Samarium-cobalt magnet scrap secondary resource
Source-labelled samarium-cobalt magnet scrap supplied by the Defence Metallurgical Research Laboratory, Hyderabad, India. Its preceding service history and manufacturing-waste category were not disclosed, so the feed is not asserted to be end-of-life devices. It is distinct from NdFeB magnet waste, the broad rare-earth permanent-magnet commodity grouping, pure Sm2Co17 and its constituent elements. The characterized preparation includes oxide phases as well as a Sm2Co17 assignment. No criticality designation or microbial recovery is inherited from the feed's constituents.
Microbial & Biochemical Mechanisms (2)
Abiotic acid-peroxide mobilization from ground SmCo scrap
separation
Hydrochloric-acid/peroxide treatment mobilized samarium and cobalt from ground scrap into a multimetal leach liquor. Higher acid concentration, temperature and duration generally increased measured extraction within the factorial design. This is an abiotic laboratory extraction assay, not microbial dissolution, isolated product recovery or an industrial recycling demonstration.
Experimental Context & Analytical Limits:
Scrap was crushed, pulverized and sieved to the minus-150 plus-106 micrometre fraction. Section 3.1 reports 32.2% Sm, 47.6% Co, 14.2% Fe and 4.2% Cu. Figure 1 assigns Sm2Co17, Cu2O and Fe3O4; this mixed feed is not treated as a pure stoichiometric alloy. Leaching used 8 g powder in 400 mL solution in a 500 mL double-walled stirred reactor with bath temperature control. The factorial experiment varied HCl 2-10% v/v, temperature 50-80 degrees C and time 1-4 h, with three center-point runs at 6% HCl, 65 degrees C and 2.5 h. Methods specify 5% v/v H2O2 for all leaches, but Conclusions specify 1%; this unresolved recipe conflict is retained. No microbial arm or matched peroxide-free series was presented. HCl stock concentration and leach stirring speed are not supplied sufficiently to convert the reported recipe to molarity or a fully specified mixing protocol.
Scrap was crushed, pulverized and sieved to the minus-150 plus-106 micrometre fraction. Section 3.1 reports 32.2% Sm, 47.6% Co, 14.2% Fe and 4.2% Cu. Figure 1 assigns Sm2Co17, Cu2O and Fe3O4; this mixed feed is not treated as a pure stoichiometric alloy. Leaching used 8 g powder in 400 mL solution in a 500 mL double-walled stirred reactor with bath temperature control. The factorial experiment varied HCl 2-10% v/v, temperature 50-80 degrees C and time 1-4 h, with three center-point runs at 6% HCl, 65 degrees C and 2.5 h. Methods specify 5% v/v H2O2 for all leaches, but Conclusions specify 1%; this unresolved recipe conflict is retained. No microbial arm or matched peroxide-free series was presented. HCl stock concentration and leach stirring speed are not supplied sufficiently to convert the reported recipe to molarity or a fully specified mixing protocol.
Curated Evidence Points:
Support
Source:
nayak2021
Sections 2.1-2.3.1 and 3.1-3.2, Figure 1 and Tables 1-2 establish the feed and chemical extraction. Table 1 retains incomplete extraction in lower-acid conditions. Table 2 reports 98.5% Sm and 99.00% Co extraction in the additional 15% v/v HCl, 70 degrees C, 3 h experiment; these are solution-extraction percentages for that reported arm, conditional on the unresolved peroxide recipe, not recovered-product yields. The resulting liquor reported in Section 3.3 contains Sm, Co, Fe and Cu, demonstrating nonselective initial mobilization rather than pure samarium recovery.
Partial
Source:
nayak2021
Table 2 explicitly caps model predictions above 100% at 100% for the 15% HCl arm, outside the factorial acid range. Capped predictions do not validate an exact complete-extraction model. Center-point replication does not establish replication of every treatment. The 5% versus 1% peroxide discrepancy prevents assignment of a single unqualified optimized recipe or causal peroxide contribution.
Partial
Source:
nayak2021_si
Tables S1-S2 report statistical fits, including significant curvature for Sm. These model statistics do not prove a unique molecular reaction pathway or supply an independently validated prediction beyond the experimental domain.
Abiotic samarium precipitation followed by oxalate and oxide conversion
recovery
Sodium-sulfate treatment removed samarium from the chemically produced liquor into a precipitate, followed by oxalic-acid conversion and calcination. Diffraction supports source-assigned samarium oxalate and oxide products. The supplementary balance does not reconcile with the reported feed samarium inventory, so no overall feed-to-product recovery percentage or independently measured product purity is accepted.
Experimental Context & Analytical Limits:
Sections 2.3.3 and 3.3 use Na2SO4 at 5% w/v, pH 1, 50 degrees C, 300 rpm and 10 min for samarium double-sulfate precipitation. The washed precipitate was converted with 0.5 M oxalic acid at room temperature, 300 rpm for 1 h and a reported 5% w/v solids loading. Filtered and dried oxalate was calcined at 800 degrees C for 1 h. These are sequential laboratory unit operations on the same study feed, not independent experiments or a demonstrated continuous plant. Later iron precipitation and Cu/Co solvent-extraction/stripping stages are described in the original flowsheet, but no isolated copper or cobalt metal product is demonstrated by their aqueous strip solutions.
Sections 2.3.3 and 3.3 use Na2SO4 at 5% w/v, pH 1, 50 degrees C, 300 rpm and 10 min for samarium double-sulfate precipitation. The washed precipitate was converted with 0.5 M oxalic acid at room temperature, 300 rpm for 1 h and a reported 5% w/v solids loading. Filtered and dried oxalate was calcined at 800 degrees C for 1 h. These are sequential laboratory unit operations on the same study feed, not independent experiments or a demonstrated continuous plant. Later iron precipitation and Cu/Co solvent-extraction/stripping stages are described in the original flowsheet, but no isolated copper or cobalt metal product is demonstrated by their aqueous strip solutions.
Curated Evidence Points:
Support
Source:
nayak2021
Sections 3.3.1-3.3.4 and Figures 2-3 support pH- and sulfate-dependent samarium removal: essentially no precipitation at pH 0.5 and about 94% at pH 1 under the stated conditions. The denominator is dissolved Sm entering that precipitation step, not original scrap Sm. Raising pH above 1 increases iron coprecipitation; varying stirring time over 5-40 min or aging over 5-15 min had little reported effect. The study reports isolation and conversion of the precipitate.
Support
Source:
nayak2021_si
Figure S1 on page S4 shows diffraction patterns assigned to Sm2O3 and Sm2(C2O4)3, supporting product formation after the stated treatment. Diffraction identification does not quantify all impurity phases or establish a numerical chemical purity.
Partial
Source:
nayak2021_si
Table S3 lists 20 g starting scrap and 12.47 g Sm2O3 product, together with an overall recovery of 84.83%. At the main paper's 32.2% Sm feed composition, only 6.44 g Sm enters; a pure 12.47 g Sm2O3 product would require more Sm than this inventory. This curator mass-balance inconsistency remains unresolved, rather than being repaired by assuming a different feed or product purity. The table also prints Sm2(CO4)3 where the figure identifies oxalate. Its 84.83% value is retained as an unverified source claim, not an accepted overall recovery measurement.
Partial
Source:
nayak2021
Figure 12 is a proposed integrated flowsheet. Section 3.4 alternates CaO and NaOH for iron precipitation, and the Cu stripping text and Figure 7 caption express different acid recipes; these are not silently reconciled into a transferable process specification. Product purity, complete multielement mass closure, recycled-water performance and suitability of the final raffinate for discharge are not independently established by the displayed flowsheet.
Sources & References
-
nayak2021: Nayak, Behera, Sarangi, Ghosh and Basu (2021; online 22 December 2020). Process Flowsheet Development for Separation of Sm, Co, Cu, and Fe from Magnet Scrap. ACS Omega 6:188-196. DOI 10.1021/acsomega.0c04132; complete original via PMC7807480, Sections 2-4, Tables 1-2 and Figures 1-12.
https://doi.org/10.1021/acsomega.0c04132 (accessed 2026-10-14) -
nayak2021_si: Nayak et al., Supporting Information, ao0c04132_si_001.pdf, four pages: Tables S1-S2 model statistics, Table S3 samarium material balance and Figure S1 product diffraction. Same experiment family as the main article.
https://pmc.ncbi.nlm.nih.gov/articles/instance/7807480/bin/ao0c04132_si_001.pdf (accessed 2026-10-14)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-14T18:49:59.799746+00:00 |
Codex (GPT-6; Codex) | CREATE | Created source-labelled SmCo scrap with abiotic leaching and qualified product conversion after full main and supplement inspection; retained peroxide and mass-balance contradictions without an overall recovery claim. |
2026-10-14T18:59:06.310276+00:00 |
Codex (GPT-6; Codex) | EDIT | Corrected the precipitation source locator to Section 2.3.3 after independently saved F1 and issue 260; conditions and scientific claims are unchanged. |
Record source: data/records/samarium-cobalt-magnet-scrap.yaml