EFFICIENCIES OF DIFFERENT MAGNESIUM SOURCES IN STRUVITE FORMATION FROM IRON PHOSPHATE WASTEWATER
The different efficiencies of struvite generation from phosphorus in iron phosphate wastewater,the components of struvite,the influencing factors,and the optimization of the conditions were compared and analyzed by using seawater,salt brine,and industrial magnesium oxide as the magnesium sources,using orthogonal test and one-way optimization method.The results showed that using seawater as the magnesium source,the phosphorus removal rate was 93.2％at the optimum reaction pH=10,n(Mg)∶n(P)=1.2,stirring speed=200 r/min,reaction time=20 min,and the purity and yield of struvite were 76.8％and 522.5 g/m3,respectively,and the amount of struvite per unit amount of Mg2+(1 g)was 4.6 g;using industrial magnesium oxide as the magnesium source,the removal rate of phosphorus reached 98.0％at the optimal conditions of pH=7,n(Mg)∶n(P)=1.4,stirring speed=250 r/min,and reaction time=1 h,and the purity and yield of struvite were 78.0％and 633.0 g/m3,respectively,and the amount of struvite per unit of Mg2+was 5.0 g.Salt brine can be used as the optimal magnesium source for this study,and at the optimum reaction of pH=10,n(Mg)∶n(P)=1.4,stirring speed=200 r/min,and reaction time=30 min resulted in 96.7％phosphorus removal,the highest purity and yield of 93.0％and 674.2 g/m3 of struvite,the maximum amount of struvite obtained per unit of Mg2+was 5.1 g at the same time.By comprehensive comparison,the effect of salt brine among the three magnesium sources is the best,and it can be used as the optimal magnesium source.
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