NICKELIFEROUS SEPIOLITE AND ITS BEHAVIOUR ON HEATING

概要

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A nickeliferous sepiolite sample from New Caledonia has been studied by means of thermal analysis, electron micrography, electron diffraction analysis, X-ray diffraction analysis, infrared analysis, chemical analysis and acid dissolution experiment. Quantitative X-ray diffraction analysis shows that this sample is a mixture of 80 % sepiolite and 20 % nickeliferous talc. The electron micrographs show that this sample is composed of fibrous particles. The heated specimens at 800℃ and 900℃ show the absorption bands at 3665 cm^<-1>, 3655 cm^<-1>, 3645 cm^<-1> and 3625 cm^<-1> in the OH region. The wave numbers of these bands are in good agreement with the data of synthetic and natural nickel-rich talc (willemseite). The intensity ratios of these peaks indicate that Ni ions are present in octahedral sites of nickeliferous talc. The value of Ni concentration ranges between 0.788 and 0.872. Using these values for nickeliferous talc and results of wet-bulk chemical analysis, the structural formula of nickeliferous sepiolite in this sample ranges between (Si_<11.98>Al_<0.02>) (Fe_<0.01>Mg_<5.67>Ni_<2.15>) O_<32.00> 5.76 H_2O and (Si_<11.98>Al_<0.02>) (Fe_<0.01>Mg_<5.82>Ni_<2.21>) O_<32.00> 5.93 H_2O. The intensities of X-ray diffraction peaks calculated using the formula of Mg_6 Ni_2-sepiolite are in good agreement with those observed.
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