Silver removal
US5536387A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Apr 27, 1995 |
| Grant date | Jul 16, 1996 |
| Priority date | — |
| Expiry date | Apr 27, 2015 |
Classification
- Technology area (CPC C)Chemistry; Metallurgy
- CPC primaryC23F2201/02
- WIPO fieldChemical engineering
- WIPO sectorChemistry
Abstract
Effluent streams from photographic processes contain both silver and thiosulphate ions, and because of the formation of complex anions it is difficult to remove the silver. The silver may be removed using a cell (12) with a cathode (24) exposed to the effluent liquid, and an anode (25) separated from the liquid by a barrier (22) permeable at least to anions. Some silver sulphide is formed electrochemically at the cathode (24); at the anode (25) water is electrolysed and becomes acidic, so the complex anions migrating through the barrier (22) generate silver sulphide chemically. The resulting silver sulphide precipitate is separated from the liquid by a filter (14).
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.