Intensified Enrichment and Leaching Strategy of Phosphorus in Sewage Sludge via Species-Targeted Conversion

Wet-chemical method for extracting phosphorus (P) from sludge incineration ash suffers from great P loss in the incineration and P-leaching stages due to the multidirectional migration of diversified P species. Existing single-process optimizations are difficult to meet the diverse and often conflicting needs of the two upstream and downstream processes to recover different P species. Herein, we developed a system-oriented strategy, HyperPhos^Ⓟ, to synergistically address multiprocess requirements. It employs a specially designed one-pot pretreatment to create a unique reaction window for the most recoverable Fe/Al-P, achieving the targeted transformation of unstable P species into homogeneous Fe/Al-orthophosphate of 85.6% in proportion. These compounds exhibited remarkable thermal stability during incineration, with volatilization loss of only 60% of conventional technical route (Conv-Tech) even at 1000 °C. Subsequently, these parts of P were completely leached out using H₂C₂O₄ or NaOH through redox reaction and chelating displacement, with the solvent concentration and the codissolution amounts of heavy metals less than half of the mean levels in the literature. Techno-economic analysis showed that HyperPhos^Ⓟ obtained 1.1-2.4 times more P than Conv-Tech, while the unit cost was reduced by up to 49.5%. These findings provide new opportunities to close the P-cycle in a sustainable, economical, and environmentally friendly approach.