2015 年 64 巻 6 号 p. 442-446
Previously, the authors reported the possibility for the use of scallop shell powder-gypsum composites as a crystallization-type phosphorus remover. However, these composites broke partially on immersing in a phosphorus solution for a prolonged time due to dissolution of gypsum. In this study, in order to improve durability of the composites in the solution, scallop shell powder-Ca(OH)2-gypsum composites were prepared and carbonated to convert Ca(OH)2 into CaCO3. The surface of the carbonated specimens were covered with dense layers composed of fine CaCO3 particles, and therefore the dissolution rete of Ca from gypsum was reduced. The thickness of CaCO3 layer increased with increasing number of carbonation. Although the carbonated specimen showed low phosphorus removal properties in the early period due to the low Ca dissolution rete, about 80% of phosphorus was removed after 10 days immersion in 50ppm phosphorus solution because Ca2+ concentration gradually increased. Moreover, the carbonation specimen had higher durability compared with the scallop shell powder-gypsum composite in the phosphorus solution.