Study on the recovery of phosphorus from waste-activated sludge incinerator ash

Several batch studies that were made up of the acid extraction and the solvent extraction were performed to recover phosphorus from the waste-activated sludge (WAS) incinerator ash. In the acid extraction, the extraction efficiency of phosphorus relied on the acid type, liquid(acid)-to-solid (L(acid)S) ratio, and acid concentration. Phosphorus in the WAS incinerator ash was completely extracted by 1 M HCl at the L(acid)S ratio of 6.4:1. Subsequently, the solvent extraction was conducted to separate and concentrate phosphorus further from the acid extract. The efficiency of solvent extraction was affected mainly by the solvent type, liquid (solvent)-to-liquid (the acid extract) (L(solv)L(acid ext)) ratio, and hydrogen ion concentration. Under the appropriate condition, 76% of phosphorus in the acid extract was extracted to 1-butanol phase, which corresponded to 80.1% as the mass fraction of phosphorus to total elements. Prior to the solvent extraction, the addition of bis (2-ethylhexyl) phosphoric acid (D2EHPA), which was available for removing aluminum from the acid extract, led to an additional increase in the term of the mass fraction of phosphorus to total elements. Overall results indicated that phosphorus in the WAS incinerator ash could be efficiently recovered and be a potential renewable resource.