Dependence of Phosphorus Recovery on Acid Type during Dissolution–Precipitation Treatment of Incineration Ash of Chicken Manure

In order to utilize chicken manure as a source of phosphorus, we used dissolution-precipitation treatment to recover phosphorus from the incineration ash of chicken manure (IACM), which was used as fuel to power a boiler. In order to recover useful phosphorus-containing solids from IACM, it was dissolved into aqueous solutions of either nitric acid, hydrochloric acid, or sulfuric acid to elute phosphorus together with various component elements, followed by the use of aqueous NH3 to form a precipitate containing phosphorus. In using nitric acid and hydrochloric acid, calcium phosphate species such as calcium hydroxyapatite (Ca10(PO4)6(OH)2) and monetite (CaHPO4) were obtained following the precipitation treatment. By contrast, the use of sulfuric acid resulted in the precipitation of magnesium ammonium phosphate (MAP) species such as struvite (MgNH4PO4∙6H2O) and dittmarite (MgNH4PO4∙H2O). Both the calcium phosphate and MAP species can be used as a slow-acting fertilizer containing phosphorus, while the MAP species could be simultaneously used as a slow-acting fertilizer containing nitrogen. It is noteworthy that the calcium phosphate species obtained in the present study was equivalent to phosphate rock, which is widely used as a raw material in phosphorous-based industries, and the natural sources of this material could be depleted in the near future. Though IACM has not been used effectively until now, this new resource shows promise as s viable alternative to the dwindling supply of the natural sources of phosphorus.