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Spent fluorescent-lamp phosphor powder secondary resource

A mixed secondary resource from spent fluorescent lamps. The curated assay concerns retorted phosphor powder supplied by Idaho National Laboratory, rather than untreated whole lamps, a single mineral species, an element, or a purified rare-earth commodity. Its total rare-earth leaching outcome is not assigned to any individual element. No criticality designation is inherited from the elements present in this waste.

Microbial & Biochemical Mechanisms (1)

Rare-earth release from retorted phosphor by Gluconobacter biolixiviant

bioleaching Microbial

Associated Organisms: Gluconobacter oxydans (NCBITaxon:442)

Acidic biolixiviant produced by living Gluconobacter oxydans B58-derived cultures solubilized rare-earth elements from retorted lamp phosphor. Cultures were centrifuged before the clarified biolixiviant contacted the solid. A pstC transposon disruption increased total rare-earth extraction relative to proxy wild-type. The endpoint is dissolved material in filtered leachate, not separation into purified products.

Experimental Context & Analytical Limits:
Laboratory assays used 20 mg retorted phosphor powder per 500 microlitres biolixiviant (4% w/v) in 1.7 mL tubes, shaken horizontally for 36 h at room temperature. Biolixiviant production followed 48 h culture in yeast-peptone-mannitol medium with kanamycin; cultures were normalized to OD 1.9, diluted equally with 40% glucose to give 20% glucose, then incubated two days at room temperature and 800 rpm. Acidity was measured as an outcome, not held at one common pH. Cultures were centrifuged at 3200 x g for 10 min before supernatant transfer to powder. Following leaching, solids were pelleted and supernatant filtered at 0.45 micrometres for ICP-MS. Each disruption strain had five biological replicates; the no-bacteria glucose control had five replicates, and proxy wild-type had fifteen. The species-level taxonomy identifier does not separately identify B58 or the mutants. Retorting conditions and a batch-specific feed composition are not established by the 2021 assay methods. No industrial bioleaching deployment or product-purity endpoint is demonstrated.
Curated Evidence Points:
Methods, Direct measurement of biolixiviant pH and Direct measurement of REE bioleaching, and Fig. 4C support the clarified-lixiviant assay. The Results report total extraction efficiencies of 5.5% for the pstC disruption and 4.7% for proxy wild-type, described as an 18% relative improvement. These rounded total-REE percentages are neither an 18 percentage-point gain nor an Nd-specific yield. Fig. 4's denominator uses previously published REE amounts in the phosphor; it is not a newly verified batch-specific total digestion here.
Results, Disrupting the phosphate transport system increases bioleaching, identifies pstC as the improved strain retaining significance after multiple-comparison correction; the broader set of six nominal improvements did not all retain significance after that correction. A proposed phosphate sensing and acid-production explanation remains a hypothesis. Fig. 4D and the glucose-control assays show residual release from poorly acidifying mgdh and pqqC disruption strains, so activity is not attributed exclusively to one enzyme. The clarified preparation was not reported as sterile-filtered before leaching, and these data do not demonstrate direct cell-mineral contact as a requirement.

Sources & References

  1. schmitz2021: Schmitz et al. (2021). Generation of a Gluconobacter oxydans knockout collection for improved extraction of rare earth elements. Nature Communications 12:6693.
    https://doi.org/10.1038/s41467-021-27047-4 (accessed 2026-10-09)
  2. 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 2026-10-09)

Curation History

Timestamp Curator Action Summary
2026-10-09T04:47:54Z Codex (GPT-6; Codex) evidence_curation Created a scoped secondary-resource record from the Schmitz et al. 2021 retorted-powder assay, keeping total-REE yields, controls, pretreatment uncertainties and laboratory scale explicit. Independent scientific review is recorded separately.

Record source: data/records/fluorescent-lamp-phosphor.yaml