Film silver recover,a new process

[Harold_V]

Harold_V:

Rough and wise,as always.How about recovering more silver than gold?.I am sure you will get too much money from silver recovering.

Regards.

Manuel

Manuel,

Funny, my customer base was established by need. I don't know if I was lucky, or it's the nature of the business, but silver came to me in about the proper ratio that allowed for inquartation of karat gold. I rarely ran out--but I made a point of not processing silver scrap without first using it as my added metal. I'm not sure I could have increased my flow ---although at one point in time I'd have gladly done so. You may understand that I no longer refine, having sold the business in the early 90's.

Unlike GSP, I ran silver on a limited basis. My cell was small in the scheme of things, so my output was not large. I would accumulate a couple thousand ounces before firing up the cell, then it would run on a continual basis until I had processed all of the anodes I had cast.

Melting once recovered silver for reuse in inquartation, for me, was not a good idea. It typically had platinum or palladium, often both, included. Allowing those metals to get too highly concentrated raises hell in the parting process---often leading to depleted electrolyte (been there, done that, caused by a heavy coating of platinum and palladium sponge that restricted free flow of silver from the anode).

I am of the opinion there's a lot of money to be made with silver----it's just that I had better success with gold.

Harold

 

[Oz]

That is a very interesting commentary Harold. I have been re-running the same silver for some time for inquartation with gold knowing full well that I was accumulating PGMs. I have yet to build a silver cell to clean my “impurities” from it. It is good to know that the high PGM content may cause problems if I understand you correctly. Oddly enough it seems that I may need to dilute my inquartation silver with additional silver when I get to the point of wanting to remove reasonably pure silver, based on your comments.

As stated above, I have no personal experience yet with a silver parting cell.

 

[Harold_V]

When I ran my wastes, after more than 20 years of operation, the yield was very high in the platinum group, due to my including the stock pot residues in the waste material. I learned to not try to recover from dilute solutions after recovering gold---the values were recovered in the stock pot.
Parting the silveranodes (the silver was recovered with copper) was a real trial. I had to hand scrape the anode to free the sludge, and it didn't go willingly. It normally sloughs off and can be scooped out, using an acid dipper.

So this makes more sense, I had included all my filters from filtering gold chloride solutions, each of which had a generous amount of silver chloride included. That was by design, knowing it would act as a collector when I processed the waste by furnace. I didn't want to use lead----for obvious reasons.

As it turned out, the plan worked exceedingly well (more by sheer luck than anything, although I did my homework regards using what I thought was the proper flux). In the recovery process, parting the doré that came from the furnace allowed for some separation of platinum and palladium from the solids, but not all. Remember, when platinum is in the presence of silver, some of it, if not all, will dissolve in nitric acid.

I strongly advise you not endlessly use the same silver to avoid problems later. I also advise you to check the nitrate solution after the silver has been precipitated with copper, especially if the solution is NOT blue. My experience indicated that if it leaned green, it was because the solution contained values. They are generally the last to come down, and appear as black smut in the silver. Test your solution, ALWAYS, with stannous chloride.

Harold

 

[Oz]

The silver I re-use is indeed recovered with copper cementation as you did. I also knew that palladium and platinum hitched a ride, I am not as sure about the occasional rhodium.

I also agree that any silver that survived inquartation then nitric would be in my saved filters.

I have not bothered to do serious research into the flux I would require as I only have several gallon containers of filter material saved as of yet.

The most informative point to me was the difficulty you had in parting the silver if PGMs were high. It is your experience that leads me to believe I needed to part my silver sooner than later.

Cementing my silver I always get that deep cobalt blue due to patience, but you are correct in stating I should check more often than I do with stannous.

 

[Harold_V]

If you have the ability to incinerate, do so. Filters will burn down to very little ash, making storage easier, but most importantly, free from acid fumes. I heated mine until all the carbon had been eliminated. You can verify that by playing oxygen on the ash, using a torch. If any carbon remains, it generally burns with a brilliant yellow/white intensity.

If, when you're ready to melt your waste materials, I'd be happy to provide the flux recipe I used. Fact is, I think I've posted it on the board before.

I had my slag assayed after recovery and found it so low in value that the company in Sparks, Nevada (now defunct) that used to process just such things for contained values, wouldn't accept it. I ran my waste in a reverberatory furnace of my own design, and it got a generous soak, insuring all the values were collected. I explored all of the slag as I cleaned the buttons and never found prills. The slag was very fluid----and reduced the values beyond my wildest hopes. It was correspondingly hard on furnace lining, but that's a small price to pay when recovering over 200 ounces of gold, to say nothing of the silver and platinum group.

Harold

 

[Oz]

It looks like we are the insomniacs in the US tonight, perhaps we should have taken it to PMs. I hope there is value to others in our multi-thread chat.

I have read your post on incineration and think somewhere on my computer I have saved your flux recipe. I have a $1 stainless steel pan that was a flea market find waiting for the day I need to reduce my filter volume. As I have a torch, it is a nice idea you have applying oxygen to the ash to assure complete combustion of the carbon as it can steal values.

Some of my delay in filter processing is in fact due to you and your mention of your “savings plan”. Small amounts compared to what has been processed to be sure, but it will work like compounded interest.

 

[Harold_V]

It looks like we are the insomniacs in the US tonight, perhaps we should have taken it to PMs. I hope there is value to others in our multi-thread chat.

I am, by nature, a night person. I generally get to sleep around 5:00 AM, and sleep until about 11:00. I followed that schedule for many of my working years. I'm far more productive if I don't get up early.

As far as others are concerned, if they can't learn anything from our conversation, I pity them. There are all kinds of subtle tidbits that are being tossed about here.

As I have a torch, it is a nice idea you have applying oxygen to the ash to assure complete combustion of the carbon as it can steal values.

I congratulate you for knowing that. I wonder how many do?

Yes, my ash was barren of carbon. Always. I heated my pan with natural gas until all the things that would burn did, then I heated the pan with my Hoke torch until the base was red. Any carbon that had not burned readily did so. I also stirred the waste with a steel rod, 3/8" diameter, to insure that everything was exposed to oxygen.

While the above took time, my reward, in the end, made the time and money spent through the years to appear as a bargain. It truly was.

Some of my delay in filter processing is in fact due to you and your mention of your “savings plan”. Small amounts compared to what has been processed to be sure, but it will work like compounded interest.

Yep! You can't spend it when it's just junk.

I had retirement in mind from the outset------that's what my gold was intended for. Turns out I saved a lot more than I realized, thanks to the waste materials. Best part of the entire thing is I had a lot of fun along the way, and learned so many things that I, otherwise, would not have learned. One of them is how little people know about gold.

Harold

 

[qst42know]

Manuel,

I up sized the batch to 5oz of film. The solution is fast through the filter the gelatin must be gone. Too fast for coffee filters. The silver on film must be very fine.

I am tracking down some better filters What grade would you suggest?

Some material settled quickly however the solution is still quite dark. After sitting for a couple of days the solution seems to be clearing the more it sits.

Because of the dark solution how do you know when all the silver is down?

 

[Juan Manuel Arcos Frank]

gst42know:

Use filter paper No. 2,it is the standard and it will work well.Almost all the silver is down,but filter the solution,darkness could not be silver,could be aminoacids,do not worry,all your silver has benn precipitated.

Regards

Manuel

 

[qst42know]

I ended up making some nitric and adding some to this solution in a couple test tubes. When the solution went clear a pinch of salt in one and a couple drops of hcl in the other with no reaction in either.

Just waiting for the filter funnel and papers to arrive.

 

[Juan Manuel Arcos Frank]

gst42know:

It is OK,I am here to see what happens.

Regards.

Manuel

 

[qst42know]

It took a while to but after running this through a vacuum filter with #5 Whatman filter papers (2.5um) I was only able to capture some of the silver. Much of it is so fine it passes right through the filter. If you were to use #2 filters most of the silver would be lost. The remaining solution was set aside to settle, then the bulk of the liquid was siphoned off. I plan to evaporate the remains.

If this were attempted on a commercial level how would one collect this material that so stubbornly defies filtration?

I will get back to you with my results.

 

[eagle2]

No doubt the expert refiners here would have a good method.

But you don`t have to filter. I would just suction off the liquid after the solids settle. Wash them with water once or twice, letting the solids settle each time. Suctioning off the liquid one last time and evaporating the last, until it is dry enough to melt to a dore` bar.


Then sell it or electo-refine it yourself.

Al

 

[Lou]

Try boiling it. Sometimes a good boil helps precipitates agglomerate and stick together.

 

[qst42know]

I tried to vacuum filter and the finest standard grade of Whatman filters was no match for this solution. In an effort to keep the waste solutions down I will give boiling a try. Its half way to evaporation anyway.

 

[qst42know]

This solution was indeed stubborn. It took a boil, settle, change water, boil and settle. Boiling and rinsing. So thanks to both Lou and eagle2. I suspect a separatory funnel may have been beneficial but I don't own one.

After much fretting and fussing the results from approximately 5-1/4oz. of this early film negatives I recovered 1.25 gm of silver. The larger ball is 1 gram and is from the first filtering of the original solution and the water I rinsed the negatives in. The second bead was from the fines that gave me such trouble and weighs 1/4 gram.

The amounts are trivial I know but this was a quest for knowledge. And this was indeed a learning experience. Thanks for all the advice and help.

A couple of the big lessons: film silver is very fine a couple days of settling makes a difference. Oxalic acid seams to have a soap like quality that keeps things in suspension. Boiling and rinsing is vital. Continuous agitation and perhaps shreading would help keep films from sticking together. The silver is very clean as evidenced by the sprouting (the surface eroptions) of the first button.

Chris

 

[Juan Manuel Arcos Frank]

qst42know:

Congratulations!

 

[hoardpm]

If I am reading this correctly if I use oxalic acid to process films there is no need to pracipitate the solution. Just let settle, syphon off the liquid then let dry and melt. Is this correct? What about the gelitan or other contanimantes that are on the films? Also, in the event that silver oxalate if formed as GSP suggests is there a way to test for it other than throwing a torch to it and hoping I dont blow up?

 

[qst42know]

This is the procedure I found for forming silver oxalate.

http://www.powerlabs.org/chemlabs/silver_oxalate.htm

It is synthesized from silver nitrate.

If you keep nitric acid out of the mix you should be OK.

Does this sound right to you Lou? GSP?

Developed film doesn't have any silver nitrate remaining does it?

 

[Lou]

Yes, it is made from silver nitrate. It's nothing much to worry about.