Extraction of Silver from Waste X-ray Films by Thiosulphate

I just found this on the internet as i will be working on film this week has anyone tried this formula i will be working with virgin and developed film.

Sorry problems with upload



Rikkiricardo

Also can anyone tell me if i was to make my own fixer will it work on developed x ray film an will it work on paper also ?


Water (at about 125°F)…………………750.0 ml
Sodium thiosulfate, crystalline………240.0 grams
Sodium sulfite, desiccated……………10.0 grams
Sodium Bisulfite………………………..25.0 grams
Water to make……………………………1.0 liter



RikkiRicardo

I think you need bleach-fix (called blix) for developed film. It converts the black metallic silver to silver chloride and dissolves it in the thiosulfate contained in the blix.

Fixer, (sodium thiousulphate), will only work on the un-developed, (virgin), film and paper.

For your developed film you need a different method, (and honestly you'd be better off just selling it as is).

Blix, (bleach/fix) is used in the development of color film negatives or color slide film. X-ray film is very similar to black and white photo film/paper and lithographic film processing. It only uses a developer bath, (which turns the exposed silver bromine/halide crystals black), then a fix bath (which strips the un-exposed silver off the film), then a water rinse before a hot air dry down.

rickbb said:

Fixer, (sodium thiousulphate), will only work on the un-developed, (virgin), film and paper.

For your developed film you need a different method, (and honestly you'd be better off just selling it as is).

Blix, (bleach/fix) is used in the development of color film negatives or color slide film. X-ray film is very similar to black and white photo film/paper and lithographic film processing. It only uses a developer bath, (which turns the exposed silver bromine/halide crystals black), then a fix bath (which strips the un-exposed silver off the film), then a water rinse before a hot air dry down.

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I was wrong about the blix. I read somewhere that ferricyanide bleaches converted silver to AgCl and just assumed that a bleach-fix would convert and dissolve Ag. This doesn't seem to be the case. I've never used it. Live and learn.

If one truly wants to dissolve the Ag from developed film in thiosulfate, they must first convert the Ag to AgCl. This can be done in hypochlorite laundry bleach. I think I read in an old Kodak book (recently posted) that from 2 - 22% of this, at room temperature, would convert all the Ag and quickly remove the emulsion at the same time, in short order. I think household laundry bleach was 6.25% but, now, most brands are stronger. After rinsing well, the resulting AgCl is finally dissolved in thiosulfate.

There are 3 basic types of medical x-ray film -
(1) Undeveloped Rare-Earth - Silver Bromide. Before being exposed to light, this film is usually a light green color. Thus, it is called "Green" film in the trade.
(2) Developed Rare-Earth - Black Silver Particles.
(3) Dry-View - Silver Behanate (almost transparent)/Silver Metal (black). Dry-View is the Kodak brand of this type film. There are others. On these, the image is developed by heat. Therefore, no silver is removed during developing. Both undeveloped and developed Dry-View contain the same amount of silver (.04-.10 tr.oz Ag/pound, depending of the manufacturer. Undeveloped Dry-view is clear (tiny bit cloudy) blue and it looks like regular x-ray film after the emulsion has been stripped. Heating with boiling water will turn it solid black. The plastic PET film base is the same on all 3, except there is an intermediate mylar layer on the Dry-View.

Industrial x-ray film is the same, except that they don't use Dry-view (yet). Industrial contains a little over 3 times more Ag than Medical Rare Earth.

There are many ways to strip film but I know of only one chemical method that will strip all 3 types. That is hot caustic soda (sodium hydroxide; lye) solution. I have used from 3% to 10%. On undeveloped and developed rare-earth film, the emulsion breaks break loose fairly quickly (10-15 min, @ 150F, @ 5% Caustic Soda), when tumbling, but it takes 200F for about an hour with Dry-View. Dry-View works best with the Caustic Soda at the higher end of the above range). The silver on the Dry-View never breaks in the caustic up but stays as a super-thin black sheet. If you strip a 3/8" triangular piece of chopped Dry-View, a 3/8" triangular sheet of black silver eventually floats off. After removal from the plastic, the black silver material is collected and then treated like the regular sludge below.

You should have no problem stripping either developed or developed Industrial film with Caustic Soda. The silver bromide on the undeveloped film will be converted to silver oxide and the black silver on the developed film will not be altered. The sludge is then incinerated and flux melted with about 30% its weight in borax and 10% in soda ash (sodium carbonate).

From what I have read, and if I understand it correctly, they use a bleach and a strong oxidizer with color film, to convert the elemental silver back to a halide so it can be removed with the fixer (thiosulfate), I believe they called this a bleach fix (for color film).
GSP it may be what you were thinking of?

Black and white film uses a different type of process and a dichromate bleach, to remove silver, but not to convert it to a halide (like color film), here silver is removed as an silver ion.

The fixer thiosulfate dissolves the unexposed silver halide.

Color and black and white film use similar, but also very different processes in developing the films, the silver in film and solutions from these processes can also be different, depending on the film type and stage of development and the solution used.

Silver from these can be in different states, silver Halide, silver thiosulfate complex, silver ions, and elemental silver, depending on photographic scrap or solution the silver is recovered from, some of these films (like developed color) or some solutions may contain little or no silver, some film or solutions (like black and white fixer solution) can contain a fair amount of silver.

I've used common bleach, (5% strength), to strip film. 1 gallon in 3 gallons of water did great for the first 6 pounds of old X-ray film then started to slow down and stopped at around 7 1/2 pounds of film. The bleach will disolve the gel rapidly at first and drops the silver out, but for large quantiy of film the bleach costs would far exceed the tried and true methods.

I read in a paper that the action of disolving the gel layer that holds the silver converts the sodium hypercolorite into sodium hydroxide and creating heat.

You then wind up with a standard NaOH stripping method that will need the goop incenrated to carbonize the gel. I've read on some posts here that Manual mixes the 2 to speed his stripping method.

I devloped my own B&W film and prints for years and did a few color rolls and slides, color was always a PIA. Very picky with temps, times, and quality of chems. Even a small difference and you ruin the whole roll. Color sildes were the weirdest, part of the process was to open the canister halfway in the process and expose it to strong light to create the reverse of a negitive, (the positive slide), then close it back up to finish devlopment. Very strange.

In the mid 80's, I experimented with stripping developed film with 10%, by volume, HCl. I'm thinking it was at room temperature. As I recall, it stripped fairly fast and resulted in silver chloride.

Well,bleach process works well having in mind that chlorine gas could be formed and it will stop (and heat) the process.Chlorine gas only exists in acidic media so we have to maintain pH high by adding some NaOH to bleach solution.This process works pretty good for big charges of film,developed or unexposed.There is an useful patent about this process.

Kindest regards.

Manuel

Manuel
would you have this Patent process for this i sure don't like just using NaOH to me it takes to long to clean and settle

RikkiRicardo

Sure!!!!....let me find it in my PC.I will post it ASAP.

Kindest regards.

Manuel

I forgot to mention.You can change black (developed) films into green (unexposed) films by using a ferric chloride(FeCl3) solution and extract the silver by dipping the films in thiosulphate solution.

Manuel--

Hello Sirs,

Kindly assist on SILVER EXTRACTION from new DIGITAL X RAY films. I have successfully extract from ANALOGUE X RAY FILMS, but couldn't from DIGITAL X RAY films.

Hope to get a useful respond ASP.

THANKS

Have a look at this thread.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=58&t=23588

Apparently much less silver and much harder to process newer dry films from digital machines.

hurla said:

Hello Sirs,

Kindly assist on SILVER EXTRACTION from new DIGITAL X RAY films. I have successfully extract from ANALOGUE X RAY FILMS, but couldn't from DIGITAL X RAY films.

Hope to get a useful respond ASP.

THANKS

Click to expand...

There's a feature on the forum called SEARCH. Hope to get you to use it ASAP.