Atmospheric leaching characteristics of nickel and iron in limonitic laterite with sulfuric acid in the presence of sodium sulfite

• Na2SO3 was used as a substitute for SO2 gas to promote AL of limonitic laterite ore.
• Acid leaching mechanism of Ni and Fe in the presence of Na2SO3 was revealed.
• Linear correlation between extraction of Ni and Fe was characterized.
• The correlation is mainly influenced by the goethite leaching under the conditions.

Atmospheric leaching of nickel from limonitic laterite ores is regarded as a promising approach for nickel production, despite its low nickel recovery and slower leaching rate than high pressure acid leaching. Sulfur dioxide can enhance the sulfuric acid leaching of laterite, but its behavior for enhancing atmospheric sulfuric acid leaching was uncertain due to SO2 losses and emission. In this study, sodium sulfite was used as a substitute for SO2 gas in the leaching and the sulfuric acid leaching characteristics of Ni and Fe from a limonitic laterite in the presence of sodium sulfite were investigated. A linear correlation exists between the extraction of Ni and Fe, indicating the difficulty in selective leaching of Ni over Fe. Most nickel is isomorphically substituted within the goethite and it is difficult to dissolve in a high oxidation–reduction potential solution environment, resulting in a low nickel recovery. SO2(aq) generated from the reaction of sodium sulfite in sulfuric acid solution, lowers the potential for the reducing reaction of FeOOH to give Fe2+, accelerating the iron extraction and nickel liberation from goethite.