Removal of high concentration of chloride ions by electrocoagulation using aluminium electrode.

Wastewater containing a high concentration of chloride ions (Cl ions) generated in industrial production will corrode equipment and pipelines and cause environmental problems. At present, systematic research on Cl removal by electrocoagulation is scarce. To study the Cl removal mechanism, process parameters (current density and plate spacing), and the influence of coexisting ions on the removal of Cl in electrocoagulation, we use aluminum (Al) as the sacrificial anode, combined with physical characterization and density functional theory (DFT) to study Cl removal by electrocoagulation. The result showed that the use of electrocoagulation technology to remove Cl can reduce the concentration of Cl in an aqueous solution below 250 ppm, meeting the Cl emission standard. The mechanism of Cl removal is mainly co-precipitation and electrostatic adsorption by forming chlorine-containing metal hydroxyl complexes. The current density and plate spacing affect the Cl removal effect and operation cost. As a coexisting cation, magnesium ion (Mg) promotes the removal of Cl, while calcium ion (Ca) inhibits it. Fluoride ion (F), sulfate (SO), and nitrate (NO) as coexisting anions affect the removal of Cl ions through competitive reaction. This work provides a theoretical basis for the industrialization of Cl removal by electrocoagulation.