Rare Metal Extraction & Processing: Rare Earth Metals
Sponsored by: TMS Extraction and Processing Division, TMS: Hydrometallurgy and Electrometallurgy Committee
Program Organizers: Gisele Azimi, University of Toronto; Takanari Ouchi, University of Tokyo; Hojong Kim, Pennsylvania State University; Shafiq Alam, University of Saskatchewan; Kerstin Forsberg, KTH Royal Institute of Technology; Alafara Baba, University of Ilorin
Monday 2:30 PM
February 24, 2020
Room: 13
Location: San Diego Convention Ctr
Session Chair: Shafiq Alam, University of Saskatchewan; Takanari Ouchi, University of Tokyo
2:30 PM Keynote
Supercritical Fluid Extraction of Rare Earth Elements from Waste Fluorescent Lamp: Jiakai Zhang1; Gisele Azimi1; 1University of Toronto
With promoted use of fluorescent lamps and the increasing amount of fluorescent lamp waste, its phosphors have become an ideal secondary source for critical materials, such as yttrium, europium and terbium. Conventional recycling processes based on hydrometallurgy rely on large volume of acids and organic solvents and generate large volumes of hazardous waste. Here, a novel environmentally friendly process based on supercritical fluid was developed to recycle the critical rare earth elements from waste fluorescent lamp. The proposed process uses supercritical CO¬2 as the solvent, which is inert, safe and abundant, along with tributyl-phosphate nitric acid (TBP-HNO3¬) chelating agent. An extraction efficiency of 50% was achieved without sample pretreatment. Pretreating samples with mechanical activation (ball milling) for 1 h resulted in 20% improvement in extraction efficiency. High resolution transmittance electron microscopy showed that during mechanical activation the sample becomes polycrystalline with nano-sized crystallite size, resulting in enhanced leaching efficiency.
3:00 PM
Supercritical Fluid Extraction of Rare Earth Elements from a Canadian Ore: Jiakai Zhang1; Kimberly Watada1; Nattanai Kunanusont1; Maziar Sauber2; Gisele Azimi1; 1University of Toronto; 2CanmetMINING, Natural Resources Canada
Rare earth elements (REEs) are essential in many critical green technologies. Conventional REE processing methods rely on large volumes of acids and organic solvents and generate significant volumes of hazardous waste. In recent years, supercritical fluid extraction (SCFE) has emerged as an alternative green extraction process for the recovery of REEs from primary and secondary resources. In this study, the SCFE process was used for the extraction of REEs from a Canadian ore. The process utilizes supercritical CO2 as the solvent along with the tributyl-phosphate–nitric acid chelating agent. A fractional factorial design of experiment was used to investigate the effect of various operating factors including temperature, pressure, solid to chelating agent ratio, time and agitation on the extraction efficiency. The results of this work demonstrate the viability of utilizing SCFE as a cleaner and more sustainable option to extract REEs from primary resources.
3:20 PM
Optimizing Zr and REE Recovery from Zircon through a Better Understanding of the Mechanisms Governing its Decomposition in Alkali Media: Yves Thibault1; Joanne Gamage McEvoy1; Dominique Duguay1; 1Natural Resources Canada
Zircon can accommodate HREEs at concentrations where their recovery can be considered. However, one drawback is the aggressive conditions required to break down the zircon structure that typically involves high-temperature treatment (> 500oC) in alkali media. In this context, the study focuses on investigating the mechanisms governing alkali-zircon interaction with the objective of defining optimal Zr/REE recovery pathways. Here we report the progress of alkali fusion experiments coupled with characterization down to the nanometer scale. Our results reveal that zircon is preferentially attacked by specific alkali species infiltrating the crystal structure along a network of defects which are progressively annealed with increasing temperature. Considering that annealing kinetics are faster than the decomposition rate, we will demonstrate that, for certain REE-rich zircons, a process can be designed where > 95% Zr and REE recovery is achieved below 200oC, while treatment at higher temperatures is detrimental, rendering the crystals less reactive.
3:40 PM
An Innovative Process for Extracting Scandium from Nickeliferous Laterite Ore: Jihye Kim1; Gisele Azimi1; 1University of Toronto
Laterite ores contain significant amounts of scandium, a strategic material with versatile applications. In this study, a two-stage process was developed to concentrate and recover scandium from nickeliferous laterite ore. In the first step, carbothermic smelting was performed at 1400–1600 ºC using lignite as a reductant and calcia and/or silica as a flux. This process resulted in a slag phase concentrated in Sc and a metallic iron phase enriched with nickel and cobalt. Under the optimum conditions, scandium was successfully concentrated in the slag phase more than 14 times than that in the starting material. In the second step, the slag phase was leached using NaOH cracking to recover Sc. A fractional factorial design methodology was utilized to investigate the effect of various operating parameters during the smelting and the leaching processes and to optimize the processes. After optimization, 88% of scandium was recovered during the NaOH cracking process.
4:00 PM
Recovery of Strategic Materials from Canadian Bauxite Residue by Smelting Followed by Acid Baking – Water Leaching: John Anawati1; Gisele Azimi1; 1University of Toronto
Sustainable sourcing of raw materials is becoming an increasingly important factor to consider in the modern economic and technological landscape. The valorization of bauxite residue, a by-product of the Bayer process for alumina production, offers an opportunity to use a material commonly considered a waste stream as an abundant and readily available resource. In this study, a two-step process was developed to extract valuable materials from bauxite residue, employing carbothermic smelting, producing crude metallic iron and a slag phase which concentrates scandium, and other elements of interest, which are then extracted by acid baking – water leaching. Systematic testing was used to optimize this process, and fundamental investigation and characterizations were used to gain an understanding of the underlying physicochemical mechanisms. This waste valorization process is intended to be integrated in a larger near-zero-waste process to sustainably recover the valuable components of bauxite residue to help build the circular economy.
4:20 PM Break
4:35 PM Keynote
The Dynamics of the Circular Economy of Rare Earth Elements: Fiseha Tesfaye1; Joseph Hamyuni2; Daniel Lindberg3; Pekka Taskinen3; Leena Hupa1; 1Abo Akademi University; 2Outotec (Finland) Oy; 3Aalto University
In order to address the current overwhelming demand for technology metals, advances in extraction methods, and legislations governing production and consumption are essential. For example, the European Commission has created a list of critical raw materials (CRMs) for the EU, including the rare earth elements (REEs), which combine both high importance and scarcity. To supplement the REEs supply in EU, the need for efficient urban mining with innovative recycling processes is strongly promoted. E-waste is one of the major secondary sources for REEs. The composition of REEs in e-waste vary greatly with the technological advancements from time to time. In this paper, future trends of selected REEs in e-waste and their recovery methods with a focus on carrier metals were examined. The dependence of REEs recovery on carrier metals was statistically analyzed. Large-scale application of selected processes for REEs recovery was investigated. Recommendations for improved REEs recycling were made.
5:05 PM
Application of Microwave Pretreatment for Rare Earth Element Recovery from Phosphogypsum: Adrian Lambert1; John Anawati1; Mugdha Walawalkar1; Jason Tam1; Gisele Azimi1; 1University of Toronto
The increasing importance of rare earth elements (REEs) in modern electronics and green energy applications, coupled with rising geopolitical supply risks, has generated interest for developing secondary REE supply chains. Phosphogypsum (PG), a waste from fertilizer production containing 0.03 – 0.4 wt% REEs, is identified as a secondary resource for REEs. Here, a novel process utilizing microwave pretreatment was developed to increase PG porosity by heating and releasing water therein, improving lixiviant diffusion into the PG particles. Optimal microwave conditions were found at low power and short duration (600 W, 5 min), which increases PG porosity with minimal conversion of gypsum to less soluble phases, and at high power and long duration (1200 W, 15 min), in which thermal PG degradation and REE release occur at the expense of gypsum conversion to less soluble phases. The highest REE extractions (80% Nd, 99% Y, 99% Dy) were achieved with the latter.
5:25 PM
Separation of Neodymium and Dysprosium by Molten Salt Electrolysis Using an Alloy Diaphragm: Tetsuo Oishi1; Miki Yaguchi1; Yumi Katasho1; Toshiyuki Nohira1; 1AIST
As a part of our ongoing study on a new REE recycling process using molten salt and an alloy diaphragm, the authors examined selective permeation of Nd or Dy ions from a melt containing both of them. A preliminary experiment revealed that selective permeation of Nd or Dy is possible under appropriate conditions.