Development of Novel Porous Phosphorous Adsorbent by Effective Uses of Waste Cement and Flyash

以机械力化学活化的硅灰石粉为原料，采用碳化法制备固结体。为了提高硅灰石固结体的除磷性能，在硅灰石中分别加入粉煤灰作骨料和水化水泥作钙源。这些添加剂制备的硅灰石固结体对磷的去除率高于纯硅灰石。然而，在低碳酸化温度下获得的样品在磷酸水溶液中由于pH的显著增加而产生细HAP沉淀。另一方面，当碳酸化温度高时，磷去除率显著降低。这是由于水泥中氢氧化钙的碳酸化导致溶解的钙离子浓度降低所致。因此，以水化水泥为钙源时，必须精确控制碳化条件，以石膏代替水化水泥作为钙源时，磷的去除率与碳化温度无关，且高于纯硅灰石。无论碳酸化温度如何，含有石膏的样品都不产生细的HAP沉淀。在磷酸水溶液中的循环浸泡试验表明，随着浸泡次数的增加，磷的去除率显著降低。浸泡5次后，样品的除磷率下降到初始值的50%。但是，通过用0.005mol/l盐酸洗涤样品以除去沉淀在样品表面的HAP，磷去除率劣化的样品恢复到初始值的95%。

Mechano-chemically activated wollastnite powder was used as a starting material to obtain consolidated bodies by a carbonation method. Fly ash as aggregate and hydrated cement as a calcium resource were added to wollastnite in order to improve the phosphorus removal property of the consolidated bodies. The wollastnite consolidated bodies obtained these additives showed higher phosphorus removal ratio than that of pure wollastnite. However, the sample obtained at low carbonation temperature generates fine HAP precipitate in a phosphoric acid aqueous solution due to significant increase in pH. On the other hand, when the carbonation temperature is high, the phosphorus removal ratio markedly decreased. This is caused by the decrease in the dissolved calcium ion concentration due to the carbonation of calcium hydroxide in cement. Therefore, the precise control of carbonation conditions is necessary when the hydrated cement as a calcium resource.When gypsum was used as a calcium resource instead of hydrated cement, the phosphorus removal ratio was independent of the carbonation temperature and higher than that of pure wollastnite. The sample containing gypsum did not generate fine HAP precipitation regardless carbonation temperature. Moreover, the sample containing gypsum showed satisfied phosphorus removal ratio at 25% amount of pure wollastnite.The cyclic immersion test in the phosphoric acid aqueous solution showed the significant decrease of the phosphorus removal ratio with increasing immersion cycle. Five times of immersion decreased the phosphorus removal ratio of the sample to 50% of initial value. However, the phosphorus removal ratio deteriorated sample was recovered to 95% of initial value by washing the sample in 0.005mol/l hydrochloric acid to remove HAP precipitated on the surface of the sample.