RAM recovery - SMB causing white sludge?

[tzcheese]

Hi there,

After some small-scale experimentation, I've just attempted my first recovery of gold from trimmed RAM and PCI boards. It went as follows:

1. Soaked fingers in a 15:1 mix of 32% HcL and 6% H202 until all contacts detached.
2. Separated detached contacts (plus some circuit board) from the solution using filter paper and let dry.
3. Put detached contacts (incl the filter paper) into a beaker and added just enough HcL to cover it.
4. Added 70% HNO3 a few drops at a time, mixing throughout, until reaction stopped (bubbling ceased + no contacts remaining).
5. Filtered solution into clean beaker and flushed with clean HcL. Resulting solution was dark yellow/brown.
6. Brainfarted and started adding SMB before neutralising excess HNO3. Lots of fizzing and noxious vapours. White sludge started building up at the bottom of the beaker.
7. Tested solution with stannous - Stain was near-black, which I read as positive for PGM.
8. Let precipitate settle fully, then separated it from solution by pouring off solution into clean beaker.
9. Added urea to solution until reaction stopped. (After digging around, this is apparently not the recommended process anymore?)
10. Added SMB again and let it sit. More white precipitate which turned cappuccino-brown over an hour or so.
11. Another stannous test on the solution. No reaction, which I read as negative for PGM.
12. Separated cappuccino sludge by pouring off solution. (I am here.)

Based on lurking around here and scanning hokes for clues (Hokes' only refers to SMB as a precursor to SO2 gas as a precipitant.), I can think of two possibilities for what's gone wrong:

1. The sludge is comprised of metal salts from base metals under the gold plating that were not removed prior to dissolving in AR. To avoid this in the future I should incinerate the contacts after the AP bath, then nitric bath them to remove any base metals that aren't soluble in HCl.
2. The SMB itself is the source of the white sludge. I suspect this because I mixed up two small amounts of clean AR, neutralising the nitric in one and not the other (to see if it was my brainfart that caused the issue), then adding SMB to both. Nothing else was dissolved in the solution. In both tests the white sludge appeared.

There's plenty of information around to help recover from the first case, but I wanted to ask the more experienced here if the second case is even a thing that can happen (eg, if I've used bad SMB) and if the process for recovery is different from the first case.

Alternatively, there might be some other scenario I'm not aware of.

Thanks for reading and for any guidance anyone can send my way.

 

[Yggdrasil]

Hi there,

After some small-scale experimentation, I've just attempted my first recovery of gold from trimmed RAM and PCI boards. It went as follows:

1. Soaked fingers in a 15:1 mix of 32% HcL and 6% H202 until all contacts detached.
2. Separated detached contacts (plus some circuit board) from the solution using filter paper and let dry.
3. Put detached contacts (incl the filter paper) into a beaker and added just enough HcL to cover it.
4. Added 70% HNO3 a few drops at a time, mixing throughout, until reaction stopped (bubbling ceased + no contacts remaining).
5. Filtered solution into clean beaker and flushed with clean HcL. Resulting solution was dark yellow/brown.
6. Brainfarted and started adding SMB before neutralising excess HNO3. Lots of fizzing and noxious vapours. White sludge started building up at the bottom of the beaker.
7. Tested solution with stannous - Stain was near-black, which I read as positive for PGM.
8. Let precipitate settle fully, then separated it from solution by pouring off solution into clean beaker.
9. Added urea to solution until reaction stopped. (After digging around, this is apparently not the recommended process anymore?)
10. Added SMB again and let it sit. More white precipitate which turned cappuccino-brown over an hour or so.
11. Another stannous test on the solution. No reaction, which I read as negative for PGM.
12. Separated cappuccino sludge by pouring off solution. (I am here.)

Based on lurking around here and scanning hokes for clues (Hokes' only refers to SMB as a precursor to SO2 gas as a precipitant.), I can think of two possibilities for what's gone wrong:

1. The sludge is comprised of metal salts from base metals under the gold plating that were not removed prior to dissolving in AR. To avoid this in the future I should incinerate the contacts after the AP bath, then nitric bath them to remove any base metals that aren't soluble in HCl.
2. The SMB itself is the source of the white sludge. I suspect this because I mixed up two small amounts of clean AR, neutralising the nitric in one and not the other (to see if it was my brainfart that caused the issue), then adding SMB to both. Nothing else was dissolved in the solution. In both tests the white sludge appeared.

There's plenty of information around to help recover from the first case, but I wanted to ask the more experienced here if the second case is even a thing that can happen (eg, if I've used bad SMB) and if the process for recovery is different from the first case.

Alternatively, there might be some other scenario I'm not aware of.

Thanks for reading and for any guidance anyone can send my way.

UREA is an feritlizer and has virtual no use in a lab.
Besides that your description don't add up much.
Ram foils some of the cleanest material you can find.
And the way you described you use of Nitric there should not be much excess.

So depending on the amount of liquid straight SMB could be ok, you just need a bit more.
Any concentrated solution of Gold will test black. Trust me there are NO PGMs in ram fingers.
So verify your SMB to be SMB get hold of some Sulfamic Acid for deNOxing.
While you are at it check your other chemicals as well.
Keep searching and lurking.

 

[lazersteve]

I would add just enough water to the sludge to see if you can get it to dissolve. If it does then add a third of its volume of HCl and heat to around 40C. If it's SMB you should smell the SO2.

Na2S2O5(aq) + 2HCl(aq)--> 2SO2(g) + 2NaCl(aq) + H2O

Steve

 

[tzcheese]

UREA is an feritlizer and has virtual no use in a lab.
Besides that your description don't add up much.
Ram foils some of the cleanest material you can find.
And the way you described you use of Nitric there should not be much excess.

So depending on the amount of liquid straight SMB could be ok, you just need a bit more.
Any concentrated solution of Gold will test black. Trust me there are NO PGMs in ram fingers.
So verify your SMB to be SMB get hold of some Sulfamic Acid for deNOxing.
While you are at it check your other chemicals as well.
Keep searching and lurking.

I'd thought gold was a PGM, but happy to be corrected. Still getting my hang on the terminology as I've never really had a reason to actually talk about this before.

I'll try verifying my chemicals. I'm confident that the acids are what they say on the bottles. The SMB is the part that isn't acting the way the descriptions say it should, so that's my suspect.

I would add just enough water to the sludge to see if you can get it to dissolve. If it does then add a third of its volume of HCl and heat to around 40C. If it's SMB you should smell the SO2.

Na2S2O5(aq) + 2HCl(aq)--> 2SO2(g) + 2NaCl(aq) + H2O

Steve

Awesome. I'll try this out on the sludge from step 6 and see where that takes me.

Thanks for the responses and guidance Yggdrasil and Lazersteve, it's much appreciated. I'll report back with the results.

 

[eaglekeeper]

If your using Stump Out for your SMB...... Make sure it is in fact SMB and not something else. I believe there is two different types of Stump Out.

 

[Shark]

PM - Precious Metals

PGM- Platinum Group Metals

We are all still learning to some degree.

Bonide Stump Out is SMB.

Spectricide Stump Remover is potassium nitrate.

Welcome to GRF.

 

[wisco_gold]

Bonide Stump Out should be smb....some other brands are potassium nitrate.

 

[eaglekeeper]

It doesn't show up very well on this pic...so I'll type out the active ingredient. I have no idea what that ingredient is, and someone new might mistake this for the good stuff. I Wikipedia that ingredient... I'm not a chemist, but it doesn't sound like a good idea to use it.

Triclopyr, (3,5,6-tricloro-2-pyridinyloxyacetic acid), as triethylamine salt...... 8.8%
inert ingredients....................................................................................................................91.2%

 

[wisco_gold]

I would hope that new or not, anyone purchasing/using a household chemical for dangerous chemical reactions would not only read the bottle but google the MSDS and give that a read. Some products do not voluntarily list proprietary ingredients and you have to contact them or look up the MSDS.

Besides having a good memory; being a good chemist requires attention to detail. I'm not saying you didn't notice, but if someone read that Bonide Stumpout was sodium metabisulfate and that they can use that to precipitate their PM's, I would hope they would notice the name of that product is different and double-check. I would hope someone check even if the name wasn't different as company's change their formulas or ingredients sometimes. I'm not naive to the fact that some people don't do take this sort of thing seriously and sadly enough every once in awhile you read about them in the news.

 

[popslab]

Not to accidentally state the obvious but the label is very important
Stump out “Stump removal”

 

[eaglekeeper]

Not to accidentally state the obvious but the label is very important
Stump out “Stump removal”

You are absolutely correct.. We here generally (not always) just use the term "Bonide Stump-out" and not always specify "stump remover". This thread is a prime example.

Just trying keep people from making a potentially painful mistake.

 

[tzcheese]

I would hope that new or not, anyone purchasing/using a household chemical for dangerous chemical reactions would not only read the bottle but google the MSDS and give that a read. Some products do not voluntarily list proprietary ingredients and you have to contact them or look up the MSDS.

Besides having a good memory; being a good chemist requires attention to detail. I'm not saying you didn't notice, but if someone read that Bonide Stumpout was sodium metabisulfate and that they can use that to precipitate their PM's, I would hope they would notice the name of that product is different and double-check. I would hope someone check even if the name wasn't different as company's change their formulas or ingredients sometimes. I'm not naive to the fact that some people don't do take this sort of thing seriously and sadly enough every once in awhile you read about them in the news.

I've read the papers with every other chemical I'm using and I take proper care and precaution when working with them. Acid burns are not a thing I want in my life. The SMB is the exception and arrived without any labeling or information other than the chemical name on the container. I didn't think to ask the supplier, I'll shoot them a message.

This is why I think it's the source of my problem. It acts like SMB (as far as I've seen in other people's examples) as far as the reaction , but it also appears to be linked to the sludge. My speculation right now it that it might've been "cut" with something to pad out the weight. As soon as the weather clears up here I can run Lazersteve's test to find out.

Thanks again to everyone for your help!

 

[eaglekeeper]

I've read the papers with every other chemical I'm using and I take proper care and precaution when working with them. Acid burns are not a thing I want in my life. The SMB is the exception and arrived without any labeling or information other than the chemical name on the container. I didn't think to ask the supplier, I'll shoot them a message.

Do you have a Home Depot or Ace hardware store near you. If so they carry Bonide Stump-Out stump remover. I looked on Lowes website and didn't see the Bonide.

 

[Shark]

Here, Home Depot carries Bonide Stump Out and Lowe’s tends to carry the Spectracide Stump Remover.

Just for kicks, I prefer the Bonide Stump Out when trying to get rid of stumps, it seems to work a little faster.

 

[AndrewSuperD]

I add Sulfamic Acid at 90C to denox then let it cool and drop any lead. I then filter it before adding the SMB. When I do add SMB, I add about 50% water to the filtered AR solution and then add powder SMB. Or, I mix SMB with enough warm water to add 50% volume to the filtered AR solution.

 

[eaglekeeper]

You should add your water for dilution prior to filtering, diluting will lower the solubility of some metal contaminates (like silver chloride) and they can be filtered out. As far as SMB you can add your SMB dry or wet. I personally add mine wet, others prefer to add dry....It works the same either way.

 

[eaglekeeper]

I prefer the Bonide Stump Out when trying to get rid of stumps, it seems to work a little faster.

I hear Tannerite works pretty quick too...

 

[tzcheese]

Do you have a Home Depot or Ace hardware store near you. If so they carry Bonide Stump-Out stump remover. I looked on Lowes website and didn't see the Bonide.

Unfortunately no, it looks like I can only get it online. That'll be the next step if it turns out that what I have isn't confirmed to be the genuine article.

On that topic...

Following Lazersteve's recommendation, I've separated a portion of the white sludge and added enough water to make it dissolve (which it did, using about twice the volume of the sludge), then added 1/3rd of the total volume in HCl and heated to 40 degrees C.

The aroma was similar, but not identical to the smell of burnt matches. There was also a small but noticeable amount of snowy-looking particulate circulating in the solution which has eventually settled on the bottom as a couple of loosely packed clouds.

To me this suggests that I am using SMB, albeit with some impurities.

So this leaves me with the question: Is it possible that the issue is as simple as me having used way too much SMB?

 

[eaglekeeper]

The aroma was similar, but not identical to the smell of burnt matches. There was also a small but noticeable amount of snowy-looking particulate circulating in the solution which has eventually settled on the bottom as a couple of loosely packed clouds.

I hope your doing this in a fume hood or outside up wind of it.

Hard to say, but maybe there's some sort of anti-caking agent in your SMB.

 

[tzcheese]

I hope your doing this in a fume hood or outside up wind of it.

Hard to say, but maybe there's some sort of anti-caking agent in your SMB.

No fume hood (yet). For now I'm working outside and at the whims of the weather, which is why it's taken me a few days to progress with this.

Speaking of progress:
Working under the assumption that the sludge was just a massive overdose of SMB, I took some of the cappuccino sludge, added water and stirred. 2/3 of the volume dissolved and has left behind something that looks an awful lot like this (not my image).

I'm currently waiting for it to settle fully.

Assuming what I have is gold precipitate, I think the question of where the sludge came from probably comes down to my application of SMB. Next time I'll try dissolving it in water before adding it to the AR as suggested earlier in the thread. In all likelihood I just got to the exciting part of the process, got impatient and added too much SMB, thinking that what I'd added wasn't enough.

Thanks to everyone here for your guidance, you guys are legends.