Rare Metal Extraction & Processing: Rare Earth Elements II and Platinum Group Metals
Sponsored by: TMS Extraction and Processing Division, TMS: Hydrometallurgy and Electrometallurgy Committee
Program Organizers: Hojong Kim, The Pennsylvania State University; Shafiq Alam, University of Saskatchewan; Harald Oosterhof, Umicore; Neale Neelameggham, Ind LLC; Takanari Ouchi, The University of Tokyo
Tuesday 8:30 AM
February 28, 2017
Location: San Diego Convention Ctr
Session Chair: Takanari Ouchi, MIT; Harald Oosterhof, Umicore
8:30 AM Student
Electrochemical Behavior of Neodymium in Molten Chloride Salts: Laure Diaz1; Jérôme Serp1; Pierre Chamelot2; Mathieu Gibilaro2; Laurent Massot2; 1CEA Marcoule; 2Laboratoire de Génie Chimique
The discovery of NdFeB permanent magnets help make many technologies perform with reduced weight and give them access to miniaturization. The industrial process of production of the alloy Nd-Fe by electrolysis used in the manufacture of NdFeB magnets consists in reducing Nd3+ ions dissolved in a LiF-NdF3-Nd2O3 salt on iron cathode at 1050°C. This route was chosen since the electroplating of neodymium in low temperature molten chloride leads to low recovery yields. This is usually attributed to the comproportionation reaction between the electrodeposited metal and its chloride salt (NdCl3) leading to the formation of NdCl2. In this work, the neodymium electrochemical behavior is studied in order to understand its reduction. Fluoride addition to chloride melts is usually used to stabilize high oxidation states in solution. Neodymium deposition yield are studied using transient electroanalytical methods. Stability of Nd2+ in each salt is also discussed through electrodeposition tests on the gram scale.
8:55 AM Cancelled
Novel Reactive Anode for Electrochemical Extraction of Rare Earth Metals from Rare Earth Oxides: Aida Abbasalizadeh1; Seshadri Seetharaman2; Prakash Venkatesan1; Jilt Sietsma2; Yongxiang Yang1; 1Delft University of Technology; 2Royal Institute of Technology
Electrolytic production of metallic neodymium is carried out in fused neodymium fluoride salts containing neodymium oxide. Two major challenges pertaining to neodymium production are a) low oxide solubility, b) possibility of anodic fluorine gas evolution if electrolysis rate exceeds oxide feed of neodymium. In this study, a novel method is proposed in which iron fluoride (FeF3) is used as a fluorinating agent to convert neodymium oxide into fluoride. EPMA and XRD results of as-converted salt show complete conversion of neodymium oxide into neodymium fluoride. In the electrolysis process, iron is used as a reactive anode, promoting electrochemical dissolution of iron into the melt, thus preventing fluorine gas evolution at the anode. Therefore, the fluorinating agent is constantly regenerated in-situ which enables the continuous conversion of neodymium oxide feed. The cathodic product is Nd-Fe alloy which can be directly used as a master alloy for the production of NdFeB magnets.
Electrochemical Formation of Nd Alloys Using Liquid Metal Electrodes in Molten LiCl-KCl Systems: Hirokazu Konishi1; Hideki Ono1; Eiichi Takeuchi1; Toshiyuki Nohira2; Tetsuo Oishi3; 1Osaka University; 2Kyoto University; 3National Institute of Advanced Industrial Science and Technology (AIST)
We proposed new separation and recovery process for RE metals from Nd magnet scraps using molten salt electrolysis and an alloy diaphragm. This new process was first applied to chloride melts, and the separation of Dy and Nd were investigated using Ni and Cu cathodic electrodes in molten LiCl-KCl-DyCl3-NdCl3systems. The highest mass ratio of Dy/Nd in Dy-Nd-Ni alloy samples was found to be 72. n the other hand, we focused on the liquid metals as the alloy diaphragms. Liquid metals have higher diffusion rates of elements than those of solid metals during the electrolysis. For the first step, in this work Sn and Zn electrodes were used as liquid metal electrodes. The alloy samples were prepared by potentiostatic electrolysis using liquid Sn and Zn electrodes in molten LiCl-KCl added DyCl3(0.50 mol%) and NdCl3(0.50 mol%) at 723 K.
9:45 AM Cancelled
Challenges in the Electrolytic Refining of Silver – Influencing the Co-deposition through Parameter Control: Ann-Kathrin Maurell-Lopez1; Bernd Friedrich1; Wolfgang Koch2; 1RWTH Aachen; 2Agosi Allgemeine Gold- und Silberscheideanstalt AG
Due to the high standards for silver in electronic uses, it is essential to control the behavior of the main impurities such as copper or palladium during the electrolytic refining. In regard to palladium, it is indispensable to control its complete transition into the anode slime. Established silver refining processes are currently operated with parameters that favor the silver cathodic deposition. Usually this requires a high precious metal stock and leads to low space-time yields. Parameter research studies show the possibility of changing these parameters to achieve a more efficient process without decreasing the silver grades. This research leads to the use of less pure electrolyte systems and more contaminated anodes plus increased current densities and accordingly increased production capacities. The research depicts the influence of the anode alloy, electrolyte composition, as well process parameters like current density and pH on the electrorefining. The applied electrode potential and therefore the applied current density shows great influence on the dissolution behavior of more noble metals than Ag at the anode and on the co-deposition of less noble metals, such as Cu, at the cathode. This phenomenon is based on the Nernst equation. The pH of the electrolyte system and thus the acid concentration influences the solubility behavior of the impurities. This leads to an influence on their concentration in the electrolyte and their co-deposition on the cathode.
10:10 AM Break
Vapor Treatment for Alloying and Magnetizing Platinum Group Metals: Yu-ki Taninouchi1; Toru Okabe1; 1The University of Tokyo
Recovery of platinum group metals (PGMs) from catalyst scraps is difficult because PGMs are chemically stable, contained as a minor component, and supported on the complex and porous structure of catalysts. In this study, a new technique that alloys PGMs with Fe was developed to separate PGMs directly from catalyst scraps. In the proposed technique, FeCl2 gas is flown through the complex and porous surfaces of catalysts and reacts with the PGMs in the scraps to form PGM-Fe alloys. After the vapor treatment, the PGMs alloyed with Fe are magnetically separated from the scraps, and the obtained PGM-Fe alloys are easily dissolved in acid such as aqua regia. The feasibility and effectiveness of the new recycling technique were examined based on thermodynamic analyses and some fundamental experiments.
Biotechnological Recovery of Platinum Group Metals from Leachates of Spent Automotive Catalysts: Norizo Saito1; Toshiyuki Nomura1; Yasuhiro Konishi1; 1Osaka Prefecture University
This paper describes a new recycling method, based upon biotechnology, in order to extract platinum group metals (PGMs) from post-consumer products. The metal ion-reducing bacterium, Shewanella algae, was found to exhibit the ability to reduce and deposit the PGM ions (Pd(II), Pt(IV), Rh(III)) into metal nanoparticles at room temperature and neutral pH within 60 min, using lactate as the electron donor. We have collected fundamental data demonstrating that the ability of S. algae cells can be applied to the recovery of PGMs from dilute solutions. When targeting leachate of spent automotive catalysts, S. algae cells can successfully allow rapid reduction and deposition of PGM ions, proposing a new bio-recovery system of PGMs from used three-way catalysts for minimizing automobile emissions. Our proposed biotechnology is linked to the development of low cost, eco-friendly recycling technology that enables the rapid recovery of PGMs utilizing microbial reactions at room temperature.
Recovering Palladium from Chloridizing Leaching Solution of Spent Pd/Al2O3Catalyst by Sulfide Precipitation: Li Qian1; Zou qiang1; Xu bin1; Yang yong-bin1; Rao xuefei1; Hu Long1; Jiang tao1; 1Central South University
On the basis of chemical composition analysis, recovering palladium from the chloridizing leaching solution of spent Pd/Al2O3 Catalyst was studied through the Sulfide precipitation tests. The relevant mechanism was also investigated in this paper. Results showed that when NaOH waspreviously added to adjust the leaching solution to pH increasing from 1.21 to 4, the recovery of palladium was nearly 100% whilst the dosage of precipitant Na2S decreased by 75%. However, at pH >11.0, the excessive addition of NaOH will result in the formation of some Pd(OH)2 from [PdCl4]2-, then the recovery rate of palladium was 98.18%. When the palladium lixivium concentration is too low or the sodium sulfide concentration is overhigh or the adding rate of sodium sulfide solution is too fast, partial over-dosage of sodium sulfide will be caused easily.In this situation, the precipitation of palladium is affected severely, namely,[PdCl4]2- could transform into soluble [PdS2]2-.
Mechanism of Intensifying Cyanide Leaching of Gold from a Calcine by the Pretreatment of Acid or Alkali Washing: Zhang Yan1; Li Qian1; Liu Xiaoliang1; Yang Yong-bin1; Xu Bin1; Li Hong-wei1; Jiang Tao1; 1Central South University
The direct cyanide leaching rate of gold from a gold calcine was only 71.33%, due to 20.71% of gold being encapsulated in the iron oxides and silicates. To enhance the cyanide leaching of gold, the calcine was pretreated by acid or alkali solutions and the relevant strengthening mechanism was also researched. The results showed that the cyanide leaching rate of gold after acid or alkali washing was increased to 82.24% and 87.07%, respectively. It was found that acid washing could remove iron oxides, but the dissolution of iron oxide particles was not complete that part of gold was still encapsulated. However, alkali washing could effectively remove silicates and obtain coarse and porous calcine particles. So the blockage of pores by silicates was the primary reason for the low gold leaching rate of calcine and alkali washing was more favorable for the exposure of gold.