Investigation on the Effect of Mesomixing on Crystal Quality during Antisolvent Crystallization of Nd<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>·8H<sub>2</sub>O
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 identifi...
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| Format: | Article |
| Language: | English |
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MDPI AG
2023-07-01
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| Series: | Metals |
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| Online Access: | https://www.mdpi.com/2075-4701/13/8/1378 |
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| author | Tinjombo Octavious Baloyi Jemitias Chivavava Alison Emslie Lewis |
| author_facet | Tinjombo Octavious Baloyi Jemitias Chivavava Alison Emslie Lewis |
| author_sort | Tinjombo Octavious Baloyi |
| collection | DOAJ |
| description | 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 × 10<sup>12</sup> to 5 × 10<sup>13</sup> m<sup>−3</sup> s<sup>−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. |
| first_indexed | 2024-03-10T23:44:43Z |
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| institution | Directory Open Access Journal |
| issn | 2075-4701 |
| language | English |
| last_indexed | 2024-03-10T23:44:43Z |
| publishDate | 2023-07-01 |
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| record_format | Article |
| series | Metals |
| spelling | doaj.art-8672bf40b13f4d6e91daf5dacba8d5552023-11-19T02:10:19ZengMDPI AGMetals2075-47012023-07-01138137810.3390/met13081378Investigation on the Effect of Mesomixing on Crystal Quality during Antisolvent Crystallization of Nd<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>·8H<sub>2</sub>OTinjombo Octavious Baloyi0Jemitias Chivavava1Alison Emslie Lewis2Department of Chemical Engineering, University of Cape Town, Rondebosch, Cape Town 7700, South AfricaDepartment of Chemical Engineering, University of Cape Town, Rondebosch, Cape Town 7700, South AfricaDepartment of Chemical Engineering, University of Cape Town, Rondebosch, Cape Town 7700, South AfricaRare 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 × 10<sup>12</sup> to 5 × 10<sup>13</sup> m<sup>−3</sup> s<sup>−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.https://www.mdpi.com/2075-4701/13/8/1378mesomixingmicromixingnon-confined impinging jet mixerKolmogorov-length scaleantisolvent crystallizationnucleation |
| spellingShingle | Tinjombo Octavious Baloyi Jemitias Chivavava Alison Emslie Lewis Investigation on the Effect of Mesomixing on Crystal Quality during Antisolvent Crystallization of Nd<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>·8H<sub>2</sub>O Metals mesomixing micromixing non-confined impinging jet mixer Kolmogorov-length scale antisolvent crystallization nucleation |
| title | Investigation on the Effect of Mesomixing on Crystal Quality during Antisolvent Crystallization of Nd<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>·8H<sub>2</sub>O |
| title_full | Investigation on the Effect of Mesomixing on Crystal Quality during Antisolvent Crystallization of Nd<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>·8H<sub>2</sub>O |
| title_fullStr | Investigation on the Effect of Mesomixing on Crystal Quality during Antisolvent Crystallization of Nd<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>·8H<sub>2</sub>O |
| title_full_unstemmed | Investigation on the Effect of Mesomixing on Crystal Quality during Antisolvent Crystallization of Nd<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>·8H<sub>2</sub>O |
| title_short | Investigation on the Effect of Mesomixing on Crystal Quality during Antisolvent Crystallization of Nd<sub>2</sub>(SO<sub>4</sub>)<sub>3</sub>·8H<sub>2</sub>O |
| title_sort | investigation on the effect of mesomixing on crystal quality during antisolvent crystallization of nd sub 2 sub so sub 4 sub sub 3 sub ·8h sub 2 sub o |
| topic | mesomixing micromixing non-confined impinging jet mixer Kolmogorov-length scale antisolvent crystallization nucleation |
| url | https://www.mdpi.com/2075-4701/13/8/1378 |
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