Carbon mineralization with concurrent critical metal recovery from olivine

Abstract

Carbon dioxide utilization for enhanced metal recovery (EMR) during mineralization has been recently developed as part of CCUS (carbon capture, utilization, and storage). This paper describes fundamental studies on integrating CO 2 mineralization and concurrent selective metal extraction from natural olivine. Nearly 90% of nickel and cobalt extraction and mineral carbonation efficiency are achieved in a highly selective, single-step process. Direct aqueous mineral carbonation releases Ni 2+ and Co 2+ into aqueous solution for subsequent recovery, while Mg 2+ and Fe 2+ simultaneously convert to stable mineral carbonates for permanent CO 2 storage. This integrated process can be completed in neutral aqueous solution. Introduction of a metal-complexing ligand during mineral carbonation aids the highly selective extraction of Ni and Co over Fe and Mg. The ligand must have higher stability for Ni-/Co- complex ions compared with the Fe(II)-/Mg- complex ions and divalent metal carbonates. This single-step process with a suitable metal-complexing ligand is robust and utilizes carbonation processes under various kinetic regimes. This fundamental study provides a framework for further development and successful application of direct aqueous mineral carbonation with concurrent EMR. The enhanced metal extraction and CO 2 mineralization process may have implications for the clean energy transition, CO 2 storage and utilization, and development of new critical metal resources.

Fizzy ore processing sequesters CO 2 while supplying critical metals

“…Carbonate minerals are the primary components of seashells and common rocks such as limestone and dolostone, which store most of the carbon on Earth for timescales of thousands to millions of years. In PNAS, Wang and Dreisinger ( 7 ) describe a metallurgical process that converts CO 2 into stable carbonate minerals while simultaneously enhancing recovery of nickel and cobalt.…”

“…These “indirect” or “two-step” processes for enhanced metal recovery dissolve silicate minerals at low pH and sequentially precipitate critical metals and carbonate minerals in a separate step. In PNAS, Wang and Dreisinger ( 7 ) demonstrate carbonation of olivine with concurrent separation of nickel and cobalt in a single step with nearly 90% efficiency. This is a “direct” or “one-step” ex situ carbonation process developed for enhanced metal recovery.…”

“…Now, Wang and Dreisinger ( 7 ) have added nickel- and cobalt-grabbing organic molecules to their process to achieve 90% conversion of olivine to magnesite with nearly 90% conversion of nickel and cobalt to sulfides. Wang and Dreisinger ( 7 ) added ethylenediaminetetraacetic acid (EDTA), as well as citrate and glycine. These chelating ligands have a high affinity for binding metals and can be used to mine them out of olivine at the atomic level.…”

“…The addition of EDTA also accelerates the carbon mineralization process by shifting the reaction style from diffusion-controlled to surface-reaction-controlled. What this means is that Wang and Dreisinger ( 7 ) saw that rather than magnesite forming thick, impenetrable coatings on olivine (like chocolate-covered raisins) it instead formed patchy and porous coatings that allowed EDTA to continue mining nickel and cobalt from olivine grains while enhancing production of magnesite from the shrinking core of olivine. As such, the addition of EDTA not only improved metal recovery efficiency but also improved carbon sequestration efficiency.…”

“…A preliminary technoeconomic analysis done by Khan et al. ( 16 ) suggests that building ex situ carbonation reactors of the sort used by Wang and Dreisinger ( 7 ) into ore processing circuits can reduce the cost of froth flotation as well as pumping and dewatering of process slurries. Wang and Dreisinger’s ( 7 ) work in PNAS is compatible with the froth flotation methods that are currently used for recovery of nickel- and cobalt-bearing sulfide minerals, which means it could be integrated into ore processing plants at new mines and potentially used to retrofit plants at existing mines.…”