Recovering Silver from Hypo fixer solution of Medical X-ray

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arsenic123

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Hello again guys, Today I got my hands of 75 liters of hypo fixer solutions used by hospitals for X-ray films of hands, legs, chest, etc. They discarded the solution and I bought them at very cheap price. Anyways I know several methods to recover silver from the solutions and I have mentioned all below. This will be useful to new comers as well as I have compiled it in 1 topic. Anyways I have some doubts and queries as well because this is the first time I am recovering from a hypo fixer solution.

1) First of all to add NaOH (lye) to drop the silver. Simply putting Naoh powder to the bucket of fixer solution (I have Medical x-ray like chest, hand, etc) and it should precipitate a powder. But Adding NaOH will give black mud from which silver is hard to be recovered. Is it correct? Or soldium sulphide is more easy and convenient method?

2) The second and the commonest procedure is to add sodium sulphide, which immediately precipitates the black silver sulphide; the liquid is discarded and the sulphide is washed and melted with a flux (litharge and soda ash perhaps) which gives a lead-silver button ready for further purification (as per the great Hoke).

3) The third and the easiest would be to add zinc powder to cement out the silver metal. The resulting silver metal could then be smelted into a bar. It would then require further refining to produce 0.999 silver. This is cleaner than sulphide method but takes longer.

4) The third option is Electrolysis. But I don’t have the tools and other stuff so I wont be using it.

5) The 4th way is sodium borohydride. It would also precipitate the silver but I am not sure if it’s a good way and never seen it.

6) The 5th option would be steel wool silver recovery canister. Still I am looking for a chemical method so I won’t be using it.

The questions that I have is when I cement It with zinc till I get no more reaction and after collecting the precipitate powder do I have to wash the powder with a dilute sulfuric at about 10% or HCl 32% to rid any excess zinc? Is it a necessary step? I am saying this because this would add more cost to recover silver and overall profit would go down.
The other question I have is after precipitating if I check the water for any un precipitated silver can I Asses silver presence by precipitating with NaOH powder again or any other method to see if the remaining water does not contain any silver after adding zinc or sodium sulphide.
The other method I know is of trying to stick a piece of copper in the solution and if the silver cements on it I can use copper for recovery for the remaining silver in the water after I use zinc or Sodium sulphide. I am saying it from a video that I have seen on this wonderful forum. http://www.youtube.com/watch?v=VEorcsJQkZ0#t=100
I am not sure if this will work for Hypo fixer solutions of hospitals. Anyways suggestions and feedback's are welcome.
As per my understating the hypo fixer solution of medical hospitals contains around 4-5 grams of silver. Please correct me if I am wrong. If anyone has done it please tell me if its more or less.

I am also looking for some cost effective methods and at the same time not to loose any silver. I just need to know which is the best method to recover because someone must have done it earlier and the solution is also uniform in most of the hospitals so I suppose one can have a good understanding regarding the process and recovery rate.

I have read many post of Samuel and he keep telling people to test it with copper wire by simply putting it in to the solution after scrape. This test would hep us determine the presence of silver in the solution but how can we know the amount of silver is per litre of KG of fixer? I found this on the forum.
1 second-------------- 12 gr/lt
2 seconds------------- 10 gr/lt
3 seconds------------- 6 gr/lt
4 seconds------------- 3 gr/lt
5 seconds------------- 1.5 gr/lt
(Source)
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=53&t=6806&p=60953&hilit=+copper+wire#p60953

Thank you
 

butcher

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Although I have studied a lot, silver recovery from fixer is not one of my interests at this point, and I have very little experience here in this area.
But if it is your interest you have a great resource to learn about it here on the forum, reading posts by GSP, and Juan Manuel Arcos Frank, and other posts you can answer many of your questions in recovery of silver from this solution...


While using NaOH to recover silver from the gelatinous film, may be a good Idea, I do not think it would be a good option to remove silver from the fixer solution.

Using a sulfide to precipitate the silver as a sulfide is a good option, although you need to convert the silver sulfide to silver (this can be done chemically in the melt by adding iron) flux alone will not convert the sulfides to gases.

using metal like copper, zinc, iron, will work to cement the silver as elemental silver, as the silver ions come into contact with the metal in solution the metal gives up an electron to the silver ion, the metal is oxidized into solution and the silver is reduced to metal (powder) by receiving the electron (from the metal in solution), this is a contact reaction so the silver ions need to come into contact with the metal (stirring every now and then to get those ions up next to the elemental metal, for the electro-chemical reaction to take place.
Zinc being a more reactive metal works well, and any metal in with the silver can be wash with acids.
Iron also a reactive metal, it has the benefit, iron and silver will not make an alloy.
Copper I would save it for testing, the metal is more expensive, less reactive, harder to wash...

Electrolysis can be used to deplete the solution of silver, but will not get all of the silver ions out of solution, you would need to use the metal displacement reaction on the remaining solution to recover the rest of the silver...

Your best bet for successful recovery of your silver is to keep studying.
 

arsenic123

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butcher said:
Although I have studied a lot, silver recovery from fixer is not one of my interests at this point, and I have very little experience here in this area.
But if it is your interest you have a great resource to learn about it here on the forum, reading posts by GSP, and Juan Manuel Arcos Frank, and other posts you can answer many of your questions in recovery of silver from this solution...


While using NaOH to recover silver from the gelatinous film, may be a good Idea, I do not think it would be a good option to remove silver from the fixer solution.

Using a sulfide to precipitate the silver as a sulfide is a good option, although you need to convert the silver sulfide to silver (this can be done chemically in the melt by adding iron) flux alone will not convert the sulfides to gases.

using metal like copper, zinc, iron, will work to cement the silver as elemental silver, as the silver ions come into contact with the metal in solution the metal gives up an electron to the silver ion, the metal is oxidized into solution and the silver is reduced to metal (powder) by receiving the electron (from the metal in solution), this is a contact reaction so the silver ions need to come into contact with the metal (stirring every now and then to get those ions up next to the elemental metal, for the electro-chemical reaction to take place.
Zinc being a more reactive metal works well, and any metal in with the silver can be wash with acids.
Iron also a reactive metal, it has the benefit, iron and silver will not make an alloy.
Copper I would save it for testing, the metal is more expensive, less reactive, harder to wash...

Electrolysis can be used to deplete the solution of silver, but will not get all of the silver ions out of solution, you would need to use the metal displacement reaction on the remaining solution to recover the rest of the silver...

Your best bet for successful recovery of your silver is to keep studying.
Thank you for the reply. I also think that Sodium sulfide is best way too but just wanted to hear from pros. Zinc is also good as it is stated in may posts which I searched. I will actually try both the methods and hopefully post pictures too. Just want to ask 1 question: Do I have to use pure zinc or I can use cheap commercial zinc too. Also even if I buy zinc powder how can we come to know that zinc is pure. Is there any way to find that zinc is pure?

Thanks
 

rickbb

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In my opinion there are 3 "good" ways to recover silver from fix.

I have not used it, but respected members here recommend the sodium sulphide method as their choice.

I have used zinc powder replacement method and it works quite well.

If you have access to an electrolytic unit that method works very well, but to justify the high equipment cost you need a continuous stream of fix. And the fix needs to have a fairly high concentration of dissolved silver salts in solution. Medical fixer generally does not have as high a concentration of silver as graphic arts, (printing or litho), fixer has.

Medical operations tend to over replenish their chemicals with their equipment set to a very high replenishment rate. Either due to untrained operators, usually a nurse or med tech. Or they have a contract for a supplier to do all of the maintenance which they also sell them the chemistry so naturally they want to make sure the chemistry in the x-ray developer is "fresh" and so have the developing unit setup to use a lot of chemistry.


The electrolytic method does have the advantage of producing almost pure silver flake, just scrape it off, wash it with water, dry and melt into bars/buttons. As well it's a turn it on and walk away operation, (with the right equipment).

If you have a good relationship with your source you may want to consider putting in a continuous electrolytic unit inline with their fixer tank to constantly recover their silver for you. It will keep them EPA compliant and keep you in silver with only occasional effort.
 

arsenic123

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Thanks for the reply. Actually I have good relation with the hospital but the problem is that they only dispose the fixers once a year or so. So I suppose buying the unit wont help me as I will get the next lot next year. I guess we have a winner then.. Sodium sulfide. :)
 

arsenic123

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rickbb said:
In my opinion there are 3 "good" ways to recover silver from fix.

I have not used it, but respected members here recommend the sodium sulphide method as their choice.

I saw this website http://www.metalminemedia.com/p/from-fixer-solution.html which says to use both Na2s and Noah in the same quantity to recover it. I am not sure about his. Either we can add Nas2 or lye. How can it says to add both in the same quantity once you determine the silver presence in fixer. Is it possible to estimate the silver and can adding both those chemicals would give same or even better result if we use any 1 of those methods?

Thanks
 

goldsilverpro

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arsenic123 said:
rickbb said:
In my opinion there are 3 "good" ways to recover silver from fix.

I have not used it, but respected members here recommend the sodium sulphide method as their choice.

I saw this website http://www.metalminemedia.com/p/from-fixer-solution.html which says to use both Na2s and Noah in the same quantity to recover it. I am not sure about his. Either we can add Nas2 or lye. How can it says to add both in the same quantity once you determine the silver presence in fixer. Is it possible to estimate the silver and can adding both those chemicals would give same or even better result if we use any 1 of those methods?

Thanks
It doesn't say Na2S OR lye. It says Na2S AND lye.
 

arsenic123

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[/quote]
It doesn't say Na2S OR lye. It says Na2S AND lye.[/quote]

Oh yes my bad. Sorry. But I meant or my intention was using both together. :)
 

Juan Manuel Arcos Frank

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Arsenic123:

R E D F L A G!!!!!!!!!!!!!....Never ever add more Na2S than needed.That link tells to use 200/250 gr. of Na2S for 5 lt of fixer which is a stupidity because you will form a lot of deadly H2S,remember,H2S is as poisonous as HCN and both must be handle with care and respect.

As a rule of thumb add double amount of Na2S as silver´s amount you have in your fixer,e.g. if you have a 5 gr/lt of silver concentration (in a 5 lt fix volume) then you have 5gr/lt x 5 lt=25 gr. of silver so add 25gr x 2=50 gr of Na2S,add it slowly and mixing well the fix.A little bit of H2S will be formed,so do it in an open and well ventilated room.Do not process more than 5 lt of fixer solution per batch unless you have a fume hood and an absorption tower.

I have never mixed Na2S and NaOH together,probably adding NaOH is used to create a basic pH which prevents H2S formation.Anyway,by checking silver concentration and adding the exactly amount of Na2S make the process safe.

Kindest regards.

Manuel
 

arsenic123

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Juan Manuel Arcos Frank said:
Arsenic123:

R E D F L A G!!!!!!!!!!!!!....Never ever add more Na2S than needed.That link tells to use 200/250 gr. of Na2S for 5 lt of fixer which is a stupidity because you will form a lot of deadly H2S,remember,H2S is as poisonous as HCN and both must be handle with care and respect.

As a rule of thumb add double amount of Na2S as silver´s amount you have in your fixer,e.g. if you have a 5 gr/lt of silver concentration (in a 5 lt fix volume) then you have 5gr/lt x 5 lt=25 gr. of silver so add 25gr x 2=50 gr of Na2S,add it slowly and mixing well the fix.A little bit of H2S will be formed,so do it in an open and well ventilated room.Do not process more than 5 lt of fixer solution per batch unless you have a fume hood and an absorption tower.

I have never mixed Na2S and NaOH together,probably adding NaOH is used to create a basic pH which prevents H2S formation.Anyway,by checking silver concentration and adding the exactly amount of Na2S make the process safe.

Kindest regards.

Manuel

Thank you for your inputs Manuel. How exactly do we calculate the amount of silver in per litre of fixer?? In my first post I have asked this question but still waiting for the answer.
 

FrugalRefiner

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arsenic123 said:
Thank you for your inputs Manuel. How exactly do we calculate the amount of silver in per litre of fixer?? In my first post I have asked this question but still waiting for the answer.
Copper wire test. This thread should help: Method for recovering silver from photo chemicals.

You should spend more time reading the forum.

Dave
 

arsenic123

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FrugalRefiner said:
arsenic123 said:
Thank you for your inputs Manuel. How exactly do we calculate the amount of silver in per litre of fixer?? In my first post I have asked this question but still waiting for the answer.
Copper wire test. This thread should help: Method for recovering silver from photo chemicals.

You should spend more time reading the forum.

Dave

Actually my first post cxame from there only. If you see the words the results of the copper wire test came from that post only but still no one confirmed if that would be applicable to all fixers. thanks
 

arsenic123

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FrugalRefiner said:
:oops: My apologies. :oops: I responded to your last post without going back to the top of the thread.

Dave

Hahaha no worries at all. Not at all offended. We are here to learn from you guys.
 

arsenic123

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Guys I dipped a pure copper in to the solution today to check the silver contents but only the color of the copper changed and nothing was attracted to copper. Here is the picture.
On the right side is copper after dipping and on the left side sample of actual pure copper. Also I will be precipitating it with sodium sulphide but here 3 quality is available and with 3 different colour. I. E yellow, brown and reddish. Which one should I use??

Thanks
 

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goldsilverpro

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Have you read Manuel's posts on the subject? It's hard to tell, but I'm pretty sure the grey color on the wire is silver.
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=50&t=3558&p=30524&hilit=copper+wire+fixer#p30524

If by quality you mean purity, I don't know. The Na2S I've seen looks like that in your photo. It is available as Na2S, Na2S.3H20 (59% Na2S), and Na2S.9H20 (32.5% Na2S).

I noticed that these Silver Estimating Papers are made in India. They are probably the same as the Kodak ones sold here. Both the wire and the papers can only estimate the Ag content. I've used both but prefer the papers. For more accuracy below 1g/l, I think Kodak recommends leaving them in for 30 sec.
http://www.metalminemedia.com/2013/04/silver-estimation-paper-use.html
 

arsenic123

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goldsilverpro said:
Have you read Manuel's posts on the subject? It's hard to tell, but I'm pretty sure the grey color on the wire is silver.
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=50&t=3558&p=30524&hilit=copper+wire+fixer#p30524

If by quality you mean purity, I don't know. The Na2S I've seen looks like that in your photo. It is available as Na2S, Na2S.3H20 (59% Na2S), and Na2S.9H20 (32.5% Na2S).

I noticed that these Silver Estimating Papers are made in India. They are probably the same as the Kodak ones sold here. Both the wire and the papers can only estimate the Ag content. I've used both but prefer the papers. For more accuracy below 1g/l, I think Kodak recommends leaving them in for 30 sec.
http://www.metalminemedia.com/2013/04/silver-estimation-paper-use.html

Thank you I already read that post and in my first post I have added those reference only. The reason I am confused is that I have seen another post where one guy puts a copper coin inside the fixer and lot of silver type dust was attracted to his coin. So I thought this would do the same thing but it changed the color of the copper so I was little confused.
I will try to get the silver estimating paper locally. Now what if I don't get the silver estimating paper here? Can I still go ahead and process it?
By quality I meant purity. Will the quality or purity of Sodium sulphide affect the silver in any way? If I get a low quality it will precipitate, right? Any ways to check the quality or purity of Sodium sulphide?
As Samuel said that one should avoid excess sodium sulphide because it will create deadly H2S. Now as its creating deadly H2S thats the reason we are adding NaOH to stop deadly H2s, correct? Will adding more sodium sulphide still create deadly h2s even after adding NaoH? will it still affect it?
Thank you very much. I will keep on adding photos for other reference also as I go on.
 

rickbb

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How much silver is attracted to the copper is directly proportional to how much silver is dissolved in the solution.

Lots of silver on the copper = lots of silver in solution.

Very little to no silver on the copper, (which is what you have), = little to no copper in solution.

Try again, but leave it in for a long time, like an hour. If it still does not show much after that then you may be wasting your time on it.

I'm not sure if there is a way to concentrate the solution, maybe a low heat evaporation to reduce the water volume?

Does the source have any type of recovery unit installed that may be stripping the silver out before they bottle it up? Most installations now days have to comply with various discharge limits and a credible x-ray equipment supplier will not install a system without one, usually an iron replacement cartridge.

Rick
 

Juan Manuel Arcos Frank

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Arsenic123:

Common Na2S will do the job pretty good,do not worry about Na2S...those yellow flakes you have that seem like french fries are OK.

The trick of this process is to determine silver content to add the correct amount of Na2S,as simple like this.If you add more Na2S than needed then you will form H2S.No need to use NaOH for common fixers used in photo processes and X ray.

You do not need silver estimating paper,copper wire will do the job nicely.Looking at your copper wires I see there is very low silver content...good fixers plate copper wire very fast(in 1 second)...so I think you have very low silver content.Take a look to the container´s bottom...probably there is a grey mud,this happens when fixer are stored for a long time.

Keep us posted about your progress.

Kindest regrads.

Manuel
 

arsenic123

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rickbb said:
Does the source have any type of recovery unit installed that may be stripping the silver out before they bottle it up? Most installations now days have to comply with various discharge limits and a credible x-ray equipment supplier will not install a system without one, usually an iron replacement cartridge.

Rick

Thank you for the reply. Its a small 30 bed hospital and I am pretty sure there is no recovery unit on it. Even if there is low silver content I will still go ahead and process it with Sodium sulphide. I am pretty sure I will recover the cost atleast. Nevertheless I will get the experience and knowledge. By the I bought 70 litres fixers at $20 only. :)
 

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