Removal of Cl- from WFGD Wastewater by Electrocoagulation using Layered Double Hydroxide Compounds as Granule Electrodes

摘要

Wet flue gas desulfurization (WFGD) wastewater contains a considerable amount of Cl - , which cancause equipment and pipeline corrosion and even reduce desulfurization efficiency. Anelectrocoagulation (EC) process with three-dimensional electrodes, consisting of layered doublehydroxide (LDH) compounds as granule electrodes and Fe as plate electrodes, was adopted to removeCl - from WFGD wastewater. Two kinds of layered double hydroxide compounds, ZnAl-NO 3 layereddouble hydroxides (LDHs) and MgAl-CO 3 calcined layered double hydroxides (CLDHs), werecomparatively investigated as granule electrodes and coupled with an EC process. The feasibility andeffectiveness of layered double hydroxides as granule electrodes for Cl - removal were proven by X-raydiffraction (XRD) and Fourier transform infrared (FTIR) characterization. The morphology and thermalstability of the layered double hydroxides were further demonstrated by means of scanning electronmicroscopy (SEM) and thermogravimetry (TG). When ZnAl-NO 3 LDHs were used as the granuleelectrode, the removal efficiency of Cl - reached 84.19% at an electrode spacing of 1 cm, a current densityof 444 A/m 2 , and an electrolysis time of 20 min. When a MgAl-CO 3 CLDH granule electrode was used,the removal efficiency of Cl - reached 83.78% under an electrode spacing of 1 cm, a current density of333 A/m 2 and an electrolysis time of 20 min. Cl - removal was enhanced by the coupling of the ECprocess with adsorption by layered double hydroxide compounds.