Chromite ore processing residue

Patent Granted A process for stabilizing chromium in a chromite ore processing residue (COPR) comprises the steps of adding an acid at 14 to consume the excess alkalinity of the COPR, resulting in a pH of less than 10; and adding a chemical reductant at 18 to the COPR to convert any hexavalent chromium present to trivalent chromium. A source of sulfate may be added to the COPR at 20 to reduce heave potential and improve its geotechnical stability.