Mohd Jais Sabtu of Sinar Harapan Kompang Association in Bachang has found his silver linings when he discovered that he could use X-Ray films to replace goat skins to make his kompang, a traditional hand-held drum. Other than a reduction in cost to create his kompang, the X-ray films also produce better sound at Malay ceremonies and functions his group plays at.
But then there is more to X-ray films than making kompang. If Mohd knows the processes, he can get his hands on the real linings, by recovering silver from:
1) films
2) negatives
3) photo processing wastes
Silver leaches into the fixer solution used in photo processing and this should not be discarded indiscriminately. According to Environmental Health and Safety (EHS), silver is a heavy metal and is toxic to the environment.
So, if you can get your hands on such wastes and would like to put them to use, and make some money in the process, following are silver recovery methods to consider:
1) Electrolysis
2) Ion Exchange
3) Metallic Replacement
4) Precipitation
To find out the cost, the advantages and disadvantages of each process, take time to read "Photographic Processing Waste Management" by Environmental Health and Safety (EHS) and EPA.
I read on Finishing that a student, Obogheneruru Orhuesie, used the electrolytic method of recovering silver for almost a year. He managed to fund his education, in a renowned university in Nigeria, from the proceeds he received from the sales of the recovered silver.
Juan M. Arcos has this recovery method to share on Finishing. He heats oxalic acid of 5% concentration to 100 degree Celsius, put the film into the acid for 20 minutes and all the silver will drop to the bottom. He said that there is no fumes, risk or environmental damage, just pure silver with this method
According to a write up on "Clean technology for the recovery of silver from processed radiographic films" by Science Direct, boiling films in oxalic acid separate the inorganic component from the polymer substrate. Recovery of silver is achieved by melting and the process recovers good quality silver and offers a very high yield.
Interested? Before you start, also read about the concerns of handling radiographic film processing chemicals posted on Carestream Health.
If Mr Mohd is aware of this, would he still consider making "kompang" out of X-ray films?
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From my InBox in relation to this posting by Ryuji Suzuki of Silver Grain:
1 and 2 are essentially the same. Only black-and-white films,
negatives and radiographic films contain silver. Among these,
medical x-ray films contain the most silver, in order to
enhance the sensitivity to allow the minimum dose of x-ray
exposure. Properly processed color materials do not contain
silver.
Each liter of exhausted fixer solution contain about 5 to 30
grams of silver. As summarized in the article you mentioned,
there are various methods and there are trade-offs among
them. Well designed electrolysis system is the best in terms
of efficient silver recovery, but it requires a large
volume.
> Juan M. Arcos has this recovery method to share. He heats
> oxalic acid of 5% concentration to 100 degree Celsius, put
> the film into the acid for 20 minutes and all the silver
> will drop to the bottom. He said that there is no fumes,
> risk or environmental damage, just pure silver with this
> method.
This method by Syed et al. seems to work, and the silver is
collected as sludge. However, polyester films will vigorously
deform at 100C temperature and may splash the hot solution. In
terms of operator safety, a boiling oxalic acid solution
doesn't sound too safe for routine work, unless operated by an
automated plant or at least trained workers. It may be ideal
if another method that uses solutions of room temperature or
40C at most. However, oxalic acid is pretty cheap, and any
alternative methods would cost more.
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