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Murayama N.,Energy and Environmental Engineering | Hara R.,Energy and Environmental Engineering | Miyoshi T.,Energy and Environmental Engineering | Shibata J.,Energy and Environmental Engineering | Udagawa E.,Jfe Holdings
Kagaku Kogaku Ronbunshu | Year: 2012

Ca-Mg-Al type layered double hydroxide (LDH) was synthesized using mixed solutions containing Ca 2+ and Mg 2+ as divalent cations by a co-precipitation method. The removal of anionic species in aqueous solution such as As(III), B, Cr(VI) and Se(IV) was examined with the reaction products obtained. The effects of Mg 2+-Ca 2+ mixing ratio on the physical properties of the products and their ability to remove anionic species were investigated. Aluminum hydroxide (AH) and hydrotalcite-like compounds (HT) were formed at pH 10 by a precipitation reaction. In the co-precipitation operation, Mg 2+ and Al 3+ were completely precipitated at pH 10, while the percentage of Ca 2+ precipitated was extremely low. The ability of the complex of AH and HT to remove B and As(III) was higher than those of AH and HT alone. For all anionic species, 90% or higher removal was achieved with the products synthesized from the solution at the mixing ratio of Ca 2+: Mg 2+ 1:1. Hydrocalumite-like compounds (HC) and HT were also produced at pH 12. All amounts of Mg 2+ and Al 3+, and 70-80% of Ca 2+ were precipitated at pH 12 to form LDH products. Products containing both HC and HT showed no increase in the removal ability in comparison with HC and HT alone. The order of solubility of the product in an anion removal operation was as follows: HC >> HT > AH. The products obtained from the Ca 2+-Mg 2+ mixed solution, namely the complexes of AH and HT or HC and HT, had higher solubility than those of HC, HT and AH. The product containing HT as a main component was consider to be superior in the removal of anionic species and the stability of LDH structure among those obtained in Ca 2+-Mg 2+-Al 3+ mixed solution. © 2012 The Society of Chemical Engineers, Japan.


Shibata J.,Energy and Environmental Engineering | Murayama N.,Energy and Environmental Engineering | Niinae M.,Yamaguchi University | Furuyama T.,Tohoku University of Community Service and Science
Materials Transactions | Year: 2012

In a present process to treat the tungsten carbide tool waste, the wastes are roasted in air and then an alkali leaching is carried out in an autoclave. An environmentally friendly process is required to recover rare metals (Co and W) from the wastes. The effect of mechano-chemical (MC) treatment on leaching of rare metals was investigated in this study. The solvent extraction and crystallization-stripping methods were applied to separate and recover tungsten and cobalt in the leached solutions. The MC treatment for the rare metal leaching is effective to dissolve rare metals from the wastes due to the change in crystalline structure of WC and oxidation of WC with KMnO4. Cobalt ions are extracted with D2EHPA by a cation exchange reaction. Tungsten in the leachate can be extracted by TOA (tri-octyl amine) as an extractant, because tungsten species exist as a form of anionic species in acidic solution. The rare metals in organic phase are recovered as insoluble salts such as oxalates and ammonium salts in the crystallization-stripping process. © 2012 The Japan Institute of Metals.


Tanaka S.,Energy and Environmental Engineering | Tanaka S.,Kansai University | Kida K.,Energy and Environmental Engineering | Fujimoto H.,Energy and Environmental Engineering | And 3 more authors.
Langmuir | Year: 2011

An alkylimidazolium-based long-chain ionic liquid (LCIL) was immobilized in silica nanopores via a supramolecular assembly approach. To discuss the characteristic features of LCIL in a confined nanospace, except for the characteristics of the host materials, we have prepared the silica host with monodisperse morphology and a nanostructured system to immobilize LCIL. The nanostructure is composed of three distinct regions: the silica framework, the hydrophobic interior of the alkyl chains, and the organic-inorganic ionic interface. Anomalous CO 2 adsorption sites were found to be well-ordered locations on the ionic interface fabricated by the π-π-stacked imidazolium heads containing inorganic anions and polar silica surfaces. © 2011 American Chemical Society.

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