We indicated, in our previous work, that tetraethylammonium (Et₄N⁺) ion is solvated in an aqueous polymer solution in a similar fashion to in water, and the Et₄N⁺ electrode can be used for a reference for the determination of transfer thermodynamic values. On the basis of this finding, we have evaluated the Gibbs free energy of transfer of selected ions from water to aqueous hydrophilic polymer solutions such as poly (ethylene glycol) and poly (acrylic acid) . X-ray absorption fine structure (XAF) measurements have allowed us to discuss the structural aspects of ions in the aqueous polymer solutions.

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We have already reported that the density and compressibility of particles can be acoustically evaluated, and have proposed a coupled acoustic-gravity field as a potentially useful physical force field. Particles are aggregated at the equilibrium position, which is determined by their acoustic properties rather than by their sizes. These acoustic properties of ion-exchange resins strongly depend on the hydration natures of counterions. Ion-exchange resins with different counterions can thus be discriminated by this acoustic-based field. This approach allows the visual identification of resins and the evaluation of the extent of an ion-exchange reaction.

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Although the leaching of sulfate from a strongly acidic cation-exchange resin has been ascribed to the contamination of sulfuric acid in the manufacturing processes, this phenomenon could be related to the hydrolysis reaction of sulfo groups in the resin. The sulfate desorption was an endothermic pseudo-zeroth order reaction. The activation enthalpy, entropy, and free energy were determined using the rate constants observed at different temperatures. The sulfate desorption was remarkably affected by the counter ions in the order of H⁺, Na⁺<Ca²⁺<La³⁺.

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The application of fitted Langmuir isotherms to experimental data for the determination of the ion exchange equilibrium constants defined in the surface Complexation model (SCM) was analyzed. Isotherms of the exchange of H⁺/Na⁺, K⁺ with sulfonated polystyrenic gel type and macroporous and hyper-crosslinked (macronet) resins were measured at 298 K and 0.01 mol/L total concentration of the external solution and the SCM equilibrium constants were deduced. Even if the diffuse layer has a significant contribution for a restricted domain, the predicted SCM isotherms are in good agreement with the experimental and fitted Langmuir isotherms. The effects of the resin texture on ion exchange equilibria were revealed.

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The adsorption kinetics and mechanism of two dissolved Cu (II) species, i.e. hydrated Cu (II) (HyCu (II) ) and its humic acid complexed (HA-Cu (II) ), on silica gel (SG) have been studied. The adsorption medium containing both Hy-Cu (II) and HA-Cu (II) was first prepared by introducing humic acid (HA) previously immobilized on SG into aqueous solution containing Hy-Cu (II) . The acidity of the solution was adjusted to pH 4.0 in order the Hy-Cu (II) to be proportionally distributed to HA-Cu (II) . The adsorption of the Cu (II) species on SG showed that Hy-Cu (II) was adsorbed much faster than HA-Cu (II), with adsorption rate constant (k^ad) of 0.48 min^-1 for Hy-Cu (II) and 0.05 min^-1 for HACu (II) . Since HA-Cu (II) complex should be anionic in nature, strong adsorption of the species on SG could not be expected. The adsorption energy (E) of 24.82 kJ mol^-1 for HA-Cu (II) complex which is significantly higher than that of 12.56 kJ mol^-1 for Hy-Cu (II) suggests that HA-Cu (II) complex is chemically adsorbed through ligand exchange after the rapid electrostatic interaction through outersphere complexation of Hy-Cu (II) on SG. This evidence indicates that the adsorption of the Cu (II) species proceeds sequentially, where the Hy-Cu (II) is adsorbed first and it then acts as a bridge for the adsorption of HA-Cu (II) .

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Alginate is an important carboxyl group containing natural polysaccharide component of many biosorbents. Protonation and the effect of pH on the binding of metal ions Pb (II), Zn (II) and Cd (II) of the alginate were studied at room temperature. Mass average molecular weight and average size of the alginate were obtained from static and dynamic light scattering studies (337±18 % kDa and 126.8 nm) . Protonation constant was obtained from pH metric titration curves by using the Henderson-Hasselbalch equation (logK_H=3.53, I=0.1 M, KNO₃) . Binding of metal ions was studied at a constant concentration of the ligand (0.25 g/liter) by increasing the concentration of the metal ions from 10^-5 to 10^-3 M, at the pH values of 3, 4 and 5, at I=0.1 M, KNO₃. Concentrations of the free metal ions [M²⁺] were obtained from a direct DC polarographic study of the equilibrium systems by applying the concept of mean diffusion coefficient. Formation constants of the M²⁺ -alginate complexes were calculated for each pH from the obtained ligand saturation vs. [M²⁺] curves evaluated by the equation of binding derived from equilibrium principles.

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Simulations are performed using a model developed to predict ion exchange performance in radial flow. The model which has been validated previously by experiments predicts the performance in a wedge-shaped annular bed. The injected solution flows radially between a port at the bed's axis and the bed's outer periphery. Flow is either outwards away from the bed's axis or inwards towards the axis. It is found that under identical operating conditions, the radial ion exchange process studied is significantly more efficient when the flow is outwards rather than inwards.

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As the thickness of bacterial cellulose (BC) microfibrils is two orders of magnitude smaller than that of plant cellulose (PC), BC is expected for increasing adsorption for various adsorbates. Therefore, in this study, adsorption behavior of Sb (III) on BC was evaluated and compared with that on PC. The adsorption capacity for Sb (III) on BC was slightly greater than that on PC, however, the initial reaction rate of adsorption of Sb (III) on BC was much faster than that on PC. The result suggested that BC is superior to PC in rapid adsorption of Sb (III), on the basis of the large surface area.

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Adsorption behaviors of the histidine-containing dipeptides, carnosine (Car) and anserine (Ans) were studied using copper (II) immobilized cation exchange resins. Commercial sulfonic acid, carboxylic acid, iminodiacetic acid (IDA), and aminophosphoric acid resins were used for immobilizing copper (II) . Adsorptions of Car and Ans were especially enhanced using copper (II) immobilized IDA resin (Cu-IDA) . Car and Ans were adsorbed on Cu-IDA even in the presence of 100 mmol/dm³ of sodium chloride. Histidine and the histidine-containing dipeptides were selectively adsorbed on Cu-IDA over other amino acids. Immobilized metal affinity adsorption is available for separation of the dipeptides from saline water.

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Glycidylmethacrylate-divinylbenzene copolymers containing ethylenediamine groups (GD-EDA) and triethylenetetramine groups (GD-TET) were prepared to develop new selective adsorbents for precious metals over base metals. It was found that GD-EDA and GD-TET are highly selective adsorbents for palladium (II), gold (III) and platinum (IV) over base metals such as copper (II), cobalt (II), cadmium (II) and iron (III) . The adsorption equilibrium of palladium (II) was quantitatively studied from acidic chloride media at 303 K using GD-EDA. The effects of the hydrogen ion and chloride ion concentrations on the adsorption of palladium (II) were examined to elucidate the chemical species of adsorbed palladium (II) on GD-EDA.

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Three phosphonate/sulfonate bifunctional resins having different molar ratios of both functional groups were prepared from three kinds of chloromethylstyrene-styrene-divinylbenzene copolymers which were prepared by suspension polymerization of three different molar mixtures of chloromethylstyrene and styrene in the presence of 10 mol % divinylbenzene as crosslinker. Selectivity sequences of these resins toward Ba (II), Cu (II) and Pb (II) were evaluated by measuring their distribution ratios as a function of equilibrium pH of aqueous phases and columnar competitive adsorption of these metal ions as well. It was revealed that the metal ion selectivity sequence of these bifunctional resins was governed by both functional groups and their molar ratios strongly affect the metal ion selectivity sequence; the selectivity sequence of the bifunctional resins approaches that of the monofunctional sulfonate resin with an increase in molar ratio of sulfonate/phosphonate and does that of the monofunctional phosphonate resin with a decrease in molar ratio of sulfonate/phosphonate. These results indicate that the concept of bifunctionality is useful for design of a resin with a novel metal ion selectivity sequence.

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The present study examined the adsorption of bioactive amines and proteins onto phosphorylated bacterial cellulose (PBC) and phosphorylated plant cellulose (PPC), which contain similar amounts of phosphoric acid groups. Physiologically important organic amines such as dopamine and serotonin are adsorbed onto PBC at neutral pH. In addition, a cationic protein lysozyme was quantitatively adsorbed onto PBC. The adsorption capacity of PBC for lysozyme (MW 14, 300) was higher than that of PPC. In contrast, PBC and PPC had similar adsorption capacities for tryptophan methyl ester (MW 219) . From these results the chemically modified bacterial cellulose can be expected to adsorb large quantities of biomacromolecules.

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Distribution of H⁺ and OH^- ion concentration and of specific electric resistance in a water dissociation layer formed in an ion exchange membrane was evaluated using the theoretical equation and electrodialysis experimental results. The change of the concentration in an anion exchange membrane was larger than that in a cation exchange membrane. When Mg (OH) ₂ was precipitated on the cation exchange membrane, the change was increased. The intensity of the water dissociation reaction is accelerated due to the auto-catalytic reaction caused by quaternary ammonium groups in the anion exchange membrane or metallic hydroxides precipitated on the cation exchange membrane.

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Fibrous metal adsorbent was prepared by radiation-induced graft polymerization of glycidyl methacrylate onto a polylactic acid (PLA) nonwoven fabric and its subsequent modification based on ring opening of epoxides with disodium iminodiacetate (IDA-Na) . The degree of grafting of PLA fabric can be controlled in the range of up to 225% by optimizing the grafting conditions such as reaction time, preirradiation dose, monomer concentration and reaction temperature. The optimal IDA group density of the prepared adsorbent was 500 μmol/g-adsorbent, and its selectivity for metal ions was Cu²⁺>Pb²⁺>Ni²⁺>Zn²⁺>Cd²⁺>Co²⁺>Ca²⁺>Mg²⁺.

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Monodispersed Chitosan microspheres containing butyric acid were prepared to develop drug carriers for colitis ulcerosa. The chitosan microspheres as carriers were prepared using SPG (Shirasu Porous Glass) membrane emulsification to examine the effect of preparation conditions (chitosan and sodium chloride concentrations and the pore size of SPG) on the physicochemical properties (specific surface area, porosity and density) of the microspheres. After the monodispersed w/o emulsion of organic acid solutions of chitosan was prepared, the monodispersed chitosan microspheres were obtained by concentrating chitosan droplets in the emulsion with the w/o emulsion containing a high concentration of sodium chloride. The monodispersed chitosan microspheres with the arbitrary size, diameter and porosity could be easily prepared by selecting experimental conditions according to the purposes. The release of butyric acid from the chitosan microspheres was measured under various conditions to determine the most suitable release condition of butyric acid into the large intestine in vitro at 309 K.

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In order to develop highly selective adsorbents for recovery of palladium (II), the palladium (II) -imprinted chitosan derivative (PIPMC) was synthesized using N- [pyridylmethyl] -chitosan (PMC) . The adsorption rate and adsorption equilibrium of precious metals on PIPMC were compared with those on PMC to elucidate the template effects. The adsorption rate of palladium (II) on PIPMC is very fast and equilibrated within one hour, while at least 10 hours is necessary to reach equilibrium by PMC. PIPMC provided the selective chelate formation spaces toward not only templated palladium (II), but gold (III), nickel (II) and copper (II) that commonly form planar complexes. The template effect of palladium (II) was studied by examining the adsorption selectivity and kinetics of palladium (II) using hydrochloric acid and 1 M aqueous ammonium nitrate solution.

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Metal adsorbent was prepared by co-graft polymerization of allylamine and methacrylic acid (or N-vinylacetamide) onto nonwoven fabrics made of polyethylene-coated polypropylene fiber using radiation induced graft polymerization method. Behavior of the resulting adsorbents in uptake of Au (III) was evaluated by both batch and columnar methods. In the column test, the breakthrough of Au (III) was evaluated with three different flow rates of 260, 520 and 1040 h^-1 in space velocity (SV) by pumping 1mM Au (III) solution into the column at pH 3. Breakthrough points of three flow rates were 163, 150 and 144 bed volumes (BV), respectively. Furthermore, the breakthrough of Au (III) was evaluated at pH range from 1 to 7 by pumping 100 ppb Au (III) solution into the column in the SV of 4680 h^-1. The breakthrough point was 175 BV at the pH 1 and 2, and went up to 179 BV at pH 3.

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It is well known that adsorbents having N-methyl-D-glucamine (NMDG) preferentially adsorb boron. The boron adsorbent developed in this study has promising properties of rapid boron adsorption from the natural water. The adsorbent was prepared by radiation induced graft polymerization of glycidyl methacrylate (GMA) onto non-woven polyethylene fabrics in aqueous medium, and following chemical modification with NMDG The resulting adsorbent was evaluated by column-mode adsorption of boron at various flow rates. Comparison between graft adsorbent and granular resin, graft adsorbent has 4 times higher bed volume (BV) at breakthrough point at space velocity (SV) 50 h^-1. The BV at breakthrough point of graft adsorbent at SV 100 h^-1 gave the same one with granular resin at SV10 h^-1.

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Sorption conditions of arsenate ions onto Sn-loaded poly (hydroxamic acid) chelating resin (Sn-PHA) have been studied. Sorption isotherms data correlated well to the Langmuir model with maximum capacity of 38.46 mg g^-1 at pH 2. Sorption process follows pseudo-second order kinetics. Intraparticle diffusion was found to take part in sorption processes. The free energy (E) was 11.18 kJ mol^-1 which shows the sorption is an ion-exchange process. Thermodynamic parameters, ΔH°, ΔS° and ΔG° were also calculated from the experimental data. Standard heat of sorption was found to be endothermic and entropy change value was calculated to be positive. NegativeΔG°value indicates that the sorption process for the arsenic anions onto Sn-PHA is spontaneous.

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Ion exchange characteristics of gel-type, macroporous and nuclear grade strongly acidic cation exchange resins from three Indian manufacturers were evaluated for their efficacy to remove Cs and Sr ions from aqueous solution, which has relevance to the treatment of Low level Liquid Waste (LLW) streams. The alkali metal ion- hydrogen ion exchange equilibria were studied by batch technique at a total ionic strength of 0.1 mol dm 3. The rational equilibrium constants were determined after incorporating activity coefficient corrections. The selectivity showed the sequence: Cs⁺>K⁺>Na⁺>Li⁺ with respect to H⁺, indicating that unhydrated ions were preferred. The log K^c vs N^M (equivalent fraction in the resin phase) plots indicated the heterogeneity in the resin phase and formation of clusters. The gel type resins showed better selectivity for Cs ion.

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Ion exchange characteristics of gel-type, macroporous and nuclear grade strongly acidic cation exchange resins from three Indian manufacturers were evaluated for their efficacy to remove Sr ion from aqueous solution, which has relevance to the treatment of Low level Liquid Waste (LLW) streams. In order to achieve this goal in proper perceptive, the alkaline earth metal ion- hydrogen ion exchange equilibria were studied by batch technique at a total ionic strength of 0.1 mol dm^-3. The rational equilibrium constants were determined after incorporating activity coefficient corrections. The log K^c vs N^M (equivalent fraction in the resin phase) plots indicated the heterogeneity in the resin phase and formation of clusters. All the resins showed unusually high selectivity for Ca²⁺ rather than Ba²⁺. This could be due to the fact that all the resins are tailor made for the demineralisation process, which requires the removal of chiefly Ca ions.

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The column characteristics of gel-type, macroporous and nuclear grade strongly acidic cation exchange resins from three Indian manufacturers were studied for the exchange of Na⁺, Cs⁺, Ca²⁺ and Sr²⁺ with respect to hydrogen ion. The ion exchange isotherms and the equilibrium constants were evaluated from the breakthrough curves using the equation given by Glueckauf and were compared with that obtained by equilibrium batch experiments. In general, the equilibrium constants derived from column experiments were comparable to batch experiments in the case of Na and Ca ions and lower than that obtained from batch technique for Cs and Sr ions. Results also indicated that among the nine resins evaluated, no single resin showed good selectivity for both Cs and Sr ions; two different resins would have to be chosen for the removal of these elements present in the Low-level Liquid Waste (LLW) stream.

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A wastewater treatment system has been developed by using a cesium selective inorganic ion exchanger. The selective separation of cesium (¹³⁷ Cs, ¹³⁴Cs) from high salt concentration and strongly alkaline evaporator bottom has a volume reduction factor about 1800-3500 at the value of the decontamination factor DF>100, for the samples of four tanks of the Hungarian PWR Paks.
Also an ion exchange treatment technology has been developed by using a mixture of ammonium-insoluble tannin and mixed ion exchange resin (MIX) for the selective separation of transuranium isotopes, including Pu, Am, Cm, and U, as well as fission and radioactive corrosion products from boric acid solution (pH-4.1) . The equilibrium and fixed bed sorption experiments resulted in Kd values of 10⁴-10⁵ ml/g, and decontamination factors of 1, 000, with a breakthrough point between 1500 BV and 5000 BV of accumulated volume.

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Ion exchange properties of hydrous metal oxides (HMeOs) for weak base anions were discussed in terms of surface complexation using the metal-ligand stability constant data base at relatively high ionic strength. The selectivity sequences of anion were correlated comparatively well with the orders of first stepwise stability constants (K₁) of the corresponding metal-ligand complexes. Conditions whether inner sphere or outer sphere surface complex forms could be evaluated by the difference in the stability constant between the OH^-/X^- (X^-: anion) and OH^-/H₂O ligand exchange reactions. These calculations suggest that the anion exchange reaction of HMeO is controlled mainly by the interactions of anions or H₂O molecules with the central metal atoms.

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We prepared W-based heteropolyacid (HPA) -layered double-hydroxide (LDH) composites. The effects of the intercalation process on the composite characteristics and the Keggin structure stability were then investigated. The HPA-LDH composites were prepared using ion-exchange method on Zn-Al (NO₃) LDH and reconstruction method on Mg-Al (CO₃) LDH. In both cases, d=1.47 nm spacing, indicating HPA intercalation to LDH, was identified. [SiW₁₂O₄₀] ^4- was hydrolyzed into [SiW₁₁O₃₉] ^8- during ion change processing, thereby obtaining [SiW₁₁O₃₉] ^8- -LDH composites.

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In a previous study, we reported that the high selectivity for nitrate ion is correlated with the inter layer spacing of layered double hydroxides (LDHs) . In this study, Mg-Fe LDH samples were synthesized by a co-precipitation method at a constant pH 10, followed by hydrothermal treatment at 150 °C. The selectivity sequence from distribution coefficients (K_d) values for Mg-Fe LDH is NO₃^-> HPO₄^2-> SO₄^2-. Nitrate ion exchange capacities are 1.6, 1.8, 1.8, 2.0 and 1.5 mmol g^-1 for Mg-Fe LDHs with Mg²⁺/ Fe³⁺ molar ratios of 2, 3, 4, 5 and 6 in parent solution, respectively.

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The cesium ion-exchange behavior of sodium difluorotetrasilicate (Na-TSM) and sodium taeniolite (Na-TAE), which belong to the mica family, in acidic media has been determined. Cs⁺ uptake in pH 1.0 decreased to about 30% to a neutral condition for Na-TSM. The amount of Cs⁺ exchange dropped dramatically for Na-TAE at pH 0.3, corresponding to about 0.5 mol dm^-3 HNO₃. After the ion-exchange reaction, scanning electron microscopy clearly showed that the layered structure was destroyed when the ion-exchange ratio decreased.

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During quarrying of sandstone, waste sandstone cake is discharged as industrial waste. We attempted to convert the cake into zeolitic materials using the alkali fusion method. Waste sandstone cake is mainly composed of crystalline phases, which were difficult to dissolve into aqueous alkali solution. By alkali fusion, most of the crystalline phases were converted into soluble phases, and could be transformed into zeolite crystals, zeolite-X and hydroxysodalite. The cation exchange capacities (CECs) of the product was almost 2.3 mmol/g, which is about 30 times higher than that of waste cake, and is higher than that of commercial natural zeolite.

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The hydrotalcite-type compounds were prepared to examine the possibility for use at elevated temperature. The combinations of di- and tri-valent metals were Ni²⁺-Al³⁺, Ni²⁺-Fe³⁺, and Co²⁺-Al³⁺ The ion exchange property was examined on chloride ion, nitrate ion, and chromate ion. The temperature examined was RT - 200 °C. Among the combination of metal ions, Ni²⁺-A1³⁺ combination was most stable and Ni²⁺ content over 0.84 in mole ratio gave a sturdy granular lump and chemically stable during the ion exchange reaction. The ion exchange reaction at the elevated temperature was examined for the sample with Ni²⁺ content around 0.84. Almost no NO₃^-as well as Cl^- ion was exchanged on the sample treated with 0.1 mol dm^-3 NaOH. As for CrO₄^2- ion, the exchange ratio was about 93 % at room temperature and almost 100 % at 120 - 200 °C. The dissolution of Ni²⁺ and Al³⁺ from the host exchanger was hardly observed below 120 °C, fairly stable at 150 °C, a small amount of dissolved Al³⁺ being observed.

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Hydrothermal synthesis of potassium titanate powders was carried out under various subcritical and supercritical water conditions (473-723 K) using titanium tetraisopropoxide and aqueous KOH solutions as starting materials. A single phase of K₂Ti₆O₁₃ was formed at 573 K or higher, whereas unidentified phase was obtained at 473K. In this paper, the hydrothermally synthesized potassium titanates powders were used for cobalt ion adsorbent under hydrothermal conditions. Co uptake on the hydrothermally synthesized K₂Ti₆O₁₃ was over 2x10^-3 molg^-1 at 473 K, whereas those at 373 K were lower in comparison with the solid state synthesized K₂Ti₆O₁₃. Cobalt ions can be adsorbed as Co₃O₄ accompanied by the structure transformation from K₂Ti₆O₁₃ to anatase under hydrothermal conditions.

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The adsorption behavior of arsenic from water on spherical porous silica particles (SiMAG) covered with magnetite was investigated under batch equilibrium conditions at 303K. The specific surface area and the pH at zero point of charge of SiMAG were 540 m²/g and 4.6, respectively. Both of As (V) and As (III) were adsorbed on SiMAG The adsorption of As (V) increased with decreasing pH, while that of As (III) was slightly dependent on pH. The adsorption capacity of SiMAG towards As (V) was 0.85 mmol/g.

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Zeolitic materials were prepared from coal fly ash in seawater and compared with those prepared in distilled water in order to evaluate the effect of seawater on the characteristics of the products. Zeolitic materials were prepared at 80°C for 24 hours in activated solutions, which themselves were prepared by dissolving NaOH in the seawater or distilled water. Using 2-3 M NaOH in seawater, zeolite-A, hydroxysodalite and herchelite were produced, as same as those prepared in distilled water. The study found that the mixture products have high cation exchange capacity (CEC=250-300 cmol/kg), which is higher than that of commercial natural zeolite. The CEC of the product prepared from 4 M NaOH in seawater is lower than that from 4 M NaOH in distilled water.

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Hydroxyapatite and its related calcium phosphate materials possess extremely high ability of ion exchange against various cations and anions. In this study, Si ion incorporated hydroxyapatites, “modified hydroxyapatite”, were synthesized by a chemical processing and subsequently hydrothermal-treatment in order to develop modified hydroxyapatites. The characterization of microstructure of these products was examined by X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectrophotometry (FT-IR) and so on. These results suggested that the hydrothermal treatment of hydroxyapatite and colloidal silica resulted in the successful synthesis of Si ion incorporated hydroxyapatite. The relation between their microstructure and synthetic conditions was discussed.

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The nanotubular titanate or titania were synthesized by hydrothermal treatments of anatase-type TiO₂ in NaOH aqueous solution. The characterization of microstructure of these nanotubular products was examined by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray absorption near fine structure (XANES) and so on. From these results, it was clearified that the nanotubes were composed of layered Na-Ti-O, and H-Ti-O nanotubes were obtained by ion-exchange of Na⁺ for H⁺ in Na-Ti-O nanotubes by washing with deionized water or dehydrated HCl solution.

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Layered double hydroxides (LDHs) have a great potential in arsenic removal due to their large surface areas and high anion exchange capacities. In this study, a new synthesis method involving fast coprecipitation followed by hydrothermal treatment has been used to synthesize stable homogeneous nano-scale MgAl-LDHs for As (V) removal. The products have been characterized using CHN, BET, XRD, FTIR, SEM, and TEM. The nano-scale LDHs synthesized in this study showed a poorer crystallinity, higher interlayer space, and smaller crystallite size than the commercial LDHs. The photon correlation spectroscopy showed that the nano-scale LDHs have a narrow particle size distribution with an equivalent hydrodynamic diameter of 122 nm. The adsorption isotherm of As (V) on the nano-scale LDHs with initial As (V) concentration 0.2-8 mg·dm^-3 was best fitted by Freundlich model, while the isotherm with initial As (V) concentration 12-200 mg·dm^-3 was best described by Langmuir model. The maximum adsorption capacity of As (V) on nano-scale LDHs was 78.1 mg/g, which was about 10 times higher than that of commercial LDHs. As (V) adsorption on nano-scale LDHs was a rapid process that achieved 92% adsorption equilibrium in 10 min. The adsorption of As (V) on nano-scale LDHs was confirmed by EDX analysis, and FTIR by showing a typical FTIR band at 830 cm^-1. As (V) adsorbed on the nano-scale LDHs was effectively desorbed using 5 w/v% NaOH solution and the LDHs were successfully regenerated using 20 w/v% Mg (NO₃) ₂.6H₂O solution. The results suggest that nano-scale LDHs as potential adsorbent for As (V) from waters, and that its reusability is possible.

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A new effective removal of dissolved humic acid in aqueous medium has been performed by mean of adsorption onto Zn/Al layered double hydroxide (Zn/Al LDH) . Zn/Al LDH was synthesized by direct precipitation method through the addition of 0.5 M NaOH solution to a mixed solution containing Zn (NO₃) ₂ and Al (NO₃) ₃ with molar ratio 0.1 : 0.05 until the acidity of the mixed solution reached pH 7.0. The removal of humic acid was based on adsorption process where the negatively charged humic acid would be adsorbed to the positively charged Zn/Al LDH surface. The optimum humic acid adsorption on Zn/Al LDH was observed at pH 5 with the first order rate constant, capacity, and energy of adsorption were 2.17 x 10^-3 min^-1, 0.194 mmol g^-1 (115 mg g^-1), and 33.89 kJ mol^-1, respectively. Literature survey showed that Zn/Al LDH is more than 6 times more effective than carbon as the most effective adsorbent of humic acid in the market.

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Binary Zr-Fe hydroxides with Zr/Fe molar ratios of 0.33, 1.0 and 3.0 were synthesized by a co-precipitation method at room temperature. The materials are amorphous with high surface area (189-220 m² g^-1) . Phosphate adsorptive properties of the materials were investigated by a batch method. Distribution coefficients (K_d) of oxo-anions at pH 9 from a mixed anion solution show the selectivity sequence as follows: Cl^-, NO₃^-, SO₄^2- < HPO₄^2-. The phosphate uptakes from a single electrolyte at pH 2 are 75 mg-P g^-1 for the present material, 50 mg-P g^-1 for amorphous ZrO (OH) ₂·1.5H₂O, and 28 mg-P g^-1 for low crystalline akaganeite (FeOOH·H₂O) . The results suggest that binary Zr-Fe hydroxide can act as phosphate adsorbent.

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Sodium hexatitanate, sodium trititanate, sodium nonatitanate, and a new iron doped sodium nonatitanate were synthesized. Common interferences present in waste waters that hinder the removal of heavy metals by these ion exchangers were investigated. The presence of K⁺, Mg²⁺ and Ca²⁺ at 0.001-0.05 M concentration had minor effect on the amount of Pb²⁺, Cr³⁺, and Ni²⁺ uptake. EDTA on the other hand, interferes tremendously with the metal uptake. Both in ternary and in single system, the selectivity series is in the order: Pb²⁺>Cr³⁺>Ni²⁺. This order changed to Cr³⁺>Pb²⁺>Ni²⁺, in the presence of 0.001-0.1 M EDTA at pH 5.

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To improve ion-exchange capacity of zeolite towards Pb (II) ion, the sequent removal of free SiO₂ using HF and of free Al₂O₃, CaO, Fe₂O₃, and MgO using EDTA solution has been performed. It was observed that the large amount of the metal ions can be dissolved from the zeolite without any significant damage to the structure of zeolite. The optimum condition was reached when 1.0 g zeolite was washed with 25 cm³ of 0.05 % (v/v) HF solution for 3 hours, and with 200 cm³ of 0.075 M EDTA solution at pH 5 for 50 hours. The HF washing improved the zeolite capacity in adsorbing Pb (II) ions from 87.7 mg g^-1 to 95.2 mg g^-1, and sequent washing using EDTA solution could further increase the capacity up to 135 mg g^-1, which is comparable to that absorbed by synthetic mordenite, ca. 152 mg g^-1.

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TiO₂ pillared porous manganese oxide nanocompound with high TiO₂ amount was successfully synthesized from birnessite (H) -type manganese oxide (H-BirMO) by intercalation of alkylamine followed by solvothermal treatment in pure titanium isopropoxide (TIIP) liquid. The effects of solvothermal treatment temperatures and chain length of preintercalated alkylamine molecules to the pillared structure were systematically investigated. The structural evolution of TiO₂ pillared porous manganese oxide nanocompound was characterized by XRD, SEM, N₂ adsorption-desorption and element analysis. The amount of intercalated TiO₂ depends on the solvothermal treatment temperatures and the water amount in samples and not connect with the basal spacing of samples. TiO₂ pillared porous manganese oxide nanocompound with high TiO₂ amount had a BET surface area of 114 m²/g with a galley height of about 1.76 nm between layers.

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Zeolite A adsorbent has been prepared for adsorption of Sr²⁺ and Cs⁺. The present adsorbent has sufficient adsorption ability for both ions, of which adsorption achieved within 1 h. The adsorption mechanism for both ions is Langmuir type, and the maximum adsorption amount at equilibrium pH of 4.00 are 3.32 mmol/g for Sr²⁺ and 1.66 mmol/g for Cs⁺, respectively. Since the pH dependencies of the adsorption of Sr²⁺ and Cs⁺ are different, selective separation of Sr²⁺ and Cs⁺ is expected to be achieved.

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Many diamide-type extractants were synthesized and tested for the extraction of actinides (III), (IV), (V) and (VI) . The diglycolamides (DGA) with two amidic oxygen and one ether oxygen, which show the tridentate feature, have the high extractability of actinides (An) . In order to increase the lipophilic property, the diglycolamides with the different functional groups attached to N atoms were synthesized and examined for their extractability. It was found that N, N, N', N'- tetraoctyl-diglycolamide (TODGA) and N, N, N', N'- tetradecyl-diglycolamide (TDDGA) exhibit the satisfactory dissolution into n-dodecane with less solubility in H²O. The results of various metal extractions using TODGA revealed that the divalent, trivalent and tetravalent metals with ionic radius of 90-120 pm gave notably high D values. After elucidation of the effect on substitution of the functional group, the chemical form of DGA to have high performance on An extraction was proposed.

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Solvent extraction is a very effective method for the separation of metal ions. Research and development of an extraction reagent with high selectivity has been carried out. We have been synthesized the multidentate ligands such as ethylenediamine derivatives having four pendant arms and evaluated the selectivity for transition metal ions. In this research, the order of selectivity for alkaline earth metal ions using N, N'-Bis (2-hydroxy-5-nitrophenylmethyl) -N, N'-bis (2-pyridylmethyl) -1, 2-ethanediamine (H²Nbbpen) as an extraction reagent was evaluated and compared to those of thenoyltrifluoroaceton (TTA) and N, N'-Bis- (2-hydroxy-3, 5-dichlorophenylmethyl) -N, N'-bis (2-pyridylmethyl) -1, 2- ethanediamine (H²dClbbpen) . The difference in the Sr-Ba extraction constants in the H²Nbbpen system was larger than those in TTA and H²dClbbpen systems.

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The Steric effect of two di-Schiff base ligands having phenylene skeleton as extractant on ion-pair extraction of divalent metal cations into nitorbenzene with picrate anion was investigated. In these extraction systems, all of the extraction except for nickel was equilibrated within 1 h, and ratio of metal: ligand: picrate in the extracted species was 1: 2: 2 or 1: 3: 2. In the extraction of nickel, 2 or 10 hours needed to be equilibrated and the Steric effect of ligands resulted in the change of the extracted species. Namely, a difference between the favorable extracted species for kinetics and equilibrium appeared by the steric effect. Consequently, nickel was extracted quantitatively and the highly selectivity for nickel was obtained.

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The extraction behavior of lanthanides from aqueous solutions into ionic liquids (ILs) and the stripping test have been investigated with N, N, N', N'-tetrakis (2-pyridylmethyl) ethylenediamine (TPEN) as a ligand. TPEN in ILs shows the extremely high extraction performance for lanthanides compared to that in chloroform. The stripping of lanthanides from ILs into a receiving phase is successfully achieved under acidic conditions. Furthermore, the leaching of TPEN from ILs into the receiving phase is negligible small, although almost all TPEN molecules in chloroform readily leach.

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The extraction and separation of the divalent metals was studied by using ionic liquid, 1-butyl-3-methylimidazolium hexafluorophosphate (BMIM-PF₆) including the extractant of 2-pyridinealdoxime (2-PA) . The divalent metals used here are Cd²⁺ and Pb²⁺ for the toxic and Ni²⁺ and Zn²⁺ for the valuable metals in industry. These metal ions in potassium nitrate of 0.10 mol dm^-3 concentration were examined to be extractable. It was observed that Cd²⁺ was extracted into ionic liquid phase better than Pb²⁺ and Zn²⁺ in the pH range of 5.15-9.83 and its extractability was reached to >99% in the pH of 7.93-9.83. The extraction equilibrium of Cd²⁺ with 2-PA into BMIM-PF₆ was found to be Cdcit _(w) ^-+3HL _(o) _??_CdL₂HL _(o) +2H⁺+cit^3-, whose mechanism is the same way as that into chloroform (CHCl₃) . The mutual separation of Cd²⁺, Pb²⁺, Ni²⁺, and Zn²⁺ can be achieved by using the different pH values of the aqueous phase in 2-PA/BMIM-PF₆ extraction system. From these results, it can be stated that the 2-PA/BMIM-PF₆ extraction system is useful to extract and separate the divalent metal ions examined in this work.

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A rapid and efficient preconcentration method was developed for the determination of trace metals in water. Trace metals [e.g., Ni (II), Cu (II), Ga (III), Cd (II), Pb (II), and Bi (III) ] in 1 dm³ of sample solution were converted into the hydrophobic chelates with ammonium pyrrolidinedithiocarbamate. The resulting metal chelates were extracted into admicelles (silica particles covered with cetyltrimethylammonium chloride), which were floated with numerous tiny bubbles to the solution surface. The floated admicelles were collected in a small sampling vessel by suction and the metals were eluted from the admicelles with dilute nitric acid. A 200-fold multielement preconcentration and subsequent determination by inductively coupled plasma-mass spectrometry were achieved within 30 min. The proposed method was applied to the analysis of river water.

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Hydrophobic cyclic polyether, decyl-l8-crown-6 (D18C6), is well known to have a selective uptake ability for strontium (II) . Calcium alginate microcapsule (MC) containing D 18C6 was fabricated for the efficient separation of strontium (II) from concentrated nitric acid solution. In this study, hybrid MCs containing D18C6 and sodium lauryl benzenesulfonate (Na-LBS) were prepared, and distribution coefficient, K_d, was improved to be over 80 cm³/g by using them. MCs were also prepared by using nitric acid and divalent metal ions, and the effect on K_dvalues was examined. The optimum condition was applied to the continuous column separation.

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p-t-Calix [4] arene with quaternary ammonium groups at upper rim has been prepared to investigate solvent extraction behavior of trivalent rare earth metals in nitrate media and precious metals in chloride media. Rare earth metals are extracted as nitrate anion complex underr a neutral condition of high nitrate concentration. Although Calix [4] arene derivative has poor extraction ability compared with the corresponding monomeric analog and the commercial quaternary ammonium extractant due to not all but partial coordination of four quartenary ammonium groups and mismatching of nitrate anion complex to coordination site. Calix [4] arene derivative shows enhanced extractability to palladium and platinum due to the effect of its cyclic and rigid structure. They are extracted as chloroanion complex at high concentration of hydrochloric acid.

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The uptake properties of radioactive nuclides on microcapsules (MCs) encapsulating DEHPA (di- (2-ethylhexyl) phosphoric acid) extractant have been studied by batch methods. The oil drops of DEHPA were uniformly encapsulated in the matrices of calcium alginate (CaALG) gel polymer. The MCs exhibited relatively large distribution coefficients (K_d) above 10³ cm³/g for trivalent metal ions (Y³⁺, Eu³⁺, Am³⁺ and Fe³⁺) . The uptake of Eu³⁺ and Am³⁺ on MCs attained equilibrium within 1 d, and high uptake percentage above 99% was obtained. The uptake of Eu³⁺ and Am³⁺ depended on equilibrium pH, and the K_d values for MCs were larger than those for CaALG in the lower pH region (< pH 2) . The MC irradiated at a dose of 188 kGy was still stable without noticeable structural damage yielding normal K_d values over 10³ cm³/g for trivalent metal ions. The MCs containing extractants were thus effective for the simultaneous removal of trivalent metal ions from radioactive waste solutions.

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