Effect of reactive crystallization parameters on the quality of struvite crystals produced in a continuous draft tube magma crystallizer with a jet pump fed with recirculated mother solution

摘要

Struvite was pptd. and crystd. from aq. soln. of MgCl2 and NH4H2PO4 by addn. of aq. soln. of NaOH in a liq. jet-pump draft-tube magma crystallizer with descending suspension flow in a mixing chamber and internal circulation of the suspension at 298 K and pH 9-11 (residence time 900-3600 s). The decrease in pH and the increase in residence time resulted in increasing the mean size of the struvite crystals up to 23.8 mm. The max. crystal size was about 160 μm. The phosphate ion concn. in the soln. decreased from 0.20% by mass down to 0.011% by mass after the pptn.