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  • Author or Editor: J. Jung x
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Aim of this work in connection with the development of materials in the periclase-forsterite-zirconia system was the determination of melting temperature and melting enthalpy of refractory compounds. The possibility of determination of the melting and solidification of minor phases in refractory materials should be proved.

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The influence of chelating agents on the separation factor, , of lithium isotopes separation was studied by ion exchange elution chromatography. Eluents contained the chelating agent having different number of coordination sites. The chelating agents used in eluent were Na-glycine (Na–Gly), 2Na-iminodiacetic acid (2Na-IDA), 3Na-nitrilotriacetic acid (3Na-NTA), and 4Na-ethylenediaminetetraacetic acid (4Na-EDTA). The ion exchanger was Dowex 50W-X8, sulfonic acid type, sodium form. As a result,6Li was enriched in resin phase, and7Li was in solution phase. The separation factor, , was gradually increased with increasing number of coordination site (=1.0022–1.0038) at the same distribution coefficient and with increasing distribution coefficients (=1.0017–1.0026) at the same concentration of chelating agents.

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Comparative thermogravimetric and heat-flux DSC investigations of phase formations by heating of sinteractive powders, which were prepared by thermal decomposition of a NiCO3∶ MnCO3=1∶2 mixture and thermal decomposition of oxalate mixed crystals NiMn2(C2O4)3.6H2O, show the metastability of the defect spinel from the oxalate precursor and its high reactivity.

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Radiation treatment in the presence of catalysts such as anatase, P25 and bentonite showed efficient removal of TCE (trichloroethylene) and PCE (perchloroethylene) compared with gamma-irradiation alone. Gamma-ray pretreatment of P25 and bentonite enhanced the decomposition of TCE and PCE, respectively. The change in the catalysts by gamma-rays was characterized by their EPR spectra. For anatase and bentonite, the peaks in the spectra increased significantly, and the pattern of the spectra changed in the case of P25. The relationship between the peaks and pollutant decomposition should be further clarified due to the complexity of the spectra.

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Ionizing radiation, such as gamma-rays and electron-beams, has been applied to modify toxicity of refractory pollutants and industrial wastewaters, however, very few studies reported the cause of toxicity changes by radiation treatment. In this work, degradation of phenol and chlorophenols (5·10−4M) by gamma-ray treatment and consequent toxicity changes were evaluated. Toxicity of 2,4-dichlorophenol (2,4-DCP) and 2,4,6-trichlorophenol (2,4,6-TCP) was gradually decreased with increasing absorbed dose of gamma-radiation. However, in the case of phenol and monochlorophenols (2-, 3-, and 4-CPs), toxicity was dramatically increased particularly, for a dose of as low as 1 kGy. Hydroquinone, benzoquinone, catechol, chlorohydroquinone, and 4-chlorocatechol were identified to be main by-products of gamma-ray treatment. From the solid phase extraction (SPE) fractionation study, toxicity-causing by-products were found to be hydroquinone, benzoquinone, chlorohydroquinone, and/or 4-chlorocatechol.

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The thermal diffusivity and the thermal conductivity of polypropylene-based composite polymer were simultaneously measured with a temperature wave analysis method. We can measure the thermal properties under cooling process which are important to consider the polymer processing. The effect of filler in the composite was analyzed by thermal diffusivity and thermal conductivity as a function of temperature. The thermal conductivity of particle dispersed composite was confirmed as a reasonable value and was explained with a series model.

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The scavenging of UO2 2+ using 4-sulfonic calix[6]arene in the presence of a strong adsorbent was studied as a function of pH. The adsorbent selected was goethite because of its strong affinity for UO2 2+ and its abundance in natural soils. In order to understand the underlying chemistry of the scavenging process, the adsorption of UO2 2+ and 4-sulfonic calix[6]arene onto goethite, respectively, and the extraction of adsorbed UO2 2+ from goethite surface were modeled using the triple-layer model. The model well explained the pH dependence of the adsorption and extraction processes. This work showed that maximum extraction was obtained around pH 10.5 in the presence of 12g/l goethite in the case of a 1:3T U(VI):T calixareneratio.

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The prediction of the adsorption behavior of natural composite materials was studied by a single mineral approach. The adsorption of U(VI) on single minerals such as goethite, hematite, kaolinite and quartz was fully modeled using the diffuse-layer model in various experimental conditions. A quasi-thermodynamic database of surface complexation constants for single minerals was established in a consistent manner. In a preliminary work, the adsorption of a synthetic mixture of goethite and kaolinite was simulated using the model established for a single mineral system. The competitive adsorption of U(VI) between goethite and kaolinite can be well explained by the model. The adsorption behavior of natural composite materials taken from the Koongarra uranium deposit (Australia) was predicted in a similar manner. In comparison with the synthetic mixture, the prediction was less successful in the acidic pH range. However, the model predicted well the adsorption behavior in the neutral to alkaline pH range. Furthermore, the model reasonably explained the role of iron oxide minerals in the adsorption of U(VI) on natural composite materials.

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Gamma-ray treatment in the presence of ozone (O3) and titanium dioxide (TiO2) showed an efficient removal of trichloroethylene (TCE) and perchloroethylene (PCE). Without gamma-irradiation, TCE and PCE were not sufficiently decomposed to comply with the water quality limit of groundwater. However, near 100% of TCE and PCE were removed at a dose of 300 Gy in the presence of O3 and TiO2, where TiO2 showed an explicit enhancement of decomposition. Cytotoxicity test using Chinese hamster V79 cells showed no toxicity of the TCE and PCE decomposition products.

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Carbonate ions significantly inhibit the decomposition of TCE (trichloroethylene) and PCE (perchloroethylene) by gamma-rays. The inhibition effect is larger in the case of TCE than PCE due to a greater dependence of TCE decomposition on hydroxyl radicals. The inhibition effect of carbonate ions was characterized by an EPR/spin-trapping technique. The intensity of DMPO-OH adduct signal decreased as the carbonate ion concentration increased and the percent of signal reduction was linearly proportional to the logarithm of carbonate ion concentration. This directly proves that the carbonate ions inhibit the decomposition of TCE and PCE by scavenging hydroxyl radicals.

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