大きな細孔構造を有する多孔質カルシウム系担体のリン除去および回収特性

抄録

In this investigation, the feasibility of phosphorus removal and recovery using a laboratory prepared Ca-based sorbent containing relatively large pores was experimentally demonstrated. Obtained results from the column experiment showed that the removal was accompanied by a leaching of Ca and relatively high pH values at the beginning of the experiment due to the hydration of CaO. After that, the elution of Ca ceased and the pH values decreased gradually to finally stabilize between 8 and 7.5. It was suggested that phosphorous uptake by the sorbent was governed by both sorption and precipitation/crystallization phenomena. The sorption capacity slightly increased with an increase in the flow rate and was associated with the increasing amount of the dissolved calcium. Maximum removal capacity was equal to 30.5 mg-P/g-sorbent, corresponding to a quantity of treated water equivalent to 4000 bed volumes. Pore sizes of the sorbent were entirely shifted to lower values due to the formation of hydroxyapatite on the surface. Furthermore, more than 75% of the sorbed phosphate was recovered using a mechanical sieving of the sorbent. X-ray measurement and P₂O₅determination revealed that the recovered product was quantitatively and qualitatively similar to a phosphate mineral ore. The sorbent was efficiently reused for a second time. However, its removal capacity was severely degraded upon the third utilization, probably because most of its calcium content was consumed. From these results, it was concluded that the fabricated sorbent could be effective for phosphorus removal and recovery.