Used photographic fixer solutions secondary resource
Silver-bearing liquid discarded after photographic fixing, represented here by used black-and-white film fixer collected from a local processing unit. This secondary feed is distinct from discarded solid films, unused fixer, developer solutions and prepared silver salts. Its composition is source-specific; constituent criticality is not inherited.
Microbial & Biochemical Mechanisms (1)
Bacterial conditioning and fungal biosorption before chemical silver recovery
recovery
Microbial
Associated Organisms:
Thiobacillus thioparus (NCBITaxon:931), Cladosporium cladosporioides (NCBITaxon:29917)
Thiobacillus thioparus MCM B-39 treated diluted fixer before silver sorption onto harvested Cladosporium cladosporioides number 1 biomass beads. Chemical elution and electrowinning followed; the final metallic product was not produced by microbial reduction. Bead viability and matrix composition are unresolved in this paper.
Experimental Context & Analytical Limits:
Sections 2.1-2.4 describe 25 mL bacterial inoculum at 10^7 cells/mL added to 250 mL nominally 1:10 diluted fixer, pH 6.5, approximately 25 degrees C and 120 rpm for four days. Centrifugation and filtration preceded sorption. Section 2.7 then diluted treated liquid to nominal 100 mg Ag/L and passed it upwards through 3 g beads in a 10 cm by 1 cm internal-diameter column with 20 min retention. The fungal biomass was grown separately, washed and granulated by a proprietary process. Alcoholic cyanide elution and electrolysis at 0.8 V and 224 mA completed the laboratory sequence; scale-up and economics were not established.
Sections 2.1-2.4 describe 25 mL bacterial inoculum at 10^7 cells/mL added to 250 mL nominally 1:10 diluted fixer, pH 6.5, approximately 25 degrees C and 120 rpm for four days. Centrifugation and filtration preceded sorption. Section 2.7 then diluted treated liquid to nominal 100 mg Ag/L and passed it upwards through 3 g beads in a 10 cm by 1 cm internal-diameter column with 20 min retention. The fungal biomass was grown separately, washed and granulated by a proprietary process. Alcoholic cyanide elution and electrolysis at 0.8 V and 224 mA completed the laboratory sequence; scale-up and economics were not established.
Curated Evidence Points:
Support
Source:
pethkar2003
Sections 2.2-2.4, Table 1 and Results pp.857-859 support real-waste origin, thiosulfate depletion with sulfur/sulfate production and subsequent silver recovery. The authors report 127 mg metallic silver and 70% overall recovery. These are source-reported process outcomes, not independently reconciled yields or product-purity measurements. The bacterial step alone did not substantially remove silver.
Partial
Source:
pethkar2003
Section 2.2 assigns 2.8 g Ag/L and 18.5 g thiosulfate/L before dilution, while Table 1 labels those concentrations as 1:10 diluted; Section 2.7 instead gives about 280 mg Ag/L after bacterial treatment. Sulfate is 32.25 g/L in Table 1 versus 31.16 in Results and 31.2 in the abstract. No repaired inventory or detection-limit-derived zero is inferred. Section 2.5 gives 1% ethanol in the eluent but Results gives 10%; the recipe remains unresolved. Cumulative column uptake is expressed per gram biomass in Results versus per gram beads in Methods; bead biomass fraction is unspecified.
Partial
Source:
pethkar2003
An uninoculated fixer control is specified, but its separate endpoint results are not presented. No matched untreated-fixer column, matrix-only control or independent replicate count is reported. Figures 1-6 concern prepared silver solutions, not real-feed recovery; plotted dose/time ranges and plateaus differ from some textual optimization claims. Fitted monolayer capacity is not cumulative column uptake, and model agreement does not establish a molecular binding mechanism. A complete process mass balance and phase/purity characterization of the recovered metal are unavailable.
Sources & References
-
pethkar2003: Pethkar and Paknikar (2003). Thiosulfate biodegradation-silver biosorption process for the treatment of photofilm processing wastewater. Process Biochemistry 38:855-860. DOI 10.1016/S0032-9592(02)00054-7; complete original text read through the author-shared six-page PDF web rendition, with Table 1 and all six original publisher figures separately checked.
https://doi.org/10.1016/S0032-9592(02)00054-7 (accessed 2026-10-14) -
ncbi_thioparus: NCBI Taxonomy 931: Thiobacillus thioparus, species; does not identify MCM B-39
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=931 (accessed 2026-10-14) -
ncbi_cladosporioides: NCBI Taxonomy 29917: Cladosporium cladosporioides, species; does not authenticate strain number 1
https://www.ncbi.nlm.nih.gov/Taxonomy/Browser/wwwtax.cgi?id=29917 (accessed 2026-10-14)
Curation History
| Timestamp | Curator | Action | Summary |
|---|---|---|---|
2026-10-14T20:48:15.758449Z |
Codex (GPT-6; Codex) | CREATE | Created the distinct used-fixer liquid resource and qualified laboratory bacterial conditioning, fungal biomass sorption and abiotic silver recovery sequence. Preserved source dilution, recipe, denominator and control limitations; no criticality or industrial deployment inferred. |
Record source: data/records/used-photographic-fixer-solutions.yaml