TLumsbay
Member
Does anyone have a reference source (or link) for optimal acid digestion temperatures for various metals? Specifically, I'm interested in Cupric AP solution. I can't seem to find any compiled data. I appreciate your input.
Optimal Acid Temperatures
- Thread starter TLumsbay
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We all just use it I guess.
If one opt for the
Cupric Chloride leach, speed is not the driving factor.
But warm seems faster than cold.
In my world cold is below freezing, not that i process much during the coldest parts of winter anyway
If speed is important, most strip the potential Tin off and use Nitric.
TLumsbay
Member
Thanks Yggdrasil, It relates back to my 1300 grams for pins I'm digesting. It's been 2+ weeks and the volume of pins do not seem to be reducing much. I run my nitric digestion at 70C based on paper's I've read to minimize the evaporative loss without much extension of time vs. 90C and was hoping to find something on Cupric A/P.
While I'd like to say " time isn't a problem", the truth is my patience wears thin after a few weeks. I was hoping to place the reaction vessel on a warmer plate but I never do something without looking at the published data first.
While I'd like to say " time isn't a problem", the truth is my patience wears thin after a few weeks. I was hoping to place the reaction vessel on a warmer plate but I never do something without looking at the published data first.
I'm not sure there has been done extensive research on this.
It's original use was etching PCB traces.
But of course it is worth a check.
You've got pins in nitric. Well, first question is, is it conc. nitric, or 50/50 nitric/distilled water? Because conc. nitric has issues dissolving much metal. The reaction products don't dissolve in the concentrated acid well, and there's also the issue of the formation of solid metastannic acid if your pins are tin brass in their cores, which is a problem no matter what concentration of nitric you use.
Cupric AP really is the best for clearing base metals from gold-plated pins. It can take some time, but the foils that result are very clean of base metal.
Copper and tin make bronze. Copper and zinc make brass. It's a very common mistake.
Dave
I searched few times with no results. As all common reactions, AP dissolution accellerates with raising temperature. Contrary, dissolution of oxygen in the solution decrease with temperature. Below room temperature, AP is working very slowly. Best case scenario would be hot AP with pure oxygen bubbling through it. That way, there would be no evaporative loss since you will adjust oxygen flow the way all will be absorbed into the solution = no outgas. But noone will probably do this since this will be expensive (if you don´t have some spare oxygen concentrator in hand).
I would say slightly higher than room temperature would help, but I would start with rt from start to deplete acid below 25% to cut evaporative loss. From my unscientific experiments, it looked like 40-60 °C were somewhere optimal, if I remember correctly. But it was years ago and we then abandoned whole AP processing due to slow turnover of material.
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I really liked the utmost simplicity of the process, and dreamed about 250L barrel rotating tumbler, isolated with some glass wool, heated by glass heating finger with thermostat to some 40-50 °C and oxygen concentrator pumping oxygen to the juice, adjusted by pressure sensor and simple magnetic valve. No noxious gasses, just HCL doing it´s job, no acidic outgas... Temperature and pure O2 should significantly speed it up... But I never had a chance to construct it, since we gone AR route for good due to turnover time. AP simply took too long with high grade thick plated material. We eventualy did it in very similar setup, but with AR. Even with AR it took whole day and more to even digest and drop the first dirty gold. Ammount of heat released by that thing is unbelievable.
Then you cement all metals from the waste solution on aluminium, take the AlCl3 liquid, evaporate it and thermally decompose to retrieve HCL and waste Al2O3. Thermal decomposition of AlCl3 is very nice, and residue is relatively powdery and does not tend to cake.
Tumbling motion really helps with dissolution, and this apparatus is easier to construct than it would seem. Mainly if you are doing bulk, like 20 or 50 kilo batch at time. In this scenario, some motion of the solid metal bulk is very helpful. Flowing liquid through it helps, but tumbling is better
There used to be a post called something like “the crock pot method”. It worked pretty well but don’t scratch the finish on the pot as it will eventually eat it as well. If I recall correctly the crock pots with hi-low setting heated up to 125F on low and 165F on high. With a good air source it worked quite well.
TLumsbay
Member
Started becoming impatient with the leaching of these pins with the solution becoming saturated every 3-4 days. I found a good paper on the topic (Yazici et.al. 2014) and applied some of their findings more than doubling the apparent digestion of the material. At a 100mM Cu2+ concentration at 75-80C, I was forming white crystal precipitate daily with ~ 75ml loss of volume. Reducing the temp to 60-65C improved volume loss considerably (<50ml) but and still forming precipitate ( I am assuming this was CuCl salt because when I filtered it off the precipitate turned the familiar bluish/green). To my surprise, the paper indicated that Cl- concentrations above 0.7M actually decreased digestion rate. Originally, to get to the 100mM Cu2+ I added 67g Cu(II)Cl to 1 liter of 31% HCl which gives me roughly a 3M Cl- concentration. So I diluted the HCl by 50% and kept my w/v around 1-2. Crystals formed within an hour (clearly without any digestion of material). So I went back to the default Cl- concentration and poured off the solution daily. It worked nicely and at minimum 2x faster. (The volume of the bubbler was set as to mimic a rolling boil).
Couple of questions I hope one of you experienced pros can answer:
1) Why would I get such a rapid formation of the precipitated when I diluted the Cl- concentration?
2) I've always been told that a good measure of saturation was the formation of precipitate. Is there a better way?
3) The paper indicates keeping the w/v ratio low, however all the recommendation I've found have been to just add more HCl when the solution appears saturated. Is this just to minimize waste?
4) I suspect that the bubbler volume may have been too aggressive, The aerator would become encased in crystals, any recommendations?
5) Why would a higher Cl- molarity ****** the metal digestion?
6) Am I way overthinking this. Should I just throw them in a 5 gallon bucket, fill it with A/P and come back to it in 8 weeks?
I ran ~ 1300 grams of pins after a 100 gram test run and have about the same left to do. I just want to plan accordingly.
Here's the paper if anyone has any interest.
E.Y. Yazici, Birloaga, I., Cui, J., Demopoulos, G. P., Dreisinger, D., Herreros, O., Kim, E., Park, Y. J., Ping, Z., Tuncuk, A., Widmer, R., Winand, R., Yazici, E. Y., Arbiter, N., Arcan, M. Ş., Beck, M., Demarthe, J. M., Deveci, H., … Gupta, C. K. (2014, November 4). Cupric chloride leaching (hcl–cucl2–nacl) of metals from waste printed circuit boards (WPCBS). International Journal of Mineral Processing.
Couple of questions I hope one of you experienced pros can answer:
1) Why would I get such a rapid formation of the precipitated when I diluted the Cl- concentration?
2) I've always been told that a good measure of saturation was the formation of precipitate. Is there a better way?
3) The paper indicates keeping the w/v ratio low, however all the recommendation I've found have been to just add more HCl when the solution appears saturated. Is this just to minimize waste?
4) I suspect that the bubbler volume may have been too aggressive, The aerator would become encased in crystals, any recommendations?
5) Why would a higher Cl- molarity ****** the metal digestion?
6) Am I way overthinking this. Should I just throw them in a 5 gallon bucket, fill it with A/P and come back to it in 8 weeks?
I ran ~ 1300 grams of pins after a 100 gram test run and have about the same left to do. I just want to plan accordingly.
Here's the paper if anyone has any interest.
E.Y. Yazici, Birloaga, I., Cui, J., Demopoulos, G. P., Dreisinger, D., Herreros, O., Kim, E., Park, Y. J., Ping, Z., Tuncuk, A., Widmer, R., Winand, R., Yazici, E. Y., Arbiter, N., Arcan, M. Ş., Beck, M., Demarthe, J. M., Deveci, H., … Gupta, C. K. (2014, November 4). Cupric chloride leaching (hcl–cucl2–nacl) of metals from waste printed circuit boards (WPCBS). International Journal of Mineral Processing.
Attachments
Air lift pump.
Use it to lift and recirculate you AP solution where it falls through your material. You will get white copper crystals very quickly if it saturates but will keep eating copper. The crystals stay in the bottom of your container, along with your gold flakes. Learning to control the volume of materials for the volume of acids will help by a lot. Close look at my two gallon bucket setup. These pumps are no longer being made, but a search of google gives pretty good “how to” on them.
Use it to lift and recirculate you AP solution where it falls through your material. You will get white copper crystals very quickly if it saturates but will keep eating copper. The crystals stay in the bottom of your container, along with your gold flakes. Learning to control the volume of materials for the volume of acids will help by a lot. Close look at my two gallon bucket setup. These pumps are no longer being made, but a search of google gives pretty good “how to” on them.
Darkthirty
Well-known member
- Joined
- Dec 21, 2016
- Messages
- 299
This link came up during an AP leach search on this site. Some of your questions should be answered ... https://cdn.imagearchive.com/goldre...307d580e055e689fa7d4cdc54954b19247a9c9ca2a1a5
The above cited link is the most comprehensive paper by a hobbyist on the subject of AP/CuCl leach parameters. I actually got permission from the original author to post the document here. I strongly recommend getting an authors permission before re-posting his/her work.
Despite what anyone tries to tell you, that document is the original spark that was the foundation of all things acid peroxide/copper chloride that you see here on the forum and around YouTube. Imagine if all the YouTube stars mentioned their source material what it would do for those that actually developed these processes. It truly amazes me what constitutes an "expert" in this day and age of instant fame. Please pardon my rant.
Steve
Despite what anyone tries to tell you, that document is the original spark that was the foundation of all things acid peroxide/copper chloride that you see here on the forum and around YouTube. Imagine if all the YouTube stars mentioned their source material what it would do for those that actually developed these processes. It truly amazes me what constitutes an "expert" in this day and age of instant fame. Please pardon my rant.
Steve
- Joined
- Apr 15, 2023
- Messages
- 124
I appreciate the "rant". There are very few things more important to a researcher than the number of citations of their publications. Giving credit to those hobbyist that share their work, encourage more sharing and peer review. Enough can't be said.
When I click on the link. This is all I see.
Edited because it showed my posting as Darkthirty's
"This XML file does not appear to have any style information associated with it. The document tree is shown below.
<Error>
<Code>AccessDenied</Code>
<RequestId>tx000000000000028815088-00649c2327-4bdec571-nyc3b</RequestId>
<HostId>4bdec571-nyc3b-nyc-zg02</HostId>
</Error>"
Edited because it showed my posting as Darkthirty's
"This XML file does not appear to have any style information associated with it. The document tree is shown below.
<Error>
<Code>AccessDenied</Code>
<RequestId>tx000000000000028815088-00649c2327-4bdec571-nyc3b</RequestId>
<HostId>4bdec571-nyc3b-nyc-zg02</HostId>
</Error>"
Works fine with me, what kind of browser do you use?
Thanks for the help.
I don't know how that happened. I clicked on reply and typed my posting. Then added copy and paste of the Error code.
Then tried to delete Darkthirty's part to just show my posting.
But then it put my post in where his quote was.
Sorry for causing an issue.
My browser is chrome on my phone. I use nord VPN if that matters.
Edited to add browser info.
I don't know how that happened. I clicked on reply and typed my posting. Then added copy and paste of the Error code.
Then tried to delete Darkthirty's part to just show my posting.
But then it put my post in where his quote was.
Sorry for causing an issue.
My browser is chrome on my phone. I use nord VPN if that matters.
Edited to add browser info.
Works like a charm from my Safari too.
Maybe try without the VPN?
