Sodium nitrite to precipitate gold from A.R.

[HAuCl4]

What is the exact reaction and by-products, please?.

They can't be nitric acid and HCL right?. I'm somewhat confused.

Ideas to re-cycle the by-products so there's no liquid waste?.

 

[Lino1406]

N+3 = N+4 + e-
Au+3 = Au - 3e-
ie, each 3 nitrite nitrogens, reduce
one gold atom, becoming NO2 (gas)

 

[Barren Realms 007]

You will have waste of some sort, not much way around that. It's how you treat it for disposal that is the main factor.

 

[samuel-a]

becoming NO2 (gas)

that can be recycled to a weak nitric acid with a proper distillation apparatus :idea:

 

[HAuCl4]

I have looked hard in the internet, and I still can't find the complete reaction and by-products.

 

[Irons]

NO2+Water= Nitric Acid

Nitric Acid + HCl= AR

Some, if not most of your Gold is going to go right back into solution.

 

[HAuCl4]

NO2+Water= Nitric Acid

Nitric Acid + HCl= AR

Some, if not most of your Gold is going to go right back into solution.

That's why I'm confused.

Hoke has sodium nitrite in her list of recommended precipitants, but does not explain the reaction. I have tried it in the past, and the gold DROPS out of solution very cleanly. I don't know what's left in the "broth", only that there is no gold.

So: I'm still confused.

edit:
NaNO2 + HCl → HNO2 + NaCl is what happens first where the excess HCl is converted to table salt. (got this from wikipedia nitrous acid).

I guess the AuCl3 + NaNO2 becomes Au + NaCl + a mixture of nitrous and nitric acid ?. That's my best guess at the moment.

 

[HAuCl4]

HCl + NaNO2 -> NaCl + HNO2

2 AuCl3 + 6 NaNO2 + 3 H2O -> 2 Au + 6 NaCl + 3 HNO2 + 3 HNO3

This is my best guess at the moment. I'm sure someone will correct me, if inaccurate.

From this, it is clear that the nitric acid can be distilled and recycled, and I don't know about the HNO2.

 

[4metals]

The HNO2 can be scrubbed in an oxygen environment with water to remake the HNO3. In a production environment by sizing the scrubber and limiting the through put by using sealed reactors a properly sized scrubber will work without instrumental control. Of course you will need a constant flow of O2.

I would suspect with ORP control you could use a water peroxide scrubber and add peroxide to provide the O2 to create the HNO3, then more conventional scrubbing could be employed.

In either case the presence of the HCl will contaminate the acid you collect but if you're re-using it as aqua regia it's not an issue.

 

[HAuCl4]

The HNO2 can be scrubbed in an oxygen environment with water to remake the HNO3. In a production environment by sizing the scrubber and limiting the through put by using sealed reactors a properly sized scrubber will work without instrumental control. Of course you will need a constant flow of O2.

I would suspect with ORP control you could use a water peroxide scrubber and add peroxide to provide the O2 to create the HNO3, then more conventional scrubbing could be employed.

In either case the presence of the HCl will contaminate the acid you collect but if you're re-using it as aqua regia it's not an issue.

Thanks again 4metals!. I was thinking an ozonizer to transform HNO2 to HNO3, but you always come up with a better alternative: An H2O2 scrubber or mixer would work fine I think. These would be batches of by-products, not continuous, I think.

I was thinking last night, that this process, as is, would produce more nitric than it consumes, and it would consume sodium nitrite to produce NaCl.

Then it occurred to me that by alternating precipitants, say sodium nitrite on occassion and SMB (or SO2) on other occassions, HCL could be the waste to be recycled, and it would produce more of that than it consumes for gold digesting, producing NaHSO4 and/or Na2SO4.

NaCl can be used / sold for de-icing roads, but what to do with the other stuff?.

One would still need to be buying sodium nitrite and SO2 / SMB, so the "loop" is not closed. Do you think it can be closed so that there is no waste or surplus of chemicals to be re-sold?.

 

[HAuCl4]

Also trying to avoid a leach/sodium chlorate cell to process the NaCl... :lol:

 

[4metals]

I only suggested oxidizing the NO2 because it is generally a difficult fume to scrub and sooner or later it brings the EPA down on you. Reconversion back to reusable HNO3 is a win win deal but it does a key piece of the work for you. The scrubbed product is a gas so it separates itself from the chemical mixture you've created to process the gold.

Since it conveniently becomes airborne and relatively free from other chemicals the process is simple and the results predictable.

If you want to start recovering the chemistry from the soup left behind it's a whole lot more difficult. It becomes more difficult as more and more different metals are introduced into the mixtures you are recovering the PM's from because you are processing waste and have no control of the input. All of the chemical equations in the world don't mean much when you don't really know what you're starting with.

I've always refined to make money, I would take the gaseous NO2 because there is a double benefit and it's predictable. I'll leave the metal soup for the waste hauler to deal with, and until he comes to me and says he can't do it, I'll concentrate on where there's money to be made.

 

[HAuCl4]

I only suggested oxidizing the NO2 because it is generally a difficult fume to scrub and sooner or later it brings the EPA down on you. Reconversion back to reusable HNO3 is a win win deal but it does a key piece of the work for you. The scrubbed product is a gas so it separates itself from the chemical mixture you've created to process the gold.

Since it conveniently becomes airborne and relatively free from other chemicals the process is simple and the results predictable.

If you want to start recovering the chemistry from the soup left behind it's a whole lot more difficult. It becomes more difficult as more and more different metals are introduced into the mixtures you are recovering the PM's from because you are processing waste and have no control of the input. All of the chemical equations in the world don't mean much when you don't really know what you're starting with.

I've always refined to make money, I would take the gaseous NO2 because there is a double benefit and it's predictable. I'll leave the metal soup for the waste hauler to deal with, and until he comes to me and says he can't do it, I'll concentrate on where there's money to be made.

Of course you are right and all these extra processes are probably not cost efficient. But since my neurons enjoy a workout...

How about putting a DBC-Sx step in the middle to isolate the base metal soup from the AuCl3 before precipitation?. That would isolate one type of waste from the "good type" of waste (before recycling) and also improve upon the quality of the gold. What do you think?.

 

[4metals]

If your talking karat scrap or scrap with just basic run of the mill base metals the solvent extraction step would help for sure. But we live in an era in which rare earth metals have been intertwined into the mix, often without our knowing, I do not know how all of the specific rare earth metals react in the extraction, that would have to be determined first.

 

[HAuCl4]

I think that's all well above my pay grade!. :lol:

I just wanted the nitric and maybe HCl back and recycled!.

I was just thinking gold, silver, copper, a little nickel and a little zinc, and a little platinum group maybe, traces of other stuff like lead, tin, etc maybe.

What metals are you talking about exactly?.

I read that DBC was very specific extractant for gold and perhaps a little copper, but maybe my information is incomplete?.

 

[4metals]

La Lanthanum used in High refractive index glass, flint, hydrogen storage, battery- electrode, camera lens

Ce Cerium chemical oxidising agent, polishing powder, yellow colors in glass and ceramics, catalyst for Self-cleaning ovens

Pr Praseodymium Rare-earth magnets, laser, green colors in glass and ceramics

Nd Neodymium Rare-earth magnets, laser, violet colors in glass and ceramics, ceramic capacitor

Pm Promethium Nuclear batteries

Sm Samarium Rare-earth magnets, Laser, neutron capture, maser

Eu Europium Red and blue phosphors, laser, mercury-vapor lamp

Gd Gadolinium Rare-earth magnets, high refractive index glass or garnets, laser, x-ray tube, computer memory, neutron capture

Tb Terbium Green phosphors, laser, fluorescent lamp

Dy Dysprosium Rare-earth magnets, laser

Ho Holmium Laser

Er Erbium Laser, vanadium steel

Tm Thulium Portable X-ray machine

Yb Ytterbium Infrared Laser, chemical reducing agent, High-temperature superconductors

Then there's Gallium which is used extensively to alloy metals.

All of these metals may or may not behave as we would like, and they would require some rather extensive analytical chemistry to determine their presence. It's bad enough for them to be present on a first go round of refining but to show up because you recycled some reagents would really be annoying.

 

[HAuCl4]

Very interesting. Thanks again!. Everyday I learn something new!.

 

[HAuCl4]

Hi again 4metals. Again thinking while sleeping:

Do these "exotic" elements follow any type of electromotive reaction series?.

Are these elements rare enough that they are worth recovering for $ ?.

How difficult or easy is to install a Sodium Chlorate cell to produce it (Chlorate and/or hypochlorite) from NaCl and electricity?.

I was thinking...how would I refine my gold if the world came to an end and there were only few survivors and no place to go shopping for chemicals?.

I must find a way to quiet my mind... :lol:

 

[SilverNitrate]

See my big gold drop video on dropping AR gold http://www.youtube.com/watch?v=AfTaHvVaOO8

 

[goldsilverpro]

Silver nitrate,

The video was kinda neat and the music was good. However, you seemed to have skipped over the most important part - actually dropping the gold. The topic of the thread is using sodium nitrite to drop gold. Is that what you used?