# sulphuric cell gold in filters



## Ian18206 (Jan 25, 2013)

hello everyone i just processed some gold filled and plated through the sulphuric cell and filtered the solution with coffee filters.
all the black powder is in coffee filters and i was wondering on how to get the gold off the coffee filters without losing any.
i was going to melt the filters and all but i don't want to risk losing any gold because i use torches to melt. any help would be greatly appreciated.
thanks


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## NobleMetalWorks (Jan 25, 2013)

Ian18206 said:


> hello everyone i just processed some gold filled and plated through the sulphuric cell and filtered the solution with coffee filters.
> all the black powder is in coffee filters and i was wondering on how to get the gold off the coffee filters without losing any.
> i was going to melt the filters and all but i don't want to risk losing any gold because i use torches to melt. any help would be greatly appreciated.
> thanks



Paper coffee filters will dissolve if you attempt to filter sulfuric acid through them. Matter of fact, you should not use any organic material around sulfuric acid unless your intent is to dissolve the organic material.

I use fiberglass to filter sulfuric acid, or polypropylene felt.

Here is the brand of fiberglass and item number I use...







You can either make what is called a charmin plug, which basically is fiberglass stuffed into the neck of a funnel. By pulling just a little out of the end and allowing it to hang out of the bottom, it will help to pull the solution through. Using a filtering flask and a vacuum pump will work even better. I use the fiberglass, and line a plastic colander with the fiberglass to filter the bulk of the black sand from the sulfuric acid. Then I process through a funnel with a charmin plug, using a filter flask and vacuum pump. Then I take all the fiberglass and immerse it in AR to dissolve the filtered material. It will look something like this.






The white material in the beaker is the fiberglass. here is a picture closer up.






What is interesting about doing this, is that if you turn the fiberglass upside down so the filtered black material is facing the bottom, and the fiberglass that has none is on top, it actually suppresses the NOx from evolving outside the beaker, so that it can be re-absorbed back into solution. You can see I do this under a fume hood because some gas will escape, but the majoring stays in solution doing it in this way. Here is another picture closer up. If you can tell, the brown color is NOx gas, and the bubbles are gas still trapped in solution under the fiberglass.






Now you might be asking yourself the question, how do you get all the solution out of the fiberglass. Good question by the way. Because you want to expand your solution anyway, I simply pour DI water through the fiberglass. I have processed the fiberglass a few times after this process, and have never recovered any more values. But I would still attempt a second digest just to make sure your process is down pat.

So far as filtering using paper coffee filters, if that is what you are intending to do, it just simply will not work. Not if you are using sulfuric acid. Anything that is biodegradable will be eaten up by sulfuric acid.

Scott


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## Ian18206 (Jan 25, 2013)

Thank you for your response and the information. But I did filter it already with coffee filters and they aren't torn at all. I diluted the solution with water before filtering. But it's all filtered already in the coffee filters and I was wondering on how to get the gold out of the filters. Thank you very much for the help!


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## NobleMetalWorks (Jan 25, 2013)

You're right, if you dilute your sulfuric acid enough, you can filter it, so long as you are pouring acid into water, and not water into acid. Obviously you know to do that or else your post would be very different. I just wanted to make that clear for anyone else reading after you.

I try to re-use the sulfuric acid as much as possible, so I filter it at full strength.

The filters can be burned so long as you are doing so in a well ventilated area and not breathing in the fumes. I process my paper filters this way just to insure I recover all the values. Incinerate, then digest the resulting material accordingly. I usually digest in dilute nitric first to make sure I dissolve any base metals, it only takes a small amount and can save you headaches later. Then I wash, incinerate and digest in AR.

Scott


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## Ian18206 (Jan 25, 2013)

Okay that sounds great. Can I burn the filter papers with a torch? If so what kind of container would you recommend doing it in so I don't lose any valuables? Thank you !


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## resabed01 (Jan 25, 2013)

If you go into the Tutorials section of the site you'll see a excellent thread about cleaning up and recovering gold from the black cell mud. I'm surprised you didn't see it, it's the first thread in the section.

The advice Scott gave you regarding the filter plug is good and is probably the fastest way to recover the gold from mud. But there is more than 1 way to skin a cat. I prefer to not filter anything at this stage and use time (I have lots of it) to allow the mud to settle between HCL/H2O washes and rinses. Mainly overnight it's settled enough to pour off the excess fluids. After I've cleaned up the mud and is relatively free of base metals I move on to dissloving the mud in HCL/clorox. It's only after this step that I'll filter out all the trash left behind.

Your question about how to free the mud from your filter papers... HCL/clorox will clean them but at this stage i don't think your mud will be very clean (still base metals present). You'll probably need to refine it a second time to get a acceptable button.


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## nickton (Aug 4, 2018)

can one use fiberglass from home insulation?


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## FrugalRefiner (Aug 4, 2018)

Yes.

Dave


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