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Original Articles

Efficiency of the Low-Current-Density Electrolytic Cell for Recovering Silver from Used Fixing Solutions

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Pages 216-218 | Received 01 Aug 1975, Published online: 22 Jul 2016
 

Abstract

The rate of dissolution of the plated silver by the fixer in an electrolytic cell sets the minimum silver level that can be achieved under given conditions of low current density, pH, etc. A smooth coating of silver resists attack better than a rough urface. New stainless steel cathodes can allow the silver concentration to be reduced to a low level. However, as the surface of the plated silver becomes rougher with further deposition the degree of attack becomes greater so that the minimum silver concentration level rises. The attack is less severe at higher pH.

Résumé

L’attaque par le fixateur de l´argent déposé limite la récupération de l’argent par électrolyse à faible densité de courant et, dans des conditions opératoires donnés (pH, densité de courant . . .) conditionne la teneur minimale en argent restant.

Une couche d´argent lisse résiste mieux à l´attaque qu´une surface rugueuse. Des cathodes en acier inoxydable neuves permettent d´abaisser la concentration minimale en argent à un niveau très bas, mais la concentration minimale en argent augmente au cours du dépôt en raison de la rugosité de l´argent déposé qui favorise l´attaque. Celle-ci diminue lorsque le pH augmente.

Zusammenfassung

Die Auflösungsgeschwindigkeit des abgeschiedenen Silbers durch die Fixierlösung bestimmt die minimal erreichbare Silberkonzentration in einer Elektrolysezelle bei vorgegebenen Werten von Stromdichte, pH etc . . . Ein glatter Silberniederschlag widersteht dabei dem Angriff der Fixierlösung besser als eine rauhe Silberoberfläche. Durch Verwendung neuer Edelstahlkathoden kann daher die Silberkonzentration zunächst herabgedrückt werden. Wenn jedoch im weiteren Verlauf der Elektrolyse die Oberfläche des abgeschiedenen Silbers rauher wird, steigt die Silberkonzentration an. Der Angriff durch die Fixierlösung wird geringer bei Erhöhung des pH-Wertes.

Riassunto

La velocità di dissoluzione di uno strato di Argento depositato elettroliticamente da parte di una soluzione di fissaggio in una cella elettrolitica raggiunge il minimo livello di Argento ottenibile in particolari condizioni di bassa densità di corrente, pH etc. Una superficie liscia di argento è più resistente di una superficie ruvida.

Catodi nuovi di acciaio inossidabile permettono di ridurre la concentrazione di argento ad un livello basso. Tuttavia, quando per ulteriore deposizione di argento la superficie di argento diventa più ruvida, il grado di attacco si fa più intenso e il livello di minima concentrazione sale. L´attacco è meno severo a pH più elevati.

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