CHEMICAL TREATMENT OF SPENT CARBON LINERS USED IN THE ELECTROLYTIC PRODUCTION OF ALUMINUM

Chemical cleaning methods were developed for the removal of leachable hazardous cyanide and fluoride impurities from spent carbon liners use d in aluminum metal production. Cyanide can be destroyed by treatment with NaOCl solutions at near-neutral pH. Fluoride can be removed by tr eatment with solutions of strong acids, e.g., 0.5 M H2SO4. This treatm ent is more effective at elevated temperatures (e.g., 80 degrees C). T he acid used in chemical cleaning can be treated in order to remove ex tracted fluoride by passing it through an alumina bed.