Silver recovery

Silver recovery is the process by which pure metallic silver can be recycled from old x-ray films. The modern process is extremely efficient with a recovery of greater than 99.9% silver.

Historically all radiographic film media employed silver salts as part of the image-producing process. Although the vast majority of radiology departments in the developed world are now filmless there is still a very large amount of traditional x-ray film in film libraries and storage. Also, many dental and veterinary practices continue to use film as the financial investment to move to filmless systems is often difficult to justify.

In the past, the x-ray film was initially incinerated, and then the ash melted to recover the silver. The resulting silver then had to pass through several stages of purification. The process was inefficient, costly, and environmentally unfriendly.

The commonest process now used is called "wash". The film is shredded and placed in large baths of a chemical reagent e.g. cyanide solution. The cyanide leaches the silver from the film. The silver is then removed from the solution by electrolysis.

The plastic substrate, usually polyethylene terephthalate (PET), can then be recycled.