Flow-electrode capacitive deionization (FCDI) has emerged as a new method in dephosphorization, for its high efficiency and continuous operation. Using conventional carbon-based materials for fabricating FCDI electrodes have limitations in conductivity, specific surface area, toxicity, and dispersion. In this study, a new carbon aerogel (CA) was synthesized using the resorcinol–formaldehyde resin via an electric heating furnace drying method. N2 adsorption–desorption isotherm and electrochemical impedance spectroscopy shows that the material has high specific surface area and a high conductivity. CA has a faster dephosphorization rate and lower energy consumption (1.74 kWh/kg-P) (1.20 μg·min−1·cm−2) than that of activated carbon (AC) when used in FCDI dephosphorization owing to its good conductivity and dispersibility. This study demonstrates the commercial application potential of CA as an FCDI electrode material for phosphorus recovery.