Sodium Thiosulfate and Natural Sulfur: Novel Potential Additives for Selective Reduction of Limonitic Laterite Ore

Abstract

The diminution of sulfide ore deposit as the main source of nickel extraction initiates the development of alternative methods to maximize the processing of low-grade nickel ore including limonitic laterites. Aiming to produce ferronickel with high nickel content and recovery, the study used sodium thiosulfate and natural sulfur as novel additives to be employed in selective reduction techniques. The reduction process was conducted at 1400 °C for 6 h in a coal–limestone bed. Ores and the as-reduced products were characterized by Emission Dispersive X-Ray (EDX) and X-Ray Diffraction (XRD) to determine the elemental composition in the product and examine the phase transformation of ores. Results showed that utilization of 10%wt Na2S2O3 resulted in a product with 14.31% Ni content and 93.22% recovery, while the employment of 10%wt natural sulfur yielded a product with 13.62% Ni content and its recovery reaching 97.91%. Phase identification of slag product using XRD pointed out that both Na2S2O3 and natural sulfur additives assisted the transformation of ore mineralogy in which the kamacite and taenite phases of metal products confirm the successful formation of ferronickel (Fe, Ni). Furthermore, slag products showed a large amount of iron compound, confirming the fact of low iron recovery.