A novel treatment processes of struvite with pretreated magnesite as a source of low-cost magnesium

By crystallization process, phosphorus can be recycled from wastewater. However, the reagent cost limits the application of struvite precipitation. Magnesite, as a low-cost magnesium source, can result in a cost savings, while the poor dissolution offset of low-cost reagent. In this study, most of the pyrolysate of magnesite was dissolved by changing the process of reagent addition; the solubility of the pyrolysate was increased at acid wastewater. The removal rate of phosphate by the pyrolysate was higher than that of magnesite, the phosphate removal rate was from 70.2 to 88.2% at 600 °C, 0.5 h to 1200 °C, 3 h. Phosphate removal rate was achieved optimal when calcination temperature was 700 °C at 2 h. By adding the pyrolysate to acid wastewater (pH ≤ 2) before NH₄Cl, phosphate removal rate was closed to that of MgCl₂ as magnesium source, while magnesite was priced at similar levels to lime.