Originally posted by Aqua_Fortis_100%
Today I extracted my silver , from X rays films, from several hospitals. I'm now washing the Ag powder and will see how much was extracted..
The procedure for extracting silver from these is VERY simple and not require any complicated technique, like burning sheets or such.
Quote: | The furnance is the only reliable method for silver extraction from films, as it used to be the commercial one. Unless you'd like to scrape off the
gelatin from the strips... |
The only chems required to extract silver from X rays and another films are : bleach , NaOH and commom sugar .. not more than this.. The Ag powder
obtained is relatively pure for chem experiments, but if you like, you can reffine it , using a torch and borax (or boric acid), and the result are
small balls of silver metal..
You only need to put the negatives/X rays films in bleach for some minutes.. The gelatine (containing silver powder) on the surface of the film will
dissolve very fast (do it outside.. bad smell) .. Initially, the powder is black, but will turn white, as the hipochlorite oxidise the Ag to AgCl and
a small amount of Ag2O..
4 Ag + 2 ClO- + H2O ---> 2 AgCl + Ag2O + 2 OH-
then, after all gelatine removed from the films, you can wash the plastic base, to remove residual silver compounds, which are removed and added to
bleach leaching solution..
Then you need to decante the solution, at least for one day (some of the ppt are very very fine) ; the white mud resting in the bottom, you can
separate and put in a pan (preferably a disposable pan... I've used enameled pan, which was fine to work) ; then you can add some water , NaOH and
sugar (in aprox. 1:2 vol. ratio (the procedure where I see this use teaspoons to make the method more "otc" possible))...
Then , boil for approx. 30 mins.. The solution quickly turn brown then black , since the silver compounds are reduced to silver..
Then you can neutralise the solution with an inorganic acid (organic acids will form and give a bad smell.. do this outside) and filtrate it with a
commom filter paper.. Most of the silver particles are easily filtrated.. then washed on filter...
Done!
If you wish to reffine the silver, you can melt borax (Na2B4O7.10H2O) and put on a porous refractory ceramic where the silver will be melted (first
the molten borax is put on the ceramic, to fill the pores and avoid the silver getting inside it).. Then Ag powder.. The boric oxide and NaBO2 (Na
meta borate?) are formed and effectively remove copper and another impurities.. The molten silver , then is dripped in a container with water, to form
small granules..
Boric acid can be used instead, or then some mixtures, like borax, Na2CO3 and NaNO3 as flux..
I dont tried reffining it, as I dont have any sort of torch lying around..
A similair procedure can be found in US 3,960,550 ("silver recovery process"), attached, but their procedure for reffining the silver is somewhat
different and dont give a very pure silver, and thus need to be repeated one or more times..
[Edited on 11-4-2008 by Aqua_Fortis_100%] |