Silver halide is used in photographic film, which has a silver emulsion applied on a polyester base. Silver, a precious metal, can be extracted from film, but the process is quite costly. Performing the task as a profitmaking business requires a silver-extracting electrolysis machine and access to a large amount of photographic or, preferably, X-ray film. About 20 per cent of silver used annually ends up in X-ray film. Another common method of silver extraction from film involves burning the film in a controlled furnace and locating the silver among the ashes. Maintaining the furnace is expensive, however, and the quality of recovered silver tends to be poor.
- Skill level:
Things you need
- Photographic and/or X-ray film
- Powerful shredder
- 2 containers
- Silver-extracting electrolysis machine
- 0.15 M sodium thiosulfate solution stored in sealed polythene bottle
- Chemical-resistant gloves
- Transparent work surface
Shred photographic and/or X-ray film as finely as possible in a powerful shredder. Collect all the shreds in a container.
Turn on a silver-extracting electrolysis machine, pour 4 litres of 0.15 M sodium thiosulfate solution, which has been stored in a sealed polythene bottle, into the machine's electrolysis chamber . Be careful while doing this task, and wear chemical-resistant gloves.
Place the film shreds in the electrolysis chamber. The length of time it takes for silver to separate from ashes depends on the machine's voltage and the sodium thiosulfate solution's concentration. The process can take from 20 minutes to three hours. Monitor the machine throughout the process. Watch for silver formations on its charger plates.
Turn off the machine after studying it for some time to ensure no more silver will form on the charger plates. Scrape the silver from the charger plates onto a transparent work surface using a sharp pencil, and then transfer the silver into a clean container.
Tips and warnings
- Electrolysis machines are available in science supply stores, but it is possible to build your own electrolysis machine if you have considerable expertise.
- Silver recovery companies purchase and recycle film. Though you might not make very much money from the film, using such companies is the best option if you have only a small amount of film.
- When looking for film, contact hospitals and photographers, and advertise locally and online. Often people are glad to have waste materials taken off their hands.
- Because of silver's high value, X-ray film is targeted by thieves. If you have a large amount of film, keep it in a secure location.
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