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19 pages, 4572 KiB

Open AccessFeature PaperArticle

Chromatographic Separation of Rare Earth Elements as MGDA Complexes on Anion Exchange Resins

by Santeri Kurkinen, Sami Virolainen and Tuomo Sainio

Metals 2023, 13(3), 600; https://doi.org/10.3390/met13030600 - 16 Mar 2023

Cited by 2 | Viewed by 3708

Chromatographic separation of rare earth elements (REE) as anionic complexes with chelating aminopolycarboxylate ligand methylglycine N,N-diacetate (MGDA) was studied experimentally. A synthetic mixture of La, Nd, and Eu were used to model a REE mixture obtained from processed secondary sources such as phosphogypsum (PG). In the REE extraction from PG, the REEs can be recovered with MGDA to obtain the REE–MGDA mixture. Three strong base anion exchange resins (Dowex 1X8, IRA-402, and IRA-410) were used as the separation materials. Successful separation of the REEs by elution with dilute HNO₃ and HCl was attributed to differences in the stabilities of the REE–MGDA complexes. The pKa values of the complexes were determined by titration to be 3.81, 3.25, and 2.96 for La, Nd, and Eu, respectively. Fractionation of the ternary La-Nd-Eu mixture (with a 1:1:1 mole ratio) were studied. La was recovered at approximately 80% purity and 80% yield, but strong trade-offs between the yield and the purity of Nd and Eu must be made. Chromatographic separation was found to be an efficient process option, considering its simplicity and the recovery of several product fractions. The initial process design offers a promising starting point for investigating more advanced process configurations for the efficient recovery of pure REE from phosphogypsum. Full article

(This article belongs to the Special Issue Separation and Purification of Metals)

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15 pages, 1441 KiB

Open AccessArticle

Recovery of Ammonium from Biomass-Drying Condensate Via Ion Exchange and Its Valorization as a Fertilizer

by Jianzhi Song, Jari Heinonen and Tuomo Sainio

Processes 2023, 11(3), 815; https://doi.org/10.3390/pr11030815 - 9 Mar 2023

Cited by 2 | Viewed by 2591

Abstract

In this study, an industrial biomass-drying wastewater condensate containing > 3200 mg/L NH₄⁺ and >8900 mg/L CH₃COO⁻ was treated in ion-exchange columns for the recovery of NH₄⁺. Two commercial resins (CS12GC and CS16GC) were studied on laboratory and pilot scales. CS16GC outperformed CS12GC by achieving better separation at the condensate temperature (60 °C), which was energy-efficient regarding NH₄⁺ removal. K₃PO₄ was used for regeneration to produce a liquid compound fertilizer containing nutrient elements (N, K, and P) as a byproduct. The N/K ratio in the byproduct was found to be adjustable by varying the operating parameters. Regeneration with 2 mol/L K₃PO₄ gave a higher regeneration efficiency (97.67% at 3 BV and ~100% at 4 BV). The stability tests performed on a laboratory scale showed that the cyclic runs of the column separation process were steady and repeatable. Based on the outcomes of the laboratory-scale tests, the pilot-scale tests applied a loading volume of 7 BV. The pilot column purified the feed and achieved the target NH₄⁺ level in the treated effluent within the seven tested cycles, revealing that the industrial application of the cation ion-exchange resin CS16GC is worth further study. Full article

(This article belongs to the Section Separation Processes)

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19 pages, 2135 KiB

Open AccessFeature PaperEditor’s ChoiceArticle

Separation of Molar Weight-Distributed Polyethylene Glycols by Reversed-Phase Chromatography—Analysis and Modeling Based on Isocratic Analytical-Scale Investigations

by Malvina Supper, Kathleen Heller, Jakob Söllner, Tuomo Sainio and Malte Kaspereit

Processes 2022, 10(11), 2160; https://doi.org/10.3390/pr10112160 - 22 Oct 2022

Cited by 5 | Viewed by 3617

Abstract

The separation of polyethylene glycols (PEGs) into single homologs by reversed-phase chromatography is investigated experimentally and theoretically. The used core–shell column is shown to achieve the baseline separation of PEG homologs up to molar weights of at least 5000 g/mol. A detailed study is performed elucidating the role of the operating conditions, including the temperature, eluent composition, and degree of polymerization of the polymer. Applying Martin’s rule yields a simple model for retention times that holds for a wide range of conditions. In combination with relations for column efficiency, the role of the operating conditions is discussed, and separations are predicted for analytical-scale chromatography. Finally, the approach is included in an efficient process model based on discrete convolution, which is demonstrated to predict with high accuracy also advanced operating modes with arbitrary injection profiles. Full article

(This article belongs to the Special Issue Advances in Green Chemistry Analytical Techniques)

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16 pages, 4596 KiB

Open AccessArticle

Direct Production of Ni–Co–Mn Mixtures for Cathode Precursors from Cobalt-Rich Lithium-Ion Battery Leachates by Solvent Extraction

by Niklas Jantunen, Sami Virolainen and Tuomo Sainio

Metals 2022, 12(9), 1445; https://doi.org/10.3390/met12091445 - 30 Aug 2022

Cited by 13 | Viewed by 3628

Abstract

A novel solvent extraction scheme was developed for the processing of Co-rich lithium-ion battery (LIB) leachate to a Ni–Co–Mn (NCM) sulfate mixture that can be directly used in the precursor synthesis of LIB cathodes. Conventional hydrometallurgical recycling of spent LIBs usually aims at separation of Li, Ni, Co, and Mn into pure fractions, which is simplified here. Operating pH and the number of extraction stages for each separation were evaluated from batch equilibrium experiments. Two continuous countercurrent extractions with bis(2-ethylhexyl) hydrogen phosphate (D2EHPA) and one with Cyanex 272 were studied in bench-scale mixer-settler equipment, and a Ni–Co–Mn solution with n(Ni):n(Co) = 14.16 and n(Ni):n(Mn) = 8.06 was obtained. The Ni:Co:Mn molar ratio in the NCM mixture can be adjusted to, for example, 8:1:1 using a Co-rich raffinate from the same process, and no additional transition metal salts are required for tuning the composition. Stripping raffinate containing 102.7 g L⁻¹ Co at 99.8% relative purity was obtained from Cyanex 272 extraction. The main benefit of the process concept is that the solvent extraction separations can be operated with less stringent requirements than when producing pure metal salts. Full article

(This article belongs to the Special Issue Extractive Metallurgy for the Sustainable Supply of Metals in Lithium-Ion Batteries)

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15 pages, 3210 KiB

Open AccessArticle

Solvent Extraction for Separation of 99.9% Pure Cobalt and Recovery of Li, Ni, Fe, Cu, Al from Spent LIBs

by Pratima Meshram, Sami Virolainen, Abhilash and Tuomo Sainio

Metals 2022, 12(6), 1056; https://doi.org/10.3390/met12061056 - 20 Jun 2022

Cited by 27 | Viewed by 9079

Abstract

In this work, hydrometallurgical recycling of metals from high-cobalt-content spent lithium-ion batteries (LIBs) from laptops was studied using precipitation and solvent extraction as alternative purification processes. Large amounts of cobalt (58% by weight), along with nickel (6.2%), manganese (3.06%) and lithium (6.09%) are present in LiCoO₂ and Li₂CoMn₃O₈ as prominent Co-rich phases of the electrode material. The pregnant leach solution (PLS) that was generated by leaching in the presence of 10% H₂O₂ using 50 g/L pulp density at 80 °C for 4 h contained 27.4 g/L Co, 3.21 g/L Ni, 1.59 g/L Mn and 3.60 g/L Li. The PLS was subjected to precipitation at various pH using 2 M NaOH but the purification performance was poor. To improve the separation of Mn and other impurities and in order to avoid the loss of cobalt and nickel, separation studies were carried out using a solvent extraction technique using di-(2-ethylhexyl) phosphoric acid (D2EHPA) and bis-(2,4,4-trimethylpentyl) phosphinic acid (Cyanex 272). Overall, this study examines the fundamentals of separating and synthesizing 99.9% pure Co sulfate from leach liquor of spent laptop LIBs with remarkably high cobalt content. Full article

(This article belongs to the Special Issue Extractive Metallurgy for the Sustainable Supply of Metals in Lithium-Ion Batteries)

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