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) extr...
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2022-01-01
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| author | Andrei Shoppert Irina Loginova Julia Napol’skikh Aleksey Kyrchikov Leonid Chaikin Denis Rogozhnikov Dmitry Valeev |
| author_facet | Andrei Shoppert Irina Loginova Julia Napol’skikh Aleksey Kyrchikov Leonid Chaikin Denis Rogozhnikov Dmitry Valeev |
| author_sort | Andrei Shoppert |
| collection | DOAJ |
| description | 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 (Fe<sub>2</sub>O<sub>3</sub> and Al<sub>2</sub>O<sub>3</sub>) from RM. This article studies the possibility of selective Sc extraction from alkali fusion red mud (RMF) by diluted nitric acid (HNO<sub>3</sub>) leaching at pH ≥ 2 to prevent co-dissolution of Fe<sub>2</sub>O<sub>3</sub>. 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<sup>−1</sup>. Sc extraction was 71.2% at RMF leaching by HNO<sub>3</sub> at pH 2 and 80 °C during 90 min. The leaching solution contained 8 mg L<sup>−1</sup> 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 (E<sub>a</sub>) 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. |
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| spelling | doaj.art-22fde5afa75940958776af1f93fdaf512023-11-23T14:29:02ZengMDPI AGMaterials1996-19442022-01-0115243310.3390/ma15020433Selective Scandium (Sc) Extraction from Bauxite Residue (Red Mud) Obtained by Alkali Fusion-Leaching MethodAndrei Shoppert0Irina Loginova1Julia Napol’skikh2Aleksey Kyrchikov3Leonid Chaikin4Denis Rogozhnikov5Dmitry Valeev6Laboratory of Advanced Technologies in Non-Ferrous and Ferrous Metals Raw Materials Processing, Ural Federal University, 620002 Yekaterinburg, RussiaDepartment of Non-Ferrous Metals Metallurgy, Ural Federal University, 620002 Yekaterinburg, RussiaDepartment of Non-Ferrous Metals Metallurgy, Ural Federal University, 620002 Yekaterinburg, RussiaDepartment of Non-Ferrous Metals Metallurgy, Ural Federal University, 620002 Yekaterinburg, RussiaDepartment of Non-Ferrous Metals Metallurgy, Ural Federal University, 620002 Yekaterinburg, RussiaLaboratory of Advanced Technologies in Non-Ferrous and Ferrous Metals Raw Materials Processing, Ural Federal University, 620002 Yekaterinburg, RussiaLaboratory of Sorption Methods, Vernadsky Institute of Geochemistry and Analytical Chemistry, The Russian Academy of Sciences, 119991 Moscow, RussiaBauxite 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 (Fe<sub>2</sub>O<sub>3</sub> and Al<sub>2</sub>O<sub>3</sub>) from RM. This article studies the possibility of selective Sc extraction from alkali fusion red mud (RMF) by diluted nitric acid (HNO<sub>3</sub>) leaching at pH ≥ 2 to prevent co-dissolution of Fe<sub>2</sub>O<sub>3</sub>. 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<sup>−1</sup>. Sc extraction was 71.2% at RMF leaching by HNO<sub>3</sub> at pH 2 and 80 °C during 90 min. The leaching solution contained 8 mg L<sup>−1</sup> 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 (E<sub>a</sub>) 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.https://www.mdpi.com/1996-1944/15/2/433waste recyclingrare earth elementsacid leachingkineticsshrinking core model |
| spellingShingle | Andrei Shoppert Irina Loginova Julia Napol’skikh Aleksey Kyrchikov Leonid Chaikin Denis Rogozhnikov Dmitry Valeev Selective Scandium (Sc) Extraction from Bauxite Residue (Red Mud) Obtained by Alkali Fusion-Leaching Method Materials waste recycling rare earth elements acid leaching kinetics shrinking core model |
| title | Selective Scandium (Sc) Extraction from Bauxite Residue (Red Mud) Obtained by Alkali Fusion-Leaching Method |
| title_full | Selective Scandium (Sc) Extraction from Bauxite Residue (Red Mud) Obtained by Alkali Fusion-Leaching Method |
| title_fullStr | Selective Scandium (Sc) Extraction from Bauxite Residue (Red Mud) Obtained by Alkali Fusion-Leaching Method |
| title_full_unstemmed | Selective Scandium (Sc) Extraction from Bauxite Residue (Red Mud) Obtained by Alkali Fusion-Leaching Method |
| title_short | Selective Scandium (Sc) Extraction from Bauxite Residue (Red Mud) Obtained by Alkali Fusion-Leaching Method |
| title_sort | selective scandium sc extraction from bauxite residue red mud obtained by alkali fusion leaching method |
| topic | waste recycling rare earth elements acid leaching kinetics shrinking core model |
| url | https://www.mdpi.com/1996-1944/15/2/433 |
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