Holmium element Critical Material

Holmium association with harvested cyanobacterial biomass

Experimental Context & Analytical Limits:
The study reports Arthrospira platensis CNMN-CB-02 from the Institute of Microbiology and Biotechnology, Technical University of Moldova. The official collection lists CB-02 as Spirulina platensis. NCBI maps both species names to Limnospira platensis; the species identifier does not verify a strain genome or a strain-specific NCBI node. Living cultures were exposed to Ho(III), supplied as Ho(NO3)3·5H2O, in separate single-element treatment series at 10, 20 and 30 mg/L elemental concentration. These are not mixed-REE selectivity assays. Supplementation occurred on day 1 with 0.4 g/L inoculum, followed by five more days of cultivation. Flasks held 500 mL of nutrient medium, including 8 g/L bicarbonate and 0.08 g/L EDTA, at pH 10.0 and 30 degrees C. Illumination was reported as 55 µM photons/m2/s; the paper uses this nonstandard printed unit, retained without silently converting it. Cultures were shaken at 100 rpm for 45 min twice daily, 12 h apart. Controls were cultures grown without added REEs. Experiments were reported in triplicate, with Student t-tests against controls. Biomass was retained on 5-8 µm filters and part was dried for instrumental neutron activation analysis (NAA); reference materials supported analytical quality control. The methods do not describe a post-filtration wash, a biomass-free exposure control or cell-surface versus intracellular fractionation. NAA measures total element in the harvested dried fraction, not free-ion speciation or aqueous depletion. Initial solution concentrations were checked by ICP-OES, but no final dissolved-element balance is reported for this experiment. No desorption, isolated product or industrial demonstration was tested.

Curated Evidence Points: