Method for regenerating seasoned aqueous fixing or bleach/fixing solutions
AssigneeEastman Kodak Company
InventorsDidier J. Martin, Christian G. Guizard, Jean-Francois Diaz
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Abstract
The invention concerns a method and a device for the selective extraction of the halide ions from photographic baths. According to the invention, the solutions to be treated are subjected to a first nanofiltration step 2 in diafiltration mode, then to a second nanofiltration step 3 in concentration mode. The method makes it possible to prolong the activity of the fixing or bleaching/fixing baths during the processing of photographic products.
Claims12
A method for regenerating a seasoned aqueous photographic fixing or bleaching/fixing solution containing thiosulfate ions, other substances and a high concentration of halide ions, said method having a step of recovering the silver ions contained in the aqueous solution and comprising the steps of:
- a) diluting said fixing or bleach/fixing solution with a volume of water between 0.1 and 10 times the volume of the solution;
- b) subjecting said diluted fixing or bleaching/fixing solution to a first step of nanofiltration, at a low flow rate and concentration factor, so as to form a retentate with a high concentration in thiosulfate ions and said other substances and low in halide ions, and a permeate with a high concentration of halide ions and low in thiosultate ions and said other substances;
- and
- c) subjecting the permeate produced by the first nanofiltration step to a second nanofiltration step at a flow rate and concentration factor higher than those used in step b), so as to form a retentate with a high concentration in thiosulfate ions and said other substances and low in halide ions and a permeate substantially containing none of the thiosulfate ions and said other substances.
Dependencies are inferred from the claim text.