Efficient and selective recovery of iron phosphate from the leachate of incinerated sewage sludge ash by thermally induced precipitation.

• Thermally induced precipitation was firstly proposed for FePO 4 recovery from ISSA. • The leachate successfully recycled for five times to recover FePO 4 precipitates. • A high phosphorus recovery rate of 81.1 ± 1.8% was achieved from sludge leachate. • Low cost of ∼$26.9/kg-P was achieved for recovering phosphorus from ISSA. • The FePO 4 precipitates were used to promote plant growth and synthesize LiFePO 4. Phosphorus recovery from incinerated sewage sludge ash (ISSA) is important but hindered by low selectivity. Here, a novel strategy of acid leaching followed by thermally induced precipitation was proposed for the efficient and selective recovery of FePO 4 from ISSA samples. A high phosphorus leaching efficiency of ∼ 99.6% was achieved with 0.2 mol/L H 2 SO 4 and liquid to solid (L/S) ratio of 50 mL/g. Without removing various co-existing ions (Al3+, Ca2+, SO 4 2–, etc.), high-purity FePO 4 of ∼ 92.9% could be facilely produced from this highly acidic H 2 SO 4 leachate (pH = 1.2) by simple addition of Fe(III) at a molar ratio of 1:1 to the phosphorus and reacted at 80 °C for thermally induced precipitation. The remained acid leachate could be further reused for five times to continue leaching phosphorus from the ISSA samples and produce the FePO 4 precipitates with a high phosphorus recovery efficiency of 81.1 ± 1.8%. The selective recovery of FePO 4 from the acid leachate was demonstrated more thermodynamically favorable compared to other precipitates at this acidic pH of 1.2, and elevated temperature of 80 °C towards thermally induced precipitation. The estimated cost of this strategy was ∼$26.9/kg-P and lower than that of other existing technologies. The recovered FePO 4 precipitates could be used as a phosphate fertilizer to promote the growth of ryegrass, and also as a precursor to synthesize high-value LiFePO 4 battery material, demonstrating the high-value application potential of the phosphorus from the ISSA. [Display omitted] [ABSTRACT FROM AUTHOR]