Gold back in solution when washing?

[AndrewSuperD]

Hi all. Did a 440g+ batch of DDR2/3 memory. I followed this process:

1. Incineration
2. Magnetic separation
3. Gravity separation
4. Hot nitric acid with stir bar
5. Decanted and washed after No reaction
6. Dissolved with AR
7. Tested with stannous with decent purple stain
8. Added Sulfamic acid
9. Filtered and dropped with SMB
10. Began washing with HCl

At this point I noticed the solution turning yellow so I stannous tested and got light purple stain on paper after two minutes. Pics attached. The volume of powders also decreased.

I then went and reread Harold’s process and I forgot to add tap water to the wash. I assume at this point it wouldn’t have made a difference because I had left over nitric in the powders and I’ve formed a weak Aqua Regia? I thought I added plenty of sulphamic. So I’m not sure how this is happening unless I really over added nitric and I didn’t add enough sulphamic. I got little to no reaction with sulphamic. I probably should have added a gold bead to consume all nitric. Nonetheless…at this point I assume I should carry on with Harold’s process and drop the gold wash with SMB again (it’s all I have to use). Thoughts on my assumptions?

 

[AndrewSuperD]

Adding a picture of gold after 1/3 of Harold’s process. I stopped before Ammonium Hydroxide as I don’t have any and it’s not worth it to me yet. I need more material. As it stands, this is the clumpiest gold I’ve ever had. I was hoping for ~2g but I don’t think I’m going to get there.

 

[AndrewSuperD]

.78g. Disappointed with the weight. I thought these ddr2/3 bga memory chips were .5% by weight?

 

[Yggdrasil]

Hi all. Did a 440g+ batch of DDR2/3 memory. I followed this process:

1. Incineration
2. Magnetic separation
3. Gravity separation
4. Hot nitric acid with stir bar
5. Decanted and washed after No reaction
6. Dissolved with AR
7. Tested with stannous with decent purple stain
8. Added Sulfamic acid
9. Filtered and dropped with SMB
10. Began washing with HCl

At this point I noticed the solution turning yellow so I stannous tested and got light purple stain on paper after two minutes. Pics attached. The volume of powders also decreased.

I then went and reread Harold’s process and I forgot to add tap water to the wash. I assume at this point it wouldn’t have made a difference because I had left over nitric in the powders and I’ve formed a weak Aqua Regia? I thought I added plenty of sulphamic. So I’m not sure how this is happening unless I really over added nitric and I didn’t add enough sulphamic. I got little to no reaction with sulphamic. I probably should have added a gold bead to consume all nitric. Nonetheless…at this point I assume I should carry on with Harold’s process and drop the gold wash with SMB again (it’s all I have to use). Thoughts on my assumptions?

Whole sticks including chips?

 

[Martijn]

How did you add the sulfamic acid? Decsribe the process in detail.
Things of importance are volume and temperature, agitation, amounts and time.

 

[AndrewSuperD]

Whole sticks including chips?

Just the chips. The gold fingers were processed separately.

 

[Yggdrasil]

Do what Martijn said.
So can we see if anything jumps out at us.

 

[AndrewSuperD]

How did you add the sulfamic acid? Decsribe the process in detail.
Things of importance are volume and temperature, agitation, amounts and time.

I add the sulphamic acid when the solution is hot ~80C - 90C. I place some sulphamic in the cap of the sulphamic bottle and add that way. It sometimes clumps and I don’t want a big clump to fall into the solution. I watch the solution for any reaction (fizzing) and will add again in same manner if solution has a reaction. Then I’ll stir the solution. I’ll add in the same manner again until I see no reaction. I dont measure as I think I’m careful adding 2ml of nitric at a time to the AR until I have no reaction. Once I’m done adding Sulphamic I set a 15 min timer and when done I remove from heat and add some tap water ice. Then, when cool, I filter with cotton ball in funnel. I wash through with water till clear.

 

[AndrewSuperD]

Do what Martijn said.
So can we see if anything jumps out at us.

Thanks so much for the review/help.

 

[Yggdrasil]

I add the sulphamic acid when the solution is hot ~80C - 90C. I place some sulphamic in the cap of the sulphamic bottle and add that way. It sometimes clumps and I don’t want a big clump to fall into the solution. I watch the solution for any reaction (fizzing) and will add again in same manner if solution has a reaction. Then I’ll stir the solution. I’ll add in the same manner again until I see no reaction. I dont measure as I think I’m careful adding 2ml of nitric at a time to the AR until I have no reaction. Once I’m done adding Sulphamic I set a 15 min timer and when done I remove from heat and add some tap water ice. Then, when cool, I filter with cotton ball in funnel. I wash through with water till clear.

How was the Stannous after SMB?

 

[AndrewSuperD]

How was the Stannous after SMB?

The stannous test after the first SMB drop was negative. I put the beaker on heat and let it settle for almost a whole day.

 

[Yggdrasil]

Well maybe there was no more Gold.
The amount of Gold depends on age and design of the chips.
And some has Aluminum bonding wires in stead of Gold.

 

[AndrewSuperD]

Well maybe there was no more Gold.
The amount of Gold depends on age and design of the chips.
And some has Aluminum bonding wires in stead of Gold.

Maybe not. It’s just frustrating. I’ll keep all waste just in case I (or anyone) think of something. It might be that my incineration was inadequate? I’ll take another look at that material this weekend. Oddly enough after I added the tap water (recall I did 1/3 Harold’s process) to the HCl I added for washing, the stannous test which was positive with no tap water, resulted negative after the tap water add. Why might that be? Too diluted? Thanks for your time.

 

[Yggdrasil]

We always keep our waste solutions in a stock pot.
And from time to time we process it with cementing on copper with heavy air bubbling or stirring,
before treating it for waste disposal.
It will drop any PMs that has managed to sneak by.

Edit for spelling

 

[Shark]

How did you separate your metallic's from the ash?

 

[AndrewSuperD]

How did you separate your metallic's from the ash?

I take small scoops of material at a time and lay them in a flat plastic container. I use a device like the magnetic grabber (attached picture) multiple times over the same material. I drop the magnetic material from about six inches onto a clean plastic surface so the dust scatters off the materials, then use the magnetic grabber again. I’ll then put the dust back in with the main materials.

I’m hoping the problem I have here is that my sifting procedure left a good amount of material which I’ve done nothing with yet. I did look at it under a microscope and saw no gold but maybe I should take another crack at it. Wash it, sift again, etc…

 

[AndrewSuperD]

We always keep our waste solutions in a stock pot.
And from time to time we process it with cementing on copper with heavy air bubbling or stirring,
before treating it for waste disposal.
It will drop any PMs that has managed to sneak by.

Edit for spelling

Yep, as do I. I was referring to the sediment left in the filter after the AR process. Maybe something still in there or maybe like you said, that’s all there was.

 

[orvi]

It happen to me quite often, that after washing dirty gold drop (pins digestion in AR - so heavy copper/tin/lead solutions), some trace ammount of it re-dissolve into the solution. I always check after first wash with stannous. It seems like a lot - but when you are washing the gold, you use little ammounts of HCL - thus overall it isn´t that bad Personally, I keep the first washing (HCL) and add it to the next batch I process. If you are after the exact yield, you can cool the solution, and bit of SMB and boil it again to the final negative test. Boiling it helps to agglomerate newly formed gold particles.

We discussed this in our shop a bit... But we did not came to any certain conclusion about how this happen.
It could be that boiling in HCL together with atmospheric oxygen can be sufficient to oxidize some gold in these conditions... Also, there could be some impurities adsorbed onto gold surface, which alter the oxidation potentials and make it easier to oxidize the gold. Because - I always seen redissolved gold only in the first wash. No matter how violently I was boiling the gold powder afterwards in HCL nor ammonia, no gold redissolved.

 

[Martijn]

Maybe not. It’s just frustrating. I’ll keep all waste just in case I (or anyone) think of something. It might be that my incineration was inadequate? I’ll take another look at that material this weekend. Oddly enough after I added the tap water (recall I did 1/3 Harold’s process) to the HCl I added for washing, the stannous test which was positive with no tap water, resulted negative after the tap water add. Why might that be? Too diluted? Thanks for your time.

That is weird. Water should not hold back a stannous test result, it should only be lighter.
You said you had a purple result before the SMB. That indicates a very low gold concentration to start with. You usually need to dilute to see the dark stain turn purple.

 

[AndrewSuperD]

It happen to me quite often, that after washing dirty gold drop (pins digestion in AR - so heavy copper/tin/lead solutions), some trace ammount of it re-dissolve into the solution. I always check after first wash with stannous. It seems like a lot - but when you are washing the gold, you use little ammounts of HCL - thus overall it isn´t that bad Personally, I keep the first washing (HCL) and add it to the next batch I process. If you are after the exact yield, you can cool the solution, and bit of SMB and boil it again to the final negative test. Boiling it helps to agglomerate newly formed gold particles.

We discussed this in our shop a bit... But we did not came to any certain conclusion about how this happen.
It could be that boiling in HCL together with atmospheric oxygen can be sufficient to oxidize some gold in these conditions... Also, there could be some impurities adsorbed onto gold surface, which alter the oxidation potentials and make it easier to oxidize the gold. Because - I always seen redissolved gold only in the first wash. No matter how violently I was boiling the gold powder afterwards in HCL nor ammonia, no gold redissolved.

Thank you so much for the reply. I appreciate the detail and the sharing of experience. As outlined above, I kept the first wash and tested with stannous with a positive result. I then added tapwater and tested with stannous resulting in negative. Curious about this, I began to evaporate the excess liquid volume. I forgot to turn off the hot plate and all the liquid evaporated leaving a glistening and brown bottom of the beaker. I added 100 mL of hydrochloric acid and the brown bottom and glistening material went nowhere. So I added 1 mL of nitric and redissolve all material in the beaker. I again tested with stannous with a positive result. Picture attached. The camera Flash washed out how dark the test result was. In my natural light, it looks darker. I then added so Fama Cassett (hahahahaaa talk to text - added sulphamic acid) in the manner I described above and that’s where it’s sitting right now. It’s covered with a watch glass waiting for my next drop with SMB. That will be tonight.