Yoshio Onodera

Alkali Hydrothermal Synthesis of Zeolites from Coal Fly Ash and Their Uptake Properties of Cesium Ion

Zeolites were synthesized from coal fly ash by hydrothermal treatment with KOH solutions. K-H zeolite (K2Al2Si4O12-nH2O) was produced under optimum conditions of 160°C, 3 d, 1 M (=mol/dm3) KOH and liquid-solid ratio of 15cm3/g. The uptake behavior of radioactive cesium for the products was investigated by batch and column methods. The uptake equilibrium of Cs+ for the above product was attained within 2h yielding the distribution coefficient of above 104 cm3/g. The uptake of Cs+ was followed by a Langmuir adsorption isotherm and the maximum uptake capacity was estimated to be 3.34 mmol/g. The successive removal of Cs+ was accomplished through the column packed with granular composites of product-alginate gel polymer.

Selective Uptake of Cesium by Ammonium Molybdophosphate (AMP)-Calcium Alginate Composites

The uptake properties of Cs+ for ammonium molybdophosphate (AMP, (NH4)3PMo12O40.3H2O) and its composite with alginate gel polymer have been studied by the batch and column methods. The free energy for the ion exchange ([NH+ 4]ad+Cs+NH+ 4+[Cs+]ad) was found to have a relatively low value of -9.7 kJ/mol compared to other inorganic ion exchangers, indicating high selectivity of AMP for Cs+ ions. The fine crystals of AMP exchanger were granulated with calcium alginate (CaALG) gel polymer as an immobilization matrices. The uptake rate of Cs+ for AMP-CaALG composite was fairly fast and the uptake attained equilibrium within 3 h; the uptake was above 96% even in the presence of 5M (=mol/dm3) NaNO3. The distribution coefficient of Cs+, Kd-Cs, decreased in the order of coexisting ions, H+>Na+>K+>NH+. In a wide HNO3 concentration region of 10-2-5M, the Kd,cs value for the composite was around 104cm3/g, while those for other elements, Na+, Sr2+, Co2+, Eu3+ and Am3+, were less than 102cm3/g. The uptake of Cs+ followed a Langmuir adsorption isotherm, and the uptake capacity of Cs+ increased with the content of AMP immobilized in the composite. The trace amounts of Cs+ in the presence of HNO3 were selectively adsorbed on the composite column.

Effect of exchangeable cation on the swelling property of 2:1 dioctahedral smectite—A periodic first principle study

We used both localized and periodic calculations on a series of monovalent (Li+, Na+, K+, Rb+, Cs+) and divalent (Mg2+, Ca2+, Sr2+, Ba2+) cations to monitor their effect on the swelling of clays. The activity order obtained for the exchangeable cations among all the monovalent and divalent series studied: Ca2+ > Sr2+ > Mg2+ > Rb+ > Ba2+ > Na+ > Li+ > Cs+ > K+. We have shown that, in case of dioctahedral smectite, the hydroxyl groups play a major role in their interaction with water and other polar molecules in the presence of an interlayer cation. We studied both type of clays, with a different surface structure and with/without water using a periodic calculation. Interlayer cations and charged 2:1 clay surfaces interact strongly with polar solvents; when it is in an aqueous medium, clay expands and the phenomenon is known as crystalline swelling. The extent of swelling is controlled by a balance between relatively strong swelling forces and electrostatic forces of attraction between the negatively charged phyllosilicate layer and the positively charged interlayer cation. We have calculated the solvation energy at the first hydration shell of an exchangeable cation, but the results do not correspond directly to the experimental d-spacing values. A novel quantitative scale is proposed with the numbers generated by the relative nucleophilicity of the active cation sites in their hydrated state through Fukui functions within the helm of the hard soft acid base principle. The solvation effect thus measured show a perfect match with experiment, which proposes that the reactivity index calculation with a first hydration shell could rationalize the swelling mechanism for exchangeable cations. The conformers after electron donation or acceptance propose the swelling mechanism for monovalent and divalent cations.

Selective Uptake and Recovery of Palladium by Biopolymer Microcapsules Enclosing Cyanex 302 Extractant

Selective uptake and recovery of platinum group metals are an important subject in the high level liquid waste treatment. An extractant having a strong affinity for palladium, bis(2,4,4-trimethylpentyl) monothiophosphinic acid (Cyanex 302, HA), was enclosed into microcapsules by utilizing highly immobilizing ability of biopolymer (alginate and alginic acid gel polymers). The uptake of Pd2plus, Ru(NO)3+ and Rh3+ for granular microcapsules has been studied by batch and column methods. A relatively large distribution coefficient of Pd2plus, Kd,Pd, of above 104 cm3/g was obtained in the presence of 0.2–0.5 M HNO3 and the separation factors of Pd/Ru and Pd/Rh were estimated to be above 102. The uptake of Pd2+ on microcapsules followed a Langmuir-type uptake isotherm and the maximum uptake capacity was estimated to be 0.72–0.96 mmol/g. These metal cations were chromatographically separated through the column packed with HA-alginate microcapsules.

Layered structure of hybrid films of an alkylammonium cation and a clay mineral as prepared by the Langmuir–Blodgett method

Hybrid monolayers of a clay mineral and an amphiphilic alkylammonium (octadecylammonium) cation have been prepared by spreading the alkylammonium cation onto surfaces of clay suspensions. π–A isotherm curves at various clay concentrations indicate that the floating monolayers of the amphiphilic alkylammonium cation are hybridized with clay platelets at an air–clay suspension interface, and that the density of the alkylammonium cation in the hybrid monolayer is dependent on the concentration of the clay in the suspension. The hybrid monolayers were deposited on glass surfaces by horizontal dipping to form hybrid multilayers. The p-polarized infrared external reflection spectra of the hybrid multilayers show that the alkyl chains of the alkylammonium cations in the film are almost perpendicular to the film surface. According to the X-ray diffraction data of the multilayers, the thickness of a unit layer (one clay layer and one alkylammonium cation layer) decreases with the increase in the clay concentration in the suspension used for the film preparation. A model of a layered structure of the hybrid multilayer has been proposed.

Uptake and Recovery of Platinum Group Metals Ions by Alginate Microcapsules Immobilizing Cyanex 302 Emulsions

This paper deals with a novel preparation method for the microencapsulation of emulsified extractant into alginate gel polymer matrices, characterization of microcapsules and chromatographic separation of PGMs (Platinum Group Metals) ions in nitric acid solutions.

Uptake and Recovery of Ruthenium by Alginate Gel Polymers

The uptake and recovery of ruthenium ions were investigated by using alginate gel polymers. The uptake of RuNO3+ attained equilibrium within 2 d and the uptake percentage was above 90%. The distribution coefficient (Kd ) of RuNO3+ for barium alginate (BaALG) tended to slightly decrease with increasing HNO3 concentration, while a relatively large Kd value of 52.0cm3/g was obtained even in the presence of 6.7 M HNO3, indicating a high affinity of BaALG for RuNO3+ ions. The separation factor of RuNO3+ and Rh3+ was 16.0 in the presence of 2.5 M HNO3. The Ru ions were uniformly dispersed throughout the gel particle and the maximum uptake capacity was estimated to be 1.30 mmol/g. The RuNO3+ ions were effectively adsorbed on the packed column of BaALG and eluted with concentrated HNO3 solution.

Selective Uptake and Recovery of Cesium Ions by Composite Columns of Ammonium Molybdophosphate (AMP)-Calcium Alginate

This paper deals with a new procedure for the preparation of AMP-calcium alginate composites, their breakthrough and elution properties of radioactive cesium from highly concentrated NaNO 3 solutions by using the packed columns.

2,3,7,8-Tetrachloro dibenzo-p-dioxin can be successfully decomposed over 2:1 dioctahedral smectite—a reactivity index study

2:1 Dioctahedral smectite family has shown its capability to decompose 2,3,7,8-tetrachloro dibenzo-p-dioxin (TeCDD) using the active hydroxyl hydrogen attached with the central octahedral aluminum, as monitored using density functional theory (DFT). From the values of the local softness and the charge on the hydrogen atom of the bridging/structural (occurring on the surface) hydroxyl attached to octahedral/tetrahedral metal site present in smectite used as a first approximation to the local hardness, it is concluded that the local acidities of the inorganic material systems are dependent on several characteristics which are of importance within the framework of hard-soft acid-base (HSAB) principle. The first step in this process of decomposition is the abstraction of chlorine bound to TeCDD using surface hydrogen of smectites. This results in non-chlorinated dibenzo-p-dioxin (NCDD), which is less toxic than TeCDD. The second step is the formation of a dative bond between oxygen of NCDD and hydroxyl proton of smectite, with the breaking of Cz.sbnd;O bond of NCDD. The reaction mechanism is postulated within the helm of DFT using Fukui functions for all possible chlorinated and non-chlorinated dioxin varieties along with clay clusters. The material is identified to act for the decomposition of dioxin.

Topotactic valence manipulation to design strontium manganate: a first principle study

First principle periodic calculation was used to determine the feasibility of topotactic exchange and stability of bivalent metal cations inside lithium manganate, which help solid-state chemists to rational design and construction of new-nonmolecular materials. Among the bivalent metal ions strontium-incorporated lithium manganate shows better performance. The location and orientation of the metal cations are also monitored. Projected density of state calculations using periodic boundary conditions justifies the superiority of strontium-incorporated material. The spin and orbital ordering in the material is also explored. The findings further help to propose a novel topotactic valence manipulation scheme for related compounds.