Separation of metal ions absorbed on a resin and installation for recycling photographic effluents including an exchanger and an electrolytic vessel

Process for separating metal ions absorbed on a cation exchange resin, which comprises:

• contacting the cation exchange resin with a polar solvent containing an eluting agent or a mixture of eluting agents containing at least one organic or mineral ligand capable of complexing the metal ions to be separated so as to obtain an eluting solution charged with metal complexes;
• circulating a direct electric current in a voltameter containing the eluting solution charged with metal complexes thereby forming an electrolyte between at least a first cathode made of a first metal identical to that of the metal ions to be recovered by deposition, and at least one anode with a given electric potential while keeping the cathode at an electric potential having a lower value than the oxidation-reduction potential of the metal ion to be deposited during deposition;
• and finally
• setting up at least a second cathode made of a second metal and readjusting the cathode electric potential and the anode electric potential to provide a desired anode/cathode potential difference corresponding to new values depending on the second metal to be recovered;
• the electric current applied to the electrodes being amplitude modulated as a function of time and ending with discontinuous electrolysis comprising phases of stoppage of deposited metal during which the potential applied to the cathode or cathodes is greater than the equilibrium potential of the electrolyte, alternating with active phases of deposition during which the potential of the cathode or cathodes is brought to a value corresponding to that of the apparent level of diffusion of the complexes to be electrolyzed and containing the metal ions to be recovered;
• the durations and ratios of the durations of the two phases being determined in such a way that electrolysis is synchronized with the elution reaction.