Process for recovering silver from photographic chemical effluent
OwnerNorman B. Rainerinventor
Life of this patent
Estimating the term…
Abstract
A process for absorbing silver from photographic hypo solutions involves passing the hypo solution through a bed consisting of a multitude of a sponge product confined within a vessel. The sponge product is derived from an open-celled cellulosic sponge into which there has been incorporated 30% to 80% by weight of a polymer produced by the thermal interaction of polyethyleneimine (PEI) with a polycarboxylic acid. The polymer further contains an activating multivalent cation and between 90% and 300% water. Silver is eluted from the sponge product employing aqueous solutions of a complexing agent such as an ammonium compound or a cyanide compound. Following a water wash, the bed of sponge product is ready for its next cycle of silver absorption.
Claims8
A process for removing silver from a photoprocessing hypo solution comprising:
- a) passing said solution through a bed of open celled sponge product containing a gel form of a polymer produced by the thermal interaction of polyethyleneimine (PEI) with a polycarboxylic acid, said polymer containing chemically bonded thereto a substantially saturation amount of an activating multivalent metal cation and containing between 90% and 300% of water based upon the dry weight of the polymer, the rate of passage of said solution through said bed being between 0.05 and 2.0 bed volumes/minute (bvm),
- b) eluting silver from said bed by passing through said bed an aqueous solution of a complexing agent selected from the group consisting of ammonium compounds and cyanide compounds, and
- c) washing said bed with water, thereby removing said complexing agent and preparing said bed for re-use, beginning at step a.
The process of claim I wherein said sponge product has a cuboid configuration having a volume less than one cubic inch.
Dependencies are inferred from the claim text.