Oops! - forgot to remove base metals...

[Anonymous]

Hi All,
I have just started refining computer parts on a small scale and have been using The poor man's AR method.
my first attempt went well as i was only using plated fingers and got good results.
(i assume this was due to the small amount of base metals involved)
My recent attempt has caused problems as i forgot to remove the base metals and was refining a mixture of plated fingers, old CPU's ( cracked open) and plated pins.

I soaked everything in AR and got a very dark brown liquid (no doubt full of base metals) which i separated from the sediment that was left (which contained the remains of the ceramic CPU parts) but found that there was a considerable quantity of gold flecks and films in the sediment.
My first question is: does this mean that the gold has not dissolved and that the AR has been used up dissolving the base metals?

I filtered the resultant dark brown AR and kept the filtered sediment. (Also keeping the filtered AR)
my second question is: can i still drop any gold from this AR solution with the obvious amount of base metals contained within? and if a treatment is required what can i do?

What was left of the boards, CPU's etc i washed with water so i could remove the unwanted parts - my intention is to clear out the rubbish and, as i can see gold in the sediment, dry this sediment and process again with AR.

when i started to filter out the water wash from the ceramic etc i found that there was a yellow/orange layer/precipitate in the solution and this is considerable when filtered out. My third question is: what is this orange precipitate? ( i have kept everything except the filtered water used to wash off the acidy boards and CPU's which was a clear pale green colour)

Have i screwed it all up? and if not can i still come back from this with something to show for it?

any help is much appreciated.
Scottyboy

 

[Harold_V]

Ahhh! The wonders of processing with AR, or other aggressive chemicals, without first addressing base metals. Will you guys ever learn?

Yep---you can recover from this mess. It's dead easy, but you're going to have to rethink the process. It makes no sense to put everything back in solution, no more than it makes sense to have put the base metal in solution along with values in the first place.

Here's the basic outline.

Incinerate the solids. They should be heated to at least 1,100° F.

Screen, crushing anything that won't pass through the screen. (Use a mortar and pestle for the crushing). Do not worry about crushing ceramic bits from SPU's. Allow them to accompany the screened material to the wash cycle as they are.

Run a magnet through the material. Anything that comes from the magnet should be placed in your stock pot (you do have one, don't you?). That way traces of values that hitch a ride will be recovered eventually.

Do a heated wash with HCl. Rinse well. Tap water is acceptable (and desirable---there are no benefits in using distilled water in this case).

Dissolve the remaining solids with the acid of choice (AR, for example), and treat as required in order to precipitate the values.

Wash the recovered values well, following a good procedure (Hoke talks about washing the gold in her book. Do NOT overlook this process).

While your wash solutions should be barren, only a fool trusts his eyes. Test each and every solution with stannous chloride to insure you are not discarding values. If you find traces when testing with stannous chloride, the solutions should go to your stock pot, where they will be recovered.

As has been noted regularly, I did not process e scrap aside from the odd batch. Lazersteve suggests that you not combine types of e scrap when processing. That's excellent advice. Each type has its own requirements, which may or may not be compatible with those of other types. Learn to run individual batches to limit the problems that are typical of combining lots.

You made no mention of having tested the filtered solution, to see if it contained values. Remember my comment about only a fool trusts his eyes when evaluating a solution? You must test with stannous chloride----no one can tell you the status of the solution. That's the wonder of dissolving values along with base metals. Only you can tell if all of the base metal has been dissolved, or where the gold is, and in what state. A perfect example of NOT dissolving values with base metals included.

If you do not have stannous chloride for testing, I'd rather not be involved with you and your problems. I don't have time to chase my tail. Read Hoke again, and pay attention to testing.

Harold

 

[Anonymous]

Thanks for the reply and the advice Harold.

Yes, I have been testing with stannous and nothing positive has been chucked.
I will heed your advice and treat all the solids as suggested.

Regarding the base metal rich AR solution - It does test positive.
Would you suggest i precipitate, wash and re-process the precipitates?

thanks again

 

[Harold_V]

Regarding the base metal rich AR solution - It does test positive.
Would you suggest i precipitate, wash and re-process the precipitates?

Yes, that would work, or you might simply cement the values on copper. I think I'd make the decision based on if you can precipitate without any further treatment (evaporation, for example) or not.

That your solution tests positive is a pretty good sign you dissolved all of the base metals. Had you not, given enough time, the values would have cemented. That's one of the hazards of handling the values when there's a lot of base metals present. I fear that you may not have eliminated them totally, however, so you may find cemented values in the solids. That's the reason for incineration, washing, then reprocessing.

Harold

 

[Oz]

It can be a bear cementing all the values out of AR on copper with the nitric there in any quantity. You also get a fair amount of copper 1 chloride from the process.

It is also problematic trying to triple evaporate an AR solution with significant base metals present trying to remove nitric.

You may wish to evaporate to dryness then incinerate and process more carefully.

These are just my observations and your mileage may vary. This is one of the reasons why AR is not typically recommended for direct processing of scrap electronics unless it is done very carefully in order to have an endpoint with little or no nitric unconsumed.