Recover phosphorus as vivianite using a dual-chamber electrochemical reactor

Phosphorus (P) removal and recovery not only alleviate P shortage but also reduce the risk of water eutrophication. This study devised a tailored dual-chamber electrochemical reactor separated by a cation exchange membrane (CEM) to recover P from wastewater. The anode-released Fe2+ reacted with PO4-P in the anode chamber to form vivianite. The CEM hindered the migration of the produced OH− from the cathode, preventing OH− from reacting with Fe2+ to generate undesired side products. The P removal efficiency of the dual-chamber reactor was 2.2 times that of the single-chamber reactor (without CEM). The purity of generated vivianite from the dual-chamber reactor reached 98.3 % as determined by the EDS analysis. Different operating parameters including initial P concentration, anolyte pH, and applied current density were examined to evaluate their effect on P removal and vivianite formation. Results showed that a high P concentration (400 mg/L), a moderate pH (6.5), and an adequate applied current density (5.66 mA/cm2) were conducive to vivianite production. The P removal rate and efficiency were 0.033 mg/(cm2·min) and 92.8 %, respectively. XRD and SEM-EDX analyses confirmed the formation of vivianite. The operating cost for electrochemical crystallization of vivianite was estimated to be 1.94 USD/kg P, lower than the traditional fluidized bed crystallization technology.