Multiple element approach to P recovery and recycling: A green and sustainable strategy by using fused magnesia waste ash

Recovery of phosphorus through controlling the crystallization of struvite (MgNH4PO4<middle dot>6H(2)O), a slow-release fertilizer, is highly attractive, but costly if large amounts of magnesium and alkali have to be added. In this study, a strategy for synchronously recovering phosphorus and nitrogen resources from wastewater and magnesium resources from solid waste was proposed. We demonstrated the fused magnesia waste ash (FMWA), an industrial by-product of magnesia which might serve as a cost-effective source of magnesium and alkali. The results showed that a recovery efficiency of 93.0 % PO43- and 88.8 % NH4+ from synthetic wastewater and 46.6 % Mg2+ from the FMWA was achieved when the ratio of [Mg2+]:[NH4+]:[PO43-] was 1.8:1:1. The magnesium release potential of FMWA was 10 times more than that of other known magnesium-containing solid wastes, due to the process in electric melting furnace damaged the lattice structure of magnesite and converted magnesite to magnesia. XRD analysis showed that crystalline struvite was the major product. The undissolved components of FMWA (MgCO3, MgO and SiO2) acted as crystal seeds, increasing the particle size and accelerating struvite precipitation. The application of FMWA for phosphorus fixation can reduce costs by 98.3 % compared with MgCl2. This research paves the way for employing FMWA in efficient recovery of phosphorus from wastewater, simultaneously achieving the resource utilization of industrial waste.