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25 pages, 8271 KiB

Open AccessArticle

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

by Pavel Grudinsky, Liliya Pasechnik, Anfisa Yurtaeva, Valery Dyubanov and Dmitry Zinoveev

Crystals 2022, 12(11), 1578; https://doi.org/10.3390/cryst12111578 - 5 Nov 2022

Cited by 10 | Viewed by 3035

Abstract

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. Full article

(This article belongs to the Special Issue Extractive Metallurgy and Chemistry)

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9 pages, 978 KiB

Open AccessArticle

Measurement of ⁹⁰Sr in Marine Biological Samples

by Fangfang Deng and Feng Lin

Molecules 2022, 27(12), 3730; https://doi.org/10.3390/molecules27123730 - 9 Jun 2022

Cited by 10 | Viewed by 2121

Abstract

Strontium-90 (⁹⁰Sr) is one of the most hazardous radionuclides, and it contributes to radiation exposure by ingestion. The routine determination of ⁹⁰Sr in marine biological samples is highly desirable given the development of the nuclear power industry. A fast, simple, and low-detection-limit method was developed for the measurement of ⁹⁰Sr in marine biological samples based on determining ⁹⁰Y by means of coprecipitation and solvent extraction with bis-2-ethylhexyl-phosphoric acid (HDEHP) in n-heptane. The interfering ²¹⁰Bi is removed using Bi₂S₃ precipitation. The separation and purification of eight samples per day can be accomplished through this method. The detection limit of ⁹⁰Sr for this method is 0.10 Bq/kg (ash weight). The radiochemical procedure was validated by fitting the decay curve of the sample source and by the determination of ⁹⁰Sr standards. Full article

(This article belongs to the Special Issue Environment Radioactivity Analysis, Monitoring and Tracer Applications)

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18 pages, 4574 KiB

Open AccessArticle

Competitive Adsorption of Ionic Liquids Versus Friction Modifier and Anti-Wear Additive at Solid/Lubricant Interface—Speciation with Vibrational Sum Frequency Generation Spectroscopy

by Dien Ngo, Xin He, Huimin Luo, Jun Qu and Seong H. Kim

Lubricants 2020, 8(11), 98; https://doi.org/10.3390/lubricants8110098 - 12 Nov 2020

Cited by 10 | Viewed by 3850

Abstract

A modern lubricant contains various additives with different functionalities and the interactions or reactions between these additives could induce synergistic or antagonistic effects in tribological performance. In this study, sum frequency generation (SFG) spectroscopy was used to investigate competitive adsorption of lubricant additives at a solid/base oil interface. A silica substrate was used as a model solid surface. The lubricant additives studied here included two oil-soluble ionic liquids (ILs, [N888H][DEHP] and [P8888][DEHP]), an antiwear additive (secondary ZDDP), an organic friction modifier (OFM), and a dispersant (PIBSI). Our results showed that for mixtures of ZDDP and IL in a base oil (PAO4), the silica surface is dominated by the IL molecules. In the cases of base oils containing OFM and IL, the silica/lubricant interface is dominated by OFM over [N888H][DEHP], while it is preferentially occupied by [P8888][DEHP] over OFM. The presence of PIBSI in the mixture of PAO4 and IL leads to the formation of a mixed surface layer at the silica surface with PIBSI as a major component. The SFG results in this investigation provide fundamental insights that are helpful to design the formulation of new lubricant additives of desired properties. Full article

(This article belongs to the Special Issue In Commemoration of Professor Duncan Dowson: Tribology: Hydrodynamics, Elastohydrodynamics and Biotribology)

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29 pages, 2803 KiB

Open AccessArticle

Extraction Chromatography Materials Prepared with HDEHP on Different Inorganic Supports for the Separation of Gadolinium and Terbium

by Fabiola Monroy-Guzman, Celia del Carmen De la Cruz Barba, Edgar Jaime Salinas, Vicente Garibay-Feblés and Tobias Noel Nava Entzana

Metals 2020, 10(10), 1390; https://doi.org/10.3390/met10101390 - 19 Oct 2020

Cited by 11 | Viewed by 4631

Abstract

Bis(2-ethylhexyl)phosphoric acid (HDEHP) is frequently used as an extractant in the separation and recovery of lanthanides by solvent extraction and extraction chromatography, where HDEHP (stationary phase) is fixed on an inert support and the mobile phase is an aqueous solution. Because the results of extraction chromatography strongly depend on the support material, in this study, we aim to prepare solid extractants (extraction chromatography materials) with different inorganic supports impregnated with HDEHP for the adsorption of Gd and Tb from HCl solutions, putting emphasis on the effect of the supports on the solid extractant behavior. Gd and Tb partition data were determined in HCl solutions from the prepared extraction chromatography materials using elution analysis. Solid extractants were characterized by X-Ray diffraction, electron microscopy, and infrared spectroscopy in order to determine their properties and to explain their extraction behavior. The characterization of the solid extractants showed a heterogeneous distribution of the HDEHP on the surfaces of the different supports studied. The irregular shape of the support particles produces discontinuous and heterogenous silanization and HDEHP coatings on the support surface, affecting the retention performance of the solid extractant and the chromatographic resolution. Full article

(This article belongs to the Special Issue Solvent Extraction of Transition Metals)

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12 pages, 3348 KiB

Open AccessFeature PaperArticle

Recovery of Metal Values from Ni-Cd Cake Waste Residue of an Iranian Zinc Plant by Hydrometallurgical Route

by Sushanta Kumar Sahu, Maryam Kargar Razi, Mathieu Beuscher and Alexandre Chagnes

Metals 2020, 10(5), 655; https://doi.org/10.3390/met10050655 - 19 May 2020

Cited by 7 | Viewed by 4972

Abstract

This paper concerns the development of an environment-friendly hydrometallurgical flowsheet dedicated to the recovery of zinc and nickel from a waste residue collected from an Iranian zinc plant. In particular, valuable metals from Ni-Cd cake waste generated at this plant were recovered by a simple hydrometallurgical process using minimum acid for leaching, and solvent extraction step was designed such that addition of sodium hydroxide was not required and the effluent generated is safe to dispose off. The waste was leached with a mixture of hydrochloric acid and sulfuric acid in the presence of hydrogen peroxide in order to achieve a good selectivity towards iron and calcium. Afterwards, cementation was performed at pH 5 in order to remove cadmium. Liquid–liquid extraction was then implemented to produce high-purity solutions of zinc and nickel. Zinc-nickel separation was obtained at pH 2 by using a mixture of bis-(2-ehtyl-hexyl)-phosphoric acid (HDEHP) and tris-2-ethylhexyl amine (TEHA) diluted in an aliphatic kerosene. TEHA did not directly participate but helped in the extraction of zinc by scavenging the protons released by HDEHP. Therefore, no alkaline solution was necessary for maintaining the equilibrium pH during liquid–liquid extraction. Finally, this flowsheet allowed to recover more than 95% of zinc and nickel from the residue with more than 99% purity. Full article

(This article belongs to the Special Issue Challenges in the Development of Sustainable Extractive Metallurgy Processes)

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12 pages, 2090 KiB

Open AccessArticle

Solvent Extraction of Didymium by TBP, Aliquat 336 and HDEHP in The Presence of Ca(NO₃)₂

by Petr I. Matveev and Vladimir G. Petrov

Appl. Sci. 2020, 10(6), 2032; https://doi.org/10.3390/app10062032 - 17 Mar 2020

Cited by 7 | Viewed by 3757

Abstract

Three commercially available extractants (tri-butyl-phosphate (TBP), di-(2-ethylhexyl)phosphoric acid (HDEHP) and Aliquat 336 (a mixture of quaternary ammonium bases)) were tested for separation of Pr(III) and Nd(III) in both static and dynamic modes. In the case of HDEHP, phase stability and influence of nitric acid were considered. Extraction isotherms were constructed, and influence of water-soluble complexing agents on the separation factor was investigated for Aliquat 336. In the case of TBP, influence of calcium nitrate in aqueous phase on the extraction efficiency was investigated. Model countercurrent experiments were conducted for TBP and Aliquat 336. It was shown that TBP is the best choice due to its high capacity and cation extraction order (Nd > Pr). Full article

(This article belongs to the Section Chemical and Molecular Sciences)

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11 pages, 1678 KiB

Open AccessFeature PaperArticle

Electrochemical Impedance Spectroscopy (EIS) Characterization of Water/Sodium Bis(2-Ethylhexyl) Sulfosuccinate-HDEHP/n-Dodecane Reverse Micelles for Electroextraction of Neodymium

by Shannon Anderson, Mikael Nilsson and Egwu Eric Kalu

ChemEngineering 2017, 1(1), 3; https://doi.org/10.3390/chemengineering1010003 - 23 Jun 2017

Cited by 3 | Viewed by 4876

Abstract

The extraction and separation of metal ions in the lanthanide series using the liquid-liquid extraction (LLX) technique poses a major challenge due to the chemical similarities of the metals and hence interest exists in devising a technique to improve the separation factor. In this work, sodium bis(2-ethylhexyl) sulfosuccinate (AOT) is explored for improved organic phase conductivity to aid the use of an imposed external field to improve the LLX. The electrochemical impedance spectroscopy (EIS) technique was used to determine the effect of molar water content, AOT and HDEHP (bis(2-ethylhexyl) phosphoric acid) concentration, and the temperature on the reverse micelle solution conductivity. Results showed that as AOT concentration and water content increases, conductivity increases until the reverse micelles collapse. The addition of HDEHP caused a significant drop in solution conductivity. For a mixed AOT and HDEHP system and at a small applied external field range of 0–1.4 kV m⁻¹ and 60 rpm stir rate, a significant improvement in Nd extraction was observed relative to the traditional LLX using HDEHP only. With AOT only, a 40% improvement in extraction was observed with applied field relative to the absence of field. Cost consideration favors the use of mixed AOT and HDEHP at a slow stir rate for improved Nd extraction. Full article

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