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 1.74% Ni, 0.14% Co and 40.8% 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= 1: 2: 3) to obtain the combined ratio of 6 : 1: 2: 3 (sulfuric: gluconic: lactic: citric acid), simultaneously increasing the temperature from 60 to 90 °C, and increasing the final combined concentration of the acids from 3.5 M to 5 M, significantly increased nickel and cobalt recoveries by 80.4 and 68.7%, respectively, and slightly increased iron extraction by 5.05% all when compared to using the optimal combined ratio of organic acids. The use of 5 M sulfuric acid alone as a leaching agent, at 90 ° C, resulted in an 81.11% increase in iron dissolution than the 6: 1: 2: 3 combination. The results obtained indicated that the reaction rate was controlled by the chemical reaction, and the activation energies of 42.71 kJ/mol for nickel and 84.57 kJ/mol for cobalt were consistent with this conclusion.