Rare Metal Technology 2020

Solvent extractionSolvent extraction is a mature technology that is used in many industrial applications for the extractionExtraction and/or purification of metals contained in aqueous solutions. Such a technology could be advantageously utilized to produce high-grade salts of lithiumLithium, cobaltCobalt, nickel, and manganese from mine or lithium-ion batteryLithium-ion battery recyclingRecycling. However, nickel–cobaltCobalt–manganese separation is not easy by means of commercial extractants. Such a separation could be achieved providing that process operation would be always optimized. ModellingModelling tools could help achieve this goal. This paper presents the development of a global model implementing a physicochemical model and an engineering model, which can predict the influence of pH, flowrates, and mixers-settlers arrangement on the performances of liquid–liquid extractionExtraction.

In this study, a fundamental investigation of the crystallizationCrystallization process of Li2CO3Li2CO3 from Li2SO4 solution by adding Na2CO3 was performed. Experimental data indicated that at optimum conditions, 90% Li from Li2SO4 was recovered as Li2CO3Li2CO3 solid with 1% impurity in the product and the reaction reached equilibrium within 1 h. The presence of impurities, i.e., CaSO4 and Na2SO4, in the initial Li2SO4 solution had significant negative impact on both lithium recoveryLithium recovery efficiency and purity level of the final Li2CO3 product. A feeding rate of Na2CO3 solution into Li2SO4 solution or adding seed in the initial Li2SO4 solution showed minimal effect on the recovery of the product. Seeding properly helped to form the final crystal in desired shape and size with narrow range of particle size distribution.

This study puts the emphasis on developing and optimizing efficient hydrometallurgical processes to recycle a lithium-ion batteryLithium-ion battery of an electric vehicle utilizing systematic experimental and theoretical approaches based on design of experiment methodology. Two leachants, i.e., HCl and H2SO4 + H2O2 were utilized and on the basis of fractional factorial design for the metal leachingLeaching efficiency, the most effective leachant was selected as H2SO4 + H2O2. In this case, 1.5 M H2SO4 with 1.0 wt% H2O2 at a liquid-to-solid ratio of 20 mL g−1 and temperature of 50 °C for 60 min resulted in the recovery of 100% lithiumLithium , 98.4% cobaltCobalt , 98.6% nickel, and 98.6% manganese. Moreover, a process mechanism of H2SO4 + H2O2 leachingLeaching of all four metals was proposed. Finally, the Co, Ni, and Mn co-precipitate and Li2CO3Li2CO3 precipitate were combined to regenerate a new cathode active materialCathode active material .

The endowment of NigeriaNigeria with solid mineral resources has warranted the present call for economic diversification from petroleum exploration. There is strong demand for lithiumLithium and industrial lithiumLithium compounds in a wide array of applications such as in the health sector, among others. This study reports the extractionExtraction of lithiumLithium from polylithionite orePolylithionite ore obtained from Keffi, NigeriaNigeria in chloride media. The effects of experimental conditions, such as roastingRoasting temperature and time, mix ratio, and calcine-to-liquid ratio, were investigated using the Li ore assayed 3.25 wt% Li. The best ratio of polylithionite:NaCl:CaCl2 was 1:1:1 at 900°C and 5 min roastingRoasting . Acidic leachingAcidic leaching of the residual lithiumLithium with defined conditions leached lithiumLithium with 83.82% efficiency. Beneficiation of lithiumLithium -leach-liquor for industrial value addition shall be reported in due course.

Ion-exchange adsorbents such as delithiated lithiumLithium titanium oxides (LTOs) are highly effective for selective lithiumLithium adsorption from brines resources. In this work, we have synthesized LTO from waste titania slagTitania Slag and immobilized on a diatomaceous earth (DE) support. Titania slagTitania Slag was hydrothermally treated in alkaline solution to remove slag impurities. Acidic leachingAcidic leaching followed by hydrolysis was performed to dissolve impurities and immobilize TiO2 on DE. Subsequent solid-state synthesis with Li2CO3Li2CO3 resulted in the formation of LTO. Batch adsorption studies show that around 99% of lithiumLithium was adsorbed from a buffered 50 ppm Li. Thermodynamic and kinetic studies show the lithiumLithium adsorption to be an endothermic, chemisorption process.

Rare earth elements (REERare Earth Elements (REE)) are highly requested by modern industry, being indispensable for construction of electric vehicles and environmentally friendly energy sources. Challenge in their production lies in their joint occurrence and similar chemical properties. It can be answered by using solid phase extractionExtraction, applying highly selective nanostructured adsorbents. The latter are bearing organic ligands with high specific affinity to particular REERare Earth Elements (REE) grafted on their surface via covalent bonding. This work is a comparative study to demonstrate the ligand properties in relation to distinct REERare Earth Elements (REE) as a function of various operating conditions, such as concentration of solutions and pH. Mechanisms of adsorption are elucidated with a variety of techniques including FTIR (Fourier-transform infrared spectroscopy), solid-state NMR spectroscopy (Nuclear Magnetic Resonance), and EXAFS spectroscopy (extended X-ray absorption fine structure) in combination with analysis of particles bearing adsorbed cations by SEM-EDS (scanning electron microscopy/energy dispersive X-ray spectroscopy) and of solutions by complexometric titration. Recommendations are elaborated for specific choice of ligands and adsorption–desorption conditions for improved separation of single REERare Earth Elements (REE). The results are verified in separation of REERare Earth Elements (REE) from complex leachates both by magnetic nanoadsorbents and by mesoporous microparticles applied as a sorbent in High Performance Chelation Ion Chromatography (HPCIC).

This work details the procedures and steps for the synthesis of new magnetocaloric materials starting from the outputs generated by recyclingRecycling for re-use in magnetic refrigeration application. The outputs utilized were a rare earth elementRare Earth Elements (REE) -rich product obtained during the hydrometallurgical processing of nickel–metal hydride (NiMH) batteries. This stream contained a mix of rare earth elements (REEs), mainly lanthanum and cerium. After removing some impurities from this feed, especially aluminium, we have used the obtained product in the manufacturing of advanced REEs-based magnetocaloric materials, especially manganites-, orthoferrites-, and REEs-based alloys. The composition of the output from hydrometallurgical processing of NiMH batteries and typical compositions of magnetocaloric materials was determined using inductively coupled plasma-optical emission spectroscopy. The magnetocaloric oxides were successfully synthesized by using conventional solid-state reactionSolid-state reaction method. Carbothermic and calciothermic reductionCalciothermic reduction methods were used for the synthesis of the as-cast alloy. The X-ray diffraction analysis shows that the magnetocaloric oxides are well crystallized with presence of secondary phases. The effect of temperature on the crystal structure is briefly described.

ScandiumScandium is a rare and expensive metal that is in increasing demand because of its unique properties. Laterite oreLaterite ore is known to contain scandiumScandium in appreciable amounts. In this study, a two-stage process called “acid roastingRoasting–water leachingLeaching” was developed to extract scandiumScandium from laterite oreLaterite ore with minimal co-extractionExtraction of iron. In this process, the ore was mixed with concentrated sulfuric acidSulfuric acid (98 wt%) and roasted in a furnace at or above 600 °C. The roasted ore was then leached in water at ambient conditions. During acid roastingRoasting, Fe2(SO4)3 is decomposed to Fe2O3, which is insoluble in water, and thus it can be separated during the leachingLeaching process. A fractional factorial design methodology was utilized to investigate the effect of various operating parameters during the roastingRoasting and leachingLeaching processes and to optimize the processes. After optimization, 80% of scandiumScandium was recovered with less than 15% co-extractionExtraction of iron.

With promoted use of fluorescent lamps and the increasing amount of fluorescent lampFluorescent lamp waste, its phosphorsPhosphors have become an ideal secondary source for critical materials, such as yttrium, europium, and terbium. Conventional recyclingRecycling processes based on hydrometallurgyHydrometallurgy rely on a large volume of acids and organic solvents and generate large volumes of hazardous waste. Here, a novel environmentally friendly process based on supercritical fluidSupercritical fluid extractionExtraction was developed to recycle the critical rare-earth elements from waste fluorescent lamps. The proposed process uses supercritical CO2 as the solvent, which is inert, safe, and abundant, along with tributyl-phosphatePhosphate nitric acid (TBP–HNO3) chelating agent. Rare-earth elementRare-earth Elements (REE) extractionExtraction efficiencies of 50% was achieved without sample pretreatment. Pretreating samples with mechanical activationMechanical activation (ball milling) for 1 h resulted in a 20% improvement in extractionExtraction efficiency. High-resolution transmittance electron microscopy showed that during mechanical activationMechanical activation the sample becomes polycrystalline with nano-sized crystallite size, resulting in enhanced leachingLeaching efficiency.

Rare-earth elements (REEs) are essential in many critical green technologies. Conventional REERare-Earth Elements (REE) processing methods rely on large volumes of acids and organic solvents and generate significant volumes of hazardous waste. In recent years, supercritical fluidSupercritical fluid extractionExtraction (SCFE) has emerged as an alternative green extractionExtraction process for the recovery of REEs from primary and secondary resourcesSecondary resources . In this study, the SCFE process was used for the extractionExtraction of REEs from a Canadian ore. The process utilizes supercritical CO2 as the solvent along with the tributyl-phosphatePhosphate –nitric acid chelating agent. A fractional factorial design of the experiment was used to investigate the effect of various operating factors including temperature, pressure, solid to chelating agent ratio, residence time, and agitation rate on the extractionExtraction 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.

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 (>500 °C) in alkali media. In this context, the study focuses on investigating the mechanisms governing alkali–zircon interaction with the objective of defining optimal Zr/REERare-Earth Elements (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 that are progressively annealed with increasing temperature. Considering that annealing kineticsKinetics is faster than the decomposition rate, we demonstrate that, for certain REERare-Earth Elements (REE) -rich zircons, a process can be designed where >95% Zr and REERare-Earth Elements (REE) recovery is achieved below 200 °C, while treatment at higher temperatures is detrimental, rendering the crystals less reactive.

Laterite ores contain significant amounts of scandiumScandium, a strategic material with versatile applications. In this study, a two-stage process was developed to concentrate and recover scandiumScandium from nickeliferous laterite oreLaterite ore. In the first step, carbothermic smeltingCarbothermic smelting was performed at 1400–1600 °C 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 cobaltCobalt. Under the optimum conditions, scandiumScandium 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 crackingNaOH cracking to recover Sc. A fractional factorial design methodology was utilized to investigate the effect of various operating parameters during the smeltingSmelting and the leachingLeaching processes and to optimize the processes. After optimization, 88% of scandiumScandium was recovered during the NaOH crackingNaOH cracking process.

Sustainable sourcing of raw materials is becoming an increasingly important factor to consider in the modern economic and technological landscape. The valorization of bauxite residueBauxite residue , a by-product of the Bayer process for alumina production, offers an opportunity to use a material commonly considered to be 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 residueBauxite residue , employing carbothermic smeltingCarbothermic smelting , producing crude metallic iron and a slag phase which concentrates scandiumScandium , and other elements of interest, which are then extracted by acid baking–water leachingAcid baking–water leaching . Preliminary process tests were carried out, and fundamental investigation and characterizations were used to gain an understanding of the underlying physicochemical mechanisms. This waste valorizationWaste valorization process is intended to be integrated into a larger near-zero-waste process to sustainably recover the valuable components of bauxite residueBauxite residue to help build the circular economyCircular economy .

As a part of our ongoing study on a new rare-earth elements recyclingRecycling process using molten salts and alloy diaphragms, selective permeation of Dy through an alloy diaphragmAlloy diaphragm is investigated in LiCl–KCl eutectic melts containing NdCl3 and DyCl3 at 450 °C. In this process, the permeation of rare-earth elements is carried out via the following three steps: (a) cathodic reduction of rare-earth ions to form alloys on one side of the diaphragm, (b) diffusion of rare-earth atoms in the diaphragm, and (c) anodic oxidation of rare-earth atoms to ions on the other side of the diaphragm. A preliminary experiment reveals that Dy selectively permeates the diaphragm under an appropriate condition.

ElectrodialysisElectrodialysis (ED) is an ionic exchange membrane process for separation of different components and species. In desalination, a large part of the energy is used to sustain a concentration difference between the solutions, but in the processes of exchanging in selective manners, the energy need is lower and more directed towards ohmic losses in the membranes. The latter has relevance to several hydrometallurgical industries, as they very often accumulate undesired species in their process streams and currently apply intensive (energy and chemical) routes to remove these species. Here, we describe the principle of ED and discuss opportunities for component and salt separation using ion-exchange membranes by providing a brief reviewReview of ED in the hydrometallurgical sector.

Heavy rare-earth elements (HREE) are considered as a group of critical elements of high supply risk. The most abundant mineral containing HREE is xenotimeXenotime , YPO4, but to extract Y and the substituting HREE tough handling to dissolve the phosphatePhosphate is required. EudialyteEudialyte , on the other hand, is much less common but is easy to leach. The mineral is basically an alkaline zirconiumZirconium silicate and it is leachable at pH < 3. This means that even organic acids or dilute mineral acids may be used for the dissolution. However, the challenge with eudialyteEudialyte is that silicates are also dissolved and after a while these silicates form gels. Usually, the silicates are referred to as silicic acids. Such gels have a detrimental effect on chemical processes where fluid flows are imperative. This work is a reviewReview of efforts conducted by both universities and private enterprises on solving this challenge.

ScandiumScandium can be extracted from waste streams of other industrial processes, particularly the bauxite residueBauxite residue and TiO2 acid waste, by acidic leachingAcidic leaching and solvent extractionSolvent extraction of the leach solutions. Stripping of the organic phase using NH4F solutions produces strip liquors containing Sc (>2000 mg/L). ScandiumScandium can be separated from these liquors by anti-solvent crystallizationAnti-solvent crystallization of (NH4)3ScF6(NH4)3ScF6 . In this study, the extent to which impurities co-precipitate as separate crystalline phases or are incorporated into the crystal lattice of (NH4)3ScF6(NH4)3ScF6 was investigated. The impurity metals Fe, Zr, and U co-precipitated with the Sc phase. Moderate Ti precipitationPrecipitation was only observed from strip liquors containing mainly Fe and Ti impurities. Detection of these phases by powder XRD was difficult due to almost similar peak positions of the ammonium metal hexafluoride salts. However, EDS confirmed that the impurity metals were present in the precipitates in relative abundances that matched non-proportionally those of the initial strip liquors, except for Ti. SEM images showed that (NH4)3ScF6(NH4)3ScF6 crystals obtained from strip liquors containing predominantly scandiumScandium were bigger (2–3 μm) compared to crystals of the mixed precipitate samples (<2 μm) obtained from strip liquors containing relatively high impurity levels. This could be attributed to surface diffusion impediment of one metal ion by other metal ions at the solid–liquid interface and surface incorporation of foreign metal ions on the growth steps or kinks of one solid phase, thereby reducing the crystal growth rate of that phase. The excess supersaturation is then consumed by crystal nucleation as observed.

Battery production for electric vehicles has increased rapidly in the last decade, and the projections show an ever-increasing demand for the next years. This leads to a need for recyclingRecycling of valuable metals used in batteries, such as nickel, for a sustainable development. Nickel can be recovered from process streams or side streams in hydrometallurgical industry as nickel sulfateNickel sulfate by crystallizationCrystallization , in order to obtain high-purity products for applications like battery-grade nickel sulfateNickel sulfate . In this work, NiSO4·6H2O was precipitated by cooling crystallizationCooling crystallization in a temperature-controlled batch reactor, and uptake of Na, Cl, and Mg, impurities commonly found in hydrometallurgical industries, were investigated. Increasing the initial impurity concentrations in the reactor caused increased impurity content in the precipitates, and the highest uptake was provided by Mg. Characterization of final products with X-ray diffraction (XRD) showed that the precipitating polymorph was altered at high impurity concentration. The results of partial dissolution studies indicated that uptake of Cl was negligible, and Na was weakly adsorbed on the crystal surface, while Mg was also incorporated in the bulk of the crystals, possibly explained by the similar properties of Mg and Ni.

As the world demand for pure tinPure tin and its compounds are quite steady with an estimated projection of 5% per annum and coupled with its wide array of applications in iron and steel industries in Sub-Sahara Africa, the need for continuous ore purification has become paramount. Thus, the treatment of Nigerian cassiterite oreCassiterite ore for industrial value addition by selective acid leachingLeaching and solvent extractionSolvent extraction was investigated. The effects of leachant concentration, temperature, and particle size on ore dissolution rates were examined. At optimal leachingLeaching conditions, 76.7% ore reaction was achieved within 120 min. Tin recovery from the leach liquor by 0.5 mol/L tributyl phosphatePhosphate (TBP) in kerosene at 27 $$ \pm $$ 2 °C gave 89.31% efficiency. Stripping of tin from organic-loaded phase recorded 98.9% purity and beneficiated to obtain high-grade tin chlorideTin chloride (SnCl2, melting point: 239.7 °C; density: 3.89 g/cm3), suitable as steel coatingSteel coatings indices in some defined indigenous steel industry.

IndiumIndium as a so-called hitchhiker metal is extracted almost entirely in course of the primary zinc production. Thus, a strong dependence on the output of the corresponding base metal is given. Taking the annual growth rate of approximately 3% in zinc production and the one of indiumIndium , respectively, around 15% into account, it is obvious that a shortage in indiumIndium is faced. Because of the relative new application area of indiumIndium in high-tech products, a great potential of dumped metal is present in the residues of the past production. Therefore, the present paper describes the characterization and the possible treatment of such an iron precipitationPrecipitation residue, including the thermodynamic background for a pyrometallurgical extractionExtraction of indiumIndium and silverSilver .

The use of molten salts as “solvents” offers interesting possibilities for the treatment of ores, industrial by-products as well as scraps, allowing the development of processes that are mid-way between pyro- and hydrometallurgyHydrometallurgy , with the advantage of salts offering a wide choice of chemical and electrochemical properties. The molten mixtures can be fed to industrial electrolytic cells (electrometallurgy) where the reactions can take place. One example of this type of reactions is the selective chlorinationSelective chlorination using gaseous mixtures in a molten chloride salt mixture. Within the frame of the EU-financed project PLATIRUS (GA 730224), the possibility of selective chlorinationSelective chlorination of platinum group metals (PGM)Platinum Group Metals (PGM) contained in spent automobile catalyst samples, using a molten salt as reaction media was investigated. To predict the selective separating conditions of the PGMs from the sample matrix, the Pourbaix-type E-pO2− diagrams of the most relevant components in the spent catalystSpent catalyst were compared with those of relevant chlorinating gaseous mixtures, i.e., Cl2/O2. This allowed to predict the optimal chlorinating conditions, which were tested and confirmed experimentally using Cl2 gas.

Sodium and calcium salts roastingRoasting are main processes for the production of vanadium compounds using vanadium slagVanadium slag as raw material. These processes suffer from heavy pollution and operation difficulty, respectively. Based on the principle regarding ferrovanadium spinel oxidation, as well as investigation of vanadium phases’ in situ transformation, a clean and efficient vanadium extractionExtraction process featuring non-salt vanadium slagVanadium slag roastingRoasting , ammonium meta-vanadate conversion, was established. The new process is expected to be able to realize high vanadium recovery and reduce exhaust gas and wastewater at source. Further, the tailing can be comprehensively utilized in conjunction with ironmaking process. This process may provide scientific and technical support for the green upgrading of vanadium industry.

Present research work focuses on the recovery of precious metalsPrecious metals (Ag, Au, Pd, and Pt) from the leach liquor of small populated chips present in the hard disk of computers. Initially, the hard disks were dismantled to separate the printed circuit boards (PCBs) followed by its depopulation to liberate the mounted small electronic components. The liberated black chips were pulverized to ~100 mesh and chemically analysed. The powdered black chips containing ~0.6% Ag, ~0.3% Au, ~0.01% Pd, ~0.0003% Pt, and 20% Cu on mass basis were first leached in nitrate medium for maximum dissolution of non-ferrous metals along with Ag leaving Au, Pd, and Pt in the residue. About 99.99% of precious metalsPrecious metals were leached out from the residue using suitable lixiviant. The obtained leach liquor was purified using advanced separation techniques (solvent extractionSolvent extraction / ion-exchange/ precipitationPrecipitation ) from which marketable products (metals/ salts) could be produced.

Vanadium slag Vanadium slag is composed of many complex phases with various kinds of elements, occurrence forms, and chemical forms. At present, sodium roastingSodium roasting –water leachingLeaching can effectively extract vanadium; this technique has been widely used in industrial production, but the current researches to evolution law of the V-concentrating phase in V-slag during the roastingRoasting process focus on the macro-level, not directly on micro-level and especially at interface reactionInterface reaction process. Consequently, the microstructure, phase compositions, mineralogical morphology, and elements distribution on the surface of vanadium slagVanadium slag during the roastingRoasting process were investigated by various surface analysisSurface analysis techniques. It is essential to truly understand and control the sodium roastingSodium roasting –water extractionExtraction process, so the atomic evolution law can be of a great significance to optimize operating conditions in order to raise vanadium recovery rate.

Huge scarcity of rare earth metals (REMs)Rare Earth Metals (REMs) globally, lack of good natural resources, and generation of tremendous coal ash containing REMsRare Earth Metals (REMs) of power plant attracted the researchers to work in this area. The analysis of geologically distributed heterogeneous coal samples at CSIR-NML, India reports the presence of 0.5–1.5 kg/Ton REMsRare Earth Metals (REMs) in particular seam of coal at Indian eastern part. In this regard, systematic leachingLeaching studies were made to recover REMsRare Earth Metals (REMs) from Indian coal ash using hydrometallurgical technique. Maximum dissolution of REMsRare Earth Metals (REMs) from coal ash take place using HCl of concentration ranging between 2 and 6 M at elevated temperature. From the obtained leach liquor, more than 90% REMsRare Earth Metals (REMs) were recovered using oxalate precipitationPrecipitation . The process developed has tremendous potential to be commercialized after feasibility studies.

Compared to other electronic goods, life span of children’s toys is very less, which resulted in the generation of huge amount of batteries and environmental pollution. Initially, the batteries are discharged, dismantled, crushed, and physically beneficiated to get black powder, metallic fraction, and plastics. Further, the black powder of batteries was processed for systematic leachingLeaching studies and found that 95.6% Mn and 86.05% Co were leached in 2 mol/L H2SO4 at 30 ℃ in 120 min using 10% H2O2 (v/v) as an oxidant, maintaining the pulp density 75 g/L. From the leach liquor, at pH 5–8 and above 12, the oxides of Co and Mn were obtained, respectively. The developed process has potential to be transferred in an industry after scale-up studies.

In this paper, water leachingLeaching and acid leachingLeaching were combined to treat secondary dust of a rotary hearth furnaceSecondary dust of rotary hearth Furnace to achieve zinc enrichment. First, the solubles ZnCl2, KCl, and NaCl in the dust were dissolved into the water solution through water leachingLeaching treatment, and separated from the other insoluble components in the dust. Then in order to recover zinc from slag, acid leachingLeaching was used to treat the residue. The acid leachingLeaching experiment showed that the leachingLeaching rate of zinc would increase with the increase of HCl concentration. Finally, in order to recover the zinc, NaOH precipitator was added to the aqueous solution and the acid solution, respectively. The experimental results showed that the content of Zn5(OH)8Cl2 increased first and then decreased with the increase of the precipitator. The total recovery rate of zinc metal can reach 79.46% after the dust is treated by water leachingLeaching and acid leachingLeaching.

Volatilizing residues are commonly produced during the process of sublimating technical-grade molybdic oxide or oxidizing-volatilizing molybdenite concentrate, which contains a certain amount of Mo mainly existing in the form of molybdates. To achieve a deep Mo recovery from volatilizing residues, this work presented a new composite leachingLeaching reagent that consisted of sodium hydroxide (NaOH) and sodium phosphatePhosphate (Na3PO4). It was found that the leachingLeaching of Mo in NaOH solution could be remarkably intensified with the addition of Na3PO4. Specifically, it showed that more than 90% of Mo was leached out from this material with 160 g/L NaOH and 20 g/L Na3PO4 at 95 °C for 120 min and liquid–solid ratio of 6 mL/g. Meanwhile, the rare earths were enriched in leach residue.

The treatments of blast furnace dustBlast furnace dust such as returning to blast furnace sintering, their use as flocculants and cement raw materials and adsorbents, recyclingRecycling carbon and iron, as well as recovering rare and high-valued metalsHigh-valued metals were discussed. The current processing status of blast furnace dustBlast furnace dust in the iron and steel industry and the research trend of rare precious metalsPrecious metals represented by indiumIndium were investigated. Finally, some advanced research directions on dealing with blast furnace dustBlast furnace dust were analysed in the context of solid waste recyclingRecycling; meanwhile, the advantages and disadvantages of pyrometallurgyPyrometallurgy and hydrometallurgyHydrometallurgy in the metallurgical industry were analysed by means of the process of indiumIndium extractionExtraction.

The widely applied methods to extract vanadium are sodium roastingSodium roasting and calcified roastingRoasting. However, these roastingRoasting methods have difficulties in recyclingRecycling of wastewater and efficient utilization of leachingLeaching residue, which contains high concentration of sodium or calcium sulfate, due to the variety of roastingRoasting additives radically. Therefore, a novelty extractionExtraction medium by roastingRoasting with MgOMgO and leachingLeaching with sulfuric acidSulfuric acid was introduced in this study. The oxidation and roasting mechanismRoasting mechanism were systematically studied, providing a theoretical basis for industrial extractionExtraction of vanadium. The result shows that under the optimum conditions, the roastingRoasting temperature of 900 °C, the Mg/V molar ratio of 0.6, and the roastingRoasting time of 1.5 h, the leachingLeaching efficiency of vanadium is above 90%. In the processes, vanadium spinel is converted into Mg2V2O7 and Mn2V2O7.

MarmatiteMarmatite often associates with copper sulfide ore with the role of Cu2+ in marmatiteMarmatite dissolution being important in hydrometallurgyHydrometallurgy. In this work, we found that cupric ionsCupric ions (Cu2) can accelerate marmatiteMarmatite dissolution significantly at high temperature, regardless of sulfuric acid concentrationSulfuric acid concentration (pH 0.5–2.5). MarmatiteMarmatite dissolved faster at lower acid concentrations and compared with cupric-free conditions, and the concentration of zinc dissolved in the presence of Cu2+ ions increased by 5500 mg/L. When the acid concentration was high (pH above 2.5), the acceleration effect of high Cu2+ concentration was more obvious. In addition, the consumption of Cu2+ was low at high acid concentration (pH below 1.5), but Cu2+ consumption increased significantly at low acid concentration (pH above 2.5). X-ray diffraction (XRD) of the leachingLeaching residues proved that no copper-containing mineralogical phase was produced at high acid concentration, but copper-containing products were formed at low acid concentration. Kinetic analysisKinetic analysis showed that marmatiteMarmatite dissolution was mainly controlled by surface reaction. The reaction between Cu2+ and marmatiteMarmatite should be different at different concentrations of sulfuric acidSulfuric acid.

The scrap magnet contains significant amounts of rare earth metals such as neodymium, praseodymium, dysprosiumDysprosium , and terbium. In the twenty-first century, faster growing rate of hi-tech industrialization leads to the generation of the secondary wastes across the globe, which is becoming an environmental concern. To resolve the environmental issue vis-à-vis to meet the demand for rare earth metals, this investigation is focused on the development of a suitable process for extractionExtraction of Nd, Dy, Pr, and Tb from the scrap permanent magnet using leachingLeaching followed by solvent extractionSolvent extraction . During leachingLeaching , oxidation roastingRoasting process was adopted to minimize the dissolution of iron. The resulted leach liquor was subjected to liquid–liquid extractionExtraction of Nd, Pr, Dy, and Tb using organophosphorus derivatives reagents. Process optimization followed by extractionExtraction isotherm study was carried out to obtain quantitative extractionExtraction of these metals from the aqueous media. The crowding effect was further investigated to improve the separation factor of the RE metals and reported.

In order to inhibit magnesiteMagnesite effectively, a new macromolecule reagent, sodium polyacrylateSodium polyacrylate (SP), is introduced. Micro-flotationFlotation results indicate that SP can strongly inhibit the flotationFlotation of magnesiteMagnesite in a wide pH range. When pH = 9, the flotationFlotation recovery of magnesiteMagnesite is 90%. After increasing the dosage of SP to 10 mg/L, the flotationFlotation recovery of magnesiteMagnesite declines to below 20%. Mineral crystal structure and solution chemistry show that SP easily absorbs the Mg2+ active sites on the surface of magnesiteMagnesite . Meanwhile, SP could form a bridge among the magnesiteMagnesite particles and lead to the flocculation and sedimentation, thus inhibiting the magnesiteMagnesite flotationFlotation .

The dissolution efficiency of vanadium is the key to improve the recovery of vanadium from vanadium-bearing converter slag by calcification roastingRoasting-acid leachingLeaching process. An improved process, which involves roastingRoasting with calcium–magnesium salts, followed by acid leachingLeaching, was found to have a positive effect on the vanadium recovery. In this process, CaO–MgO–V2O5 is the basic system in the roastingRoasting step. In this study, the dissolution behavior of calcium vanadatesCalcium vanadates (CaV2O6, Ca2V2O7, and Ca3V2O8) and magnesium vanadatesMagnesium vanadates (MgV2O6, Mg2V2O7, and Mg3V2O8) in sulfuric acidSulfuric acid was investigated. The effect of parameters, such as stirring speed, solid/liquid ratio, and pH value, on the dissolution behavior of vanadates were determined. The results shown that both of solid/liquid ratio and pH value have significantly effects on the dissolution efficiency of vanadium, while stirring speed has a relatively minor effect under the studied conditions. Furthermore, the dissolution efficiency of magnesium vanadatesMagnesium vanadates has been found much higher than that of calcium vanadatesCalcium vanadates.

PRICE is an acronym for PRocess Industries in the Circular EconomyCircular economy . The main objective of the project is to prepare the collaborating industrial partners to the circular economyCircular economy . This competence building project gathers industrial partners, research institutes, and the two largest universities in Norway. The participants are: Boliden Odda, Glencore Nikkelverk, KA Rasmussen, NOAH, Solberg Industri, Yara International, SINTEF industry, University of Oslo, and the Norwegian University of Science and Technology (NTNU). To reach this ambitious goal, there are sub-objectives: increased recirculation and recovery of metals and minerals—in general and between the participants in PRICE; understanding the behaviour (speciation) of and recovery or removal of valuable elements and toxic components present at low concentrations in process solutions; use of electrochemical means to enhance separation of elements present in trace concentrations; and assessment to evaluate the impacts of circular economyCircular economy value-chains through environmental modellingModelling (LCA) and techno/economic optimization.

The leachingLeaching residue in zinc smeltingSmelting system is taken as the research object, and the experiment of leachingLeaching residue in reduction leachingLeaching under sulphuric acid–sulfur dioxideSulfur dioxide system is carried out. The effects of reaction temperature, liquid–solid ratio, initial sulfuric acid concentrationSulfuric acid concentration , partial pressure of SO2, and stirring speed on leachingLeaching rate of medium leachingLeaching residue under sulfuric acidSulfuric acid -sulfur dioxideSulfur dioxide reduction conditions were studied. The leachingLeaching rates of zinc 95.24%, iron 98.66%, indiumIndium 95.04%, and copper 0.036% in medium leachingLeaching residue can be obtained at the conditions of temperature of 105 °C, time of 4 h, liquid–solid ratio of 8 ml/g, initial sulfuric acid concentrationSulfuric acid concentration of 120 g/L, SO2 partial pressure of 200 kPa, and stirring speed of 500 r/min.