Discussion about video in recovery of gold from used filter papers

[4metals]

In our new video section in the library we have posted a video by Sreetips which is a 2 part video of his complete process to recover the values from his used filter paper collection. Personally I have never processed sweeps in small quantities to have any practical hands on experience with the method he uses. And I have never been a big fan of the hot sulfuric peroxide method.

My goal here is to start a discussion of his method from the video and once this discussion develops I can link it to the video section so anyone can click the link and end up on the discussion thread. This can be done with any video you may want to question or critique, but please start a thread specific to the video you want to question and name it accordingly.

So please let the discussion begin about Sreetips 2 part recovery of gold from used filter papers video found in the video section. (And ONLY about that video!!!!)

 

[Martijn]

There was a lot of smoke from both the fire and the papers. Green flames indicating salts being bunt off.

As filters will contain metal salts, and filters from AR will likely have silver chloride, I was wondering if burning gold chloride and silver chloride salts lead to losses?

A method I used was soaking the filters in warm water and adding SMB to it. Then i added sulfuric acid and iron nails with lots of stirring to convert any silver chloride to silver.
Lots of washing to get the pH to neutral and test the rinse water for salts with NaOH.

Then I incinerated the paper mass.
I think it cuts on smoke and toxic gases.

If you incinerate all carbon completely, the sulfuric and H2O2 are not needed imo. I did not see much difference in the solution clearing up anyway in the video.

Then a nitric bath to get the Ag and Pd out, followed by AR.
I would have let the AR solution go longer and stop when adding nitric would not cause a reaction. I think he had more to dissolve from the ash.

 

[4metals]

I always wet the papers with a dilute SMB solution as well. I also added all of my test papers and spill cleanup papers to the drum to process. Then I dried the papers until they could be shoveled into an incinerator.

If you incinerate all carbon completely, the sulfuric and H2O2 are not needed imo

I agree with this and having had the luxury of having an incinerator capable of reaching the temperatures to burn off the carbon I never needed any pre treatment.

But if a burn pile is your incinerator you use what you have. In that case strong caustic is also effective but I was hoping for a side by side comparison from someone who has used both caustic for the purpose of dealing with the carbon and used ( not together but on separate lots ) the sulfuric and peroxide.

 

[4metals]

Then i added sulfuric acid and iron nails with lots of stirring to convert any silver chloride to silver.

I do not see the benefit of this step. It is not like you have fine powder you can tumble with the sulfuric and nails to assure Silver chloride to iron contact, the Silver chloride is mixed with a lot of paper and fiber and the ability to have the iron physically touch some Silver Chloride is pretty random that it will not be effective. This will more than likely create some large paper coated iron spitballs with little conversion.

 

[Martijn]

I do not see the benefit of this step. It is not like you have fine powder you can tumble with the sulfuric and nails to assure Silver chloride to iron contact, the Silver chloride is mixed with a lot of paper and fiber and the ability to have the iron physically touch some Silver Chloride is pretty random that it will not be effective. This will more than likely create some large paper coated iron spitballs with little conversion.

What happens to the silver chloride when treating filters the way sreetips does it? Does he recover it after AR?

 

[haveagojoe]

I have been thinking about processing my filters from AP, I'm not sure incineration is really necessary for me since I think there won't be such a wide range of contaminants as mixed waste filters including from AR, and also I don't have as many filters as Sreetips had to deal with. Would I be correct in thinking that aside from removing contaminants, the main reason for incineration is to reduce the volume of the material? I think in my case it will be fine to dissolve the gold in the filters directly without incinerating. I've seen it done this way in other videos and it seems the main disadvantage is that the filters partially dissolve into a pulp which clogs the new filter and makes it slow, but since this is a once-in-a-while process I'm ok with that.

 

[4metals]

What happens to the silver chloride when treating filters the way sreetips does it? Does he recover it after AR?

Most of what sreetips processes is karat gold which has been inquarted and parted so there is very little Silver Chloride anyway

 

[4metals]

I have been thinking about processing my filters from AP, I'm not sure incineration is really necessary for me since I think there won't be such a wide range of contaminants as mixed waste filters including from AR, and also I don't have as many filters as Sreetips had to deal with.

The filter papers retain a slight amount of liquid because papers retain liquids. So every paper has a minute quantity of liquid long since dried and containing a very very small quantity of Gold. If you just re wet those papers you will never rinse out all of the gold containing liquid all over again. By burning it you make it into a material that will retain less liquid and rinse better. I would not skip the burning step.

I know plenty of refiners who save the papers and burnables in a convenient sized pail and when it fills up they burn it and save it in it's much reduced burned volume until they accumulate a large quantity to process. Unless you are sloppy and leave metals behind or decant liquids aggressively processing papers is a lot of effort for little payoff.

 

[haveagojoe]

The filter papers retain a slight amount of liquid because papers retain liquids. So every paper has a minute quantity of liquid long since dried and containing a very very small quantity of Gold. If you just re wet those papers you will never rinse out all of the gold containing liquid all over again. By burning it you make it into a material that will retain less liquid and rinse better. I would not skip the burning step.

I know plenty of refiners who save the papers and burnables in a convenient sized pail and when it fills up they burn it and save it in it's much reduced burned volume until they accumulate a large quantity to process. Unless you are sloppy and leave metals behind or decant liquids aggressively processing papers is a lot of effort for little payoff.

My papers contain quite a lot of black powder which could be gold, or base metals. I'm considering trying to redissolve them with HCl and peroxide without burning, I think whatever is left after refiltering will be so little as to not be worth bothering with.

 

[4metals]

My papers contain quite a lot of black powder which could be gold, or base metals. I'm considering trying to redissolve them with HCl and peroxide without burning, I think whatever is left after refiltering will be so little as to not be worth bothering with.

Everything that has seen precious metals in a refinery is considered valuable and processed at some point. Conventional wisdom dictates burning but you should "have a go Joe" you may be right!

 

[haveagojoe]

Conventional wisdom dictates burning

If I were to burn them, is it necessary to do it as a closed incineration such as in a saucepan with a lid, in a fire as Sreetips does? Hoke suggests burning them in a frying pan with a gasoline (p216)- obviously I wouldn't add gasoline but would it be ok to just set them on fire? I'm guessing there is a possibility that some gold particles might be carried away by the heat and smoke but for a small quantity it seems like it might be alright to just light the edges one by one and let them burn up slowly.

Edit to add- I have about 50 or so filters to deal with at the moment

 

[4metals]

I would use a sealed can with a small hole in the lid to limit oxygen but prevent pressurizing to cause an explosion. This will gas off all of the volatile gasses when the can is placed in a fire. When the fire dies down open the can and the papers will appear charred and they will be pyrolyzed. Or essentially charcoal. Now a torch will easily ignite them and the carbon will burn off leaving a fine ash.