Using Aqua regia

[phoenix_phx_]

Hello!

This is my first post, i hope you won't be angry

I heard about usin aqua regia during gold recovery. I have dissolved electronic elements in AR. The liquid is dark green. I'm sure that gold is in it. Now, I want retake gold. I want neutralize acids using CaCO3. Than use FeSO4(II) * 7H2O to deduct gold.

I red about it and many people says that it works. Do you think that it will be?

Thank you for answering.

 

[peter i]

There are a couple of traditional ways to do it:

Either boil the AR solution to remove surplus nitric acid

or add urea until it stops fizzing (carefully, it may foam quite a lot)

Make sure there are no solids in the beaker, then drop with a reducing agent like ferrous sulphate og SMB.


Calcium carbonate is a bad way to go.

 

[phoenix_phx_]

Okay, have I to add HCl to dilution to reduce gold? After boiling AR.

 

[peter i]

No, the reductant is SO2 (from a cylinder or from adding a solution of NaHSO3) or Fe(II)-ions from FeSO4.

Both SO2 and Fe(II) are relatively mild reductants, thus leaving base metals in solution, reducing only the noble metals.
This selective reduction is a great thing for leaving the base metals behind.

But if any nitric acid remain, the gold will dissolve again, and you will have to keep adding reductant until all nitric is consumed (very irritating!)

 

[phoenix_phx_]

I understand I think, I can use NaOH to neutralize acids, than I will use SO2 or FeSO4(II) * 7H2O to deduct gold. But I don't know how it (NaOH) will have influence on other ractions. I know that it won't move gold.

 

[peter i]

Nooooooooooooooooooooooooooooooo!

You either boil the solution or add urea.

If you add a hydroxide solution you will precipitate metal oxides or hydroxides, and any inorganic chemist will tell you, that they usually are a nightmare to filter and decant! (and will lock down some of your noble metals)

 

[phoenix_phx_]

Hmm.... I thougt that it will not work.

You know, it's good to talk with someone who knows better than me. Now, I know what I musn't do. Thank you one more time.

 

[Harold_V]

Hmm.... I thougt that it will not work.

You know, it's good to talk with someone who knows better than me. Now, I know what I musn't do. Thank you one more time.

Do not boil your solution. Heat it slowly, keeping it under a boiling temperature at all times. If you allow it to boil, you'll lose values in the discharged vapors. If you see any color in the vapors coming off the solution, you must lower the heat. Proper evaporation is a slow process. When your solution has condensed, and has thickened and changed color, add some HCl and stir with a glass rod. That expels nitric.

Harold

 

[phoenix_phx_]

I undestand. HCl helps too in deducting gold?

 

[Platdigger]

When you say you "have dissolved electronic elements in AR"

Do you mean gold plated pins and the like?
Randy

 

[phoenix_phx_]

I meaned all elements from PC, phone ect. (with gold, checked) dissolved in AP

 

[peter i]

Do not boil your solution. Heat it slowly, keeping it under a boiling temperature at all times. If you allow it to boil, you'll lose values in the discharged vapors.
Harold

Sorry
I stand corrected.

 

[phoenix_phx_]

From what I know, Nitric Acid have boiling point in 83 °C (181 °F). It's steams very easyly.

 

[Harold_V]

I meaned all elements from PC, phone ect. (with gold, checked) dissolved in AP

I have stated, time and again, that AR is not to be used to recover gold from low grade wastes, with only a few exceptions. Dissolving copper based metals is definitely NOT one of them. How you folks learn to use AR in that fashion is hard for me to understand----it's certainly not recommended by anyone that knows the least bit about refining.

You should stop doing what you're doing and learn better processes. Even if you achieve success, the gold quality that comes from a solution that is saturated with base metals will be suspect, and likely won't be able to be improved to an acceptable level without re-refining. Washing alone isn't likely to do the job.

Harold

 

[Harold_V]

Do not boil your solution. Heat it slowly, keeping it under a boiling temperature at all times. If you allow it to boil, you'll lose values in the discharged vapors.
Harold

Sorry
I stand corrected.

That's a lesson I learned the hard way, peter. In my early years of refining, I worked with a fan in a window (no fume hood) and was evaporating a gold solution too quickly. Outside the window I had my travel trailer stored on a concrete pad. Imagine my surprise when I looked at the side of the trailer a few days later, to find it well covered with purple dots of gold in a fan-like pattern. It alone was what prompted me to build a fume hood with a filter system, for which I was generously rewarded each time I cleaned out the hood, to say nothing of the recovered values from the filters. If you handle large volumes of values, the losses can be appreciable.

Harold

 

[Harold_V]

I undestand. HCl helps too in deducting gold?

As far as I know, excess HCl does no harm. I suppose it all depends on what you use for precipitation. I used SO2 (from a cylinder) and ferrous sulfate---each with no regard to the amount of HCl in solution. If I could filter my gold chloride, I didn't worry about the amount that remained. Too much made filters fail, which was the only ruling factor. I always determined if the nitric had been expelled by adding a fair amount of HCl to the concentrated solution that was being evaporated.

Harold

 

[goldsilverpro]

When I started refining, in 1966, I used a standard AR mix of 3/1 or 4/1, HCl/HNO3, and always evaporated to eliminate the HNO3. In about 1980, I worked for a guy that ran mostly karat gold - about 50 to 100 oz/day. He never evaporated or used urea. His trick was to only use enough nitric to dissolve the gold - with no excess. Then, after dissolving, diluting, and filtering, he could directly use sodium sulfite to precipitate the gold. To dissolve, he would first cover the gold with a calculated excess of HCl and heat. Then, he would add small increments of nitric. When a small addition of nitric produced no reaction, he was finished. There's a little more to it, but that was the general idea.

When I later owned a refinery, I totally adopted his method. It dissolved a bit slower, but was faster overall, since evaporation wasn't necessary. Occasionally I would have to evaporate, but it was rare.

I have covered this method in greater detail in previous posts. I know it goes against present thinking, but it really works well.

 

[phoenix_phx_]

This is great idea. Naturally, use amount of acid that you need. After dissolving there is no more HNO3 in dilution. Rest of it we can neutralize by urea. I understand all.

There is one question. I know one method- AR. Can you give me any links (or names) about another methods please? I don't want give you more work with newbies.

 

[skyline27]

The Acid-Peroxide (AP) method is great for plated items. I have used it on fingers, pins and cpu's. The fumes are not as bad as AR but it can be a slow process. Use concentrated H2O2 for a lttle extra punch.

 

[goldsilverpro]

If you don't use an excess of nitric, you don't need any urea. Even if you have a very slight excess of nitric, the first addition of SMB or sodium sulfite will take care of it.