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3927148
Critical Mineral Assessment of Mineral Carbonation Waste Streams
Date
August 14, 2023
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To achieve a net zero emission pathway, CO2 capture and removal technologies are needed to decrease greenhouse gases by storing CO2 in stable forms. Simultaneously, a sustainable domestic supply of critical minerals (CM) is necessary to support clean energy production and decarbonization goals. Mineral carbonation (MC) is one CO2 removal pathway that takes advantage of natural silicate weathering processes to transform atmospheric CO2 into environmentally inert carbonate minerals. The silicate rocks that are amenable to MC processes are readily abundant and include both mafic and ultramafic rocks such as basalt, dunite, peridotite, and serpentinite. These mafic and ultramafic rocks used in mineral carbonation processes can also host low-grade concentrations of several critical minerals, including Ni, Co, Cu, Li, rare earth elements (REE) and platinum group metals (PGM). This project aims to evaluate mafic and ultramafic feedstocks for the potential of CM as a value-added byproduct for mineral carbonation processes. The critical mineral content and mode of occurrence in representative mafic/ultramafic feedstocks were analyzed through multimodal characterization methods (electron microscopy, XRF, XRD, ICP-MS, chemical leaching procedures). Ni was measured in most ultramafic feedstocks in the 2,000-3,000 ppm range and is presumed to reside within olivine minerals (except for one laterite sample where Ni was measured at ~9,000 ppm). Chromite was ubiquitous as accessory minerals throughout the dunite and serpentinite samples. Within the chromite of the Twin Sisters dunite, PGM were found as nano- to micro- meter scale inclusions. Chemical sequential leaching procedures indicated the mobility of Ni and Co along with Mg and Fe during a mild hydrochloric acid leach, further suggesting the residence of Ni within the olivine. These characterization results, in conjunction with geochemical modelling, will be used to direct recovery pathways of the CM while maintaining the original value proposition of ultramafic rocks for mineral carbonation.
Red mud is a type of aluminum industrial waste, typically in the form of a slurry, that results from the caustic digestion of bauxite (an aluminum ore) in the Bayer process…