This water-treatment paper tests metallic bismuth microspheres as a reducing material to remove bromate, a disinfection by-product, from water, with and without ultraviolet light. Because bismuth can enter treated water, the authors also measured residual dissolved bismuth: it stayed between 10 and 20 µg/L in the reactor experiments and was not detected (below 0.3 µg/L) after passing the water through natural clinoptilolite.
Key numbers
- Residual bismuth in treated water after reaction: 10 to 20 µg/L across the initial bromate concentrations tested (p. 4151; detailed values in supplementary Table S6, not reviewed).
- After clinoptilolite filtration (60 mesh, 0.5 m/h, 15 cm bed) bismuth was not detected, below 0.3 µg/L (p. 4151).
- Mechanical agitation increased residual bismuth through abrasion of the microspheres (p. 4151; supplementary Table S7, not reviewed).
- Bismuth in water was measured by ICP-AES (Optima 8300) (p. 4150).
Methods (brief)
Bismuth microspheres were made solvothermally and used in stirred reactors with bromate solutions of 0.20 to 5.00 mg/L under nitrogen, with or without ultraviolet light. Bromate and bromide were measured by ion chromatography and residual bismuth by ICP-AES. Removal of residual bismuth was tested with a clinoptilolite filter column.
Evidence fitness
The paper supports the statement that a bismuth-based water-treatment material can release bismuth into treated water at tens of µg/L under laboratory conditions, and that a simple mineral filter brought it below the reported detection limit. It does not support statements about bismuth in real drinking water supplies, since no full-scale or field system was tested.
Limitations
Laboratory reactor conditions only; the per-condition residual bismuth values sit in a supplement that was not reviewed here. The detection limit of the ICP-AES method is given only as the not-detected threshold of 0.3 µg/L. The authors’ statement that excessive bismuth intake accumulates in tissues and affects kidneys, liver and circulation is background citing other work.
Related evidence
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