Recovery Of Scandium Research Articles

Dynamic and mass-exchange parameters of scandium recovery by TVEX-TBP in column mode from the solution after salt chlorinator cake leaching

The paper deals with scandium extraction with Levextrel-type resin named TVEX contained tributyl phosphate (TVEX-TBP) in the column mode from the clarified solution formed after leaching salt chlorinator cake formed at Zaporozhye Titanium & Magnesium Combine Ltd. It was found that TVEX-TBP featured high extraction parameters. Total dynamic exchange capacity was defined. Mass-exchange parameters were calculated for scandium extraction in the column mode taking into account the impact of external diffusion kinetics: time to form the equation concentration front, front parallel transfer time, concentration and kinetic recovery factors, kinetic factor of external diffusion, linear speeds of the solution in the column and the equilibrium concentration front motion. The calculated mass-exchange parameters may be used to design the column cascade for scandium extraction from the clarified leaching solution of the salt chlorination cake in column mode. There are the following advantages of scandium extraction with TVEX-TBF in the column mode in comparison with its recovery in a reactor cascade: simpler hardware design and process control, the possibility to better wash TVEX from impurities, getting a strippant higher Sc concentration, reduced TVEX abrasion.

Bioleaching of Scandium from Bauxite Residue using Fungus Aspergillus Niger

Bauxite residue (BR) is the main by-product of the alkaline production of alumina from bauxite containing significant amounts of valuable metals such as scandium that belongs to rare-earth elements (REEs), classified by the European Community as critical raw materials (CRMs). BR is considered a hazardous waste due to its huge volume and high alkalinity making its disposal a serious universal environmental problem. The recovery of scandium from Greek BR can be an excellent approach for waste management and resource efficiency of the waste using environmentally friendly biometallurgical methods. In this work, bioleaching of scandium from bauxite residue using the fungus Aspergillus niger was studied. Bioleaching experiments were performed using the Taguchi experimental design, in batch cultures with BR at various pulp densities (1, 5 and 10%, w/v), sucrose concentrations (40, 90 and 140 g/L) and fungus suspension of 2, 4, and 6% v/v under one-step bioleaching condition and subculturing. The highest Sc recovery equal to 46%, was achieved in 20 days at 1% pulp density. Biosorption phenomena were observed during the leaching process. Lactic, acetic, oxalic and citric were the main organic acids identified.Graphical

Microstructured silicon substrates impregnated with bis(2,4,4-trimethylpentyl) phosphinic acid for selective scandium recovery

The recovery of trace amounts of scandium from process tailings represents a challenging yet critical task for the growing demand for sustainable and renewable technologies. As an important step toward addressing the environmental and technical concerns related to current scandium separation approaches, we developed novel extractant-impregnated surfaces (EIS) that held a thin layer of extractant within a micropillar texturized substrate. Compared with traditional solvent extraction, the EIS requires significantly less volume of extractant and no agitation. About 95 % of scandium is separated from the complex feedstock prepared from industrial waste bauxite residue, and the selectivity of scandium is more than 200 times higher than that of aluminum. Adsorption isotherm and kinetic studies are performed, and the experimental data are in good agreement with the Langmuir isotherm model and indicate pseudo-second-order kinetics. Cryo time-of-flight secondary ion mass spectrometry depth profiling is conducted on post-extraction EIS to unveil the scandium ions transport behaviour. Moreover, it is confirmed the EIS scheme and its underlying principles can be applied to sandblasted polytetrafluoroethylene substrates, which proves the potential of using EIS design at larger scales.

Extraction of scandium from bauxite residue by high-pressure leaching in sulfuric acid solution

Rare earth elements, such as yttrium, scandium, neodymium, and praseodymium, have been reported to be associated with minerals in bauxite and transferred to the refining residue when bauxite is refined to alumina (Al2O3) by Bayer Process. In terms of price, scandium is the most valuable rare-earth element in bauxite residue. This research discusses the effectiveness of scandium extraction from the bauxite residue through pressure leaching in sulfuric acid solution. The method was selected to obtain high scandium recovery and leaching selectivity to iron and aluminium. Series of leaching experiments were conducted under variations of H2SO4 concentration (0.5–1.5 M), leaching duration (1–4 h), leaching temperature (200–240 °C), and slurry density (10–30% (w/w)). Taguchi method with L9:34 orthogonal array was adopted to design the experiments. Analysis of Variance (ANOVA) was performed to determine the most influential variables of the extracted scandium. The experimental result and statistical analysis revealed that the optimum condition for scandium extraction was at 1.5 M H2SO4, a leaching duration of 1 h, a temperature of 200 °C, and a slurry density of 30% (w/w). The leaching experiment carried out at this optimum condition resulted in scandium extraction of 90.97% and co-extracted iron and aluminium of 32.44% and 75.23%, respectively. Analysis of Variance showed that solid/liquid ratio was the most influential variable with a contribution of 62%, followed by acid concentration (21.2%), temperature (16.4%), and leaching duration (0.3%).

Recovery of scandium from silicate minerals by high-pressure leaching in sulfuric acid

This study investigated the leaching of scandium from a Sc-bearing silicate ore. The Sc concentrate obtained by beneficiation pre-enrichment has 1.03 × 10−4 wt% Sc and 14.66 wt% Fe. The main Sc-bearing minerals are limonite, chlorite, sericite, and hornblende, in the form of isomorphism. High-pressure leaching (HPL) with sulfuric acid (98 wt%) and NaF was used to dispose this samples. The Sc leaching efficiency of 91.82% was obtained under the optimum conditions, which are pressure of 5.0 × 105 Pa, A/O value of 1.1, L/S value of 1.8, NaF dosage of 2 wt%, at 130 °C for 6 h. The X-ray diffraction (XRD) and scanning electron microscopy (SEM) results show that the residue is mainly quartz phase in the multi-hole shape. Compared with ordinary leaching for silicate, high-pressure leaching has significant advantages in saving acid and energy consumption.

Selective extraction equilibria of Sc(III), Y(III), Fe(III) and Al(III) from acidic media with toluene mixture of deep eutectic solvent (DES) composed of TOPO and isostearic acid.

A deep eutectic solvent (DES) composed of isostearic acid and TOPO was newly found out and investigated for selective recovery of scandium. The four elements used in this study are scandium, iron, yttrium, and aluminum. It was difficult to separate the four elements owing to the overlap of extraction behavior when isostearic acid or TOPO alone in toluene was used, respectively. However, scandium was able to be selectively extracted from other metals using DES prepared by 1:1mol ratio of isostearic acid and TOPO without toluene. In DES consisting of isostearic acid and TOPO, synergistic and blocking effects with three extractants acted on the extraction selectivity for scandium. Both effects are proved also from the fact that scandium was easily stripped with diluted acidic solutions such as 2M HCl and H2SO4. Thus, DES extracted selectively scandium and back-extraction was easily achieved. In order to elucidate these phenomena above, the extraction equilibria of Sc(III) using DES dissolved in toluene was investigated in detail. The extraction mechanism of scandium by DES in toluene indicates that the extracted chemical species vary with pH, and that trivalent scandium is extracted by forming stable metal complexes with DESs consisting of five molecules of isostearic acid and five molecules of TOPO.

Ternary extractant system consisting of PC-88A, TOPO, and Versatic 10 for recovery of scandium(III) from nickel laterite processing liquors

Solvent extraction of scandium(III) from an aqueous solution, which simulates a concentrated scandium solution generated from nickel/cobalt mixed-sulfide production process, was performed using a ternary mixed extractant system. Addition of tri-n-octylphosphine oxide and a long-chain alkyl carboxylic acid (Versatic 10) to an organophosphonic ester (PC-88A) drastically improved the separation factor of scandium over zirconium in comparison with that of a single extractant system. The optimum mixing ratio in the ternary extractant system was 10 mol% PC-88A, 60 mol% tri-n-octylphosphine oxide, and 30 mol% Versatic 10. The degree of scandium extraction was 90%, and the separation factors between scandium and other metals (i.e., Al, Fe, Ni, Cr, and Zr) were > 140 at pH 2 with the optimized ternary extractant system. The operating conditions for a countercurrent multistage extraction of scandium were investigated by McCabe–Thiele analysis. Ninety-nine percent recovery from 1800 mg dm−3 scandium was achieved by two- to three-stage countercurrent extraction at the flow ratio (A/O) = 1.01. The stripping efficiency of scandium reached >98% with 7 mol dm−3 H3PO4. Based on the results, a conceptual flowsheet for scandium recovery from waste solutions of laterite ore leachate is proposed.

Solubility of ammonium metal fluorides in aqueous ethanol mixtures - implications for scandium recovery by antisolvent crystallization.

The recovery of scandium from waste streams of other mining and metallurgical processing industries is gaining research interest due to the scarcity of scandium-containing ores. Hydrometallurgical techniques such as leaching, solvent extraction and crystallization amongst others have been successfully applied to recover scandium salts from such waste streams. Scandium can be recovered as (NH4)3ScF6 by antisolvent crystallization from NH4F strip liquors obtained after solvent extraction. The coextraction of metal impurities such as Fe, Al, Zr and Ti causes contamination of the final solid product. The extent of coprecipitation of ammonium metal fluorides depends on their initial concentration in the strip liquor and their solubility in the NH4F-antisolvent mixtures. Here, the solubility of ammonium metal fluorides of Sc, Zr, Fe, Al and Ti is reported separately in 3 mol L-1 NH4F-ethanol mixtures at 25 °C as well as in a system containing all five solid phases. The solubility of (NH4)3ZrF7 is slightly higher than that of (NH4)3ScF6, while the solubilities of (NH4)3FeF6 and (NH4)3AlF6 are significantly lower in comparison to (NH4)3ScF6. The solubility of (NH4)2TiF6 is 1-2 orders of magnitude higher than those of other ammonium metal fluorides. When a mixture of ammonium metal fluoride salts is dissolved in the same 3 mol L-1 NH4F-ethanol mixture as for the individual salts, the resultant solubility of the ammonium metal fluorides of Sc, Zr and Fe decreases significantly, while the resultant solubility of ammonium aluminum hexafluoride increases. This is likely due to changes in solution speciation with increased NH4F concentration and ionic strength.

Process Evaluation of Scandium Production and Its Environmental Impact

With the advancement of technology and a global shift towards clean energy, the need for rare earth metals is increasing. Scandium, a rare earth metal, has been extensively used over the decades in solid oxide fuel cells and aluminum–scandium alloys that have a vast, evolving market in aerospace, automobiles and 3D printing. However, the market struggles to maintain the supply chain due to expensive production processes and the absence of uniform global distribution of primary sources. Therefore, identification of alternative sources and technological advancements for scandium recovery are needed. To this end, an effort has been made to provide a review of the advances in different technologies applied in scandium recovery from diverse sources. Emphasis has been given to the improvements and upgrades to technologies in terms of environmental impact and recovery efficacy. An attempt has been made to discuss and deliver a clear representation of the challenges associated with every source for scandium recovery and the major developments in solving them. The environmental impact of scandium recovery and recycling has also been discussed.

Recovery of Scandium, Aluminum, Titanium, and Silicon from Iron-Depleted Bauxite Residue into Valuable Products: A Case Study

Bauxite residue is a high-iron waste of the alumina industry with significant contents of scandium, aluminum, and titanium. This study focuses on the recovery of Sc, Al, Ti, and Si from iron-depleted bauxite residue (IDBR) into valuable products. Iron depletion was carried out using reduction roasting followed by low-intensity magnetic separation to enrich bauxite residue in Al, Ti, and Sc and reduce an adverse effect of iron on scandium extraction. Hydrochloric high-pressure acid leaching, aluminum precipitation by saturation of the acid leachate, solvent extraction of scandium using di(2-ethylhexyl) phosphoric acid (HDEHP) and tributyl phosphate (TBP), alkaline leaching of the acid residue with subsequent silica precipitation were used to obtain appropriate selective concentrates. As a result, scandium concentrate of 94% Sc2O3, crude alumina of 93% Al2O3, titanium concentrate of 41.5% TiO2, and white carbon of 77% SiO2 were prepared and characterized. Based on the characterization of the treatment stages and the obtained valuable products, the prospect for the application of the suggested flowsheet was discussed.

Synthesis of environmental-friendly ion-imprinted magnetic nanocomposite bentonite for selective recovery of aqueous Sc(III)

A novel reusable ion imprinted nanocomposite magnetic bentonite(IIPNMB) was prepared for selective recovery of aqueous scandium. Based on the fact that oxyphosphorus functional groups in sodium tripolyphosphate have good affinity to Sc(III) and chitosan is rich in hydroxy and amino active sites, they were chosen to build ion imprinted layers. Mesoporous IIPNMB showed good adsorption performance. The pseudo second-order kinetic model and Langmuir model fit the experimental data. According to XPS features, the amino, hydroxyl, PO and PO bonds of the adsorbents had electrostatic interaction and complexation with Sc(III), leading to the good selectivity of IIPNMB for Sc(III). In addition, the material atomic structure was proposed based on the chemical structure of IIPNMB for DFT calculation of ion imprinting adsorption, which clearly proved that the adsorption process of Sc(III) was stable, and it gave another proof for the mechanism of the selective extraction.

Recovery of scandium and aluminum from limonitic laterite intermediate product

The discovery of Sc-rich Ni-Co laterite highlights the potential of the extraction of Sc from Ni-Co laterite. In the nitric acid pressure leaching (NAPL) process of treating limonitic laterite, Sc precipitates with Al and concentrates in Sc-bearing Al residue. Thus, this intermediate product becomes an important resource for Sc. This paper presents a combined process to recover Sc and Al from Sc-bearing Al residue, which consists of alkaline leaching, acid leaching and solvent extraction. First, by controlling alkalinity, 94.3% Al was separated from the Sc-bearing Al residue, while 96.8% Sc was enriched in leach residue. Then, the obtained Sc-rich residue was totally leached with sulfuric acid. Moreover, Sc in leach solution was synergistically extracted by 10% Di-(2-ethylhexyl) phosphoric acid (P204) and 5% Tributyl phosphate (TBP). Finally, the co-extracted impurities in the Sc-loaded organic phase were scrubbed by HCl solution, followed by the Sc was stripped with NaOH solution. Sc-bearing Al residue is an advantageous Sc resource, and the proposed process could achieve comprehensive utilization of Sc-bearing Al residue in a facile way.

Scandium Recovery from Aqueous Solution by Adsorption Processes in Low-Temperature-Activated Alumina Products.

In this paper, we studied the scandium adsorption from aqueous solutions on the surface of low-temperature-activated alumina products (GDAH). The GDAH samples are industrially manufactured, coming from the Bayer production cycle of the Sierra Leone bauxite as aluminium hydroxide, and further, by drying, milling, classifying and thermally treating up to dehydroxilated alumina products at low temperature. All experiments related to hydroxide aluminium activation were conducted at temperature values of 260, 300 and 400 °C on samples having the following particle sizes: <10 µm, 20 µm, <45 µm and <150 µm, respectively. The low-temperature-activated alumina products were characterised, and the results were published in our previous papers. In this paper, we studied the scandium adsorption process on the above materials and related thermodynamic and kinetic studies.

Selective recovery of scandium with acid solutions of magnesium sulphate from ESP dust generated by bauxite sintering plants

Among potential sources of scandium and other rare earth elements (REEs) there are semiproducts generated by the alumina industry. They include red mud and ESP dust generated by sintering plants. Most of the previous research studies focused on red mud leaching using a variety of strong acids. However, because of the need to neutralize the caustic alkali present in red mud, as well as to dissolve iron and other macrocomponents, the above process is associated with a high consumption of reagents. This paper examines the possibility to selectively recover REEs from ESP dust at high pH values in the presence of magnesium cations. It is shown that the prior water leaching of ESP dust helps achieve a double rise in the REE concentration and considerably lower the concentration of Na2O in the solid residue. For selective recovery of REEs, the authors used weak solutions (pH = 2&divide;5) of sulphuric acid with magnesium sulphate. The latter help to desorb REEs from the surface of minerals contained in the solid residue. Over 75% Sc was recovered through solid residue leaching conducted at the temperature of 80 oC, liquid-to-solid ratio of 10:1 and duration of 60 min at pH = 2. The recovery of iron and titanium did not exceed 1&ndash;5%. With all other conditions being equal, raising pH to 3.5 would lead to a drop in the scandium recovery to 63% while the recovery of iron and titanium would drop to 0.2%. It was also found that, as the result of sulphuric acid leaching, the calcium that is present in the initial ESP dust gets precipitated in the form of gypsum and a certain amount of REEs may get carried away. This research was carried out as part of Grant No. 22-29-01515 of the&nbsp;Russian Science Foundation; the concentration of rare earth elements in&nbsp;the solid residue was determined through inductively coupled plasma mass&nbsp;spectrometry, supported through an assignment of the Government of the&nbsp;Russian Federation under Grant No. 075-03-2021-051/5.

Scandium prospects in the Yakutian Diamond Province

Prerequisites and signs of scandium deposits in the ancient weathering crusts and in the oxidation zones in the Upper Paleozoic strata in West Yakutia are defined and substantiated. The prerequisites include: the presence of scandium sources&mdash;basic rocks, kimberlites and carbonatites; the spread of the ancient formation and ground oxidation which conditions migration of scandium; the presence of weathering crusts of the Carboniferous and Mesozoic ages, with alkaline and adsorptive barriers which concentrate scandium; good prospecting at depths up to 100 m. These prerequisites govern the relevance of the research as there is a possibility of scandium recovery from ore by in-situ leaching. Ancient oxidation in the strata and in the fractures in the gray-colored Сarboniferous&ndash;Permian formations and in the underlying weathering crusts is detected in the Ulakhan-Kurung-Yuryakh area of the Malaya Botuoba region in the Yakutian Diamond Province. Ancient epigenetic processes are confirmed by zonal limonitization and clarification of primary gray-colored rocks, and by redistribution of uranium, vanadium and gallium with the increased background contents of V and Sc. The X-ray fluorescence analyses performed in the Malaya Botuoba, Middle Markha and Ygyatta diamond-bearing regions revealed areal concentrations and promising scandium ore occurrences in the ancient weathering crusts and in the Late Paleozoic formations. In the weathering crust, in Suldyukar kimberlites, scandium concentrations exceed 100 ppm and feature high (up to 0,n%) contents of V, Co, Ni, La and Ce. The outstanding concentrations of scandium are found in the Triassic&ndash;Jurassic Dyakhtar clayey rocks representing a derivative weathering crust in the Nakyn diamondiferous field.

Separation and recovery of scandium from high pressure sulfuric acid leach liquor of limonitic laterite

Extraction of Sc from Sc-rich limonitic laterite without interfering with the main nickel-cobalt production circuit will significantly enhance the economic value of laterite. A process for separation and recovery of Sc from high pressure acid leach (HPAL) liquor of limonitic laterite was proposed in this paper. Based on the chemical composition of the leach liquor, precipitation thermodynamic analysis and experiments were conducted. The results indicated that after a first step to precipitate Fe3+ at pH = 2.5 and 90 °C, Sc could be enriched through a second step precipitate at pH = 4.8 and 60 °C to 267 g/t in Sc-containing precipitate. Then, Sc was re-leached from the Sc-containing precipitate via 1 mol/L sulfuric acid at L:S ratio of 5 mL/g, 80 °C, and 40 min. Meanwhile, gypsum in the Sc-containing precipitate transformed into calcium sulfate hemihydrate during leaching. After that, Sc was synergistically extracted from the leach solution via 5% P204 and 2.5% TBP. Moreover, impurities extracted into the organic phase during the extraction of Sc were scrubbed by HCl. Finally, Sc was stripped by NaOH. By using this process, Sc could be efficiently recovered from limonitic laterite in a facile way.

A selective hydrometallurgical method for scandium recovery from a real red mud leachate: A comparative study

The aim of this study was to recover Sc as the main product and Fe as a by-product from Hungarian bauxite residue/red mud (RM) waste material by solvent extraction (SX). Moreover, a new technique was developed for the selective separation of Sc and Fe from real RM leachates. The presence of high Fe content (∼38%) in RM makes it difficult to recover Sc because of the similarity of their physicochemical properties. Pyrometallurgical and hydrometallurgical methods were applied to remove the Fe prior to SX. Two protocols based on organophosphorus compounds (OPCs) were proposed, and the main extractants were evaluated: bis(2-ethylhexyl) phosphoric acid (D2EHPA/P204) and tributyl phosphate (TBP). The results showed that SX using diethyl ether and tri-n-octylamine (N235) was efficient in extracting Fe(III) from the HCl leachate as HFeC14. Over 97% of Sc was extracted by D2EHPA extractant under the following conditions; 0.05 mol/L of D2EHPA concentration, A/O phase ratio of 3:1, pH 0–1, 10 min of shaking time, and a temperature of 25 °C. Sc(OH)3 as a precipitate was efficiently obtained by stripping from the D2EHPA organic phase by 2.5 mol/L of NaOH with a stripping efficiency of 95%. In the TBP system, 99% of Sc was extracted under the following conditions: 12.5% vol of TBP, an A/O phase ratio of 3:1, 10 min of shaking time, and a temperature of 25 °C. The Sc contained in the TBP organic phase could be efficiently stripped by 1 mol/L of HCl with a stripping efficiency of 92.85%.

Recovery of scandium from acidic waste solutions by means of polymer inclusion membranes

Scandium is a raw material with properties that promise considerable potential for application in alloys to enable aviation fuel savings and as dopants for use in sustainable energy production using solid oxide fuel cells. Despite these attractive properties, scandium is rarely used due to its scarcity and unreliable supply. Therefore, new strategies for scandium recovery are of economic priority. In this study, polymer inclusion membranes (PIMs) consisting of PVDF-HFP, 2-NPOE and DEHPA, were optimised for selective scandium separation from real TiO2 production waste. With the optimised system, >60% of the scandium was recovered with high selectivity, resulting in scandium mole fraction at more than two orders of magnitude higher in the receiving phase than in the original waste. This suggests PIMs may be an effective way to recover scandium from bulk waste, thus easing the scarcity and insecurity that currently limit its bulk application.

Preparation of ultra-high pure scandium oxide with crude product from titanium white waste acid

Recovery of scandium from titanium white waste acid is an essential source of scandium. Simple and economical production of high purity scandium remains a challenge. A new extractant, N,N,N',N'-tetracyclohexyl-diglycolamide (TCHDGA), was synthesized, and the separation performance of scandium from impurity metal ions (Ti, Mn, Ba, Fe, Al and Mg) was investigated. The effects of mixing time, acid concentration and temperature on the scandium extraction were considered. The extraction mechanism was studied by infrared spectroscopy and the Equimole Series Method. Under optimized conditions, the extractant shows a strong affinity to scandium in the nitric acid medium and high extraction separation factors between scandium and these impurity metal ions. A process for the purification of scandium was established. The crude product obtained from titanium white waste acid, 95% purity scandium oxide, can be purified to 99.99% after only one step of extraction, scrubbing, and stripping. This technology is economical and straightforward and can realize the high-value recovery of scandium in the titanium white waste acid.

Selective adsorption and recovery of scandium from red mud leachate by using phosphoric acid pre-treated pitaya peel biochar

In recent years, the global demand for scandium has increased due to its essential role in the high-technology industry. Red mud leachates constitute a significant source of scandium and an efficient and environmentally friendly approach that attracted considerable interest. In this study, H3PO4 activated biochar (P40s) is manufactured from pitaya peel (PP) as a novel material to be used for scandium adsorption and recovery from red mud leachates. The material was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), nitrogen adsorption isotherms, X-ray photoelectron spectroscopy (XRF), zeta potential, and element analysis (such as C, H, O, N and P) to characterize adsorbents. The results indicated that the phosphorus-containing functional groups were successfully introduced to improve the physicochemical properties of biochar. The pseudo-second-order kinetic model and Freundlich isotherm fit experimental data, verifying that the scandium adsorption by activated biochar is dominated by chemisorption and belongs to multilayer sorption. The maximal adsorption capacity of 750 °C calcinated H3PO4 activated biochar (P40-750) was 20.77 mg/g. Notably, the adsorbent was better for selective recovery of Sc3+ from Al3+, Fe3+, Dy3+, Y3+ coexistence ions. The separation coefficients (SF) of scandium for aluminum, iron, dysprosium, and yttrium are 137.03, 27.04, 77.74, and 208.25 times respectively, at pH3. Importantly, scandium is efficiently extracted from the leaching solution of red mud with an 83% recovery rate. Meanwhile, P40-750 exhibited a stable scandium adsorption capacity after 5 adsorption/desorption cycles. Overall, P40-750 could be considered a low-cost and environment-friendly biosorbent for recovering scandium from red mud leaching solution.