Pilot-scale phosphorus recovery from biogas slurry to produce battery-grade FePO4: Chemical enhanced primary treatment coupled adsorption process

Abstract

Recovering phosphorus (P) from wastewater was expected to bring win–win profits for environmental protection and clean energy industries. Ferric phosphate (FePO4) was a key raw material for lithium-ion battery production for new energy vehicles, which was a more valuable and promising product for recovering P from wastewater. There were challenges in recovering high-purity FePO4 from wastewater with complex components, especially in achieving large-scale recovery. Here, a pilot-scale platform, the Chemical Enhanced Primary Treatment (CEPT) coupled Fe@aminated-polyacrylonitrile (Fe-NH2-PAN) adsorption, was established for recovering battery-grade FePO4 from biogas slurry. The platform stably removed over 80% of PO43− from biogas slurry during long-term operation, the removed PO43− was enriched in chemical sludge and Fe-NH2-PAN, and then was leached into H2SO4 solution. FePO4 crystal was successfully recovered from the leaching solution (822.35 ± 15.91 mg/L PO43−) with a recovery rate of over 75%. Importantly, the lithium-ion battery prepared from recovered FePO4 exhibited excellent and stable electrochemical performance (with stable discharge specific capacity of 100.4–106.7 mAh/g at 1.0 C). This study provides a new path for large-scale P recovery in WWTPs.