Silver recovery system data Page: 3 of 25
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Abstract
In August of 1990 thelSRSThotography Group began testing on a
different type of silver recovery system. This paper will describe the
baseline study and the different phases of installation and testing of the
system.
Introduction
The original silver recovery system that was used by SRS Photography
was installed when a move was made to a new building in August of 1985.
This system made use of electrolytic recovery units and iron based
chemical recovery cartridges. (Previously the group sent out spent fixer to
a central location on site for silver recovery.)
The new building was required to make use of a Trade Waste
Equalization tank to minimize the impact on the site sanitary sewer system.
Analysis of the total effluent from the waste tank was performed in
September of 1985. It showed that the silver content of the wastewater
was well below the federal guideline for hazardous waste.
The silver recovery system is maintained by the designated Quality
Control Photographer. It is his responsibility to maintain the system and
account for the silver that is recovered. While working with the system,
the Quality Control Photographer began to suspect that it was not the best
possible system for the SRS photo lab.
Electrolytic silver recovery was not very efficient. The lowest silver
concentration SRS photo was able to achieve was approximately 80 ppm.
(still hazardous waste) It was necessary to "tail" the units (allow the
chemicals to flow through a steel wool chemical recovery cartridge) to
bring the concentration of silver down to safe levels.
Another problem with the electrolytic silver recovery units was the
formation of silver sulfide. Silver sulfide is formed when the electric
current in the fixer is too high in relation to the available silver. This
causes the current to begin removing the sulfides from the fixers. This
"burning" of the silver caused it to form a soft dark sludge that fell to the
bottom of the desilvering chamber. Cleaning the silver recovery chamber
became a very messy job when silver sulfide was present.
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The biggest concern with the electrolytic system was the hazardous
waste that it produced. The silver flake contained dissolved silver in
amounts greater than 5ppm. In seven out of the nine chemical recovery
ch
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Boulineau, B. Silver recovery system data, report, August 26, 1991; Aiken, South Carolina. (https://digital.library.unt.edu/ark:/67531/metadc1069263/m1/3/?rotate=270: accessed July 16, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.