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 2+ ) promotes the removal of Cl − , while calcium ion (Ca 2+ ) inhibits it. Fluoride ion (F − ), sulfate (SO 4 2− ), and nitrate (NO 3 − ) 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.