The effect of inorganic acids on reducing iron impurities during iron-rich laterite ore leaching

The Recovery of nickel from lateritic ores as the main oxide resources has been always debated. Since it consists of ۱.۷۴% Ni, ۰.۱۴% Co and ۴۰.۸% Fe, co-dissolution of iron occurred by using common lixiviation like sulfuric acid. Therefore, some leaching agents should be sought due to promoting a high dissolution of nickel/cobalt and a negligible iron recovery. This research investigates the effect of using organic acids such as gluconic, lactic and citric acid along with sulfuric acid on recoveries of Ni/Co from an iron-rich laterite ore. The results showed that adding sulfuric acid to the optimal combined ratio of the organic acids (gluconic: lactic: citric= ۱: ۲: ۳) to obtain the combined ratio of ۶ : ۱: ۲: ۳ (sulfuric: gluconic: lactic: citric acid), simultaneously increasing the temperature from ۶۰ to ۹۰ °C, and increasing the final combined concentration of the acids from ۳.۵ M to ۵ M, significantly increased nickel and cobalt recoveries by ۸۰.۴ and ۶۸.۷%, respectively, and slightly increased iron extraction by ۵.۰۵% all when compared to using the optimal combined ratio of organic acids. The use of ۵ M sulfuric acid alone as a leaching agent, at ۹۰ ° C, resulted in an ۸۱.۱۱% increase in iron dissolution than the ۶: ۱: ۲: ۳ combination. The results obtained indicated that the reaction rate was controlled by the chemical reaction, and the activation energies of ۴۲.۷۱ kJ/mol for nickel and ۸۴.۵۷ kJ/mol for cobalt were consistent with this conclusion.

Keywords:

Laterite , nickel , Cobalt , Organic acids , Atmospheric leaching