Enhanced phosphate removal under an electric field via multiple mechanisms on MgAl-LDHs/AC composite electrode.

Abstract Phosphorus removal is essential to avoid eutrophication in water bodies. Layered double hydroxides (LDHs) are widely used to scavenge phosphate through intercalated ion exchange or surface complexation. Moreover, LDHs have attracted increasing attention as electrode modifiers for supercapacitors. Researchers have begun to re-delve the electrosorption technology according to the fundamental principle of electrical double layers. Herein, we propose a new phosphate removal method inspired by the adsorption characteristic and electrical double-layer capacitive properties of LDHs through electrosorption via capacitive deionization. We present a series of experiments to study the enhanced phosphate removal under an electric field via multiple mechanisms on the MgAl-LDHs/AC electrode. The uptake of phosphate by MgAl-LDHs/AC was investigated as a function of phosphate concentration, applied voltage, electrode materials, and temperature. The MgAl-LDHs/AC electrode possessed a salt removal capacity of 67.92 mg PO 4 3−·g−1 (1.2 V, 250 mg·L−1 KH 2 PO 4 , 30 °C). The electrosorption kinetics of phosphate ions onto the capacitive deionization electrode followed the pseudo-second-order kinetics model rather than the pseudo-first-order kinetics model. Furthermore, the adsorption isotherms of phosphate on the MgAl-LDHs/AC electrode fitted the Freundlich model better than the Langmuir model. The proposed method could be used for phosphate removal. Graphical abstract Unlabelled Image Highlights • A new phosphate removal method was proposed under electrostatic field. • Phosphate removal capacity reaches 67.92 mg PO 4 3−·g−1 for 250 mg·L−1 KH 2 PO 4 solution. • Influence of different experimental parameters on the electrosorption was examined. • Multiple mechanisms exist in electrosorption of phosphate on MgAl-LDHs/AC electrode. [ABSTRACT FROM AUTHOR]