Silver Recovery
from Photographic Baths
Silver in the form of thiosulfate anionic complex [Ag(S2O3)2]3- can be removed from photographic processing solutions by a number of techniques including electrolysis, reduction by fine steel wool (also called metallic replacement), precipitation and ion exchange.
The electrolysis and metallic replacement techniques convert silver thiosulfate complex to metallic silver. By the precipitation technique, the silver complex is removed in the form of precipitates under the action of a precipitating agent such as sodium sulfide or trimercapto-s-triazine. The silver anionic complex can also be fixed on anionic exchange resins.
The ion exchange technology works well on dilute solutions like wash water. The anionic resins such as the strong base Amberjet™ 4200 and the weak base Amberlyst™ A24 are the resins of choice.
A well controlled ion exchange system can reduce the silver to a level of 0.1 to 0.5 ppm. This technology produces relatively clean water that may be recycled through the system. When the resin is exhausted, the silver is stripped off from the resin in a concentrated form using a regeneration solution of ammonium thiosulfate.
Recommended Products
For sampling, pricing, availability or more information please contact your Rohm and Haas representative.
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Strongly basic anion exchange resin with a polystyrenic backbone. High operating capacity |
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| Amberlyst™ A24 | Weakly basic anion exchange resin with an acrylic backbone. High operating capacity and efficient regeneration |
Further Reading
- R. Mina, "Silver Recovery from Process ECP-2 Wash Waters by Ion-Exchange Methods," Journal of the SMPTE, 90:754-759, September 1981.
- P. R. Quinnones, "In-Situ Precipitations as the Regeneration Step in Ion-Exchange for Silver Recovery," Journal of the SMPTE, 93:800-807, September 1984
