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Materials like metallic iron and its alloys are essential to daily living and industrial production. The benefits of using electrolysis technology to prepare iron and its alloys are great efficiency, controllability, and environmental protection. This study focuses on the feasibility of the electrochemical method for the direct preparation of metallic iron and Si–Fe alloys in iron ores with high fluoride content. The electrochemical behavior of Fe(II) and Fe(III) in molten SiO2–CaO–CaF2 slag on tungsten electrodes was investigated by using cyclic voltammetry and square wave voltammetry methods. It was determined that the reduction of Fe(II) ions follows a one-step two-electron transfer process: Fe(II) + 2e− → Fe(0). The reduction of Fe(III) involves a two-step electron transfer process: Fe(III) + e− → Fe(II) and Fe(II) + 2e− → Fe(0), respectively. The Fe(II)/Fe(0) process is an irreversible reaction controlled by diffusion. The diffusion coefficient of Fe(II) is DFe(II) = 1.5 × 10−6 cm2 s−1. The cathodic deposits of iron were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) combined with energy dispersive X-ray spectroscopy (EDS). The findings indicate that the production of Fe2Si alloy through electrolysis is more favorable when Fe(II) is present in the slag, while the production of metallic iron is more favorable when Fe(III) is present in the slag. This work provides a basis for the electrochemical direct preparation of Fe–Si alloy and metallic iron in high fluorine iron ore. [ABSTRACT FROM AUTHOR]

The evolution of mineral phase structure during the reduction and melting separation of an rare earth (RE)-rich iron mineral (RER-IM) is investigated. The results show the iron oxides are reduced to their metallic iron or FeO at 1373 K. When reduction time is 180 min, the reduction degree is 84%. Both bastnaesite (RE(CO3)F) and monazite (REPO4) are transformed into Ca2RE8(SiO4)6O2 during carbothermic reduction at 1373 K. The mineral with a reduction degree of 84% is melt-separated in a graphite crucible at 1773 K for 20 min, the resulting slag contains 20.64% RE2O3, with RE existing in the form of Ca2RE8(SiO4)6O2. Moreover, P from the reduction of Ca3(PO4)2 dissolves in iron with a content ranging from 1.2 to 2.21%. The type of RE phase that occurs in the slag is related to the distribution of P between slag and iron. A low P content in the slag facilitates the formation of Ca2RE8(SiO4)6O2, but a high content in the slag favours Ca3RE2[(Si, P)O4]3F. Thus, it is confirmed that the RE phase structure is controlled by the distribution of P between slag and iron. [ABSTRACT FROM AUTHOR]

Titanium is an excellent structural and functional material. At present, the production of titanium has long process cycle, high energy consumption, serious pollution and other characteristics, so the development of low-cost titanium production methods has extremely far-reaching significance. In this work, the electrochemical reduction process of Ti(IV) and Ti(II) in the CaF 2 -CaO melt were investigated by cyclic voltammetry and square wave voltammetry measurements at 1740 K, respectively. In the CaF 2 -CaO-5 wt% TiO 2 melt, Ti(IV) ions were reduced to Ti by one step. One measure was taken to lower the valence state of Ti ions: Ti(IV) ions in the melt was changed to Ti(II) by adding Ti0. Ti(IV) ions were reduced in two steps: in the CaF 2 -CaO-5 wt% TiO 2 -Ti0 melt, Ti(IV) → Ti(II) and Ti(II) → Ti, respectively, and in the CaF 2 -CaO-5 wt% TiO, the Ti(II) ions were reduced in a single step: Ti(II) → Ti. It was found that both migration and mass transfer affected the reduction processes. In contrast to the Ti(IV) reduction to Ti process, the Ti(II) reduction to Ti process showed a higher diffusion rate. Electrolytes and electrodes were analyzed after titanium electrodeposition by XRD. It was found that there were no metal titanium was detected in the electrolyte placed close to the cathode after electrodeposition. It believed that the formed metallic Ti reacted with dissolved O2- in the melt to form TiO. The reduction process of Ti(IV) on the iron electrode was investigated, the metal Ti was reduced by alloying process, the oxidation of Ti was hindered, there was a dense structure layer of CaTiO 3 outside the reduced metal Ti that prevented the ions transfer and affected the Ti(IV) ions migration process, which might be the main factor that the Ti(IV) reduction process was controlled by migration. The lower valence state of Ti in the melt promoted the formation of Ca 2 TiO 4 , which increased the ion migration rate and decreased the mass transfer rate. It was suggested that titanium or titanium alloys may be prepared by reducing the valence of Ti(IV) in minerals and altering the melt composition. It is feasible to prepare titanium and titanium alloys by MOE short process using ore as raw material. [Display omitted] • The reduction processes of titanium with different valence states were investigated. • The effects of migration and mass transfer of Ti ions was figured out. • We found the continuous reduction of Ti (IV) is hindered due to the presence of CaTiαOβ. [ABSTRACT FROM AUTHOR]

We proposed a simple and high value-added technology for recycling NdFeB waste. Neodymium was successfully separated from FeNd alloy by chemical dealloying reaction FeNd + 2NdCl 3 → 3NdCl 2 + Fe in molten chlorides. In the dealloying process, the porous iron alloy with small pores (around 10 nm) and high surface area (2 ∼ 20 × 104 cm2 cm−3) was prepared. The separated neodymium can be recycled as metallic neodymium by spontaneous disproportionation 3NdCl 2 (l) → 2NdCl 3 (l) + Nd(s). In other words, the FeNd alloy only needs to be dipped in molten chloride to obtain metallic neodymium and porous iron alloy by the chemical dealloying method. And the LiCl-NdCl 3 salts can be recyclable. [Display omitted] • The chemical dealloying method of recycling NdFeB wastes was proposed. • The reaction process of the chemical dealloying method was revealed. • Nd was separated from FeNd alloy while porous iron alloy was prepared. Neodymium-iron-boron (NdFeB) magnets are the rare earth products with the largest output, and their recycling is of significance for the sustainable development of rare earth resources. Currently, the recycling technology of NdFeB wastes is more concerned with the recovery of rare-earth elements, while iron is regarded as a low-value by-product. In this work, chemical dealloying method in molten chlorides was proposed to separate neodymium from FeNd alloy and simultaneously to prepare porous iron alloy. The effects of the molar ratio of reactants, dealloying temperature and time on the separation efficiency of neodymium were investigated. The maximum separation efficiency of neodymium from FeNd alloy can reach 96 %. The separation process of neodymium and the formation process of porous iron alloy were estimated based on the ICP, XRD, XPS, SEM-EDS analyses of recycled products. Neodymium was separated from FeNd alloy by the reaction with Nd(III) ions to form Nd(II) ions in molten chlorides, while the porous iron alloy was formed. The formed Nd(II) ions can be transformed into Nd(III) ions and metallic neodymium particles by the disproportionation reaction. In the process, Nd(III) ions can act as a complement to react with FeNd alloy. And neodymium was recovered in the form of metallic neodymium and NdOCl from the chloride melt and the rinsing solution of porous iron alloy, respectively. The formed porous iron alloy had the surface area of unit volume in the range of (2 ∼ 20) × 104 cm2 cm−3, the pore width around 10 nm and good hardness. The porous iron alloy is a high value-added product. [ABSTRACT FROM AUTHOR]