a bright prospect as an effective drug for treating hyperphosphatemia if the adverse gastrointestinal effects can be overcome.

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Separation of Cephalosporin-C was investigated on synthetic adsorbents in a column liquid-chromatography to obtain fundamental data for industrial application. Two types of synthetic adsorbents with different porosity were tested, and their chromatographic behaviors were compared. The difference in the chromatographic peak sharpness and the peak separation can be explained by the difference in the porosity of the adsorbents.

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Zirconium (IV) loaded Diaion CRP 200 methylenephosphonate resin was tested in the column mode removal of fluoride by repeating the adsorption-elution-regeneration procedure for a long term. This ligand exchanger was highly selective to fluoride; no interference of chloride, nitrate, and sulfate was observed. On the contrary, their sodium salts enhanced the breakthrough capacity of fluoride. In addition, it was clarified that the reloading of small amount of Zr (IV) in each regeneration step overcompensate the loss of Zr (IV) from the column in the preceding elution process, accompanying with the marked increase in the breakthrough capacity of fluoride.

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The titled bifunctional fiber (FVCPS-f) were prepared by treating chloromethylated vinylbiphenyl-grafted polyethylene-coated polypropylene fiber (0.9 denier, length 3.8cm) with triethyl phosphite, chlorosulfonic acid, and conc. hydrochloric acid, in successive. Phosphorus and sulfur contents of FVCPS-f were 1.8 and 0.74 mmol/g, respectively and its acid capacity was 4.2 meq/g. Its breakthrough capacity (BC) for Fe (III) gradually decreased with an increase in flow rate of feeds from 20 to 1000 h^-1 in space velocity (SV) ; for instance, its BC at a SV 1000 h^-1 was 0.12 mmol/g, whereas commercially available phosphonate resin and monofunctional phosphonate fiber were not able to give practically meaningful BC at such an extremely high flow rate.

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A bifunctional cation exchange resin (R4PS) having both phosphonate and sulfonate groups was derived from macroreticular poly (ω-bromobutylstyrene-co-divinylbenzene) . Phosphorus and sulfur contents of R4PS were 2.2 and 2.5 mmol/g, respectively, and its acid capacity was 6.6 meq/g. R4PS exhibits the characteristic metal ion selectivity, which is different from that of each monofunctional resin containing phosphonate or sulfonate group alone. In the strongly acidic region below pH 2, R4PS has higher capacities for uptake of Fe (III) than does a corresponding monofunctional phosphonate resin. In column-mode uptake of Fe (III) from strongly acidic feeds, R4PS exhibited excellent kinetic performances because of its high swelling in the wide pH range.

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Chloromethylstyrene-grafted polyethylene-coated polypropylene fiber (0.9 denier, length 3.7cm) was functionalized by reaction with diethyl iminodiacetate and subsequent hydrolysis of the ester introduced. An acid capacity of the resulting chelating fiber (FIDA-f) was 4.3 meq/g. Although a maximum permissible flow rate of feeds was depressed with an increase in the conditioning pH of the FIDA-f column, breakthrough profiles of Pb (II) were independent of the flow rate of feeds up to 800h^-1 in space velocity (SV) . The usefulness of FIDA-f was demonstrated by quantitative removal of Pb (II) from 600 bed volumes of a Pb (II) -spiked river water (5ppm) at a flow rate of SV 400h^-1.

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The humic compounds removal from tap water by separate scavengers and their combinations was investigated. It was shown, that adsorption of humic compounds can be improved using a combination of weak-base macroporous anion-exchange resin Dowex MWA-1 and bituminous granular activated carbon F-300 in comparison with the individual performance of these adsorbents. Utilization of the investigated combination of adsorbents for water purification allows to increase velocities of filtration (decrease the dimension of adsorption plants), increase capacity of activated carbon and decrease demand of the regeneration agent. Purified water has a low content of humic compounds and a constant mineral composition.

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The removal of humic compounds is an urgent task in tap water treatment in Ukraine. The use of polymeric recycled scavengers is most perspective for the purification of water up to the requirements needed for drinking and technical water. This study shows results for the extraction of the humic compounds from water by strong- and weak-base anion exchange resins with various porous structures. The results show that SDVB-base anion exchange resins Dowex 11, Dowex MSA-1 and Dowex MWA-1 are most effective. Studies were performed by static and dynamic conditions. Mechanism of the adsorption of humic compounds by anion exchange resins and the application for different tasks of water treatment were shown.

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Active sites, capacity, energy, and rate constant on the adsorption of Zn (II) and Cd (II) on chitin isolated through deproteination followed by demineralization processes of crab (Portunus pelagicus Linn) shell have been investigated. The chitin possessed acetamide functional group that was suggested to exist in two different chemical forms of NHC (O) CH₃ and NHC (OH) =CH₂. It means that one hydrogen ion in CH₃ in the acetamide can be conjugated to oxygen carbonyl to form C-OH. The active site responsible for the adsorption of Zn (II) and Cd (II) would be nitrogen on the acetamide functional group. The adsorption dataa for both metal ions were fit quite well with the Langmuir isotherm model, resulting the adsorption capacities of 3.2×10^-4 and 2.8×10^-4 molg^-1 for Zn (II) and Cd (II), respectively, and adsorption energies of 15.1 kJ mol^-1 for Zn (II) and 17.9 kJ mol^-1 for Cd (II) . It was also revealed that Zn (II) was adsorbed slightly faster than Cd (II) with first order adsorption rate constants of 2.7×10^-3 min^-1 for Zn (II) and 2.6×10^-3 miri^-1 for Cd (II) .

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Crystalline α-ZrP was loaded onto the interior surface of porous materials including polymer resin, silica gel and alumina tube, in which α-ZrP is distributed uniformly in the pore. This modification method can be applicable to the various size and shape of the porous matrix for the desired applications. The α-ZrP loaded polymer resin revealed high affinity toward the adsorption of soft metals including Pb (II) and Cd (II) . Due to the remarkable selectivity, fast kinetics and chemical stability the present resin was effectively applied to the pre-concentration of trace amount of Pb (II) .

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Hydrous titanium oxide (HTiO) was prepared using titanium chloride and NaOH/NH₄OH and the precipitation effected over the pH range 1 to 12. The materials were characterized by chemical analysis, X-ray, particle size distribution, surface area, water sorption to characterize the surface groups and pH-titration to evaluate the point of zero charge. The characterization by various techniques was not satisfactory in the case of HTiO prepared using NaOH, as sodium was incorporated in the matrix, while HTiO prepared using NH₄OH showed features reflecting the effect of pH of precipitation on the overall characteristics.

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Among the various techniques employed to study the state of water present in ion exchangers, vapour pressure isotope effect during the dehydration of different ionic forms of the exchanger provides useful information on the primary and secondary hydration shells around the ions and their temperature effect. The hydration numbers obtained by analyzing the water sorption isotherms by D'Arcy and watt equation are in consonance with those obtained for these ions in exchanger phase and electrolyte solutions. These information can be used to understand the nature of electrolyte solutions and the ion exchange selectivity.

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Ion-exchange behavior between sodium ion and various metal cations (alkali, alkaline earth and a few transition metal cations) in hydrated molybdenum bronzes were investigated in [NaCl] +n [M (n+) Cl_n] =1M solution. The selectivity of ion exchange was in the order of Cs>Rb>K>Li for alkalin metal and Ba>Sr>Ca>Mg for alkaline earth metals. Transition metal cations gave similar ion exchange behavior to each other. The effect of the change in structure was hardly observed. The results suggest that the ion exchange behavior depends on the property of metal ions. The change in MoO₃ interlayer spacing depends on the hydration energy, i.e. the surface charge density of metal cations. Hydrated sodium bronze can exchange with other metals and can extract metal ions in the solution. This property may be useful as the ion exchanger

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Hexagonal hydrogen molybdenum bronze was obtained from alkali decamolybdate with tunnel structure by the reduction with nascent hydrogen. A maximum amount of inserted hydrogen was H/Mo=1.5. Hydrogen insertion accompanied the change in the amount of structural water and the removal of alkali ions. NMR spectrum proved the existence of several types of proton. We proposed the various models of proton clusters and the proton distribution of each model. We also discussed the effect of alkali ions in the tunnel-site by the results of the simulation of NMR spectrum.

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The sorbents to remove heavy metal ions from water solutions are developed by the modification of kaolinite, meta-kaolinite and aluminium oxyhydride by polyphosphates. The adsorption isotherms of Ni²⁺, Co²⁺, Cr³⁺ at the adsorbents demonstrate high adsorption capacity (300 to 100mg/g depending on the sorbent type) and high selectivity of the materials with respect to the sorbed cations. The distribution coefficients in the Henry region, K_d=5⋅10⁵-1⋅10⁴cm³/g, are comparable to the values characteristic to organic chelate forming sorbents. The decrease of pH to 2 results in almost complete desorption of heavy metal ions from the sorbents.

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A series of Li₂Mn_1-xTi_xO₄ (x≤0.5) samples was prepared by solid-state region at 850°C. Selective lithium extraction from Li₂Mn_0.5Ti_0.5O₄ was studied by chemical analysis and XRD and TG-DTA measurements. The lithium exaction from Li₂Mn_0.5Ti_0.5O₄ was carried out in H₂SO₄ solutions with different mole ratios of H⁺ in the solution to Li⁺ in the solid ( [H⁺] _l/ [Li⁺] _s) at 50°C. The lithium extraction was found to proceed through a mechanism of Li⁺/H⁺ ion exchange when ( [H⁺] _l/ [Li⁺] _s) ≤0.2, accompanied by a lithium dissolution process when ( [H⁺] _l/ [Li⁺] _s) ≥0.4. The lithium-extracted product retains the monoclinic structure of Li₂Mn_0.5Ti_0.5O₄.

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Adsorption behavior of ammonium ion on both the crystalline Linde Type A zeolite with sodium ions (Na-LTA) and the noncrystalline pseudomorph after Na-LTA were investigated. Na-LTA transformed to the amorphous phase which preserves original morphology, that is, noncrystalline pseudomorph, by a treatment of acid solution. The pseudomorphic transformation of Na-LTA was occurred by 0.06 M HCl treatment and was confirmed by powder XRD method and SEM. The adsorption amount of ammonium ion on the noncrystallne pseudomorph was ca. 45% of that on the crystalline Na-LTA, but was comparable to that of natural zeolite such as mordemte and clinoptilolite. The linear relationship between the amount of adsorbed ammonium ion and the amount of dissolved sodium ion on the noncrystalline pseudomorph after Na-LTA was obtained. It indicated that the ammonium adsorption on the noncrystalline pseudomorph was occurred by the ion-exchange mechanism.

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Natural mordenite from Shimane Prefecture, southwest Japan, was treated at temperatures of 50-200°C and autogeneous pressure for 7 days, changing the NaOH concentration from 1 to 10M (M=mol dm^-3) . The several types of zeolites, such as phillipsite, hydroxysodalite and analcime were obtained by the transformation from mordemte after alkali hydrothermal treatments. The formation of hydroxycancrinite was observed for the first time under the hydrothermal treatment of the natural mordenite and the conditions were determined for the transformation. These results indicated that the phases of the zeolite formation from mordenite were clearly dependent on both NaOH concentration and treated temperature. The present results may provide a technology for the improvements of low-grade natural zeolites into high-grade ion exchangers.

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A new ion-exchanger for heavy metal ions was prepared with straw as main raw material. The removal process of Cu²⁺, Cd²⁺, Co²⁺ and Ni²⁺ from zinc sulphate solutions (both simulated and industrial solutions) with the ion-exchanger has been investigated as function of pH of solution, amount of ion exchanger, reaction time and temperature. After the solutions had been treated, the concentrations of Cu²⁺, Cd²⁺, Co²⁺ and Ni²⁺ can be reduced from 4.27, 8.56, 0.24 and 0.18 mmol/dm³ to 0.0018, 0.0052, 0.0075 and 0.0089 mmol/dm³ respectively. The loss of zinc ion in the solution was less 1% (mass fraction) .

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Layered manganese oxide (birnessite) was prepared by oxidation of Mn (NO₃) ₂ with H₂O₂ in NaOH solutions. The product had a composition of Na⁺_0.44 (Mn^III_0.44Mn^IV_0.56O₂) ^0.44-⋅0.5H₂O and the negative charge of the host MnO₂ layer due to Mn^III was counterbalanced by Na⁺ in the interlayer. This Na-bimessite was treated with a hydrochloric acid solution to exchange Na⁺ with H⁺. The H-birnessite obtained was further treated with an n-propylamine solution, and the interlayer distance nearly doubled to 1.41 nm by the incorporation of propylammnonium ions (PA) . The PA-bimessite was suspended in a VCl₃ solution, and V ions were intercalated. The V-birnessite had a composition of V⁵⁺_0.08 (H_0.3Mn^III_0.7Mn^IV_0.3O₂) ^0.4-⋅0.3H₂O, and it was found that the interlayer V ion was oxidized to 5+, possibly by Mn^IV in the host layer. This compound was expected to show better charge-discharge properties as a battery material than Na-bimessite, since multi-valent V⁵⁺ ions were likely to attract the layers more strongly and to support the layered structure more firmly.

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A layered perovskite type oxide, HCa₂Nb₃O₁₀, can incorporate mono- and divalent metal ions from aqueous solution. n-Pentylamine intercalates into the interlayer of HCa₂Nb₃O₁₀ and the resulting oxide had an excellent reactivity for metal ions such as Cs⁺, Ca²⁺ or Sr²⁺. The mechanism of the intercalation of the metal ions into the hydrophobic interlayer in aqueous medium was studied.

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Identification of iron oxide species on the framework of zeolite-Y by using EDTA dissolution method and Electron Spin Resonance (ESR) method has been studied. Encapsulation of iron ions in the framework of zeolite was carried out by ion exchange method using ultrasonic cleaner and then followed by dissolution using EDTA solution. The iron ode was determined by using chemical analysis and Electron Spin Resonance (ESR) . From the ESR spectra it was found that encapsulation of iron oxide to the framework of zeolite-Y tends to form two type of iron oxide species, the first type is as Fe₂O₃ or FeOOH (iron oxo species) that are located at site SI on the inner surface of sodalite and the second type as polycationic species that is located at site SII on the outer surface of sodalite.

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A novel λ-type manganese dioxide (λ-MnO₂) adsorbent has been developed for selectively recovering Li⁺ from seawater. This adsorbent can be prepared from spinel-type lithium di manganese tetra oxide (LiMn₂O₄) using ion exchange of Li⁺ by hydrogen ion. In batchwise adsorption, λ-MnO₂ adsorbent can effectively adsorb Li⁺ in high pH region like seawater (pH=8.1) with quite high selectivity more than 800 molar ratio of Li⁺/Na⁺. In chromatographic separation, Li⁺ can effectively adsorbed on the adsorbent packed into column, while Na⁺ is scarcely adsorbed in adsorption stage. In elution stage, Li⁺ can be concentrated more than 50 times compared with initial lithium concentration in feed solution of adsorption stage, while little Na⁺ was eluted. The selectivity of Li⁺/Na⁺ can be achieved to 1500 times in molar base.

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The substitution of foreign metals for iron in goethite (α-FeOOH) contributes to the change of adsorptive properties for metal ions, Cu^II, Pb^II, and Zn^II, in aqueous solutions. Selective removal of Pb^II from low-pH solutions was enhanced by the addition of Mn in the synthetic process for Mn-substituted goethite particles. This enhancement was caused by the formation of specific surface sites for the selective adsorption.

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Ion-exchange reaction of three types of synthetic hydroxyapatites was attempted with Eu³⁺ and Tb³⁺ ions for the purpose of preparing phosphors. The ion-exchange reaction was observed when the concentration of Eu³⁺ and Tb³⁺ nitrate solutions was less than 10 mmol/dm³, however, in the case of higher concentrated solution hydroxyapatites were dissolved partly to yield EuPO₄⋅H₂O and TbPO₄⋅H₂O. The emission intensity of the ion-exchanged products depended not only on the uptake amount of Eu³⁺ and Tb³⁺ ions but also on the Ca/ (P+C) ratio of the starting HAps.

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The sorption behavior of ions on active carbons (ACs) was compared for three elements of the copper group, Cu, Ag and Au, between a basic AC and an acidic AC, and between a deaerated and aeratedd conditions. The difference among the sorption conditions was explained by assuming that the sorption proceeds partly by an ion exchange and partly by the reductive sorption. It was also discussed in terms of electrochemical impedance spectroscopy and quantum chemical analysis.

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The mesoporous silicas doubly imprinted with both surfactant micelles and metal ions acting as templates were prepared to develop highly selective adsorbents by cocondensation of tetraethoxysilane (TEOS) and copper-3- (2-aminoethylamino) propyltrimethoxysilane (Cu (appts) ₂²⁺) in the presence of structure-directing cationic cetyltrimethylammonium bromide (CTAB) surfactant micelles. Removal of the metal ion and the surfactant results in the formation of different-sized imprints within adsorbents: the pores that give the gel enhanced selectivity for the target metal ion and the cylindrical pores that give the gel an overall porosity which includes large surface areas and excellent metal ion transport kinetics. The measurement of adsorption equilibri-um and kinetics of copper ion on these adsorbents provided the high adsorption capacity and selectivity, coupled with fast kinetics, for copper ions used as templates.

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Intercalation reaction of two enzymes, catalase and glucose oxidase (GOD) into α-zirconium phosphate, α-ZrP, was examined. The intercalation in aqueous solution was carried out in two different procedures. In the first procedure, colloidal mixture of α-ZrP and propylamine was prepared in advance and the enzyme was added to the colloidal mixture. The exfoliated lamellae were produced in the mixture and the intercalation was expected to occur on the occasion of re-cohesion of the exfoliated lamellae. α-ZrP was added in the enzyme-propylamine mixed solution in the second procedure. Simultaneous accommodation of enzyme with propylamine was expected to occur. Most of the products were amorphous irrespective of the preparation procedures. Under suitable condition, catalase and GOD intercalation compounds showed significant enzyme activity with relatively long life.

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Layered γ-titanium phosphate (γ-TiP), Ti (HPO₄) ₂⋅2H₂O, is well known as the host material of intercalation compounds and the inorganic ion-exchanger of H⁺/metal ion system. It was found to have high ion-exchange selectivity for Rb⁺ and Cs⁺ among alkali metal ions. The ionexchange reactions for these ions progressed in two steps according to pH. Part of water molecules in the mterlayer of γ-TiP was taken away during ion-exchange reaction and an amorphous γ-TiP resulted. This phenomenon was first studied by thermal analysis and further investigation was carried out using solid NMR of ¹H and ¹³³Cs in detail. Moreover, the interaction between Fe²⁺ and Cs⁺ for the ion-exchange reaction was investigated. Despite Fe²⁺ was hard to adsorb to γ-TiP, the amount of sorbed Fe²⁺ increased when Cs⁺ coexisted and the amount of sorbed Cs⁺ decreased.

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The mesoporous silicate (MCM-41) was synthesized from sodium silicate solution and cetyltrimethylammonium bromide. Experiments about capturing behavior of MCM-41 for transition metal ions (cobalt, nickel, copper, or zinc) with acetylacetone have been conducted to assess the potential of MCM-41 as selective capturing materials. The amount of captured metal ions on MCM-41 was calculated by subtracting the final concentration from the initial concentration of metal ions analyzed by ICP-AES. In the case of copper, the amount of captured metal ions was increased by addition of acetylacetone. The chemical state of copper captured on MCM-41 was estimated by X-ray absorption near edge structure (XANES) analysis. The amount of metal ions captured with acetylacetone from the solution at pH 5.9 was found in the following order; Ni<Co<<Cu<Zn. These results demonstrated the potential of MCM-41 as selective capturing materials.

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Layered inorganic material, γ-titanium phosphate (γ-TiP), was applied as a host material for drug delivery use. Hygroscopic diclofenac sodium (DFS) was selected as a model drug to improve its anti-humidity and anti-oxidation. The intercalation was carried out in ethanol solution of DFS. Propylamine was used as the third compound to expand interlayer gallery and/or exfoliate lamellae. The amount of intercalated DFS was almost independent on the concentration of propylamine added. The drug release characteristics was also investigated. The release rate of DFS from the intercalation compound was slower than DFS powder and almost all DFS intercalated was released within 120 min.

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A monoclinic titanic acid (M-TiA) was synthesized by Li⁺/H⁺ ion exchange reaction with an 0.5 M (M=mol dm^-3) nitric acid solution from Li₂TiO₃. The Li₂TiO₃ was obtained by heating a mixture of Li₂CO₃ and anatase type TiO₂ with molar ratio of 1: 1 at 700, 750, 850 or 950°C for 24h. X-ray diffraction pattern of M-TiA-750 was indexed to a monoclinic structure (space group C2/c), with the lattice constant a=0.52794, b=0.90859, c=0.96445nm, β=99.461deg. The pH titration curves of M-TiA on the Li⁺/H⁺ exchange system indicated a weak monobasic acid. M-TiA showed high uptake for lithium ion in the pH range 3.5-10, and relatively low uptake was observed for sodium ion in the pH range 5.0-10, whereas no appreciable amount of uptakes were observed for potassium, rubidium, cesium and calcium ions in the pH range 3-10. An extremely high selectivity was found for lithium ions as compared with other alkali metal ions.

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Operating parameters of an ion-exchange membrane electrodialytic salt manufacturing plant (NaCl production capacity: 200, 000t/year) using brine discharged from a reverse osmosis seawater desalination plant are discussed. The energy consumed in the salt manufacturing process was assumed to be supplied by a simultaneous heat-generating electric power unit using a back-pressure turbine. The number of evaporators was selected to minimize the electric power shortfall of the salt manufacturing process but to be larger than zero. The electric power shortage was assumed to be made up by purchased electric power. The salt manufacturing energy required using the brine discharged from a reverse osmosis seawater desalinating plant was 80% of the salt manufacturing energy using seawater. The optimum electrodialytic current density at which the salt manufacturing energy required is minimal was 3 A/dm² for both cases.

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In previous studies, charged mosaic membranes having two different fixed charges in the membrane matrix indicated an unique transport behavior such as preferential material transport. In this study, the composite charged mosaic membrane endurable to mechanical pressure in practical application was investigated from the same aspect of solute and solvent transport as before. Lp and ω estimated by taking account of active layer thickness were satisfactorily consistent with those in mosaic membrane without reinforcement. On the other hand, the reflection coefficient, σ turned out to be the negative value that suggests preferential material transport and to be independent of active layer thickness.

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An ion exchange membrane with a high cross-linking structure close to the membrane surface was prepared and evaluated for its diffusion dialysis performance. Cross-linking at the membrane surface was carried out by soaking the base membrane (4-Vinylpyridine and Divinylbenzene copolymer) in n-Hexane containing Dibromoalkane. Then the cross-linking structure was formed next to the surface by pyridine and Dibromoalkane interaction. After that, the inside of the membrane was quatemized by CH₃I. The ion exchange membrane obtained shows a greatly improved metal rejection for diffusion dialysis compared with the membrane having no surface modification.

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Membrane permeation characteristics of lactic, succinic, and citric acids were examined over a wide range of pH 1 to 11 in electrodialysis. These carboxylic acids permeated through an anion-exchange membrane, but did not through a cation-exchange membrane. The flux of each carboxylic acid was significantly affected by solution pH: The flux increased rapidly at pH about 2 and reached a maximum, whereas the flux of succinic and citric acids gradually decreased with increasing pH. All the experimental results were analyzed with a mathematical model which considered dissociation equilibrium of carboxylic acids, electroneutrality in the solution, ion-exchange equilibrium, and ionic flux in the anion-exchange membrane. The model successfully explained the observed flux of carboxylic acids.

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