Pilot-scale removal and recovery of dissolved phosphate from secondary wastewater effluents with reusable ZnFeZr adsorbent @ Fe3O4/SiO2 particles with magnetic harvesting

Advanced nanocomposite magnetic particles functionalized with ZnFeZr-adsorbent are developed, characterized and tested for the removal and recovery of phosphate directly from spiked secondary wastewater effluent (∼10 mg/L PO4-P). The phosphate loaded particles can be extracted from the liquid phase via magnetic separation, regenerated in a NaOH solution where phosphate desorption takes place, and reused in numerous cycles. Laboratory experiments demonstrate their reusability and stability in 60 consecutive adsorption/desorption runs where under optimal conditions > 90% total P-recovery efficiency is reached. In addition, pilot tests are performed to verify the proof-of-concept by upscaling the technology and maintain high efficiency of phosphate removal and recovery after treating 1.5 m3 wastewater in 20 cycles. Effluent concentrations <0.05 mg/L PO4-P can be achieved in the treated wastewater. The reclaimed desorption solution is concentrated with phosphate ions through its repetitive application, attaining up to 38-times enrichment (∼380 mg/L PO4-P) compared to the initial concentration in wastewater. The P-rich eluate is used as a source for subsequent precipitation of a solid fertilizer product such as struvite.