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

以机械力化学活化硅灰石微粉为原料，采用碳化法制备固结体。为了改善硅灰石固结体的除磷性能，在硅灰石中加入了骨料飞灰和水化水泥作为钙源。与纯硅灰石相比，得到的硅灰石固结体具有更高的除磷效率。然而，在较低的碳化温度下得到的样品，由于pH的显著增加，在磷酸水溶液中会产生细小的HAP沉淀。另一方面，碳化温度较高时，除磷率明显下降。这是由于水泥中氢氧化钙的碳化导致溶解的钙离子浓度降低所致。因此，水化水泥作为钙源时，需要对碳化条件进行精确控制，石膏替代水化水泥作为钙源时，除磷效果与碳化温度无关，且比纯硅灰石的除磷率高。无论碳化温度如何，含石膏的样品都不会产生细小的HAP沉淀。此外，当纯硅灰石加入量为25%时，石膏样品的除磷效果较好，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，除磷效果显著降低。浸泡5次后，样品的除磷率降至初始值的50%。用0.005mol/L的盐酸洗涤，去除沉淀在样品表面的羟基磷灰石，可使变质样品的除磷效率恢复到初始值的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.