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 (Mg²⁺) promotes the removal of Cl^-, while calcium ion (Ca²⁺) inhibits it. Fluoride ion (F^-), sulfate (SO₄^2-), and nitrate (NO₃^-) 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.