Seshadri Seetharaman | TU Delft Repository

Use of iron reactive anode in electrowinning of neodymium from neodymium oxide

Journal article (2019) - Aida Abbasalizadeh, Seshadri Seetharaman, Prakash Venkatesan, Jilt Sietsma, Yongxiang Yang

Electrolytic production of metallic neodymium is carried out in fused neodymium fluoride salts containing neodymium oxide. Two major challenges pertaining to neodymium production in fluoride salts are a) low solubility of neodymium oxide in fluoride melt, b) possibility of anodic gas evolution (CO, CO ₂ , CF ₄ , C ₂ F ₆ ). In this study, iron is used as a reactive anode in the electrolysis process, promoting electrochemical dissolution of iron into the melt, preventing PFC (perfluorocarbon) gas evolution at the anode. Further, the rare earth oxide is converted to rare earth fluoride by the use of iron fluoride formed as the result of iron dissolution. Thus, the fluoridizing 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 used as a master alloy for the production of NdFeB magnets. ...

Electrochemical extraction of rare earth metals in molten fluorides

Conversion of rare earth oxides into rare earth fluorides using fluoride additives

Journal article (2017) - Aida Abbasalizadeh, Annelies Malfliet, Seshadri Seetharaman, Jilt Sietsma, Yongxiang Yang

In the present research on rare earth extraction from rare earth oxides (REOs), conversion of rare earth oxides into rare earth fluorides with fluoride fluxes is investigated in order to overcome the problem of low solubility of the rare earth oxides in molten fluoride salts as well as the formation of oxyfluorides in the fluorination process. Based on thermodynamic calculations, a series of experiments were performed for converting the rare earth oxides into rare earth fluorides using AlF3, ZnF2, FeF3, and Na3AlF6 as fluorinating agents in a LiF–Nd2O3 system. The formation of neodymium fluoride as a result of the reactions between these fluxes and neodymium oxide is confirmed. The rare earth fluoride thus formed can subsequently be processed through the electrolysis route in the same reactor, and rare earth metal can be produced as the cathodic deposit. In this concept, the REO dissolution in molten fluorides would become unnecessary due to the complete conversion of the oxide into the fluoride, REF3. The results of XRD and EPMA analysis of the reacted samples indicate that AlF3, ZnF2, and FeF3 can act as strong fluorinating agents for the neodymium oxide giving rise to a complete conversion of neodymium oxide into neodymium fluoride. ...

Novel reactive anode for electrochemical extraction of rare earth metals from rare earth oxides

Book chapter (2017) - Aida Abbasalizadeh, Seshadri Seetharaman, Prakash Venkatesan, Jilt Sietsma, Yongxiang Yang

Electrolytic production of metallic neodymium is carried out in fused 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 the electrolysis rate exceeds feeding rate of neodymium oxide. In this study, a novel method is proposed in which iron fluoride (FeF3) is used as a fluorinating agent to convert neodymium oxide into neodymium fluoride. Electron Probe Micro Analysis (EPMA) results of as-converted salt show a complete conversion of neodymium oxide into neodymium fluoride. In the electrolysis process, iron is used as a reactive anode with 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 a Nd–Fe alloy which can be directly used as a master alloy for the production of NdFeB permanent magnets. ...

Electrochemical recovery of rare earth elements from magnets

Conversion of rare earth based metals into rare earth fluorides in molten salts

Journal article (2017) - Aida Abbasalizadeh, Annelies Malfliet, Seshadri Seetharaman, Jilt Sietsma, Yongxiang Yang

In the present work, selective extraction of rare earth (RE) metals from NdFeB magnets is investigated by studying the effects of various fluxes, viz. AlF₃, ZnF₂, FeF₃ and Na₃AlF₆ in the LiF-NdFeB system. The aim is to convert RE from RE magnet into the fluoride salt melt. The results show the complete selective separation of neodymium (also dysprosium) from the magnet and formation of rare earth fluoride, leaving iron and boron unreacted. The formed rare earth fluoride can subsequently be processed in the same reactor through an electrolysis route so that RE can be deposited as a cathode product. The results of XRD and EPMA analysis of the reacted samples indicate that AlF3, ZnF2 and FeF3 can act as strong fluorinating agents for extraction of rare earth from NdFeB magnet, converting the RE to REF3. The results confirm the feasibility of the rare earth metals recovery from scrap NdFeB magnet as raw material. The fluoride conversion-electrolysis route suggested in the present work enables the extraction of rare earth metals in a single step using the above-mentioned fluxes. ...