Silver-containing waste is one of the problems
associated with photography. Photographic film is coated with
an emulsion that contains silver halides. These halides are
light sensitive and undergo changes when exposed to light.
These changes become images on negatives when developed in a
solution of ammonium or sodium thiosulphate.
To prepare photographic emulsion, a solution
of silver nitrate is slowly added to a solution of potassium
bromide forming silver bromide, the light sensitive coating on
photographic film. In the process of making film, there is the
possibility that the excess silver nitrate solution could be
discharged into the sewer system. Millions of liters of
silver-containing photochemical waste are created each year.
This silver waste is toxic to fish and also means the
companies are losing large amounts of a valuable metal.
Silver is not just used in photography and
jewelry. It has many new uses in nanotechnology, zeolites, and
even circuit boards.
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