Waste treatment issues

[Jimbriese]

Hey all so I just ran into a snag I am in the process of cleaning up some waste for some tests I have done and got pulled away from for a bit and of course my note book that had what was what listed disappeared (wife kid not sure which one) found outside and unreadable. So I took and filtered and combined everything HCL, AR, and nitric into one vessel about 3 liters total acid and rinse water. Added my copper coil 1/4”x3/8” in about a 5 inch diameter coil with bubbler for agitation let sit for two days had a black cement on bottom of vessel and some stuck to coil appeared nothing else was cemented the second day so I pulled the coil and set into another vessel and used spray bottle to rinse off as much of the black cement. Left solution for 12 hours to settle while I went to work came home and found the solution went from a dark green to a bright blue and all the cement is gone. Will test solution tonight when I get home. My best guess is it created cucl2 when trying to cement out any values. So my question. the black cement (which I have a very small amount of in the water from rinsing the coil) would this be PM’s or something else? I can get pics later if needed.

Like I said this was from a bunch of small tests on some heavy flash plating on boards there was some small surface mounts resistors, and caps the little tiny ones everything else was removed before running samples to try and find a way to get the plating off the boards as I have a lot of these board with the heavy flash plating from various industrial boards not consumer grade.
The test were run on just a handful of small boards with much less gold plating. Still working on finding a feasible way to get this plating without a lot of waste as some of this plating is contact plating for other board and buttons and is just as thick or thicker than gold plated fingers but through the whole board not feasible to cut like fingers. See first pic I have about 8-10 lbs of boards like this. And more with a lot of just flash plating through the whole board second pic. Mainly looking at the ones like the first pic but using ones like the second pic for testing the second pic show the surface mounts that were left for the testing I did.
Before I continue I am going to warm in oven to melt solder with a air vibrator that is used on hoppers to shake the solder and the rest of the surface mount from the boards. Then soak in HCL to dissolve any tin left. Rinse incinerate run through impact mill then pan out as much ash as possible then recover gold and other pm’s.
That’s my plan but any input would be appreciated.
Thanks
Jim

 

[Martijn]

So much to comment on, lets start with dealing with waste and the reactivity series, or the same process in a similar thread: When in doubt cement it out

The black cement came out on copper, so it can only be lesser reactive metal than copper. (i.e. precious metals)

Copper salts, when concentrated in water is mostly green, when diluted, it becomes blue.
Copper salts do not dissolve metals which have cemented out on copper (except for Pd, but that's going too far for you at this point I think)
So you still had free nitric in there which together with the HCl creates AR. Which dissolves pm's.

Keep the copper in there until it stops dissolving, or use the solution to dissolve more base metals, like those traces from your boards. Once the nitric is gone, use it as AP, or the Cupric Chloride leach.

Incinerating PCB's is not something I would recommend, and creates a lot of dioxines, other nasty stuff, possibly a loss of gold, etc etc. not sure how that works, but that is well discussed here in the past. just don't.
Learn to use the search function and start digging those gems out of our database.

The oven and HCl bath are fine in my opinion, some go straight for AP in stead and collect the components from the AP.

Good luck, have fun and be safe.

 

[Jimbriese]

Here is pics of the Stannious test fist was right after then the third pic is after ten minutes and it is brown in the spoon and yellow green on filter paper would the be a positive for Pd?
The other pic is the cement I rinsed off the copper coil in a separate vessel it’s heavy and settled out in about 10 minutes when I transferred to a smaller beaker.
And yes I’m not quite ready to work with Pd at this time but still want to recover and store till I am ready to start with Pgm’s
Added the copper back but without the bubbler right now and yes I’m seeing a reaction lots of tiny bubbles guessing one of the solutions must have had some free nitric left.
Thanks
Jim

 

[Jimbriese]

Well I figured out where the free nitric came from I had some gold plated pins I ran in a final fresh batch of nitric to clean up foils and did not get much of a reaction with I set aside for the next batch. Was listed in note book that disappeared. (Thanks babe thought I was going crazy)

And with it being in with HCL I don’t want to run the boards with gold plating as that will mix gold in with the Pd if that’s what the black cement was?