MOFs-derived Fe, N-co doped porous carbon anchored on activated carbon for enhanced phosphate removal by capacitive deionization

Abstract

Excessive phosphorus (P) emissions can cause water eutrophication and severe ecosystem degradation. Capacitive deionization (CDI) has demonstrated excellent potential for phosphorus removal owing to its environmental friendliness and quick removal/release of phosphate. In this study, novel metal–organic frameworks (MOFs)-derived Fe, N-co doped porous carbon anchored on activated carbon (Fe@N/C) was fabricated as an anode for phosphate uptake. Activated carbon provides a conductive framework to accelerate electron transfer and promote phosphorus adsorption. Fe@N/C electrode exhibit the best adsorption capacity for phosphorus at low concentrations (5 mg P/L) under a 1.2 V electric field, suggesting that N species and Fe species facilitate phosphate adsorption. The impact of initial phosphorus concentration, applied voltage, electrode material, and initial pH on phosphorus uptake by Fe@N/C was investigated. In addition, the phosphorus adsorption mechanism was revealed to be dominated by ligand exchange, electrostatic attraction, and electric field. Furthermore, the energy consumption and operating costs for phosphorus removal by CDI at 1.2 V were calculated to be as low as 5.18 KWh/Kg P (0.0223 KWh/m3) and 0.00173 $/m3, respectively. This study provided a new approach for constructing MOFs-derived carbon composite electrodes in the field of CDI.