Sekisui Kaseihin Kogyo Kabushiki Kaisha

Yukiyoshi Iwamoto

Tadashi Nishino

Masayuki Nagai

The present invention provides a method for dissolving slightly soluble sludge which is produced during chemical conversion coating of metal, which comprises agitating the sludge in an aqueous suspension containing hydrogen type strongly acidic cation exchange resin; exchanging metallic components in the sludge with the resin and adsorbing the metallic components on the resin; dissolving oxyacid components in the sludge into liquid phase; and recovering the metallic components from the resin and the oxyacid components from the resin and the oxyacid components from the solution. The sludge can be dissolved by simple operation and equipment, and effective components in the sludge can be recovered at high yield. The method contributes to effective re-utilization of resources and to prevention of environmental pollution and makes it possible to use the resin semipermanently by regenerating the used ion exchange resin.

Method for dissolving sludge and recovering constituents therefrom

The presence of carbon dioxide contained in a gas can be detected through measurement of the change in the electrical resistance of a hydroxyapatite in contact with carbon dioxide gas. The sensitivity of the hydroxyapatite to carbon dioxide gas can be enhanced by the formation of a composite of the hydroxyapatite with an inorganic carbonate, e.g., sodium carbonate or calcium carbonate. The sensitivity to carbon dioxide gas can be further enhanced by the formation of a composite of the hydroxyapatite with an inorganic halide, e.g., calcium chloride.

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Tokyo, Japan

Tadashi Nishino