Aqua regia process commenced

[jdgold]

Hi

I have started aqua regia process for gold recovery from sweep dust. Here is what I have done

I have 1 kg of sweep dust with approx 4 gms of gold (have got someone extract 4 gms of gold from another 1kg of sweep dust of same batch).

1) I burnt the sweep dust in oven to make fine ash.

2) added 2 letre HCL + 0.5 letre HNO3 to the 1kg sweep.

3) I have boiled for 1 hour on slow heat.

There are still red fumes coming out from it. I WANT TO KNOW HOW MUCH LONGER I HAVE TO BOIL IT?

After burning is completed, how much quantity of following should I add?

1) Urea
2) SMB
3) Water

Please let me know.

 

[Anonymous]

JD, I would recommend that you have a good search round the forum as to how to make AR.

As a helping hand I would point out that you've added far too much Nitric to the mixture. Search that as well and you'll find some good pointers.

Also search Urea and you'll find plenty of useful pointers.

I hope that helps you on your journey and points you in the right direction Sir.

Oh and as a last pointer. I strongly suggest that you are outside and far far away from those red fumes coming off the AR - - search NOX.

Jon

 

[Geo]

Lots of problems to list. Starting with preparing the material. Sweep material can have any number of metals. These metals can be removed in a nearly selective way. Using pretreatments with the acids you have and incineration between the two, you can remove a large part of the contaminating metals leaving the gold untouched. Making the AR solution to finally dissolve the gold will take much less acid after the base metals are removed and the solution well be much cleaner and easier to work with. Study on the suggested process of adding nitric in smaller increments, lowering the need if not totally getting rid of the need, to use urea. Do not premix AR solution to one part nitric acid to three parts hydrochloric acid. Use heat but do not boil reactions with AR. You should never boil unless you intend to boil and always cover the reaction with a watch glass or suitable cover. In an AR reaction, the only reason you would need to boil would be to dissolve PGM's. Sweeps may contain PGM's so this is another way to use acids to separate metals. In sweeps that are suspected of containing PGM's, treat the material twice in AR solution. The first at ambient temperature and the next in near boiling temps. Remember, the more concentrated the acid is, the more heat it takes to make it boil. Due to evaporation, by the time the acids comes to a boil, it is hot enough to cause a life changing event. This is very quick to say but it takes a lot of time studying to make it all work. Be sure to check out all the comments you receive and take them to heart cause we are all trying to keep you safe.

 

[FrugalRefiner]

jdgold,

After reading your post, my first reaction was to scold you for not having a complete understanding of the process before you started, not studying Hoke enough since this is exactly the type of process she describes, not spending enough time reading the forum, etc. But I don't guess any of that will help you now that you're already in the middle of the process.

I have started aqua regia process for gold recovery from sweep dust. Here is what I have done

I have 1 kg of sweep dust with approx 4 gms of gold (have got someone extract 4 gms of gold from another 1kg of sweep dust of same batch).

1) I burnt the sweep dust in oven to make fine ash.

You started well by incinerating, though, depending on the "oven" you used, you may not have reached as high a temperature as you should. Before your next batch, use the search function. Search for the word "incinerate" with the author "Harold_V". It will help.

2) added 2 letre HCL + 0.5 letre HNO3 to the 1kg sweep.

You might have benefited from a boil in just HCl that would have helped by dissolving some of the base metals before you dissolved your values. Again, it might help on your next batch.

3) I have boiled for 1 hour on slow heat.

Be sure to use a watch glass over your vessel whenever you're boiling a solution to prevent losses.

There are still red fumes coming out from it. I WANT TO KNOW HOW MUCH LONGER I HAVE TO BOIL IT?

Well, you boil until the material is dissolved. There may be some material left that will not dissolve, but since you still have red fumes we know there is plenty of nitric. Then you move on to deNO_xing, that is, getting rid of the excess nitric acid. You can do this by repeated evaporations as Hoke teaches, by adding a refined gold button as Harold_V has taught, or by using sulfamic acid. Although urea was used in the past, it is no longer recommended as it doesn't really neutralize excess nitric acid and it can cause dangerous and/or hard to refine compounds.

After burning is completed, how much quantity of following should I add?

1) Urea
2) SMB
3) Water

Please let me know.

I'm not sure what you mean by "after burning is completed".

As I recommended above, don't use urea.

The usual recommendation for the amount of SMB is approximately the same weight of SMB as you expect in the weight of gold. You may need more than that, but it's a good starting point. After you've added it and allowed it to react, test a bit of your solution with stannous chloride. If it tests positive, add more SMB.

As far as water, you'll see varying recomendations. If you evaporate your solution till it's very concentrated, you'll want to add several times its volume of water. If you don't evaporate, you probably don't need to add any.

Before you try this again, study some more. You never mentioned using a magnet to remove iron. We haven't talked about cooling your pregnant solution to precipitate silver, or adding a bit of sulfuric to precipitate lead, or when to filter, etc., etc.

I hope this will help with your immediate issues. We'll expect you to do a lot more studying before you try again.

Dave

I see Geo has already responded while I was typing.