Xenotime concentrate primary resource
A mixed natural mineral concentrate represented by the laboratory feed studied by He et al. (2024), containing source-assigned xenotime, monazite, zircon, almandine and ilmenite. Its deposit, supplier and concentration history are not specified in the reviewed article and supplement. Particle counting and density conversion estimated about 82.0 wt% xenotime and 2.7 wt% monazite; these are sample-specific phase estimates, not measured product purity. The feed is distinct from the xenotime-(Y) mineral species, monazite species, elemental rare earths, a rare-earth commodity and a secondary waste resource. No criticality designation is inherited from its constituent elements.
Microbial & Biochemical Mechanisms (1)
Bacterial enhancement of rare-earth mobilization from mixed phosphate concentrate
bioleaching
Microbial
Associated Organisms:
Bacillus thuringiensis (NCBITaxon:1428)
A culture identified by the authors as Bacillus thuringiensis enhanced aqueous rare-earth release from the mixed concentrate relative to corresponding abiotic controls. Unbuffered cultures acidified strongly; enhanced release also occurred in MES-buffered medium near pH 6. Metabolite profiles and separate organic-acid leaching assays support a contribution from proton attack and organic ligands, without resolving each metabolite's contribution in the living culture. This is laboratory bio-weathering and mobilization, with partial immobilization in secondary precipitates, not an isolated rare-earth product or an industrial recovery process.
Experimental Context & Analytical Limits:
The isolate came from topsoil at the Renju regolith-hosted rare-earth deposit in Guangdong, China; that location is not established as the concentrate's origin. Section 2.2 refers to sequence comparison by BLAST but supplies no isolate accession or independently verifiable sequence in the reviewed article and supplement. Concentrate was crushed and sieved to 48-74 micrometres, washed ultrasonically with ethanol and ultrapure water and freeze-dried. Assays used 0.5 g of sterile feed and 100 mL medium in 250 mL flasks, approximately 1e6 CFU/mL initially, 180 rpm and 25-28 degrees C for 30 days. Cells were harvested in exponential phase and washed three times. Medium contained, in g/L, glucose 10, NH4Cl 1, MgSO4.7H2O 1 and KCl 0.2, initially pH 6, with or without 20 mmol/L MES. No additional phosphorus was supplied. Each medium had a biotic feed arm, an abiotic feed control and a cells-only control. Time-course measurements used three replicates; metabolomics on days 4, 8 and 15 used six biotic-feed and five cells-only replicates. CFU counts exclude attached cells. Aqueous elemental analyses used centrifuged, 0.22-micrometre-filtered samples and ICP-MS. Separate chemical tests used 0.1 g feed in 20 mL of HCl or 1 mmol/L organic-acid solution, initial pH 3, 5 or 6, at the same temperature and agitation for 96 h in triplicate. These chemical assays were not a 30-day pH-trajectory-matched replacement for the biological experiment.
The isolate came from topsoil at the Renju regolith-hosted rare-earth deposit in Guangdong, China; that location is not established as the concentrate's origin. Section 2.2 refers to sequence comparison by BLAST but supplies no isolate accession or independently verifiable sequence in the reviewed article and supplement. Concentrate was crushed and sieved to 48-74 micrometres, washed ultrasonically with ethanol and ultrapure water and freeze-dried. Assays used 0.5 g of sterile feed and 100 mL medium in 250 mL flasks, approximately 1e6 CFU/mL initially, 180 rpm and 25-28 degrees C for 30 days. Cells were harvested in exponential phase and washed three times. Medium contained, in g/L, glucose 10, NH4Cl 1, MgSO4.7H2O 1 and KCl 0.2, initially pH 6, with or without 20 mmol/L MES. No additional phosphorus was supplied. Each medium had a biotic feed arm, an abiotic feed control and a cells-only control. Time-course measurements used three replicates; metabolomics on days 4, 8 and 15 used six biotic-feed and five cells-only replicates. CFU counts exclude attached cells. Aqueous elemental analyses used centrifuged, 0.22-micrometre-filtered samples and ICP-MS. Separate chemical tests used 0.1 g feed in 20 mL of HCl or 1 mmol/L organic-acid solution, initial pH 3, 5 or 6, at the same temperature and agitation for 96 h in triplicate. These chemical assays were not a 30-day pH-trajectory-matched replacement for the biological experiment.
Curated Evidence Points:
Support
Source:
he2024
Sections 2.3 and 3.2-3.4 and Figures 1-3 show enhanced aqueous rare-earth release in both bacterial feed arms compared with their abiotic controls. The unbuffered culture reached about pH 3 and the text reports a maximum total rare-earth concentration of about 716 micrograms/L on day 15, followed by a decline and partial increase. The buffered culture reached about 343 micrograms/L at day 30. These are filtered aqueous concentrations, not cumulative extraction fractions or isolated product yields. The later decline and observed precipitates prevent treating solution concentration as total mineral loss.
Partial
Source:
he2024
Figures 4-6 and Sections 3.5-3.6 and 4.2 link bacterial growth to organic-acid profiles and show acid-dependent chemical leaching, including tartaric-acid activity near pH 6. Many tested organic acids perform similarly to HCl at pH 3; proton and ligand contributions depend on conditions. Normalized MS signals are not absolute extracellular acid concentrations. No genetic intervention, spent-medium reconstruction or individual-metabolite contribution in the live culture was demonstrated. Figure 5's caption calls the cells-only comparator Exp-Control, whereas its legend and Methods identify it as Exp-Bt; the abiotic mineral control remains a separate arm. Section 2.4 prints 0.22 mm for chemical-solution filters, whereas Section 2.5.1 specifies 0.22 micrometres for analyzed suspensions. These preparation descriptions are not silently harmonized.
Partial
Source:
he2024_supplement
Figure S1 and Tables S2-S4 support a mixed mineral feed and distinct rare-earth distributions among its phases. Phase weight fractions derive from particle counts and assumed densities. Quantitative source inconsistencies remain: Figure S1 repeats the same reference-card number for almandine and ilmenite; xenotime Yb and Lu values in Tables S3 and S4 do not agree under straightforward oxide-to-element conversion. Main Table 1's TiO2 content also does not close against the tabulated phase fractions and compositions. Its printed P2O3 and U2O3 labels are retained as source uncertainties, not silently relabeled. Whole-feed Y was above the XRF upper limit, not absent. These limitations preclude a new closed elemental mass balance or a precise recovery efficiency from the phase estimates.
Partial
Source:
he2024
Table 3 estimates 0.03% xenotime and 0.3% monazite dissolution for the unbuffered day-15 solution. These are two-component calculations from aqueous rare-earth composition, not measured separate-mineral mass losses. They assume the two phosphates supply the dissolved rare earths and negligible differential re-sorption or precipitation. Figure 7 and Section 4.3 show secondary REE- and P-bearing precipitates, but their mineral identities could not be established by micro-XRD, TEM or Raman. Rhabdophane- or churchite-type assignments are proposed analogies, not identified products. This qualifies the dissolution model and supports only conditional preferential monazite dissolution, without proving a general species-level rate ratio.
Context_only
Source:
he2024_supplement
Actual Figure S6 models phosphate saturation and Figure S7 compares modeled and measured solution composition; their numbering is reversed in the contents list. Table S7 and Text S1 apply the concentrate's 1.38 square metres/g surface area to both phosphate phases by assumption. Phase-specific rates therefore are model dependent. Main Equation 1 also calls this a prepared granite sample despite the study's concentrate feed. No calculated mineral-specific rate is promoted to a direct measurement or an industrial design parameter here.
Sources & References
-
he2024: He Y, Ma L, Liang X, Li X, Zhu J and He H (2024). Resistant rare earth phosphates as possible sources of environmental dissolved rare earth elements: Insights from experimental bio-weathering of xenotime and monazite. Chemical Geology 661:122186. DOI 10.1016/j.chemgeo.2024.122186; complete 56-page GFZ author postprint including repository cover, Figures 1-7 and Tables 1-3.
https://doi.org/10.1016/j.chemgeo.2024.122186 (accessed 2026-10-12) -
he2024_supplement: He et al. (2024), original publisher Supplementary Materials, 16 pages, Figures S1-S7, Tables S1-S8 and Text S1. Actual item captions are used; the page-2 contents list has inconsistent figure and table numbering.
https://ars.els-cdn.com/content/image/1-s2.0-S0009254124002663-mmc1.pdf (accessed 2026-10-12) -
ncbi_thuringiensis: NCBI Taxonomy 1428, Bacillus thuringiensis, species in the Bacillus cereus group. This maps the authors' species name and does not independently identify their experimental isolate.
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=1428&mode=Info (accessed 2026-10-12)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-12T07:41:53Z |
codex (GPT-6) | CREATE | Added a distinct mixed xenotime-concentrate resource from the complete primary postprint and publisher supplement. Preserved abiotic controls, strain uncertainty, source inconsistencies and model-dependent dissolution boundaries without claiming recovery. |
Record source: data/records/xenotime-concentrate.yaml