Recovery of Calcium Phosphate from Composted Chicken Manure and Industrial Waste

Abstract

Bench-scale experiments were carried out to examine the potential of recovering calcium phosphates from composted chicken manure. Ca2+ and phosphate ions were eluted from composted chicken manure using HNO3 that released less K+ from composted chicken manure compared to HCl and H2SO4. After filtration, the eluate pH was increased to 6.0 using aqueous ammonia to precipitate calcium phosphates, forming calcium hydroxyapatite which is known as a principal component of phosphate rock. The purity of recovered calcium phosphates was more than 95 mol%, suggesting that composted chicken manure could potentially be used as a secondary source of calcium phosphates for industrial applications. Using this technology, calcium phosphates could also be recovered from industrial wastes such as dephosphorization slag, chemical industry sludge, and spent fluorescent phosphorus powder (called bag powder).