Extraction Of Scandium Research Articles

Assessing the Efficiency of Ion Exchange Resins for the Recovery of Scandium from Sulfuric Acid Leaching Solutions

Scandium, a valuable element with restricted production sources mainly situated in China and Russia, is typically obtained as a by-product during the production of various materials. As the demand for scandium grows in the expanding aluminum and fuel cell industries, and with significant investments in rare earth mining in the USA and Australia, there is a need to explore alternative recovery sources. This research investigates the recovery of scandium from an acid pregnant leaching solution using ion exchange resins. The pregnant leaching solution was obtained after the leaching of bauxite residue with sulfuric acid. Commercial resins with different functional groups were tested for their performance in scandium extraction. In addition, the co-adsorption of impurities, such as iron and titanium, was studied. The feed solution consisted of 12.7 mg/L Sc and main impurities of 272 mg/L Fe and 33.6 mg/L Ti and was pretreated before the ion exchange process by acidification with sulfuric acid and iron powder addition to suppress silica gel formation and minimize the Fe(III) content in the solution accordingly. Among the tested resins, a D2EHPA-impregnated resin had high selectivity for Sc towards Ti, while a monophosphonic resin was also a promising option since it had a higher capacity for Sc but co-extracted Ti. These findings offer promising opportunities for the recovery of scandium from acid leaching solutions and could contribute to addressing the growing demand for this valuable element.

THE TECHNOLOGY OF EXTRACTION AND ENRICHMENT OF SCANDIUM FROM URANIUM-PHOSPHORUS-RARE EARTH CONCENTRATE

The paper presents the results of pilot tests of scandium extraction technology from uranium-rare-earth phosphorite to obtain high-purity scandium oxide Sc2O3. It is shown that scandium in phosphorites is accompanied by thorium and rare earth elements (REE), which requires the development of a technology for the complex processing of raw materials. Scandium with a purity of 99.0% was obtained from a concentrate of various degrees of enrichment and shavings of scandium alloys by dissolving them in sulfuric acid, extraction, and selective precipitation with oxalic acid. In the process of testing, scandium oxides were obtained with a purity of 99.0; 99.9, and 99.99%, suitable, for example, for the production of alloys based on magnesium for medical purposes.

Study on the extraction of poor scandium from low-grade rare earth ores

ABSTRACT Based on the analysis of chemical composition and the phase of scandium-containing clay type rare earth ore in a place in China, it is found that the content of scandium in the ore is 18.55 g/t. Due to the low leaching rate of direct acid leaching, the effect of the roasting process on the leaching rate of scandium from the raw ore was investigated. By comparing the operation of the two leaching processes, oxidised roasting-hydrochloric acid leaching and alkali roasting-hydrochloric acid leaching, we obtain the optimal technical conditions for both leaching processes. At the same time, the mechanism of alkali roasting was investigated and the conclusions obtained are of some reference for the extraction of scandium from low-grade rare earth ores.

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.

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%).

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.

Recovery of Uranium, Thorium, and Other Rare Metals from Eudialyte Concentrate by a Binary Extractant Based on 1,5-bis[2-(hydroxyethoxyphosphoryl)-4-ethylphenoxy]-3-oxapentane and Methyl Trioctylammonium Nitrate

Eudialyte-group minerals are of scientific interest as important concentrators of rare elements (mainly Zr and REE) in agpaitic alkaline rocks and a potential source of REE, Zr, Hf, Nb, and Ta for industrial use. Extraction of uranium(VI), thorium(IV), zirconium(IV), hafnium(IV), titanium(IV), and scandium(III) by a binary extractant based on 1,5-bis[2-(hydroxyethoxyphosphoryl)-4-ethylphenoxy]-3-oxapentane and methyl trioctylammonium nitrate from eudialyte breakdown solutions is studied. Extraction isotherms were obtained and exhaustive extraction was investigated. It is shown that uranium, thorium, hafnium, zirconium, scandium, and titanium are almost completely recovered in two-stage extraction by a mixture of 1,5-bis[2-(hydroxyethoxyphosphoryl)-4-ethylphenoxy]-3-oxapentane and methyltrioctylammonium nitrate in 1,2-dichloroethane. Quantitative characteristics were compared for uranium(VI), thorium(IV), zirconium(IV), hafnium(IV), titanium(IV), and scandium(III). It was shown that the extraction efficiency of the metals by the binary extractant based on 1,5-bis[2-(hydroxyethoxyphosphoryl)-4-ethylphenoxy]-3-oxapentane and methyltrioctylammonium nitrate in 1,2-dichloroethane is much higher in comparison with the commercially available tributyl phosphate.

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.

Extraction of Rare-Earth Elements from Silicate-Based Ore through Hydrometallurgical Route

The European Union and several countries/regions classified the rare-earth elements (REEs), such as lanthanum, cerium, neodymium, and scandium, as critical due to the risk of supply interruption. For this reason, the growing demand for REEs has resulted in forgotten reserves receiving economic interest. So, the search for new sources and the development of chemical process is important, such as silicate-based ore. Since there is almost no literature on the extraction of REEs from this source, a new approach was developed in the present study. Direct leaching and acid baking were studied using sulfuric acid. The effect of the acid concentration, temperature, solid-liquid ratio, oxidizing/reducing medium, and acid dosage were studied. Results showed that the extraction of REEs achieved up to 80% at 90 °C in oxidizing medium, and scandium and iron achieved 13.5% and 65.0%, respectively. For the acid baking experiments, the results were better than direct leaching for REEs at over 85%. The scandium leaching rate was lower than direct leaching. On the other hand, the extraction of iron was lower in acid baking than direct leaching. The iron and scandium extraction rates were higher in lower temperatures (<200 °C) and acid dosages, achieving 50% and 6.3%, respectively. Future studies should explore thermal treatment before acid leaching.

Extraction of scandium from sulphuric acid-based red mud leach liquors

Equimolar mixtures of di-2-ethylhexylphosphoric acid (D2EHPA) with trin-butylphosphate (TBP) or trioctylamine (TOA) in kerosene were used for extracting scandium from sulphuric acid-based red mud leach liquor. The results showed that when using a D2EHPA-TOA mixture, the overall extraction of scandium (ЕSc) tends to rise from 37 to 68% as the concentration of sulphuric acid rises. At the same time, the extraction of concomitant elements tends to decrease and remains way below the Е Sc . When using a D2EHPATBP mixture, the rising acidity of the solution does not lead to any significant increase in scandium extraction so that the latter remains quite high (i.e. 82–85%) while the extraction of the concomitant elements is significantly lower. A five-stage countercurrent extraction process was performed using a mixture of 0.1 mol/L D2EHPA and 0.1 mol/L TBP with 2 mol/L sulphuric acid to recover scandium from the liquor with minimized amounts of concomitant metals. The results showed that a 96.8% of scandium can be recovered after a three-stage countercurrent extraction process with 97% aluminium, 95% iron, 87% titanium and 54% zirconium removed from the liquor. A 4.7 mol/L sulphuric acid solution with an organic to aqueous ratio of 1:1 was used to wash the organic phase after a three-stage extraction process. For reextraction, a solution containing 2.5% NaOH and 6.5% Na2CO3 was used at a 2:1 aqueous to organic phase ratio. The solution was filtered to separate the solid phase. The precipitate was washed and dried and a primary 3.42% concentrate was obtained. Based on the obtained data, the authors describe a scandium extraction process using sulphuric acid-based red mud leach liquor. The new scandium concentration by extraction process parameters were tested on an enlarged scale at the Intermix MET site. A 100 g experimental batch of primary scandium concentrate containing, %: 2.2 Sc; 21.8 Тi; 4.3 Na; 0.6 Al; 1.7 Fe; 5.0 Zr; 0.0056 Y, was obtained from a 260-litre red mud leach liquor. For this, a cascade of five centrifugal extractors was used at the extractant saturation stage. An 8-litre mixture of 0.1 mol/L D2EHPA and 0.1 mol/L TBP in Exxsol D100 was used. The organic phase was in recycle, and due to that its saturation was 340 mg of scandium per litre of extractant.

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.

Efficient Selective Extraction of Scandium from Red Mud

ABSTRACT The huge reserves of red mud have a significant potential source of scandium. The scandium can be recovered from red mud by direct acid leaching but the extraction yields are generally low, and the leaching efficiency of iron and silicon is higher. Therefore, the highly selective process steps (a combined sulfation-roasting-water leaching process) were studied to extract scandium from red mud, and in order to minimize costs and waste generated. This study focuses on the phase transformation mechanism and leaching behavior of Sc, Na, Al, Fe, Ti, Ca, and Si in the red mud sulfation-roasting-water leaching process. The results show that the maximum Sc leaching efficiency of 91.98% was obtained at optimum conditions: the roasted at 1023 K for 60 min, the ratio of sulfuric acid to red mud of 0.9 mL/g, the leaching temperature is 323 K, the liquid-to-solid ratio of 5 mL/g, and stirred constantly at 200 rpm leach for 2 h. While the leaching efficiencies of Ca, Na, Fe, Al, Si, and Ti are 21.05%, 93.26%, 1.21%, 9.51%, 1.42%, and 0, respectively. The sulfation-roasting-water leaching process proves to be a promising technique and commercially viable process that allows selective extraction of scandium from red mud, which may contribute to provide options for the treatment of red mud produced continuously by the aluminum industry.

Technospheric mining of scandium from hydrometallurgical tailings of nickel laterite processing: Selection of lixiviant and optimisation of leaching variables

• Extraction of scandium from a residue of nickel laterite processing was studied. • Five different leaching agents were examined to extract scandium from the residue. • Oxalic acid was found to be the most effective. • Scandium dissolution of up to 94% was achieved. In this study, the potential of tailings generated from hydrometallurgical processing of nickel laterite ores as a source of scandium was investigated. The use of an atmospheric leaching process was proposed and five different lixiviants, namely sulphuric, phosphoric, oxalic, citric and ascorbic acids, were examined systematically to extract the scandium. Characterisation results showed that the nickel laterite residue sample contained about 148 ppm scandium and that the major crystalline phases of the sample were quartz, chromite, magnetite and akaganeite. Results of the leaching experiments suggested that most of the scandium was hosted within the refractory iron-bearing minerals, namely magnetite and chromite, based on the apparent correlation between the scandium dissolution and iron and chromium dissolutions and the composition of crystalline phases in the leached residues. Oxalic acid was found to be the most effective lixiviant to overcome the refractoriness of these minerals and render the scandium accessible for dissolution. To further improve the leaching performance with oxalic acid, the effects of acid concentration, stirring speed, pulp density, temperature and leaching duration on the leaching efficiency were studied. It was found that the scandium dissolution can reach up to 94% in 0.75 mol/L of the acid at a temperature of 95 °C, pulp density of 100 g/L, leaching time of 24 h and stirring speed of 600 rpm. These results demonstrated that the simple, atmospheric leaching process with an organic acid is feasible to extract scandium from nickel laterite residues.

High-Selective Extraction of Scandium (Sc) from Bauxite Residue (Red Mud) by Acid Leaching with MgSO4.

Bauxite residue, also known as red mud (RM), from alumina production is the most promising technogenic material for the production of scandium (Sc) and other rare earth elements (REEs). Conveniently, RM is processed by using a strong acid (pH < 2.5), which lead to co-dissolution of iron and other undesirable major components. In this work, for the first time, the possibility of selective extraction of scandium from red mud by using highly diluted acid (pH > 4) in the presence of MgSO4 was shown. The effect of temperature (40–80 °C), time (0–60 min), pH (2–5), and the MgSO4 concentration (12–36 g L−1) on Sc extraction efficiency was evaluated. It was shown that Sc extraction was higher than 63% even at a pH of 4, at 80 °C, after 1 h, while more than 80% could be extracted at a pH of 2. Iron extraction reduced from 7.7 to 0.03% by increasing the pH from 2 to 4. The kinetics study using the shrinking core model (SCM) has shown that diffusion through a product layer is a rate-limiting stage of the process at high temperatures (>60 °C) and low pH (<3), whereas, at lower temperatures and higher pH values, the leaching rate is limited by diffusion through the liquid film.

Direct Phosphoric Acid Leaching of Bauxite Residue for Selective Scandium Extraction

Bauxite residue, the high alkaline and fine-grained byproduct of Bayer process for alumina’s production, is a material rich in numerous minerals and elements of high value and techno-economical interest in high tech applications such as rare earths, including scandium. Lately, the European Committee has characterized scandium as a critical element because of its risk supply chain. Scandium's high concentration in Greek bauxite residue classifies the waste as a candidate for low cost and high availability of the element, additionally improving its environmental fingerprint. For scandium recovery, hydrometallurgical treatment with inorganic acids is the most common, effective and simple method. In this study, the efficiency of phosphoric acid is investigated for scandium recovery by a direct leaching of bauxite residue without pretreatment. Multi leaching variables, such as acid molarity, solid/liquid ratio, process temperature and leaching time, were examined and optimized individually as well as in a comparative way aiming to scandium selective extraction (mainly with regard to iron) and process viability. A Sc selective recovery of 40% was obtained for phosphoric acid molarity 5 M, solid/liquid ratio 10%, leaching time, 60 min under ambient conditions with low iron leachability, no gel formation and no energy consumption.

Extraction Separation of Ti(IV) and Fe(II) Using D2EHPA from the Raffinate Obtained After Extraction of Scandium from Titanium Dioxide Waste Acid

Extraction Separation of Ti(IV) and Fe(II) Using D2EHPA from the Raffinate Obtained After Extraction of Scandium from Titanium Dioxide Waste Acid

Studying the extraction of scandium(III) by macrocyclic compounds from aqueous solution using optimization technique

Studying the extraction of scandium(III) by macrocyclic compounds from aqueous solution using optimization technique

Selective Scandium (Sc) Extraction from Bauxite Residue (Red Mud) Obtained by Alkali Fusion-Leaching Method.

Bauxite residue, known as “red mud,” is a potential raw material for extracting rare-earth elements (REEs). The main REEs (Sc, Y, La, Ce, Nd, Nb, and Sm) from the raw bauxite are concentrated in RM after the Bayer leaching process. The earlier worldwide studies were focused on the scandium (Sc) extraction from RM by concentrated acids to enhance the extraction degree. This leads to the dissolution of major oxides (Fe2O3 and Al2O3) from RM. This article studies the possibility of selective Sc extraction from alkali fusion red mud (RMF) by diluted nitric acid (HNO3) leaching at pH ≥ 2 to prevent co-dissolution of Fe2O3. RMF samples were analyzed by X-ray fluorescence spectrometry (XRF), X-ray diffraction (XRD), electron probe microanalysis (EPMA), and inductively coupled plasma mass spectrometry (ICP-MS). It was revealed that Sc concentration in RMF can reach up to 140–150 mg kg−1. Sc extraction was 71.2% at RMF leaching by HNO3 at pH 2 and 80 °C during 90 min. The leaching solution contained 8 mg L−1 Sc and a high amount of other REEs in the presence of relatively low concentrations of impurity elements such as Fe, Al, Ti, Ca, etc. The kinetic analysis of experimental data by the shrinking core model showed that Sc leaching process is limited by the interfacial diffusion and the diffusion through the product layer. The apparent activation energy (Ea) was 19.5 kJ/mol. The linear dependence of Sc extraction on magnesium (Mg) extraction was revealed. According to EPMA of RMF, Sc is associated with iron minerals rather than Mg. This allows us to conclude that Mg acts as a leaching agent for the extraction of Sc presented in the RMF in an ion-exchangeable phase.

Extraction of Scandium from Red Mud of Alumina Refining by High Pressure Acid Leaching in Sulfuric Acid Solution

Extraction of Scandium from Red Mud of Alumina Refining by High Pressure Acid Leaching in Sulfuric Acid Solution

A novel synergistic extraction system for the recovery of scandium (III) from sulfuric acid medium with mixed Cyanex923 and N1923

High extraction capability and outstanding selectivity are very attractive in the solvent extraction process. Scandium (Sc(III)), as a primary rare earth element (REE), generally lacks independent large-scale deposits and is mainly recovered as a by-product during the processing of mineral. However, the difficulty of stripping has been always a crucial problem to be solved in the scandium extraction system. This study aims to improve stripping performance while enhancing extraction efficiency for scandium. Herein, a novel synergistic extraction system for the recovery of scandium with a mixture of Cyanex923 (A, a mixture of four trialkylphosphine oxides) and N1923 (B, primary amine R1R2CHNH2) in sulfuric acid medium was put forward. The effect of the molar fraction (X) of Cyanex923 on the extraction of scandium was systematically investigated. The experimental results demonstrated that the coupled Cyanex923-N1923 exhibited an obvious synergistic effect on Sc(III). The maximum synergistic enhancement coefficient (Rmax) was calculated to be 2.20 when the molar fraction (X) of Cyanex923 was 0.4, and the H2SO4 concentration was 0.25 mol·L−1. Moreover, the synergistic extraction mechanism was discussed combined with multiple techniques including slope analysis method, FT-IR and NMR characterizations, to which the structure of extracted complexed was deduced to be Sc(SO4)1.5∙(A)0.5(B). Thermodynamic experiment was also explored in detail. More importantly, stripping with only 2 mol·L−1 HNO3 produced a relatively high stripping rate of 95%. The synergistic system still presented excellent reusability even after five treatment cycles. Finally, this study pointed out a potential industrial application value for the separation and recovery of Sc(III) from the sulfuric acid leaching liquor of nickel laterite ores.