AR Process not completing

[chawimac]

Hi All,

I am having problems getting the AR process to finish dissolving my gold. Here is what I am doing:

I am using technical grade chemicals, mixing 4 Parts HCI + 1 part HNO3. Nitric gets added in two batches. Heat is added after second nitric addition reaction subsides.
Gold comes from scrap jewelry that is melted and poured in water to obtain popcorn. Vacuum pin is obtained to assay material before processing.

The problem arises at the end of the process. The silver sludge left behind has about 5% gold! I can't seem to get it all out!

Below a picture is included of the small reactor I set up in my shop. (Reactor)

Next is a picture of the XRF of the material that goes into the reactor. (Input)

Also what the material looks like after the process. (Output in Reactor)

The final product. (Au/Ag Bar)

Assay of the final product. (Output)

Hmmm I reached my pic limit. Anyways, what I find is that when the input material is 8-9% silver the resulting sludge is very white. When it is closer to 11% silver it gets pretty black. At 12% or so I get this problem. I thought the max silver content for this process was 15%. I would love to hear everyone's opinion ans thoughts on this.

The silver sludge gets washed with water sever times, drained, mixed with soda ash and anhydrous borax in equal parts, melted and poured.

Oh BTW I have been warned before about being un-explicative, so you can reference my other post where I learned a ton about Nitric!

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=53&t=13236

Thnx!

 

[Barren Realms 007]

Did you inquart this with silver to bring it down to 6K and then run the shot from that in nitric to remove the silver, PD and any other base metals before running this material thru AR?

 

[chawimac]

No.

Its a 2 kilo batch, not practical to inquart and should not be necessary.

 

[Barren Realms 007]

No.

Its a 2 kilo batch, not practical to inquart and should not be necessary.

The problem arises at the end of the process. The silver sludge left behind has about 5% gold! I can't seem to get it all out!

Hmmm, well you know I realy don't know then.

You might do a search on Steve's web site and find some information on your problem with silver chloride stopping your process because it covers your gold in a shell that the AR will not penetrate.

 

[butcher]

Nice reactor.
I do not know if this will help. I am assuming you have in-quartered the gold, made shot and have dissolved as much base metals in nitric as you could.
Is it possible the percentage of gold to silver ratio in this shot, how well the melt was stirred and how well they were mixed in that melt, and how well the nitric reacted to remove the silver, and what form the gold was in after the nitric parting (powders or pitted gold shot), and whether you crushed the clumps and reacted with more diluted nitric and heat in this stage to remove silver completely as possible, or rinsing afterwards, could this be a reason you are getting the results you are?

You may have left silver un-dissolved trapped by gold in this step of parting with nitric. Maybe size of shot, how long it reacted in nitric acid and heat used, or percentage of silver to gold ratio in the in-quartering stage here may change the results?

Silver chloride can be very fluffy, and can trap liquids easily; also it is possible you are dragging some gold down with the precipitation of silver, thick solutions full of chloride salts, cooling too quickly, (or the gold is not being dissolved into solution)?

But I am not sure if this silver (and gold), we are discussing was dissolved into the solution and precipitated out, or if it was un-reacted powders left in the bottom of your reaction vessel?

If un-reacted powders (did not dissolve into the gold chloride solution of your reaction vessel during the aqua regia process) it could be here, that the silver (left from nitric parting stage), Has now protected the gold from being dissolved completely into the aqua regia, leaving silver and some gold in the bottom of the aqua regia reactor vessel?

5% gold seems a little high, in your photo of the silver the crystals are fluffy, I do have some questions, this fluffy silver chloride in the screen filter of your picture, is this silver and other powders that would not dissolve in your reactor, or were they dissolved and then precipitated back out of solution?

Were you using urea to neutralize the nitric, (more salts in solution) and how dilute are you getting your solution, before precipitating silver from your gold chloride solution, how fast are these solutions cooling after leaving the heat and pressure of your reactor?

In my mind several different things or a combination of these can be the answer to your question.

Is all of the silver and the gold dissolving into solution, (silver in the nitric step), and (gold in the aqua regia step)?

Are these metals being precipitated from concentrated solutions, or how fast or what state the precipitants form, causing other metals to be entrapped into the crystals as they form?

Then also how are you rinsing the powders?

Seems like all I have is more questions?
Sorry no real answers.

 

[martyn111]

I don't get why you think that inquartation isn't practical or necessary, but we won't argue about that.

The silver sludge left behind has about 5% gold! I can't seem to get it all out!

Have you tried 'cornflaking' your final silver output (95% silver + PGM's / 5% gold) and disolving in 50/50 nitric/ distilled water, the resulting black powder will be your gold, the silver nitrate can be cemented with copper

 

[chawimac]

I did not inquart this material.

I don't mean to be stubborn, but if I inquart 2 kilos of gold (at 50.58 purity) I would have to add 2 kilos of silver. Now I need to run 2 batches not one. The chemicals used are very dangerous and would hate to do twice the work. Thus I fail to see the reasoning behind inquarting this type of materials.

The question was what the threshold is or should be as far as silver content in the alloy to prevent the silver chloride stopping the reaction. I was told by a refiner that it was 15% with AR. Not true I gather.

Obviously I now will re-process the silver to get the gold out, but am trying to avoid this and doing twice the work.

Butcher: The picture is not a screen filter, but the bottom of the reactor. You are seeing a heating mantle. The stuff there is what did not dissolve in the reaction.

The solution gets flushed out about half hour after the reaction stops and then we add about double the volume of water. Sometimes we add ice if available but most of the silver is left in the reactor anyways. The gold that comes out from the process reads 99.6 in the XRF but there is a margin of error, so I think its a pretty good number for one run.

And yes I use urea, as in my stubborn head I fail to see why not. Even though I have been advised not to.

Thus the problem is at the end of the AR process not dropping or filtering.

Thoughts?

 

[martyn111]

What is the source of your feed material?
If you don't want to inquart and you don't want to re process your silver then the only other option I can see is you increase the gold content of your feed material until you have reduced the percentage of silver to an acceptable level for AR digestion.

 

[Geo]

I don't mean to be stubborn, but if I inquart 2 kilos of gold (at 50.58 purity) I would have to add 2 kilos of silver. Now I need to run 2 batches not one. The chemicals used are very dangerous and would hate to do twice the work.

if you have one kilo of pure gold, you would need three kilos of silver. maybe i misread, but if this is what you meant then disregard this.

 

[its-all-a-lie]

Wouldnt it be cheaper to do the job with the correct process first? This way you dont have to refine the same batch more than one time and thus saving dollars. Doing the same thing over and over again and expecting different results is the definition of insanity, i thought we were refining?.

 

[butcher]

chawimac,
We will all do what we think is best.
Maybe you could try using one of the other methods and see if you like the results better.

I am still in love with that reaction vessel it is cool.

You could also refine your silver in a cell and get the gold back there, but you would most likely need to re-dissolve it in nitric to bring up the purity first (or fool with replacing the electrolyte).

 

[Palladium]

I have read this thread twice just to make sure I was getting it. You have been giving the answer you are looking for several times in this thread, but yet you refer to it as stubbornness. Your procedure is flawed. And what I mean by that is yes you can run high gold with a high content of silver but the results are exactly what you are experiencing now. When you run gold this way it always needs cleaning up and that usually means running and dropping it again then acid washes. I didn’t hear you describe any washing procedures that you may do to clean your gold up. Did you drop the lead out before you precipitated? Refining is not a one step procedure. Most processes require many steps to separate these metals. That’s why we use the inquarting method and it works 10 out of 10 times. Until you realize this you will do nothing but have problems and wonder why. I haven’t run the numbers but geo said about 3 kilos of silver to inquart. You said you was processing like 2 kilo’s of gold. With that much money can you really not afford that much silver. Plus it eliminates the silver chloride problem. The silver collects your palladium, platinum and other metals for recovery later. It sure much makes your job and process easier. But hey! Keep doing it that way if it works for you. Try the other route and guarantee you will not be sorry. I like your setup you have there.

 

[NobleMetalWorks]

I like your reaction vessel also, what is it exactly? I don't have enough experience to be giving anyone, any advice on anything, sorry I couldn't help there. But I am very very curious about your set up. If at all possible, could you take some pictures when you have time and maybe explain it?

 

[chawimac]

I will post another thread with the reactor, fume scrubber, the works.

As far as the amount of material to inquart, if you see the pictures of the XRF you will notice the material is about 50% gold. Thus to get it to 25% it would take 2 more kilos of silver. Correct? (its a 2 kilo batch!) The starting material is gold scrap.

From what has been posted the only possible error aside from the high silver content is perhaps not mixing the metal enough when making the popcorn.

Now I am curious why everyone seems to be against the whole idea of not inquarting? I don't know how refiners work but I have seen a couple and did not see any inquart (That I have seen!). So why the attacks of insanity at the process?

As far as the washes I only use water. I am not interested in 99.999 pure gold. Its easier to just buy it. Ironically my interest is in the silver, hehe. I sell the gold at a better rate when it is almost pure, save in silver. That is why I am processing this. I like silver and think its a better bet to save in silver than gold. (Please bicker about your disagreement about my investment philosophy in another thread.)

I tested for lead, none there. Thus I did not want to use yet another deadly chemical. (See the pattern? This stuff is seriously dangerous and when you use gallons of it the danger level rises exponentially.)

I tried the silver inquart process and it kicked my butt twice until I got a hang of it. Am not fond of it at all!! I have great respect for the nitric.

So back to the original question. What is the maximum percentage of silver in the alloy to prevent silver chlorides stopping my reaction?

 

[Geo]

sounds like you need to set up a silver parting cell. the resulting silver (if done correctly) will be 99.99% so the 5% gold and other impurities will not matter as all that will be left behind in the anode slimes.

 

[chawimac]

Siver Chlorides

 

[Barren Realms 007]

I feel that is more than 5% of te 2 kilos that is shown in the 1st photo. Why have to go back and process this amount a 2nd time when you can follow the suggestions given to you and found here on the forum and do it only once. Love the reactor also BTW. 8)

 

[Palladium]

Well I don’t know how to help you if you won’t listen to reason. I’m not trying to be hard here I’m just pointing out the obvious. Yes you have seen other refiners use this process. I use the same type process when I am running karat with stones and such. I don’t use it when I’m running scrap with no stones. Why? Because it causes problems. Your already corn flaking so just adding silver to inquart at that point is no big deal. You said you like to collect the silver so for me it’s a no brainer to use that silver to collect the other metals and to make my job easier. Do you not see the reasoning in it? With all the trouble your having and the extra steps that are added because of the problems in your processing can you not see how taking the long way around can sometimes be the short cut your looking for? You’re going to have to learn to use these dangerous chemicals as you call it if you plan on doing any serious refining. Yes these chemicals can be dangerous, more dangerous than a gun is in untrained hands, but with the proper training and respect that gun can becomes a tool and not just an object of destruction. I don’t know what to tell you. Anybody else???

 

[lazersteve]

Typically gold must be 18kt (75% Au) or better and have a high surface area to avoid the silver chloride coating you are seeing when using straight AR. The silver chloride will still form, but it should not trap as much of your gold as you are currently seeing.

You can process karat gold directly in AR if you atomize the material first as detailed in a previous thread (find with a search for 'atomizer'). You can still expect some of the gold to be tied up in the resulting silver chloride.

People inquart their karat gold so as to avoid the problems you are seeing. Silver is cheap and is recycled in the process. The silver also acts as a scavenger for your Pd and Pt in the karat gold.

As you have found, cornflaking is not providing you enough surface area to ensure extraction of the gold from the silver chloride crust. You'll need a method of increasing the surface area much higher than cornflaking to see better results. Atomizing is this method in my opinion.

Steve

 

[samuel-a]

Yup... while scrolling down i thought the exact same things as Steve.

You need high surface area, you can achieve that cheaply with a high water pressure pump and large nozzle.
Situate the nozzle about 2-3/8" above water level at about 30° angle and pour slowly. Try to aim the drops into the jet, but just above where the jet meets the water. It will not atomize the metal, but will form relatively small shots.

Were i you, i would lose the Drip Tip and replace it with an anchor shape o/h stirrer.
You have plenty of ground glass joints to fit a spiral condenser to.

To summarize, to improve your process you need:
- More surface area to react.
- Vigrouse stirring.
- working at boiling temp'.

p.s - an addition funnel (for nitric) may come in handy as the reaction my be too fast and get out of hand.

edit:
p.s 2 - anyway you look at it, your AgCl and the resulting silver will have some gold reported in it. If you could press the AgCl, you will increase the recovery of gold significantly.