Method of recovering silver from photographic bleach-fix and con

Details Method of recovering silver from photographic bleach-fix and con Method of recovering silver from photographic bleach-fix and con

1971-12-20

1977-07-19

Andrews, R. L.

Chemistry: electrical and wave energy

Processes and products

Electrostatic field or electrical discharge

96 60BF, C25C 120, G03C 538

Patent

active

040367150

ABSTRACT:
An improved practical and highly efficient electrolytic method for concurrently recovering silver from photographic bleach-fix solutions which contain iron, and regenerating the bleach-fix for reuse. A substantial improvement in current efficiency at low current densities is realized by a combination of (a) adding a reductant such as sodium dithionite before electrolysis, as a reducing agent for ferric ions in the bleach-fix solution, (b) maintaining a non-oxidizing atmosphere in the cell, and (c) providing either a cation permeable membrane or a porous alundum membrane between the electrolytic cell anode and cathode, to separate a first pool of bleach-fix catholyte from a second pool of a different salt solution such as sodium carbonate as anolyte.

REFERENCES:
patent: 3554883 (1971-01-01), Green
patent: 3616332 (1971-10-01), Miller
patent: 3667950 (1972-06-01), Amano et al.
"Prep'n of Thick Coats of W," by McCawley et al., U.S. Bur. of Mines Report of Investigations 6454, 1964, pp. 7, 9.
"Metal Coating of Plastics," by F. A. Lowenheim, pp. 185-187.
"Electroless Plating Baths," Metal Finishing Guidebook Directory, 1968, p. 496.

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