Influence of amorphous calcium carbonate on strontium ion removability from aqueous solution

摘要

The Fukushima nuclear power plant accident caused an outflow of pollutants. Thus, precautionary measures must be taken by using preventive materials for the deterrence of such accidents. Herein, we aimed to develop inexpensive materials that can remove radioactive elements from an aqueous solution. We found that powders obtained from milling scallop shells, which were discarded in large quantities, removed Srsup2+/sup from aqueous solutions. The Srsup2+/sup removability of the scallop shell powder improved with milling time, indicating the influence of increase in the specific surface area on Srsup2+/sup removability. Despite of the same specific surface area, the scallop shell powder exhibited higher Srsup2+/sup removability than that of the unmilled CaCOsub3/sub. Differential scanning calorimetry evaluation for the investigation of factors other than the specific surface area revealed that the milled scallop shell powder contained amorphous calcium carbonate. Moreover, we synthesized amorphous calcium carbonate and found that it exhibited 60-times higher Srsup2+/sup removability than that of crystalline calcium carbonate. We concluded that the amorphous structure of calcium carbonate significantly affects the Srsup2+/sup removability from aqueous solutions. It was hypothesized that amorphous calcium carbonate removes Srsup2+/sup by incorporating Srsup2+/sup into the structure during crystallization in an aqueous solution.