Periodic Reporting for period 1 - CIRMET (Circular hydrometallurgy for energy-transition metals)
Okres sprawozdawczy: 2023-05-01 do 2025-10-31
CIRMET will lead to a new approach to hydrometallurgy, called “circular hydrometallurgy”, with a focus on the design of energy efficient flowsheets or unit processes that consume a minimum amount of reagents and produce virtually no waste. CIRMET has the ambitious goal to replace the traditional, linear hydrometallurgical flowsheets for extraction and refining of the “energy-transition” metals cobalt and nickel into a next-generation, circular flowsheet, which (1) consumes no chemicals other than (green) hydrogen, water and carbon dioxide (taking advantage of the unique chemical properties of carbon dioxide); (2) uses the acid for the leaching process as a “catalyst” that is continually regenerated rather than consumed; (3) reduces the net consumption of acids and bases to virtually zero through ingenious manipulations of chemical equilibria via solvent extraction; and (4) comprises a virtually zero discharge of solid and liquid waste streams. As such, CIRMET can drastically reduce the environmental footprint of hydrometallurgical processes. To enable such circular flowsheets, a new theoretical chemical thermodynamic framework for multiphase electrolyte equilibria involving two immiscible liquids and innovative unit operations for sustainable metal and sulphur recovery are developed. Hydrometallurgical processes are approached from a molecular level. Liquid-liquid equilibria are modelled by Gibbs-energy minimisation (GEM) methods, rather than by solving law-of-mass action (LMA) equations. The proof of concept of circular flowsheets is demonstrated for metal recovery from real, complex (rather than synthetic), impurity-bearing input streams: nickel laterites, cobalt nickel sulphide ores, mixed hydroxide precipitate (MHP), and mixed sulphide precipitate (MSP). Only by combining these three mutually supporting spheres of innovation – (1) the “thermodynamic framework”, (2) the “unit process level” and (3) the “general flowsheet” sphere – can CIRMET be successful.
Solvent extraction (SX) can play a central role in the development of circular hydrometallurgical processes if a solution can be found for the consumption of bases in the extraction step and acid in the stripping step of solvent extraction processes with acidic extractants. The CIRMET project develops several innovative approaches to reduce the consumption of acids and bases. The first approach is to leach with concentrated acids (so the proton activity is high), while recovering the excess acid after leaching by SX. It is important that the extracted acid is stripped from the organic phase by (hot) water, and not a base, since this would destroy the acid. The recovered acid can be sent directly to the leaching concentration, or can be concentrated further, step-by-step, to a very high concentration in a sequence of extraction and stripping steps with well-chosen phase ratios. This has been demonstrated for the recovery of methanesulfonic acid (MSA). Second, the concept of “dual SX” is being elaborated. Here, two SX circuits are coupled: one for metal extraction and one for acid removal. Between every extraction step, the protons released are removed from the aqueous solution by SX instead of adding a base. The proof-of-principle of this approach has been demonstrated for SX of iron(III). Third, acidic extractants are preloaded with Mg so that extraction involves exchange of Mg ions rather than protons. The exchanged Mg ions are recovered downstream as MgCO3, which can be reused for preloading the organic phase.
Metal carbonates are very useful to remove metal ions from a hydrometallurgical system because it will not remove the anions that are required for the regeneration of the acid. Rather than precipitating by addition of soda ash, CIRMET is developing processes based on SX-assisted precipitation of metal carbonates, using CO2 gas. The protons formed by reaction of CO2 with water are removed by acid extraction with a basic solvent and the acid can be recovered from the loaded organic phase by stripping with hot water. The proof of principle has been given for the precipitation of Li2CO3, CaCO3 and transition metal carbonates, and the process is being further optimized.
CIRMET is developing novel approaches to remove iron from hydrometallurgical systems, such as SX-assisted precipitation of FeCO3, removal of iron from the loaded organic phase by hydrolysis at high temperatures, and direct hydrogen reduction of iron in organic solutions by hydrogen gas. The proof of principle for the production of metallic iron has been given.
In CIRMET, it has been shown that the extraction mechanism at conditions observed in hydrometallurgy is different from what is currently accepted and written in textbooks; the the cobalt/nickel selectivity of acidic extractants has been explained, and it is rationalized why commercial extractants of technical grade purity perform often better than the purified extractants.
Metal carbonates are very useful to remove metal ions from a hydrometallurgical system because it will not remove the anions that are required for the regeneration of the acid. Rather than precipitating by addition of soda ash, CIRMET is developing processes based on SX-assisted precipitation of metal carbonates, using CO2 gas. The protons formed by reaction of CO2 with water are removed by acid extraction with a basic solvent and the acid can be recovered from the loaded organic phase by stripping with hot water. The proof of principle has been given for the precipitation of Li2CO3, CaCO3 and transition metal carbonates, and the process is being further optimized.
CIRMET is developing novel approaches to remove iron from hydrometallurgical systems, such as SX-assisted precipitation of FeCO3, removal of iron from the loaded organic phase by hydrolysis at high temperatures, and direct hydrogen reduction of iron in organic solutions by hydrogen gas. The proof of principle for the production of metallic iron has been given.
In CIRMET, it has been shown that the extraction mechanism at conditions observed in hydrometallurgy is different from what is currently accepted and written in textbooks; the the cobalt/nickel selectivity of acidic extractants has been explained, and it is rationalized why commercial extractants of technical grade purity perform often better than the purified extractants.
(1) To promote the concept of circular hydrometallurgy, an international symposium was organized in Mechelen (Belgium) from 9 to 11 September 2024: the 1st International Symposium on Circular Hydrometallurgy (ICHS2024). ICHS2024 brought together 150 attendees from global companies, universities, and research institutions. There were 15 keynote lectures by top metallurgists and 38 poster presentations. Sessions covered a range of topics aligned with the “12 principles of hydrometallurgy. The full programme of ICHS2024, with pdf files of the presentation can be found on the following website: https://ichs2024.cirmet.eu/programme/(odnośnik otworzy się w nowym oknie) . Due to the success of ICHS2024, a similar symposium will be organic every two years.
(2) A new process was developed to transform waste salts of hydrometallurgical processes back into the composing acids and bases. For instance, Na2SO4 is split back into NaOH and H2SO4. This process, called ADONIS, is based on robust 19th century and early 20th century inorganic chemistry and shifting of chemical equilibria. A preliminary patent application (EP24189468.2) was filed in July 2024. This process could be a major game changer in the metallurgical industry because it provides an elegant solution to the sodium sulfate problem in the sector. ADONIS addresses Principe 1 of circular hydrometallurgy: “Regenerate reagents”
(3) A synergistic solvent extraction system containing two extractants was developed for the direct lithium extraction from brines. Applying the system to a synthetic geothermal brine, an extraction percentage of 68% was obtained in a single stage, with separation factors of 620 ± 20 for Li/Na, 3100 ± 200 for Li/K, 596 ± 9 for Li/Mg and 2290 ± 80 for Li/Ca. This are the highest selectivities ever observed for lithium solvent extraction. Reference: Raiguel, S., Van Bogaert, L., Balcaen, T., & Binnemans, K. (2025). Selective extraction of lithium over alkali and alkaline earth ions by synergistic solvent extraction. Green Chemistry, 27(4), 1194-1205. DOI: 10.1039/D4GC04760E.
(2) A new process was developed to transform waste salts of hydrometallurgical processes back into the composing acids and bases. For instance, Na2SO4 is split back into NaOH and H2SO4. This process, called ADONIS, is based on robust 19th century and early 20th century inorganic chemistry and shifting of chemical equilibria. A preliminary patent application (EP24189468.2) was filed in July 2024. This process could be a major game changer in the metallurgical industry because it provides an elegant solution to the sodium sulfate problem in the sector. ADONIS addresses Principe 1 of circular hydrometallurgy: “Regenerate reagents”
(3) A synergistic solvent extraction system containing two extractants was developed for the direct lithium extraction from brines. Applying the system to a synthetic geothermal brine, an extraction percentage of 68% was obtained in a single stage, with separation factors of 620 ± 20 for Li/Na, 3100 ± 200 for Li/K, 596 ± 9 for Li/Mg and 2290 ± 80 for Li/Ca. This are the highest selectivities ever observed for lithium solvent extraction. Reference: Raiguel, S., Van Bogaert, L., Balcaen, T., & Binnemans, K. (2025). Selective extraction of lithium over alkali and alkaline earth ions by synergistic solvent extraction. Green Chemistry, 27(4), 1194-1205. DOI: 10.1039/D4GC04760E.