蛇紋石の分別定量法と労働衛生および地球科学的意義(<シンポジウム特集>蛇紋石環境と深く関わる層状ケイ酸塩)

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Serpentinite rocks have been used for road and railroad pebbles, iron manufacture, construction materials, fertilizer and magnesium resource, and others in about 3 million tons annually in Japan. Serpentinite rocks usually contain chrysotile asbestos and sometimes tremolite asbestos. Accordingly workers related to serpentine rocks have to pay attention to prevent the exposure to the dust during works. It is, however, obscure that what amount of asbestos exists in Serpentinite rock because analytical method has not been established to quantify the content of chrysotile distinguished from the other serpentine minerals. X-ray diffraction (XRD) analysis has been popularly used for quantification of minerals in rocks and other materials. Serpentine minerals such as chrysotile, lizardite and antigorite show similar XRD patterns each other, but lizardite and antigorite would be able to be determined their contents by their characteristic diffraction peaks. However, it is difficult to discriminate and quantify the content of chrysotile by only XRD analysis. This study examined various analytical methods such as XRD, infrared spectrometry (1R), transmission electron microscopy (TEM) as well as thermal analysis to know the content of chrysotile. The result is very suggestive that differential thermal gravimetric (DTG) analysis can measure the content of chrysotile distinguished from the other serpentine minerals effectively when they exist mixed in Serpentinite. The DTG peaks due to dehydroxylation of each serpentine appeared clearly in different temperatures because their hydroxyl ions were exhausted in different temperatures between the different polytypes. The mixed DTG curves composed of three different polytypes could be decomposed quantitatively into each one by peak deconvolution. Endothermic peaks of DTA did not appear quantitatively for each polytypes when they existed mixed because of the change of the thermal conductivity by the shrinkage of specimen volume due to the dehydroxylation. Many samples of Serpentinite rocks were examined by these methods, and we concluded that we can see the amount of each serpentine mineral in Serpentinite rocks by DTG method. The detection limit was about 5% in weight, but the accuracy would be increased if the result was determined with reference to the results by XRD and TEM analyses. At the symposium, the author introduced some application of the method to the fields of industrial health and geological science.
2007-02-16

蛇紋石の分別定量法と労働衛生および地球科学的意義(<シンポジウム特集>蛇紋石環境と深く関わる層状ケイ酸塩)

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