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Chemical beneficiation of cobaltiferous minerals by thermal decomposition of pyrites
Aguayo Torrez, Luis Fernando
Aguayo Torrez, Luis Fernando
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2023
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2025-06-24
Abstract
Cobalt is a transition metal whose unique properties make it indispensable in the manufacture of the rechargeable batteries needed for the energy transition. Currently, most of this metal is obtained as a by-product of the extraction of nickel and copper, which is why it is deemed as a critical and strategic metal by the US. However, there are some primary deposits previously considered marginal that have become of great economic interest, such as those found in the Iron Creek area. In this type of occurrence, cobalt is found to be encapsulated within the pyrite lattice, so none of the traditional beneficiation methods could effectively liberate and separate the low cobalt contents from the pyritic matrix.
Given the criticality of cobalt and how this metal is embedded in the pyrite (FeS2) structure, it has been proposed that the thermal decomposition of this iron sulfide to pyrrhotite (Fe1-xS) and troilite (FeS) could be an alternative chemical pretreatment that would (i) increase the cobalt content of flotation concentrates by volatilizing part of its sulfur and (ii) transform the initial concentrates into a ferromagnetic product that could be processed in a magnetic circuit to further increase the cobalt contents. Therefore, the following work presents a comprehensive review of the technical and economic feasibility of applying this thermal treatment. To this end, three cycles of experiments were performed on concentrates from the bulk flotation of sulfides and the differential flotation of cobalt. Two cover gases - N2 and CO2 - were used to evaluate the individual effect of temperature, time, gas flow rate, initial pyrite content, and their possible interactions.
The results showed the possibility of increasing the initial cobalt grades by 15-17% with the joint production of high-purity sulfur as a valuable by-product. Likewise, results showed the possibility of obtaining a highly porous ferromagnetic material suitable for its treatment in a magnetic separation circuit or for its leaching in a high-pressure vessel. A concentration flowsheet introducing a thermal decomposition circuit was designed and studied to estimate the capital (CAPEX) and operating (OPEX) expenses related to its potential implementation on an industrial scale. A preliminary economic evaluation of the proposed flowsheet yielded positive results, which suggests that the thermal treatment is a highly attractive process for the concentration of the Iron Creek minerals.
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