A Novel Process for Synergistic Recovery of P from Steelmaking Slag with High Basicity and Incinerated Sewage Sludge Ash

To alleviate phosphorus (P) resource shortage and avoid codissolution of metallic elements in conventional methods, a novel process involving high-temperature remelting, selective leaching, and precipitation was developed for P recovery from steelmaking slag and incinerated sewage sludge ash (ISSA). The treatment involved remelting the slag and ISSA to concentrate P2O5 into the 2CaO·SiO2 phase, followed by its selective leaching. Under optimal conditions (pH = 3, solid-to-liquid (S/L) ratio = 1:200), a high P dissolution ratio of 86.6% was achieved from the mixed slag with 30% ISSA with only 0.19% Fe dissolution, demonstrating excellent selectivity. The leachate was then precipitated to recover a product containing 33.4 wt % P2O5, suitable as phosphate fertilizer, while the residual slag was depleted of P (<0.2 wt %), facilitating its further utilization. The total P recovery reached 86.26%, realizing an efficient and sustainable path for P reclamation from bulk solid wastes.