Typically, film processing in the graphic arts industry involves the use of
black and white negatives and processing solutions. Silver recovery from
photoprocessing solutions (e.g., fix and washwater) can be accomplished in
two seperate manners. The first would be on-site recovery and the second
would be to send it off-site. The most common practice in the printing
industry is to perform on-site recovery.
The choice of technology depends upon the amount of silver that is either
necessary or desired to be recovered. Since may printers must meed local
sewer discharge limits, they will be required to install at least an
electrodepositon unit. Silver will be collected on the anode. The other most
common type is a chemical recovery cartridge which is usually made of steel
wool. The iron and silver in solution will "exchange" with each other and the
silver will accumulate in the bottom of the unit. Many printers will use one
electrodeposition unit in conjunction with one or two chemical recovery
To remove silver from washwater, ion exhange units are typically used. In
addition inline fixer and washwater recycling units can also be used. These
units will also incorporate a silver recovery technology to reduce the level
of silver in the solutions.
An excellent reference on this subject is the Code of Management Practice
available from the National Silver Council.