C. Boxley, R. Stolley, C. Atkins, A. Moyes, G. Lindemann
RAMACO Carbon LLC,
United States
Keywords: gallium, germanium, extraction, glycolipids, extractants, ligands, sustainability, cost effective
Summary:
Gallium (Ga) and Germanium (Ge) are co-extracted from feedstocks, such as coal fly ash, sulfide ores, and occur in ore deposits of zinc, lead, copper, and aluminum. The current extraction methods for Ga, and Ge employ hydro- and pyro-metallurgical processes. These legacy extraction methods are detrimental to the environment due to their energy intensiveness, requirement for strong acids, organic solvents, and organic carriers. This leads to the production of copious quantities of mixed hazardous waste. New sustainable and cost-effective processes for environmentally friendly metal extraction need to be developed. This presentation will detail the development of novel glycolipid-based ligands for the extraction of Ga, and Ge from leachates produced from the RAMACO Brook mine ore. The produced pregnant leachate solution (PLS), having a final target pH of 1.5, contains Rare Earth Elements (REEs), Ga, Ge, and other Critical Metals (CMs), as well as interfering metal impurities. One of the goals of the project is to devise novel and sustainable CM extractions processes that eliminate the need to precipitate impurities, reduce the amount of neutralization required, and replace Solvent Extraction (SX). A second goal is to demonstrate the improvement of the CAPEX and OPEX of CM extractions obtained through implantation of the previous goal. An evaluation of the cost effectiveness and sustainability of the novel glycolipid ligands for Ga, and Ge, extraction from a PLS will be performed. Over the past decade, GlycoSurf has designed, synthesized, and scaled several novel sugar-based (glycolipids) extractants for use as ligands for flotation separation. This project is designed to investigate several highly relevant extractants available in the GlycoSurf proprietary saccharide library. GlycoSurf will design glycolipid based extractants for Ga, and Ge recovery from the Brooke Mine PLS through the application of chemical motifs previously mastered in designing novel extractions for REEs. These bespoke ligands will be selective and specific for Ga and Ge extraction. The binding kinetics will be in the range of PPB (~500 µM). Tethering the bespoke glycolipid extractants to a solid substrate packed into a column or flow system and passing the partially neutralized PLS over the column eliminates the legacy SX precipitation step. The new extraction process of Ga, and Ge from Brook mine PLS will consist of loading on to the packed column, washing to remove interfering and unbound metals, and release of the bound metals using mild conditions. Glycolipid based extractants are known to biodegrade within 60–90 days, optimally function at a pH of 3.5, and are non-toxic to aquatic and plant life. Demonstration of higher Ga, and Ge extraction efficiency using a glycolipid ligand should accelerate the transition to greener methods. Significant decreases in energy consumption and generation of mixed hazardous materials are realized due to the reduction in the number or the complete elimination of processing steps in REE and CM recovery using SX procedures. Finally, the scalability of the novel glycolipid ligands production and the Ga and Ge extraction processes will be addressed.