AR process altered

[Marcel]

Over the weekend I visited a quite large recycling company that did have problems with their AR process. Well, I am not the ultimate expert on this procedure but I knew enough to identify their problems.
They have vast amounts high grade of e-scrap.
What they did was:

- crunch ceramic ICs with a hammer mill,
- drop the fine powder into AR
- added urea to drive out nitric
- then try to drop the PMs using SMB

Because the dropping of PMs did not always work ( I guess we know why), thy have now changed to this "procedure:

- crunch ceramic ICs with a hammer mill,
- drop the fine powder into AR
- add some HCl
- then try to precipate using fine zinc powder

By doing this they achieved a 100% drop rate.

I told them that the incineration step was missing, also the removal of base metals is absent which can cause further trouble.
They even called in chemistry professor from university to overlook their process and (of course) he was sceptical if that could work.
I felt like a fool, when I saw that it really worked and was "ordered" to melt a button for XRF testings.
They button contained almost any metal in this universe, but very few base metals ( Gold was around 95%, Ag, Pt around 1% Cu. was at 0.7%, other BM much lesser)
Now I am wondering, why this quick and dirty method worked so well. No urea, no HCl washes, no incineration. Everything I read and tried to understand about the PM recovery seemed to be useless.
The owner said, that he found this shortcut in an old german document.
I tested the remaining liquids with stannous - before and after. Before there was a deep purple color, after the process negative, zero reaction.
The zinc powder he used was very fine stuff.
He added zinc to the AR ( which was constantly moved by a magnetic rotator), until the color changed from deep red to grey, then the drop was complete. The solids were brown as usual the remaining liquid clear.
I watched the whole process three times by myself. It´s no hearsay, it really works.
And I just want to know from those who a firm at this matter, is there anything that he has overseen in doing it that way or is this quick and dirty method commonly known.

The only problem he had, was exess zinc after the drop.
He added HNO3 only again and the zinc was dissolved. Washed the solution with destilled water and the result was quite pure goldpowder.
All that took less than 30 minutes.

 

[qst42know]

The only problem he had, was exess zinc after the drop.
He added HNO3 only again and the zinc was dissolved. Washed the solution with destilled water and the result was quite pure goldpowder.
All that took less than 30 minutes.

Was the solution tested with stannous after the addition of nitric?

Some gold would be expected to dissolve adding nitric to a chloride precipitation (or should it be called a zinc cementation?).

More HCL should remove excess zinc without redissolving any gold.

 

[jeneje]

I will try this and see if it works for me. I have a few pounds ground up in my ballmill ready to process. I like to try new things and besides i have some zinc powder to use up. Will post pics as it goes along.
Ken :lol:

 

[qst42know]

One thing to keep in mind all the trace metals present will also cement out on zinc. High purity gold is not the result, but it may get you past what ever was interfering with the precipitant.

 

[nickvc]

Marcel the process is a recovery rather than refining, I can see the attractions of the process for a large batch and perhaps like me the refinery can achieve high prices for the recovered gold and platinum in that state but for many on the forum the aim is high purity metals for personal satisfaction and because assays are expensive, the added steps of redissolving the powders instead of melting and separation of the gold from the platinum and then cementation to recover the platinum would be the route I'd advise for the forum members trying this.

 

[jeneje]

Marcel, do you know and will you share the quanity they were processing in each batch.
Ken

edit for update; i started with a 5oz batch of ground up ic chips. i used 3parts HCL to 1part HNO3, let it set all night. Checking this morning i have a dark green solution. I found that the AR did not dissolve all the material. Filtered through a charman plug and now going to drop with zinc to see if there is anything in it. Will post results with pics.

 

[jeneje]

Ok, here are the pics, and NO drop with zinc. (A WORD OF CAUTION HERE ADDING ZINC TO ACID HAS A VERY VOILENT REACTION WEAR THE PROPER PROTECTION) What found interesting is the pale blue color in the spot plate using DMG although there was a little purple color it was very faint this may be a false positive or not enought material. Anyway here are the pics.
Ken
I edited the spot plate pic to show the color better

 

[Anonymous]

I always had a horrible time extracting values from crushed ceramic powder using AR.I have had good success using sodium thiosulfate.

 

[jeneje]

I always had a horrible time extracting values from crushed ceramic powder using AR.I have had good success using sodium thiosulfate.

Hey mic, first i would like to say i used to live in the Cocoa area at port st john. Is using sodium thiosulfate safe or does it have to be used in a control envoriment. Thanks for your input mic.
Ken

 

[samuel-a]

Marcel

You never mentioned what exactly was the feed stock... perhaps it was just low on BM ?

Try the same procedure with ground up mobo's and cards and you end up with quite a mess...

You have mentioned a "100% precipitation", this might insinuate to the less conscious reader for a 100% recovery. Which i have no doubt in my mind, is not achieved with this kind of procedure (the way you describe it).
Maybe you could share more details of the process so we could engineer it backwards....

In my mind, Working with wet powders is a sure guarntee for vlues lose without the use of a filter press/centrifuge filtration. Even then, there's no 100% seperation of liquide from solid, but this kind of lose is managable.

 

[Lino1406]

If the starting concentration of gold is too low
(although meaningful for us) the usual dropping
may not succeed, although when starting, the dropping
is complete. To "save" the evaporation stage with
HCl and getting the "syrup consistency" - Zinc

 

[Anonymous]

I always had a horrible time extracting values from crushed ceramic powder using AR.I have had good success using sodium thiosulfate.

Hey mic, first i would like to say i used to live in the Cocoa area at port st john. Is using sodium thiosulfate safe or does it have to be used in a control envoriment. Thanks for your input mic.
Ken

Hey Ken.
I live right on the border of cocoa,and PSJ right off of camp rd.
Thio is very safe,very cheap,and very easy to use.Send me a PM with your address,and I'll send you some to play around with.

 

[jeneje]

Hey mic i sent you a pm let know if you dont get it. Thanks alot.
Ken

 

[Marcel]

@Sam: Of course you are right about 100%. A very common problem I also see in this forum is that the gold wont drop. 100% meant, that he always succeded in dropping the gold.
The material was ceramic CPUs mixed with other ceramic and plastic ICs (large flatpacks from motherboards).
500g were processesed and milled in a hammermill (which is usallyy used for milling corn)
I forgot to mention, that he added destilled water after the HCl, then reduced the solution down to the volume before adding water. (Dont know if that makes sense at all).
Yes, the BMs were very little from the start. There was no try with low grade material.
I myself have created a mess, that wont drop due to not driving out all BMs from my solution before dissolving. So noone needs to convince me, on how important that is.

 

[Rockman]

I made my first run with AR using some scrap jewelry of 10 & 14 K that I had melted into nuggets. After 24 hours I have a very dark green solution with a green like crystal formation on top of the solution. Is this copper and brass from the reaction? I have some grey/white like mud on the bottom of the solution.

How do you burn off the copper and brass in AR? I do have Nitric acid and Muratic acid. I also have some Stannous chloride and Sodium Metabisulfate to work with. Not a lot of options in the sticks where I live to get chemicals.

 

[Rockman]

I made my first run with AR using some scrap jewelry of 10 & 14 K that I had melted into nuggets. After 24 hours I have a very dark green solution with a green like crystal formation on top of the solution. Is this copper and brass from the reaction? I have some grey/white like mud on the bottom of the solution.

How do you burn off the copper and brass in AR? I do have Nitric acid and Muratic acid. I also have some Stannous chloride and Sodium Metabisulfate to work with. Not a lot of options in the sticks where I live to get chemicals.

Another photo of the process

 

[Marcel]

I made my first run with AR using some scrap jewelry of 10 & 14 K that I had melted into nuggets. After 24 hours I have a very dark green solution with a green like crystal formation on top of the solution. Is this copper and brass from the reaction? I have some grey/white like mud on the bottom of the solution.

How do you burn off the copper and brass in AR? I do have Nitric acid and Muratic acid.

You should try to reduce basemetals before melting. Now you created some mess. Also you may not have dissolved all values.

 

[Rockman]

OK so back to my question, how do you remove copper and brass from a AR solution? I know about lead removal is it a simular process for brass and copper?

 

[butcher]

I am over simplifying this (some details are missing):

You cannot remove the base metals from solution with dissolved gold, and leave the gold in solution.
(it is possible to cement the gold using elemental copper metal, and leave most of the base metals in solution).

Normally the karat gold will be melted with three parts silver to each part gold, the calculation should take into account the base metals involved in the karat gold. this melt is poured into a stainless steel bucket of water to form shot, the shot is dissolved in dilute nitric acid (70% nitric acid : water @ 1:1 ratio), this nitric should be calculated for the amount of nitric needed to do the job, (calculate the silver and possible copper in the material, and nitric needed to dissolve them), the nitric will dissolve the silver copper and any other base metal involved, the solution is decanted from the un-dissolved gold, the silver from this solution can be retrieved by using a copper buss bar to cement out silver, which can be washed and melted, or reused, the gold powder can then be washed and dissolved without the problems you are facing now.

Trying to dissolve the karat gold directly in aqua regia you will have several problems, like the silver will form a passivated layer or coating of silver chloride which will keep the acids from attacking the gold, also the base metals involved can give some trouble in precipitation, or other troubles, these problems can be overcome but it is not an easy process.

You will most likely have trouble getting the karat gold to dissolve (some may go into solution, I would remove any un-dissolved solid and rinse it off ,store in clean jar, put rinse back into your solution, remove any free nitric from your solution using the evaporation process, dilute and filter the solution before precipitating any gold you may have in solution, use your testing procedure to see that you did get all of the gold and then treat your solution for waste.

Again I have oversimplified this:

Read Hoke's book for details, her book should be understood before you begin doing anything with these metals, or acids, also you should understand how to work with these acids, fumes and dangerous compounds, before you try any processing, and understand how to deal with your waste you will be generating, between Hokes book and reading the forum you should have no troubles, but it does take time to learn and to be able to understand, it is not hard but takes some work.

 

[wood4lif]

interesting way to speed things up a bit, depending what it is your after. im going to try this with G.F. but i agree with the fact that most base metals need to be removed for better sucess. with that being said ,my attempt to try theis on G.F. items must be done after the recovery process. but i think this might be a good way to speed uo the AR process by using zinc after getting the PH right. il let you know and post the results