& Wasyl Kunda
Silver Recovery from Spent Photographic Solutions
Thomas Etsell and Wasyl Kundas process for
recovering waste silver from photographic solutions improved the
efficiency of the process while making it essentially self-contained.
Photographic film uses a silver halide coating to
help register the image. Film processing uses a fixer chemical that
converts some of the sliver halide to metallic silver. Large uses like
photo processing labs and hospitals used thousands of gallons of the
fixer chemicals annually to processing film and x-rays.
The amount of waste silver from this process was
significant, Etsell and Kunda said in their 1992 patent claim: "during
processing about 33 1/3 percent to 40 percent of the silver remains on
the film and the remaining 60 percent to 66 2/3 percent is washed into
the photographic fixer solution." Recovering that silver made economic
and environmental sense as firms could recover some of their processing
cost, and silver, a metallic pollutant, would kept out of the waste
Nonetheless, technologies for recovering silver,
especially electroplating from the solution, tended to be costly to
build and maintain, were inefficient and could not recycle the fixer
solution. "A chemical process, which could selectively remove silver
from spent fixer solution without destruction of the thiosulfate in the
solution and which would allow the fixer to be reused, would have the
advantages of lower costs, ease of operation, and a reduced
environmental hazard", Etsell and Kundas patent application claimed.
Kunda and Etsells new process injected various
sulfate solutions into the photographic fixer solution. This reacted
with the solution and precipitated silver sulfide while maintaining the
PH and reagent levels in the fixer solution, making it available for
reuse. The silver sulfide left over from the process could be easily
extracted and processed for their metal content.
Kunda and Etsells process required no special
equipment and could be set up in smaller locations like rural hospitals.
The pair of researchers sold the North American rights for the process
to Vancouver-based Photochemical Recycling Systems. The company invested
$7 million in developing and designing a process that could be a
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