Discarded light-emitting-diode lamps secondary resource
Discarded LED lighting assemblies and their prepared mixed powder, represented here by lamps collected from electrical stores. This manufactured waste resource is distinct from fluorescent-lamp phosphor, LCD panels, an isolated LED semiconductor or its constituent elements. The selected study does not establish a universal lamp composition or which components were removed before milling. No constituent-element criticality designation is inherited.
Microbial & Biochemical Mechanisms (1)
Rare-earth mobilization by acidogenic culture supernatant
bioleaching
Microbial
Associated Organisms:
Acidithiobacillus thiooxidans (NCBITaxon:930)
Acidic supernatant produced by living Acidithiobacillus thiooxidans cultures was used to leach prepared discarded-lamp powder after centrifugation. The laboratory study reports praseodymium and neodymium mobilization, with lower source-reported extraction percentages at higher powder loadings. It does not establish direct cell contact, a unique enzyme or EPS pathway, a general advantage over reagent acid, or isolated rare-earth products.
Experimental Context & Analytical Limits:
Store-collected discarded lamps were ground manually and mechanically and sieved at 75 micrometres. Lamp models, component selection and complete pretreatment history are not supplied. Table 1 reports Pr 137 and Nd 73 mg/kg by feed digestion and ICP-OES, with Fe 321000 mg/kg; these are batch measurements, not a purified phosphor or semiconductor composition. The authors identify the culture as PTCC 1717 supplied by IROST; a current collection entry was not independently resolved. Acid generation used 100 mL modified 9K medium in 250 mL flasks, 5 g/L elemental sulfur, 30 degrees C and 140 rpm for up to 30 days, comparing 2, 5 and 10% v/v inocula. The selected 5% preparation was centrifuged at 6000 rpm for 30 minutes; sterility of the supernatant was not demonstrated. Leaching tested 10, 30 and 50 g/L powder at 30 degrees C and 140 rpm, with a 72-hour comparison and time courses to 14 days. The authors report triplicate bioleaching experiments and mean plus/minus standard error for the chemical comparison. Leaching working volume, liquid sample separation and a complete analytical recovery balance are not specified. Reagent sulfuric acid was described as 0.1 M at 10 g/L under the same nominal temperature, agitation and 72-hour duration. Actual initial pH differed: 1.2 for chemical acid and 0.8 for the culture supernatant.
Store-collected discarded lamps were ground manually and mechanically and sieved at 75 micrometres. Lamp models, component selection and complete pretreatment history are not supplied. Table 1 reports Pr 137 and Nd 73 mg/kg by feed digestion and ICP-OES, with Fe 321000 mg/kg; these are batch measurements, not a purified phosphor or semiconductor composition. The authors identify the culture as PTCC 1717 supplied by IROST; a current collection entry was not independently resolved. Acid generation used 100 mL modified 9K medium in 250 mL flasks, 5 g/L elemental sulfur, 30 degrees C and 140 rpm for up to 30 days, comparing 2, 5 and 10% v/v inocula. The selected 5% preparation was centrifuged at 6000 rpm for 30 minutes; sterility of the supernatant was not demonstrated. Leaching tested 10, 30 and 50 g/L powder at 30 degrees C and 140 rpm, with a 72-hour comparison and time courses to 14 days. The authors report triplicate bioleaching experiments and mean plus/minus standard error for the chemical comparison. Leaching working volume, liquid sample separation and a complete analytical recovery balance are not specified. Reagent sulfuric acid was described as 0.1 M at 10 g/L under the same nominal temperature, agitation and 72-hour duration. Actual initial pH differed: 1.2 for chemical acid and 0.8 for the culture supernatant.
Curated Evidence Points:
Support
Source:
nadi2025
Materials and methods, Figures 2 and 5 and Table 5 support a conditional culture-derived lixiviant observation. At 10 g/L and three days, Table 5 reports extraction efficiencies of 43 +/- 0.86% Pr and 28 +/- 0.56% Nd for bioleaching. These are source-reported percentages, not independently reconstructed yields: Equation 1 defines its concentration denominator as residual powder and its numerator as initial solution, while calling a mass in kg pulp density. The intended inventory normalization is unresolved. No purified product or complete metal mass balance was measured.
Partial
Source:
nadi2025
Table 5 gives reagent-acid results of 0.0% Pr and 80 +/- 1.6% Nd, so the chemical comparator performs better for Nd. The 0.0% Pr token is not a verified analytical detection limit. Figure 9 shows unequal pH trajectories; its chemical-acid day-one pH near 3.1 also differs from the prose value 2.5. These comparisons do not isolate an EPS or enzymatic contribution from acidity and medium composition. A no-inoculum acid production control appears in Figure 1, but that is not a pH-matched control for the later lamp leaching.
Partial
Source:
nadi2025
Quantitative inconsistencies remain: Table 6 instead labels the three-day result as Pr 46.76% and Nd 28.59%; the conclusion misnames its loading-response elements as Co and Pr, unlike Figure 2's Pr and Nd. Figure 5 shows later Nd decline and a small later Pr maximum, so three days is not an uncontested optimum for every endpoint. Abstract wording that 5% inoculum produces the most acid differs from Figure 1 and the Results, which show slightly higher sulfate at 10%. Reported sulfate includes medium background and is not a corrected sulfur yield.
Partial
Source:
nadi2025
Figures 4 and 6-8 characterize changing residual material; FTIR, XRD and selected SEM-EDX regions do not independently prove that an iron layer caused declining Nd release, quantify bulk removal, or identify an enzyme, EPS complex or dissolved REE species. Nutrient inhibition, agglomeration, hydroxide precipitation and tetrad-effect explanations are interpretations, not separately isolated causes. The Scale up section discusses future options; it reports no larger LED trial, industrial deployment or techno-economic validation.
Sources & References
-
nadi2025: Nadi, Pourhossein and Mousavi (2025). Sustainable bio-extraction of rare earth elements from discarded LED lamps. Scientific Reports 15:21655. DOI 10.1038/s41598-025-04937-x, published 1 July 2025; Materials and methods, Results and discussion, Tables 1-6 and Figures 1-9; full publisher PDF.
https://doi.org/10.1038/s41598-025-04937-x (accessed 2026-10-11) -
ncbi_thiooxidans: NCBI Taxonomy 930: Acidithiobacillus thiooxidans, species. This identifier does not identify or authenticate the study's PTCC 1717 stock.
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=930&mode=Info (accessed 2026-10-11)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-11T14:55:14.811850Z |
Codex (GPT-6; Codex) | CREATE | Created the distinct discarded LED lamp resource with centrifuged culture-acid leaching evidence, retaining chemical-comparator superiority for Nd, mismatched pH and unresolved source normalization and numerical inconsistencies. |
Record source: data/records/discarded-led-lamps.yaml