Flow-electrode capacitive deionization utilizing three-dimensional foam current collector for real seawater desalination

Abstract

The three-dimensional (3D) carbon coated nickel foam was utilized as current collector in a flow-electrode capacitive deionization (CF-FCDI) device to strengthen the charge transfer ability of FCDI device, achieving distinguished desalination efficiency for real seawater. Utilizing 30 ppi carbon coated nickel foam as current collector with 12.5 wt% AC content at 1.2 V to treat 3.5 g L−1 NaCl solution, the CF-FCDI achieved 99.8% of salt removal efficiency (SRE), 3.29 µmol cm−2 min−1 of average salt removal rate (ASRR) and 97.0% of charge efficiency (CE), surpassing most desalination performances in previous reports. Compared with the titanium mesh (TM-FCDI) and graphite plate (GP-FCDI) current collector, the three-dimensional electric field and computational fluid dynamics (CFD) simulations demonstrated that 3D foam current collector has obvious stronger competitiveness. Its intrinsic 3D interconnected open-pore structure as flow channel and 3D electric field could not only enlarge the charge contact area between the current collector and flow-electrode, but also eliminate the restriction of 0.75 mm effective charging range within the carbon slurry in traditional serpentine flow channels. Finally, the excellent desalination performance of CF-FCDI device was also verified by treating simulated seawater, real seawater samples from Yellow Sea and South China Sea with a high SRE of 99.9%, 99.8%, and 99.9%, respectively. This work introduced a new strategy for enhancing charge transfer ability and overall desalination efficiency of FCDI device by utilizing a novel 3D foam-structured current collector for real seawater desalination.