Abstract: Struvite was prepared by semi-batch method with phosphoric acid and the mother liquor from magnesium-hydroxide production as raw materials.Influences of operating conditions,such as stirring speed,feed location,feed rate,reactant concentration,and adding amount of seed,on crystal size distribution (CSD) of struvite were investigated.Results showed properly increasing stirring speed,decreasing feed rate,or decreasing reactant concentration all could make the average crystal size increase and the coefficient of variation(C.V.) decrease;feeding in the propeller area could create larger crystal size and better CSD than feeding in the surface;and seeding appropriately could cause average size of products increase significantly and the CSD more uniform.

Key words: seawater utilization, struvite, reaction crystallization, crystal size distribution