Investigation on the Effect of Mesomixing on Crystal Quality during Antisolvent Crystallization of Nd2(SO4)3·8H2O

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dc.contributor.authorBaloyi, Tinjombo Octavious
dc.contributor.authorChivavava, Jemitias
dc.contributor.authorLewis, Alison Emslie
dc.date.accessioned2023-09-19T09:29:25Z
dc.date.available2023-09-19T09:29:25Z
dc.date.issued2023-07-31
dc.date.updated2023-08-25T12:37:06Z
dc.description.abstractRare earth elements (REEs) are essential for permanent magnets that are vital for wind turbines and electric vehicles motors (EV), and are also used in a range of high-tech devices such as smartphones, digital cameras, and electronic displays. Nickel metal hydride (NiMH) batteries have been identified as a potential source due to their short lifespans and an anticipated boom in the production of EV. The aim of this study was to investigate the effect of mesomixing on crystal quality in a non-confined impinging jet mixer (NCIJM) during antisolvent crystallization of 3.2 from a synthetic leach solution of NiMH battery using ethanol at an O/A ratio of 1.1. The jet streams were supplied at a Reynolds number (Re) between 7500 and 15,000. The product slurry was allowed to further crystallize in a stirred batch crystallizer at a Re of 13,000 for 45 s. An average yield of 90% was achieved. Laser diffraction and scanning electron microscopy (SEM) were used for size analysis. The initial results were inconclusive due to the secondary mixing effect in the stirred batch crystallizer. Therefore, the experiments were repeated, and samples were collected immediately after mixing in the NCIJM onto a porous grid placed on a high absorbance filter paper to abruptly halt crystallization. The samples were analysed using a transmission electron microscope (TEM), and the acquired images were processed using ImageJ to obtain crystal size distributions (CSDs). It was found that the enhanced mesomixing conditions resulted in smaller crystal sizes and narrower CSDs. This was because the nucleation rate was found to be mass-transfer-limited, such that higher mesomixing intensities promoted the nucleation rate from 6 × 10 12 to 5 times; and, therefore, favoured the formation of smaller crystals. In parallel, intensified mesomixing resulted in uniform distribution of the supersaturation and, hence, narrowed the CSDs.
dc.identifierdoi: 10.3390/met13081378
dc.identifier.apacitationBaloyi, T. O., Chivavava, J., & Lewis, A. E. (2023). Investigation on the Effect of Mesomixing on Crystal Quality during Antisolvent Crystallization of Nd2(SO4)3&middot;8H2O. <i>Metals</i>, 13(8), 1378. http://hdl.handle.net/11427/38769en_ZA
dc.identifier.chicagocitationBaloyi, Tinjombo Octavious, Jemitias Chivavava, and Alison Emslie Lewis "Investigation on the Effect of Mesomixing on Crystal Quality during Antisolvent Crystallization of Nd2(SO4)3&middot;8H2O." <i>Metals</i> 13, 8. (2023): 1378. http://hdl.handle.net/11427/38769en_ZA
dc.identifier.citationBaloyi, T.O., Chivavava, J. & Lewis, A.E. 2023. Investigation on the Effect of Mesomixing on Crystal Quality during Antisolvent Crystallization of Nd2(SO4)3&middot;8H2O. <i>Metals.</i> 13(8):1378. http://hdl.handle.net/11427/38769en_ZA
dc.identifier.risTY - Journal Article AU - Baloyi, Tinjombo Octavious AU - Chivavava, Jemitias AU - Lewis, Alison Emslie AB - Rare earth elements (REEs) are essential for permanent magnets that are vital for wind turbines and electric vehicles motors (EV), and are also used in a range of high-tech devices such as smartphones, digital cameras, and electronic displays. Nickel metal hydride (NiMH) batteries have been identified as a potential source due to their short lifespans and an anticipated boom in the production of EV. The aim of this study was to investigate the effect of mesomixing on crystal quality in a non-confined impinging jet mixer (NCIJM) during antisolvent crystallization of 3.2 g/L Nd<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub> from a synthetic leach solution of NiMH battery using ethanol at an O/A ratio of 1.1. The jet streams were supplied at a Reynolds number (Re) between 7500 and 15,000. The product slurry was allowed to further crystallize in a stirred batch crystallizer at a Re of 13,000 for 45 s. An average yield of 90% was achieved. Laser diffraction and scanning electron microscopy (SEM) were used for size analysis. The initial results were inconclusive due to the secondary mixing effect in the stirred batch crystallizer. Therefore, the experiments were repeated, and samples were collected immediately after mixing in the NCIJM onto a porous grid placed on a high absorbance filter paper to abruptly halt crystallization. The samples were analysed using a transmission electron microscope (TEM), and the acquired images were processed using ImageJ to obtain crystal size distributions (CSDs). It was found that the enhanced mesomixing conditions resulted in smaller crystal sizes and narrower CSDs. This was because the nucleation rate was found to be mass-transfer-limited, such that higher mesomixing intensities promoted the nucleation rate from 6 &times; 10<sup>12</sup> to 5 &times; 10<sup>13</sup> m<sup>&minus;3</sup> s<sup>&minus;1</sup> and, therefore, favoured the formation of smaller crystals. In parallel, intensified mesomixing resulted in uniform distribution of the supersaturation and, hence, narrowed the CSDs. DA - 2023-07-31 DB - OpenUCT DP - University of Cape Town LK - https://open.uct.ac.za PY - 2023 T1 - Investigation on the Effect of Mesomixing on Crystal Quality during Antisolvent Crystallization of Nd2(SO4)3&middot;8H2O TI - Investigation on the Effect of Mesomixing on Crystal Quality during Antisolvent Crystallization of Nd2(SO4)3&middot;8H2O UR - http://hdl.handle.net/11427/38769 ER -en_ZA
dc.identifier.urihttp://hdl.handle.net/11427/38769
dc.identifier.vancouvercitationBaloyi TO, Chivavava J, Lewis AE. Investigation on the Effect of Mesomixing on Crystal Quality during Antisolvent Crystallization of Nd2(SO4)3&middot;8H2O. Metals. 2023;13(8):1378. http://hdl.handle.net/11427/38769.en_ZA
dc.publisherMultidisciplinary Digital Publishing Institute
dc.publisher.departmentChemical Engineering
dc.publisher.facultyFaculty of Engineering and the Built Environment
dc.rights.urihttp://creativecommons.org/licenses/by/4.0/
dc.sourceMetals
dc.source.journalissue8
dc.source.journalvolume13
dc.source.pagination1378
dc.source.urihttps://www.mdpi.com/journal/metals
dc.titleInvestigation on the Effect of Mesomixing on Crystal Quality during Antisolvent Crystallization of Nd2(SO4)3&middot;8H2O
dc.typeJournal Article
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