Efficient phosphorus recovery from simulated phosphoric acid wastewater using a tailored dual-module flow electrode capacitive deionization (FCDI) strategy

The complex and unstable thermodynamic equilibrium of phosphoric acid wastewater (PAWW) has posed big challenges to conventional phosphorus (P) recovery methods via chemical precipitation process. This study proposes a tailored P recovery strategy from PAWW based on a dual-module flow electrode capacitive deionization (FCDI) system, which includes a P recovery module and a desalination module. The dual-module FCDI system efficiently separates P from impurities in simulated PAWW, through unique flow electrode circulations. And it demonstrates reasonable electrical energy consumption for P recovery of 2.45 kWh/kg P (constant voltage of 1.2 V). Over a continuous operation of the dual-module FCDI system for approximately 26.5 h, a P-enriched solution (8298 mg P/L) is successfully recovered from simulated PAWW, and then high-purity vivianite (Fe₃(PO₄)₂‧8H₂O) product is synthesized. The P recovery efficiency of the whole process reaches 78.66 %. This study provides an environmentally friendly strategy to recover P from PAWW based on FCDI technology.