The Evaluation of the Moisture Sorption Mechanism of Chloride-Impregnated Wakkanai Siliceous Shale

Kurokawa Asami, Togawa Junya, Nabeshima Yuki, Nagano Katsunori

doi:10.1252/kakoronbunshu.37.394

Wakkanai siliceous shale (WSS) is a natural mesoporous material that has high performance of moisture adsorption/desorption in response to relative humidity. The authors have previously applied the technique of impregnation with chloride to enhance the water adsorption performance; and in the present study the moisture sorption mechanism with chloride impregnation was examined by DSC analysis. It was found that the adsorbed water in the pores was divided present in three forms: non-freezing water, freezable bound water and free water. The free water peak was not observed at water content below 320 mg/g. This water content was also consistent with the maximum amount of water adsorbed without surface wetting, which was estimated from color change of WSS surface at various water contents. In addition, from the measurement by a modified nitrogen adsorption method, it was visually shown that the mechanism of moisture sorption gradually proceeded from the smaller mesopores. Moreover, the NaCl impregnation was applied to other porous materials. From the experimental results, the impregnation of silica gel with NaCl is not effective, because of the structural weakness. Therefore the stability of the material to impregnation is an important factor.

The Evaluation of the Moisture Sorption Mechanism of Chloride-Impregnated Wakkanai Siliceous Shale

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