Electrodialytic recovery of rare earth elements from coal ashes

Electrochemical approaches for selective recovery of critical elements in hydrometallurgical processes of complex feedstocks

“…Ga was prepared in 100 mM NaCl Unaligned carbon nanotubes encapsulated in polyvinyl alcohol filters 86%–96% max recovery (except for As). Metals are recovered as oxides ( O'Connor et al., 2018 ) Redox-active functional electrode Y 0.1 M Y 3+ Aqueous Y 3+ ion imprinted ferricyanide-embedded polypyrrole film / ( Du et al., 2015 ) Electrodialysis/vacuum membrane distillation Ce 0.2 mM Ce 4+ Nitric acid Anion exchange membranes (ASV, QPPO, CJMA-3), vacuum membrane distillation (TJ [the PVDF hollow fiber membrane produced by Tianjin University of Technology], DH [the PVDF hollow fiber membrane produced by Dehong CO., Ltd., China]) 90% recovery efficiency of nitric acid at 0.1 mM for 6 h using CJMA-3 anion exchange membranes, 99.9% of Ce 4+ rejected and concentrated during vacuum distillation ( Ren et al., 2018 ) Electrodialysis Sc 20 ppm, 40 ppm, 80 ppm Sc 3+ 0.1M sulfuric acid as catholyte and anolyte in rinse compartments Anion exchange membrane (PC SA [the anion-exchange membrane obtained from PCCell with strongly alkaline with polyester reinforcement]), cation exchange membrane (PC SK the cation-exchange membrane procured from PCCell with strongly acidic with sulfonic acid functional groups]), both from PCell 99.52% of Sc 3+ removed from 20 ppm solution at 3 V ( Li et al., 2021 ) Electrodialysis Nd, Dy, Tb Anthracite coal ash leached with nitric acid Nitric acid, 0.01 M NaNO 3 Cation exchange membrane (CR67, MKIII, blank, GE Water & Processing Technologies) Tb: 90% extracted, 55% recovered Nd: 80% extracted, 74% recovered Dy: 74% extracted, 62% recovered All at 50 mA ( Couto et al., 2020 ) …”

“…Coal ash could be a viable source for the recovery of rare earth metals, because the concentration of rare earth metals is much higher in coal ash than in conventional coal. Anthracite coal ash was preferable because of its higher concentration of rare earth metals compared with bituminous coal ash ( Couto et al., 2020 ). A process was developed that used three steps: solubilization, mobilization, and removal ( Couto et al., 2020 ).…”

“…Anthracite coal ash was preferable because of its higher concentration of rare earth metals compared with bituminous coal ash ( Couto et al., 2020 ). A process was developed that used three steps: solubilization, mobilization, and removal ( Couto et al., 2020 ). The REEs of focus for the experiments were neodymium, dysprosium, and terbium; these elements were recovered from the fly ash by electrodialysis at 50 mA at 62%, 74%, and 55% recovery, respectively.…”

“…The REEs of focus for the experiments were neodymium, dysprosium, and terbium; these elements were recovered from the fly ash by electrodialysis at 50 mA at 62%, 74%, and 55% recovery, respectively. The catholyte contained approximately 50% of the light REEs from the fly ash while also containing between 38% and 50% of the heavy rare earth metals ( Table 5 ) ( Couto et al., 2020 ). These experiments show that in a mixture of a wide range of REEs, electrodialysis was able to recover several of them satisfactorily.…”

Optimization of Electric Field Assisted Mining Process Applied to Rare Earths in Soils

“…Additionally, the REE have an important role in the development of new technologies and in the production of clean renewable energy [5,8,9]. REE mining mainly occurs through hydrometallurgical processes, from minerals such as bastnaesite, monazite, and xenotime or through ion adsorption clays [10][11][12][13][14][15]. However, these mining processes may cause great negative environmental impacts, in addition to the high generation of wastewater and high energy expenditure from the separation and purification steps [16][17][18][19][20][21].…”