Phosphogypsum secondary resource
A heterogeneous calcium-sulfate-rich residue generated during wet-process phosphoric acid manufacture from phosphate rock. It is distinct from natural gypsum mineral, phosphate-rock commodity and individual rare-earth elements. Curated laboratory evidence separates synthetic single-REE-doped model powders from an industrial residue sample. Neither experiment establishes industrial recovery, and constituent-element criticality is not inherited by the residue.
Microbial & Biochemical Mechanisms (2)
Gluconobacter spent-medium leaching of synthetic phosphogypsum models
bioleaching
Microbial
Associated Organisms:
Gluconobacter oxydans (NCBITaxon:442)
Spent medium from Gluconobacter oxydans NRRL B58 mobilized rare-earth elements from separately synthesized single-REE-doped calcium-sulfate powders. The tested agent was a microbial culture-derived lixiviant; the experiment does not demonstrate a requirement for direct living-cell contact. Organic-acid complexation and kinetic effects were proposed, without resolving the full lixiviant composition or a unique pathway.
Experimental Context & Analytical Limits:
The six separate synthetic feeds were doped with Y, Ce, Nd, Sm, Eu or Yb; they were not industrial phosphogypsum or a mixed-REE waste. Powders were synthesized from calcium/REE nitrate and sulfate/phosphate solutions, aged at 80 degrees C and dried at 90 degrees C; empirical hydration states in Table 1 were approximately 0.54-0.56 waters per formula unit, so a gypsum-dihydrate identity is not imposed on them. Section 2.2 describes glucose-grown B58 culture in a bioreactor by reference to prior methods; cell-removal preparation is not explicit in this paper. HPLC measured 220 mM gluconic acid and pH was 2.1. Triplicate leaching assays used 20 mg powder in 1 mL lixiviant at 25 degrees C for 24 h and 150 rpm. Filtered leachates were measured by ICP-OES; the repository manuscript prints a 0.22 mm filter unit, whose intended unit is not independently resolved here. Comparators were deionized water, commercial gluconic acid, sulfuric acid and phosphoric acid, with separate equal-pH and equal-molarity comparisons.
The six separate synthetic feeds were doped with Y, Ce, Nd, Sm, Eu or Yb; they were not industrial phosphogypsum or a mixed-REE waste. Powders were synthesized from calcium/REE nitrate and sulfate/phosphate solutions, aged at 80 degrees C and dried at 90 degrees C; empirical hydration states in Table 1 were approximately 0.54-0.56 waters per formula unit, so a gypsum-dihydrate identity is not imposed on them. Section 2.2 describes glucose-grown B58 culture in a bioreactor by reference to prior methods; cell-removal preparation is not explicit in this paper. HPLC measured 220 mM gluconic acid and pH was 2.1. Triplicate leaching assays used 20 mg powder in 1 mL lixiviant at 25 degrees C for 24 h and 150 rpm. Filtered leachates were measured by ICP-OES; the repository manuscript prints a 0.22 mm filter unit, whose intended unit is not independently resolved here. Comparators were deionized water, commercial gluconic acid, sulfuric acid and phosphoric acid, with separate equal-pH and equal-molarity comparisons.
Curated Evidence Points:
Support
Source:
antonick2019
Sections 2.2-2.4 and 3.1-3.2, Table 2 and Figures 2-3 establish REE release into the lixiviant in these model assays. Reported percent-dissolved values were higher for spent medium than commercial gluconic acid, but the small Ce/Nd differences and overlapping uncertainty do not establish a uniformly significant advantage. Table 2 defines errors as 95% confidence intervals from triplicates. Mineral acids adjusted to pH 2.1 and water controls yielded no detectable REEs according to Section 3.1; numerical detection limits and individual null data were not supplied.
Partial
Source:
antonick2019
At equal 220 mM concentration, sulfuric acid generally performed better than spent medium; Y was an exception with broadly similar comparator behavior. Equal acid molarity does not mean matched pH. Table 2's Ce leachate concentration and percent-dissolved ordering differ between the two organic lixiviants, limiting a simple concentration-based superiority claim. Section 4.3 explicitly warns that approximately 1 wt% REE synthetic feeds differ from more dilute, mixed industrial residues. Thermodynamic simulations omit kinetic and mass-transfer effects and do not prove the proposed mechanism. Dissolved fractions are not separated products or whole-process yields.
Gluconobacter culture-associated release from Xifeng phosphogypsum
bioleaching
Microbial
Associated Organisms:
Gluconobacter oxydans (NCBITaxon:442)
A supplier-labelled Gluconobacter oxydans culture was associated with rare-earth release and declining pH during treatment of an industrial phosphogypsum sample. Source inconsistencies and unmatched controls limit this to qualitative culture-associated mobilization; no accepted extraction percentage or demonstrated microbial advantage is assigned.
Experimental Context & Analytical Limits:
Zhang et al. used Xifeng, Guizhou material ground through 200 mesh and dried. No strain accession or independent taxonomic authentication was supplied. Culture medium started at pH 6.8; Table 4 reports glucose, calcium carbonate and yeast extract at 0.1, 0.02 and 0.01 g/L. The protocol describes 250 mL flasks, 28 degrees C, 150 rpm and nutrient addition in 100 mL then 50 mL stages. Exact timing and liquid/solid accounting are unclear. Liquid-to-solid ratios 2:1, 4:1, 8:1 and 16:1 were compared; the ratio's units and handling of changing volume were not explicit. Samples were centrifuged and supernatants measured by ICP-MS. Culture removal before contact was not reported; this is not assumed to be a cell-free lixiviant assay.
Zhang et al. used Xifeng, Guizhou material ground through 200 mesh and dried. No strain accession or independent taxonomic authentication was supplied. Culture medium started at pH 6.8; Table 4 reports glucose, calcium carbonate and yeast extract at 0.1, 0.02 and 0.01 g/L. The protocol describes 250 mL flasks, 28 degrees C, 150 rpm and nutrient addition in 100 mL then 50 mL stages. Exact timing and liquid/solid accounting are unclear. Liquid-to-solid ratios 2:1, 4:1, 8:1 and 16:1 were compared; the ratio's units and handling of changing volume were not explicit. Samples were centrifuged and supernatants measured by ICP-MS. Culture removal before contact was not reported; this is not assumed to be a cell-free lixiviant assay.
Curated Evidence Points:
Support
Source:
zhang2025
Sections 2.3 and 3.2-3.3 with Figures 5-7 report increasing supernatant REE signals with declining pH in culture-containing laboratory flasks. Table 1 and XRD Figure 2 support a mixed calcium-sulfate-rich feed; individual REE host phases were not established. The observation does not itself identify the chemical form of released REEs or an isolated recovered product.
Partial
Source:
zhang2025
Figure 7 labels the release axis in micrograms/kg while Section 2.3.3 reports micrograms/L, and its plotted maximum is around day 24 rather than the conclusion's approximately day 21. Table 2's feed inventory, the stated liquid-to-solid treatment and the reported 24.67% total extraction lack a reproducible common denominator. The pH experiment compares inoculated acidic arms with an uninoculated pH 6.8 control, without a matched acidified sterile control. Figure error bars lack a stated replicate number or error definition in the inspected article. Organic-acid identities and concentrations were not measured here. Neither the 24.67% total nor 55.67% Nd claim is accepted as a verified recovery yield.
Sources & References
-
antonick2019: Antonick et al. (2019). Bio- and mineral acid leaching of rare earth elements from synthetic phosphogypsum. Journal of Chemical Thermodynamics 132:491-496. DOI 10.1016/j.jct.2018.12.034; Sections 2.1-2.4, 3.1-3.3 and 4.1-4.3, Tables 1-2 and Figures 1-3.
https://doi.org/10.1016/j.jct.2018.12.034 (accessed 2026-10-11) -
antonick_osti_copy: OSTI 1862749, LLNL-JRNL-820031 repository manuscript of Antonick et al. (2019); PDF pages 3-8, manuscript pages 1-6. Repository cover dated 1 March 2021; this is the same experiment, not a new 2021 study.
https://www.osti.gov/servlets/purl/1862749 (accessed 2026-10-11) -
zhang2025: Zhang, Qi, He, Zhang, Zhang and Su (2025). Study on the Extraction of Rare Earth Elements (REEs) from Phosphogypsum Using Gluconobacter oxydans Culture Solution. Molecules 30(3):674. DOI 10.3390/molecules30030674; Sections 2.1-2.4 and 3.1-3.3, Tables 1-2 and 4, Figures 5-8.
https://doi.org/10.3390/molecules30030674 (accessed 2026-10-11) -
ncbi_gluconobacter: NCBI Taxonomy 442 - Gluconobacter oxydans; species
https://eutils.ncbi.nlm.nih.gov/entrez/eutils/efetch.fcgi?db=taxonomy&id=442&retmode=xml (accessed 2026-10-11)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-11T09:02:35.258837+00:00 |
Codex (GPT-6; Codex) | CREATE | Created phosphogypsum identity with distinct synthetic-model and actual-residue assays; retained null controls and source uncertainties without accepting inconsistent industrial-feed yields. |
Record source: data/records/phosphogypsum.yaml