Discussion about video in recovery of gold from used filter papers

[snoman701]

I dont think the loss issues are so much from open burning, it's from the AgCl. It drags your Au up the stack with the thick white smoke.

I have saved filters for a long time, but I'm not sure if I should start out by boiling them in NaOH in hopes of converting some of that AgCl to Ag2O, or if I should tumble them in sodium thiosulfate. EIther way.

Even for polishings lots that I have already acid processed. I know there is still gold in it, I just don't know how much, and any of the standard processing methods will send some of that gold up the chimney. Just not sure if it's worth trying to avoid, because I'm not sure what the payout is.

 

[grainsofgold]

Your losses sending it out are not so much how they are doing it as it is who you are sending it to!

I never refined sweeps, I prepared them by incineration, crushing and sifting them so they were homogeneous and could be fire assayed. Then we made up large lots and shipped to a smelter in Europe. They never had issue with our results and they charged as advertised so we were happy. Years ago it was something like $2 per pound plus 2% of the PM value. And they paid on Silver. Hard to beat those rates doing it in acid.

Another way I have done this is to burn down the filters and all, ball mill and separate then load it with thinning flux and heat it for an hour or so then stir and pour it into a conical mold and knock off the tip of metal and process that the usual way -

 

[goldshark]

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

Sreetips inquarts using Nitric only. He is pretty clean as far as not overdosing it with Nitric. That being said, he has Silver Nitrate, which he then cements on Copper, turns to shot, then Ag cells it to crystals. So as 4 metals said, there should be very little, if any AgCl in the papers. There could be some from other processes, but should see if he keeps them in a separate pile.

 

[kurtak]

I have saved filters for a long time, but I'm not sure if I should start out by boiling them in NaOH in hopes of converting some of that AgCl to Ag2O, or if I should tumble them in sodium thiosulfate. EIther way.

If the AgCl (in the filters) has dried out you will not get complete conversion of the AgCl to Ag2O

You will get better recovery of the silver by using soda ash as one of your flux ingredients in a smelt - if there is "a lot" of AgCl you want the soda ash to be the main flux ingredient - like 60% (plus)

You then want to bring you smelt load up to about 800 F (in the furnace) & hold it there for about an hour before bring the temp all the way up to melt temp

You can do that by leaving the furnace lid open & controlling the flame from your burner

That will give you your best recovery of silver from filters (after incineration) with dried out AgCl

Also - when burning your filters you want to (need to) control the burn temp & as well do the burn with a lack of oxygen (lid on top of the burn pot) other wise you will not only vaporize AgCl but other PM salts in the filters

Kurt

 

[kurtak]

Here is a link to something I posted about "proper" burning of filter paper (so your values don't go up in smoke)

https://goldrefiningforum.com/threads/incinerated-filters-and-pm-salts-recovery.21638/page-2

Kurt