Transformation of phosphorus and stabilization of heavy metals during sewage sludge incineration: the effect of suitable additives and temperatures
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Phosphorus (P), an irreplaceable nutrient for all living organisms, is facing scarcity via phosphate resources. In this research, the effect of suitable additives and temperature on P and heavy metals speciation during sewage sludge (SS) thermochemical treatment was investigated. The results demonstrated that additives (CaO and MgO) could promote the conversion of non-apatite inorganic phosphorus (NAIP) to apatite phosphorus (AP). X-ray diffraction measurements indicated that the phosphorus mineral phase in sewage sludge ash (SSA) mainly was AP, with addition of MgO and CaO. Moreover, orthogonal testing revealed that the optimal molar ratio of Mg:Ca:P for P recovery as AP was 1:3.5:1 at 750 °C. Risk index results implied that the heavy metals in the phosphorus-enriched SSA have low potential ecological risk. Thermodynamic equilibrium calculations revealed that P reacted with the other metal ions was in the following order: Ca2+ > Mg2+ > Al3+ > Fe3+ > Zn2+ > K+.
KeywordsSewage sludge ash Phosphorus recovery Conversion Environmental assessment Thermodynamic equilibrium calculations
sewage sludge ash
non-apatite inorganic phosphorus
P is associated with Ca or Mg
P is associated with Al or Fe
acid soluble fraction
This work was supported by the National Natural Science Foundation of China, China (No. 51276119 and No. 51576134).
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