# processing used filters



## martymcfly (Oct 4, 2013)

After my last few trials at A/R ive been left with a few filters that have various powders still in them and was wondering the best way to go about processing them?

At the moment i dont have an incineration setup at all but was thinking of just lighting the filters so im left with just the powders and carbon and then putting these into some A/R to get out what little gold may be left.

Does this sound like an acceptable way to process these filters or would this cause some sort of mess with mixing the carbon in with the A/R?

Any comments are appreciated.


----------



## niteliteone (Oct 4, 2013)

The carbon will trap the gold in solution if you don't remove it first.
Be sure to completely incinerate and remove as much of the ash as possible to minimize loss. Use a soft flame to go over the powders to consume as much of the carbon soot as possible.


----------



## Geo (Oct 4, 2013)

if the filters are good and dry, place them in a metal container and light them. near the end, be sure to move the ash around so that air can reach all the ashes. theres no good way to remove all the carbon without loosing some values. most paper filters will burn to a white ash anyway if its good and dry.


----------



## goldenfrog (Jun 24, 2017)

Hope I'm not Hijacking this thread, but I would like help on the same topic.

I have collected filter papers for quite some time and just incinerated them.
My question is, is there a procedure for recovering both silver and gold out of them? 
I know most threads I have researched all just process with AR and pull the gold, but I know I have alot of silver in there too (mostly from impatience and inexperience). 
I guess what I am wondering is what chemicals to begin with to recover both
nitric for silver first?
HCL wash first? 
or just AR and dont worry about the silver?


----------



## Topher_osAUrus (Jun 24, 2017)

The silver, (if this is all from AR), will be in silver chloride form. So you will need to convert it to metallic silver or silver oxide first.

There are many ways to skin this cat.
You could use one of a few ways to convert it to metal silver, then leach. Or you could melt it after conversion, pour shot, then leach. 

Or you could just go after the gold, leave the AgCl in a marked "waste" bucket and save it for retirement.

A book Im reading now, mentions just mixing the incinerated ash with sodium carbonate and melting like that. I think thats a pretty bad idea though because of losses. I only mention it to show there are numerous ways to get it done.

Also, sodium hypo solution will remove agcl.
So will ammonia
-but I would only do that ammonia one if you are FOR SURE that the auric chloride has been reduced to metal. As ammonia plus gold chloride equals a very bad time.


----------



## goldenfrog (Jun 24, 2017)

Thanks for replying Topher, 
I guess what I am wanting to know is, should I process spent AR after dropping the gold? for silver then? 
or is there a better way to pull that silver (be it silver chloride or what) before dropping the gold?
Im not as rehearsed at melting things yet, I can incinerate but have had a few snags trying to melt.


----------



## Topher_osAUrus (Jun 24, 2017)

goldenfrog said:


> Thanks for replying Topher,
> I guess what I am wanting to know is, should I process spent AR after dropping the gold? for silver then?
> or is there a better way to pull that silver (be it silver chloride or what) before dropping the gold?
> Im not as rehearsed at melting things yet, I can incinerate but have had a few snags trying to melt.



I guess I am a bit confused now.
You are asking how to recover the silver from an AR solution (obtained by dissolution of the ashed filters)?
-if yes
The silver chloride in the AR solution will be very minimal, the majority of the AgCl will be in the insoluble fraction of the ashes.
Thats not to say that NO silver will be in the strong chloride solution, but, very small amounts (just enough to mess up the purity of gold if you immediately precipitated it)
To remove the silver chloride in solution, you would need to dilute and chill the solution 2-3x the volume, and it will self precipitate.
I would allow it to settle and then siphon off the clear ar solution from it. Denox the solution and drop the gold.

To the insolubles, i would rinse them well with water. Then i would put them in a cast iron skillet with a 10-20% sulfuric acid solution. Stir and stir and stir and stir and then stir a little more, after that, probably some more stirring.
The iron and sulfuric is reducing the silver chloride back to metallic silver, it is a contact process, so if the AgCl doesnt contact the iron, it doesnt convert.
After awhile, I would then remove the sulfuric solution (which you could crystalize and use that ferrous sulfate to precipitate gold with...thats another ordeal all together though, Ill stick with the original question for now)
The silver metal, now much darker after its conversion, is ready to be rinsed, dried and melted.
There is undoubtedly plenty of trash in with the lot of converted silver. Melting will help "separate the wheat from the chaff" and leave you will silver metal with some impurities. Probably some lead, from lead sulfate, gold, from the gold that couldnt get rinsed out of the silver chloride, and some other stuff too.

Hopefully I understood your question correctly, if not, sorry for the long (unneeded) reply


----------



## goldenfrog (Jun 24, 2017)

Thanks! 
Yes! that is what I was wondering! 
cool! I will give it a go!

as for your reference to making Copperas with the iron sulfate, I was looking around for that procedure too.
I am not a fan of the stinky SMB and wanted to try dropping gold with it sometime. 
How do you crystalize the iron sulfate?


----------



## Topher_osAUrus (Jun 24, 2017)

goldenfrog said:


> Thanks!
> Yes! that is what I was wondering!
> cool! I will give it a go!
> 
> ...



Butcher has a great thread on it somewhere. But, I can outline how I do it here.

Generally. I take some clean iron, and put it in a large beaker. I cover it with water, and add sulfuric in small doses to get it working at the iron. This addition of sulfuric to water can be violent so do so carefully.
After you have it around 10-20% concentration of acid put it on some heat. Let it work until it will cannot dissolve anymore iron.
Then, filter it through a fiberglass Charmin plug into another beaker. Let it cool, as this solution of ferrous sulfate cools, it will crystallize out copperas crystals (because it is super saturated)
After it has gotten as cold as it will, you can decant the solution off the crystals and put it back on the iron to dissolve more. Just add a little bit more water and a tiny bit more acid.

The crystals will be a very beautiful green color. When I use them to drop gold, all I do is dissolve them in water, I don't even need to add HCl as they are all perfect and fresh. Its lovely.

Search for "making copperas" by butcher, he has a much better post on it than this one!


----------



## goldenfrog (Jun 24, 2017)

Will do!
Thanks again!


----------



## geedigity (Jun 24, 2017)

I have been saving filters, paper towels, wipes, etc that have a least some gold, silver, palladium, platinum and of course, base metals on or in them. These are a result of a couple years of refining and I have been reluctant to incinerate for a couple reasons. The first is due to potentially volatilizing the Au if in the form of AuCl and the second is the AuCl that did not volatilize potentially getting absorbed into the carbon during incineration.

I think you are on to something Topher when you indicated that goldenfrog could reduce the AgCl by using sulfuric acid (dilute) and iron. Although it would be a bit messy, the copperas produced would also reduce any AuCl into Au.

At that point the "pulp," could be spread out, dried and then incinerated. This would seem to be a way to reduce losses due to direct incineration of filters, wipes, etc.

Does this seem reasonable at all or should I just directly incinerate material without any chemical treatment and filter the heck out of my incinerator exhaust fumes? The fumes from the incinerator go directly into a homemade afterburner and I don't have a filter on the exhaust of the afterburner. If I did need to filter the exhaust, it would need to be at a point where the exhaust fumes have cooled somewhat. 

The problem I see with the exhaust fume filtering approach is that the gold and potentially other pgms are deposited throughout the cooler areas of the exhaust system and would be losses until such time the system is cleaned out and the material recovered. 

I will continue to save the material, but it really starts to add up, no matter how careful I am with trying to prevent spills and drips.


----------



## Topher_osAUrus (Jun 24, 2017)

geedigity said:


> The first is due to potentially volatilizing the Au if in the form of AuCl and the second is the AuCl that did not volatilize potentially getting absorbed into the carbon during incineration.
> .



There is another way that is good, or better, if you think there is a lot of AuCl in the filters still. Butcher suggests doing a wash with NaOH to convert all the chlorides to oxides or hydroxides. That way the chances of volatizing are less.

I will try to find where he mentioned this, but, I havent had a lot of time to go through the forum again and bookmark the good threads again (more importantly sync my bookmarks after refinding them)

He basically stated to do a good rinse of the filters in some dilute sodium hydroxide, then let it settle, and then decant, afterwords rinsing out the sodium chloride salts (which would also cause volatile losses, if i recall correctly) 

The sulfuric leach would pulp some of the filters, and would also convert other metals from their chloride salts to metallic bits.

I usually just slowly dry my stuff, then force dry and then torch them.
After I do the sulfuric conversion, drying silver chloride with a torch is stinky (and dangerous) business.

To say which is better, is probably like comparing oranges to apples. They are both good for their own reasons, and both will help prevent scurvy.

I choose sulfuric solely because I don't like the idea of going blind from one drop of something, yes sulfuric can maim and disfigure me for life (if improperly handled), but Im already blind in one eye, so I dont take chances lightly in that regard.
I also like that there is no intermediate step before conversion to metallic, unlike with NaOH, where it goes to AgO first, then needs more treatments.

Again, all preference

Edit to finish:
I forgot you brought up the carbon absorption.
Im not sure how much of it is an absorption vs being an actual precipitation. Rose mentions carbon being an excellent reducer of gold, in that it will leave a shiny deposit on a chunk of charcoal. Now I know, and realise that there are substantial differences between carbon and activated carbon, and in that aspect, I am unsure if the activated carbon will absorb the gold in its chloride form, or if it will reduce it to metallic gold as well. Im at a birthday party right now, so I am not with my books, but will be home shortly and post a new reply when I find the pertinent information. But, I dont recall activated carbon being mentioned in his book, or many others for that matter.


----------



## FrugalRefiner (Jun 24, 2017)

Topher_osAUrus said:


> Im at a birthday party right now, so I am not with my books, but will be home shortly and post a new reply when I find the pertinent information.


How to know you're addicted to the forum! :lol: :lol: :lol: 

Dave


----------



## Topher_osAUrus (Jun 24, 2017)

FrugalRefiner said:


> Topher_osAUrus said:
> 
> 
> > Im at a birthday party right now, so I am not with my books, but will be home shortly and post a new reply when I find the pertinent information.
> ...


 :mrgreen: 

Hello, my name is topher, and I have an addiction. :lol: 

"The solution of trichloride of gold is also decomposed by many reducing agents, such as most organic substances, metals and protosalts; heating the solution in every case hastens the decomposition. The reduction by organic matter is assisted by the action of light, which is especially efficacious in the presence if starchy and saccharine compounds, or of charcoal or ether. In direct sunlight the last reagent deposits a bright mirror of metallic gold."
-Rose, Metallurgy of Gold (pg25)

I believe I am thinking of another excerpt, but will have to find it, as I foolishly did not annotate it in the back of the book.
Nevermind, next page I found it

"the precipitation by means of charcoal is of especial importance in view of its adoptation in practice.."


----------



## geedigity (Jun 25, 2017)

Thank you.


----------



## andreworange (Jul 24, 2017)

My name's Andrew and I'm a forum addict.....


----------



## goldsilverpro (Jul 24, 2017)

andreworange said:


> My name's Andrew and I'm a forum addict.....


  I've felt like that for the last 10+ years.


----------



## UncleBenBen (Jul 24, 2017)

I've been able to quit drinking, smoking, biting my nails and half a dozen other habits. At one point I was even addicted to the Hokey Pokey, :shock: 
But I turned myself around! :roll:

Yet I've tried the gum, the patches, hypnosis. I even got married so I could be constantly nagged about it. But I still can't kick this forum habit!


----------



## Shark (Jul 24, 2017)

I spent a few days on the forum from a hospital bed waiting for open heart surgery. Since then I have been on the forum at two other times, from a hospital bed. After 49 years of smoking I quit cold turkey, but the forum has been a tough nut to crack. I am quickly beginning to believe I may have a problem as well. :shock:


----------



## anachronism (Jul 24, 2017)

Yeah but Shark you're a fighter. Utmost respect.

Jon


----------



## upcyclist (Jul 28, 2017)

goldenfrog said:


> as for your reference to making Copperas with the iron sulfate, I was looking around for that procedure too.
> I am not a fan of the stinky SMB and wanted to try dropping gold with it sometime.
> How do you crystalize the iron sulfate?


I'm pretty sure both copperas and SMB work by releasing sulfur dioxide gas ("the stinky"), which is what actually precipitates your gold. In larger scale settings, SO2 gas is often used directly.


----------



## Topher_osAUrus (Jul 28, 2017)

upcyclist said:


> goldenfrog said:
> 
> 
> > as for your reference to making Copperas with the iron sulfate, I was looking around for that procedure too.
> ...



Copperas has a different reduction reaction for precipitation.

Lazersteve has the formula posted half down or so
http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?t=3791

I like using copperas, a lot.
If its stuff I have made, I just use the crystals straight. No water to dissolve them, or HCl to turn the aqueous solution green.
Hi yield stuff, needs dissolved and treated first, then filtered before use.

Break time over.. Back to work


----------



## upcyclist (Jul 28, 2017)

Topher_osAUrus said:


> upcyclist said:
> 
> 
> > goldenfrog said:
> ...


I stand corrected, then.

I use it undissolved as well--I use ice to dilute, so I know there's plenty of water available.


----------



## Topher_osAUrus (Jul 28, 2017)

upcyclist said:


> I use it undissolved as well--I use ice to dilute, so I know there's plenty of water available.



Do you use hi-yield, make your own, or get some pure stuff from a chem company?

I've never had good luck with hi-yield or other. It seems once they dry the crystals out they start to oxidize quickly and after dissolving the bulk of them in water, there is always little orange-brown-rusty bits at the bottom. After I add HCl to it, it of course turns green and I hear bubbles from the bottom (I assume the colored bits reacting with the HCl)

...anyways, the not so long-short of it.
If you get the oxidized stuff and add it directly to the auric chloride, some of those iron bits may be difficult to wash out of your lovely pure gold powder.

However, if you get the pure, non oxidized stuff, or make your own and store it properly. Disregard all of that posted above.


----------



## nickvc (Jul 28, 2017)

The one problem with copperas is that it will leave traces of iron in your precipitated gold if it is not very clean, changed from that nice green coloured crystals to a straw like colour, if that occurs dissolving in hot water and adding Hcl is recommended.


----------



## upcyclist (Jul 28, 2017)

I think mine actually came from a food- or wine-producer place. It's still green.

Also, I tend to do first drop with copperas, second with SMB.


----------



## Topher_osAUrus (Jul 28, 2017)

upcyclist said:


> I think mine actually came from a food- or wine-producer place. It's still green.
> 
> Also, I tend to do first drop with copperas, second with SMB.



I figured a wise man such as yourself would have such a good practice.  



nickvc said:


> The one problem with copperas is that it will leave traces of iron in your precipitated gold if it is not very clean, changed from that nice green coloured crystals to a straw like colour, if that occurs dissolving in hot water and adding Hcl is recommended.



I bought a bunch of used chems from a member last year, and the copperas was all oxidized. It was a mix of straw colored to dirt brown. With some little specs of light green.
I did not want to take the chance, so I ended up dissolving it and crystalizing it again. 

I love the practice of copperas first drop. Smb 2nd, if 3rd is required, oxalic. But, I only do that for jewelers that are using the gold for their work.
It gives me peace of mind, knowing that it is about as pure as I could possibly ever get it (without trying to replicate Lou's insane ultra pure gold method!)

Okay-thread derail over.. Got to unload my last bit of stuff, since we just pulled into town.. Home sweet home


----------

