We examined the extraction of phosphorus (P) from sewage sludge incineration ash with heavy-metal-free alkaline wastewater for the recovery of P for the manufacture of phosphate fertilizer. The major components of the ash were P (13 wt%), silicon, calcium, aluminum, iron, magnesium, barium, potassium, and sodium. The lead content was at risk of exceeding the Japanese regulation value (100 mg kg^<-1>). The efficiency of P extraction by the alkaline wastewater (0.5〜1.0 mol L^<-1> alkali) was similar to that of extraction with NaOH (also 0.5〜1.0 mol L^<-1>) at 70℃. No toxic heavy metals were present in the P fraction. The resultant calcium phosphate contained 300 g kg^<-1> of P. Our results support a possible strategy for the production of high-quality P fertilizer from sewage sludge and industrial wastewater.
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