# Silver trap cores-how to process?



## Ignatz61 (May 1, 2009)

I have some silver window traps that I can't seem to get any silver out of.
I have dry rusty looking cores, some of the iron screen is still visable. They are from photographic fixer tanks. I melted in a crucible with borax and steel rods stuck in the mix as suggested. The sulphur reacted with the steel as the rods came out with a bit of a taper to them. When I poured into a cone mold and cooled a hammer strike broke it into peices with no visable silver at the bottom as I was expecting. 
What am I missing?
I left the cucible in the funace for about 45 mins. after it all was molten.


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## goldsilverpro (May 1, 2009)

It sounds like you did it correctly. 

It's likely that there was no silver in the cartridges. A company I worked for processed steel wool cartridges contained in from 1 to 5 gallon buckets, by the truckload. All had supposedly been on fixer tanks. On the average, I would guess that 2/3 of them either contained no silver or not enough silver to profitably treat them in the furnace. After opening them, the workers could simply look at them and tell what was good, fair, or worthless, from experience.

As the silver cements onto the steel wool, the steel wool dissolves proportionally.

(1) Best silver recovery. If all of the steel wool has been used to drop silver, there will be no steel wool left and the gray colored granular silver would be in a heavy black sludge on the bottom of the bucket.

(2) Moderate silver recovery. Only portions of the steel wool would remain, in chunks or slivers. Some of the silver sludge would be on the bottom and some might be visibly stuck to the remaining steel wool.

(3) No silver recovery. The steel wool cartridge is mostly intact, although usually quite rusty. There is no granular silver in the bottom of the bucket and none is observed stuck to the steel wool.

I would say that, from your photo, your material is category (3). I see no silver and the cartridge appears to be nearly intact. A side view photo would be good. Are there any small silver BBs visible in the slag?


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## Ignatz61 (May 2, 2009)

Thanks GSP for your help. Here is the side view.
I have three types of material in this batch.

1. The intact cores shown in the pictures. They seem to have little or no silver in them.

2. about 10 lbs of rust colored powder that looks like the same material as the cores but all broken up into powder with a few small chunks. about 5lbs. of this yielded 9.8 oz of metallic silver.

3. I have about 30 lbs of wet black muck with a few firm chunks. I have not run any of this yet.

From what you said I am thinking the black muck may have the highest yield. I am assuming the same procedure? 
Can I dry it by slow roasting in the crucible then turn up the heat once it is dry? Or does it need to be dried first then melted?


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## goldsilverpro (May 2, 2009)

I would definitely dry the wet material before putting it in the crucible. It is touchy and generally unsafe to put wet material in a crucible and heat it. I have done it but I've had a few mishaps, usually when I was rushing things - take your time and do it safely. 

If the crucible is too cold, the liquid can quickly soak into the crucible. Then, when heated, the crucible can split. I did this once and ended up with two half-thick crucibles, one inside the other.

If the crucible is too hot, the wet material can spew out. I once had the ceiling above the furnace covered with silver.

Dry it first in a metal pan over a little heat. Maybe a SS tray sitting over the warm furnace.

After drying, the melting method outlined in your first post should work fine.

Iron slag is fairly viscous and you'll likely end up with Ag BBs hung up in the slag. We usually hung up about 4% of the Ag. When we accumulated about 25 tons of slag, we farmed it out to a company that had a giant reverberatory furnace. 

With many types of refining, it often is not profitable to try and get that last little bit.


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## Sylar (May 4, 2009)

Wouldn't it be easier to first dissolve the iron in dilute sulfuric acid, leaving the silver in metallic form?


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## goldsilverpro (May 4, 2009)

To me, drying and melting would be far simpler and faster than dissolving in acid.


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## Ignatz61 (May 5, 2009)

How long a soak does it need for the iron to react with the sulphur? I left it in the furnace for about 15 mins. once liquid with several steel rods soaking in it. When I poured into a cone mold I got very little silver but the layers went from a crusty, light (Non dense) brittle flux down to a dense almost silver colored metalic but brittle material. Is this silver that has nos yet converted or lost the sulphur? Would a longer melt have converted more silver?
I ran some of the black muck which I would think would be the richest in silver same results as above.


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## goldsilverpro (May 5, 2009)

You may not have enough borax in there. I would use at least twice as much borax as you have sludge. What kind of furnace are you using? How hot is it running (what color)? I hope you say it's an open top gas crucible furnace, with a lid, and it is at a full yellow (no orange) or light yellow heat. Are you using rebar. I would cut the rebar long and stir it with the rebar occasionally. It may take an hour or more at full heat. Be patient.

You should only have 2 layers after pouring. Silver only on the bottom and a black almost totally glassy slag on top. If you see powdery gray material in the slag, it is silver and either the melt wasn't hot enough, you didn't use enough borax, or you didn't leave it in long enough. On top of the slag you may see some shiny flakes (silicon carbide) if you are using silicon carbide crucibles. Don't worry about that.


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## Ignatz61 (May 5, 2009)

oops,
I used only a small amount of borax in a #8 crucible half full. 

I am using a natural gas, open top crucible furnace with a swing lid at about 2000 degress F. Measured with a pyrometer.

I am using cold rolled steel rods as I have no rebar. I can't see much difference there. 

So, tomorrow I will use copious amounts of borax, stir with steel rods letting them soak in the molten metal for an hour, them pour into cone mold.
By the way it was amazing to see how much steel was eaten up during the soak. A 5/8" dia. rod was tapered to a point after 30 mins..
Thanks yet again GSP!!


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## goldsilverpro (May 5, 2009)

It takes a lot of iron to chew up that sulfur. Only when all the sulfur is combined with the iron, will the iron stop being eaten. It sounds like the amount of borax and the dwell time could be the problems. Extra borax won't hurt. It's purpose is to thin out that viscous iron sulfide slag. Make sure you stir every so often with the rods. Otherwise, only the sulfur next to the rods will combine. 

The directions I've given are not exact. I do everything by eye and am not very dogmatic about things. I've probably never done anything the same way twice. Everything is an experiment.


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## Harold_V (May 6, 2009)

If my experience matters, you should expect a third layer, the one made up of sulfur and iron, which will be a distinct layer above the silver you recover, but under the glassy flux (note that I poured to a large cone mold). The best description I can offer is that the layer will look much like cast iron. The finer grain appeared to me to indicate that all of the silver had been converted. I re-fired some of mine a couple times until I understood the relationship between the grain size and color of the sulfide and the lack of silver. I found the color to deepen and grain size to shrink considerably once the silver had been removed. 

The use of mild steel, regardless of the source, is acceptable, but be certain to avoid any of the leaded steels. Plain 1018 (cold rolled) is fine, and may well be very similar, chemically, to rebar. 

Harold


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## Ignatz61 (May 6, 2009)

Hi Harold,
Yes I am getting 3 layers and cast iron is a good way to describe one, the grain seems large. The top layer is full of gas pockets making it very light.
I am melting another batch as I am typing this.
This time I used much more borax as GSP suggested and I will let it "cook" for a while.
I have saved the flux from each batch as you said I will also re-run them until I fully understand what it looks like when the silver has all been removed.


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## goldsilverpro (May 6, 2009)

It's been a long time since I've done this. In fire assaying, this intermediate layer is called a "matte" and is made up of iron sulfide and I think that's what you have. It is described as being blue-gray and brittle and looking like galena (which looks metallic). It will always carry some silver in it. 

The matte is soluble in molten soda ash, according to one of my fire assay books, and can possibly be made to go into the slag by adding soda ash along with the borax.

I don't remember any matte forming. Squeezing my memory a bit, I do remember we usually used both borax and soda ash in most silver melts, as a matter of course. I would guess the ratio was about 1 part soda ash to 4 parts borax. 

I would suggest you try this on a small amount. I can't see any way that it would hurt. It may reduce or eliminate this matte.


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## Harold_V (May 6, 2009)

A simple test is to run only the matte, using borax and soda ash. Be certain to heat for a prolonged period--and have free iron (steel scrap) in the material. I found that when all of the values had been liberated, the loss of steel was eliminated. If, upon running a second time, you get little or no silver, you'll know you've done as well as can be expected. Try to compare the appearance of the sulfide layer (the matte) with some that has been run only once. If you see no change, and you didn't recover any additional silver in the second heating, you'll know you have successfully recovered the values. 

Again, I strongly recommend a cone mold. 

Harold


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## goldsilverpro (May 6, 2009)

Harold,

What were you using this process on? Silver from steel wool canisters? Ore? Something else?


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## qst42know (May 6, 2009)

When iron is used in fire assaying the flux is heavy on soda ash to create a fluid alkaline slag. Though what you are trying to accomplish is somewhat different a fluid slag will prevent values being trapped while the iron is decomposing. Also from assaying texts if your material needs to roast a long time you can add NaCl (salt) as a molten cover to prevent silver losses due to oxidation.


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## Harold_V (May 7, 2009)

goldsilverpro said:


> Harold,
> 
> What were you using this process on? Silver from steel wool canisters? Ore? Something else?


The waste material I processed. A great deal of the material involved was from the stock pot, which commonly accepted solutions from which gold had been recovered, and contained traces of platinum or palladium. Considering the solution was laden with SO2, it, too, got reduced. A great deal of sulfur was included in the waste material, yielding a correspondingly large amount of matte. It was much easier to re-fire the matte than to introduce iron in the reverb. 

I also had one other experience, but for the life of me I can't recall the circumstances. My thoughts are the doré that I received from a geologist. He provided a great deal of slag along with the metal. Assuming that was the case, it was the first time I used scrap steel to recover the values from matte. Needless to say, I was duly impressed!

Harold


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## Ignatz61 (May 7, 2009)

These are the cores from photo processing (fixer). They are steel wool (actually it looks like iron screen coiled into a cylinder with fluid flow through the center.
Yestarday's melt yielded nothing but a lot of that cast iron looking mateial.

Can somone tell me how to get metallic silver after I disolve some of this material in Sulphuric acid? I just want to do a small sample to verify there is or is not silver in these things.
Is it silver sulphate? and is the procedure similar to silver cloride?

I have about 100 lbs of this stuff but am about to give up on it for a while, unless I can be sure there is silver in there


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## Platdigger (May 7, 2009)

Problem with using sulfuric is that it will disolve your iron.
In fact, I believe your sulfuric would have to be conentrated and heated to disolve the silver.

How about sodium or ammonium thiosulfate to use as a leach for a test for silver...
Anyone?
Manuel?....


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## Ignatz61 (May 7, 2009)

I was thinking disolve the iron and leave the silver?

This picture show the last melt I did. The steel rods I had soaking in the melt showed signs of reacting with the sulphur, but all I get is this dense "cast iron" like material all the way down to the bottom of the cone.


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## Juan Manuel Arcos Frank (May 8, 2009)

Yes Sir,Platdigger is right...sulphuric acid dissolves silver when it is hot.The way to precipitate this silver sulphate is adding some "coperas" which is ferric sulphate.

In my opinion they are silver cartridges recovery unit (SCRU) but I look them in the pics almost new...I mean,the had very little use because the steel wool dissolves and the silver goes down in a black mud(check the original container looking for some mud)..the steel wool seems pretty new..anyway...you can dissolve the iron and live the silver with cold sulphuric acid or you can disssolve both with nitric acid and recover and refine the silver with Karo syrup method.

Be careful about the brown fumes released...do it outside or use some NOx preventing like hydrogen peroxide.I am not in my town due to the Influenza epidemic but I promess to post some technical information about SCRU as soon as possible.

Regards

Manuel


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## Ignatz61 (Jun 2, 2009)

Thanks everyone,
I have had no luck lately with the rusty material. I have 15lbs of the black sludge but it too isn't yielding any silver. I get the cast iron type material. It is heavy and sometimes there are small beads of silver in it. Almost like the iron is starting to react but not finished. I have let it stay in the furnace from minutes after going liquid to 2 hours with the same results.

Does the dense cast iron like layer always contain silver or can it be just the iron from the screen/steel wool?

Is there an easy test (chemical) that I can preform to determine if there is silver in the material before wasting anymore time melting?

I was thinking about the nitric vs sulphuric acids. I geuss I will try a cold soak in sulphuric to get the iron into solution then wash and dissolve the solids in nitric, then recover any silver from the nitric (cement with copper?)


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## Juan Manuel Arcos Frank (Jun 4, 2009)

Ignatz61:
Yeah...there is a method to check if you have silver in your material.Take 20 gr of your material,add 50 ml. of nitric acid (50% concentration),do it outside because brown fumes will be released...once that the reaction stops pour off the liquid then add some common salt to the liquid...if you see a white precipitate (silver chloride) which is insoluble in water then probably you have silver in your material.

I guess that you only have iron and silver in your material...the white mud could be lead chloride or mercury chloride...lead chloride dissolves in hot water(silver chloride do not),mercury chloride does not dissolve in amonia but silver chloride dissolves on amonia.

I hope it helps.

Regards

Manuel


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## jim_geo7 (Feb 18, 2021)

I'm absolutely new here and new to the process of recovery of any kind of metal. However, I have several silver traps as a result of being the person that used to maintain radiology for a veterinary practice now gone digital. I wasn't the best at keeping up with the silver traps and several of them required being changed due to splitting open. I think there might be a lot of silver in these canisters. Also I have easily 100 pounds of large radiological films, which as I understand it, can be stripped with bleach to remove the silver. My question is this, how do I go about removing the silver from the canisters? Do I just break them open and wash the contents out to get a gray slurry and then follow the process described in this discussion?


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## Lino1406 (Feb 20, 2021)

Films - can be stripped by 10% NaOH. Iron mixed with silver, in principle dissolve the iron with AR and get some of the silver converted as AgCl


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