Recovery of erythorbates from photographic solutions

DETAILED DESCRIPTION OF THE INVENTION The process of the present invention is directed to the recovery of erythorbate values from spent photographic solutions.
The photographic solution may contain erythorbic acid or salts thereof, for example, potassium erythorbate, as the sole developing agent.
The photographic solution may contain alkyl esters of erythorbic acid, for example, methyl erythorbate, as the developing agent.
The photographic solution may also contain any combination of erythorbic acid, salts thereof, or esters thereof.
The erythorbate values may be present as the sole developing agent in photographic compositions or may be in combination with other co-developing agents.
Non limiting example of such other agents include alkali metal carbonates, for example, sodium carbonate and potassium carbonate; 3- pyrazolidone compounds such as phenidone (1 phenyl-3-pyrazolidone); alkali metal sulfites such as, for example, sodium sulfite; metal chelating agents such as, for example, sodium ethylenediaminetetraacetic acid (EDTA); bromides such as, for example, potassium or sodium bromide; and organic antifogging agents such as tetrazoles.
A typical photographic solution will contain any combination of the above listed components.
During the development of an image on a photographic medium, various components of the medium, notably the erythorbates, are converted to oxalic acids.
Depending on the degree of decomposition, the spent photographic solution is normally at a pH of from about 7.
5 to about 13.
In the first step of the process of the present invention, a spent photographic solution is acidified by passing over an acidic cation exchange resin, for example, a sulfonic acid type resin.
An example of such a resin is Ambedite IRC-200 (Rohm and Haas, Philadelphia, Pa.
) which is regenerated or activated with a mineral acid such as hydrochloric acid, sulfuric acid, phosphoric acid or nitric acid.
The acidified solution generated by passage through the acidic cation exchange resin is then passed over a weakly basic anion exchange resin, for example, an amine type resin