抄録
Three kind of typical calcium silicate powders, i. e. wollastonite, tobermorite and xonotolite, were mechano-chemically activated in air for 24h with a vibration ball-mill. The cakes of the vibration ball-milled calcium silicate added with a fair amount of water were carbonated at 50°C or 80°C in 0.33MPa CO2 for 3h in order to obtain the specimens with a different carbonation ratio. The removal efficiencies of phosphorous for the carbonated specimens were investigated by immersing them in Na2PO4 aqueous solution containing 5ppm phosphorous. After immersing the specimens for prescribed duration in the test solution, the remaining amount of phosphorous in a supernatant liquid was measured by an inductively coupled plasma spectroscope. In the case of the specimens with lower carbonation ratio, about 80% of phosphorous in the Na2PO4 test solution was removed by immersing for 5 to 10 days. In this case, however, very fine precipitation of calcium phosphate was formed. On the other hand, well carbonated specimens showed lower dephosphorizing rate, and it took above 40 days to remove 80% of phosphorous in the test solution. In this case, no fine precipitation was observed even after immersing the specimens for 40 days. It was necessary to obtain the consolidated bodies of calcium silicate with above 50% of carbonation ratio for the removal of phosphorous without fine precipitation of calcium phosphate.
