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 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.
- 1. Masebinu SO, Muzenda E. Review of silver recovery techniques from radiographic effluent and X-ray film waste. Proceedings of the World Congress on Engineering and Computer Science 2014 Vol II WCECS 2014, 22-24 October, 2014, San Francisco, USA http://www.iaeng.org/publication/WCECS2014/WCECS2014_pp613-617.pdf
Physics and imaging technology: x-ray
- x-ray production
- x-ray tubes
- tube rating
- interaction with matter
- beam collimators
- air gap technique
- intensifying screen
- x-ray film
- image intensifier
- digital radiography
- digital image
- x-ray artifacts
- radiation units
- radiation safety
- as low as reasonably achievable (ALARA)
- radiation protection
- background radiation
- background radiation equivalent time
- deterministic effect
- dose limits
- inverse square law
- lead apron
- radiation damage (biomolecular)
- radiation damage (skin injury)
- stochastic effect
- radiation detectors