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:
Alternatively, there might be some other scenario I'm not aware of.
Thanks for reading and for any guidance anyone can send my way.
After some small-scale experimentation, I've just attempted my first recovery of gold from trimmed RAM and PCI boards. It went as follows:
- Soaked fingers in a 15:1 mix of 32% HcL and 6% H202 until all contacts detached.
- Separated detached contacts (plus some circuit board) from the solution using filter paper and let dry.
- Put detached contacts (incl the filter paper) into a beaker and added just enough HcL to cover it.
- Added 70% HNO3 a few drops at a time, mixing throughout, until reaction stopped (bubbling ceased + no contacts remaining).
- Filtered solution into clean beaker and flushed with clean HcL. Resulting solution was dark yellow/brown.
- 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.
- Tested solution with stannous - Stain was near-black, which I read as positive for PGM.
- Let precipitate settle fully, then separated it from solution by pouring off solution into clean beaker.
- Added urea to solution until reaction stopped. (After digging around, this is apparently not the recommended process anymore?)
- Added SMB again and let it sit. More white precipitate which turned cappuccino-brown over an hour or so.
- Another stannous test on the solution. No reaction, which I read as negative for PGM.
- Separated cappuccino sludge by pouring off solution. (I am here.)
- 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.
- 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.
Alternatively, there might be some other scenario I'm not aware of.
Thanks for reading and for any guidance anyone can send my way.