Why not just AR instead of AP then AR?

[hammerdown]

I just want to make sure I'm understanding the basic underlying principal jist of AP & AR in regards to clean plated boards & card fingers.

AP is initially used to remove the gold plating/flashing from the nickle and copper substrate of the PCB that it was bonded to during fabrication, creating a copper leach as some say... correct? Of in which that AP is now more accurately called CuCl2 that can be used over & over again for repeated recovery processing. Then, after recovering & washing the foils/particles, process through AR (or HCL/CL) to dissolve the recovered gold alloy to seperate from the impurities within the gold alloy so that pure gold can be persipitated out & recovered, which appears to just be a suped up AP process so that gold too can be dissolved... correct? So, assuming my jist understanding is somewhat on point, then why not just skip the AP / CuCl2 recovery step and place the clean boards (no solder, components or iron contaminants) and/or fingers right into AR? Would it be due to the usual nickle layer between the gold & the copper substrate as a wanted avoidance that could hinder the AR recovery?... The solder mask material possibly getting dissolved as well further complicating matters?

As mentioned before, I am not necessarily looking to cut corners or whatever to be impatient or rushed, but rather trying to better under why waste time with what appears to be an unnecessary step where the 2nd step sounds like it would pretty much elimenate the need for the 1st step for this type of material. I have yet to evolve past my experience past the CuCl2 leech recovery process with PCB gold plated material, but just often wondered why bother when the AR or HCL/Cl step appears to combine both steps 1 & 2 into 1 single step. I do so apologize if this has been addressed before. I do try to use the forum search.

 

[Yggdrasil]

If one can guarantee that ALL of the base metas are dissolved in AR/HCl+Cl or whatever method used, it will be ok. But most of the PCBs are multi layer and will contain several layers of copper traces on which the gold will cement out on.

That is the reason why the AP method are used first or if cheap Nitric is available some use that.

Then you have a small amount of gold with minute amounts of base metal that is easy to dissolve and you can easily see when it is completely dissolved.

 

[mls26cwru]

there is also the concern of Tin... In AR, I believe two things can occur (if others could please correct me if I am wrong)... 1: form metastannic acid with the nitric acid component, and 2: form Stannous chloride with the hydrochloric acid component. The first makes filtering really tough. the second can turn your gold in solution into colloidal gold causing some irrecoverable losses.

while you can try to make sure the feed stock is clean, all it takes is a little extra tin to cause a nightmare.

Since you have to get rid of the copper anyway, copper chloride offers a way to do that cheaply and eliminates tin that may have slipped by.

 

[nickvc]

With most scrap you can go straight to AR but it comes with a price which some find hard to bear, for a start you have metals which can and will tie up some values and problems with precipitating decent gold, it will also consume way more acids for little advantage and possibly leave you with gold tied up with tin chloride which then means incineration.
Follow the processes outlined here on the forum if you want less stress, once you have those down pat start small experiments but expect failures along the way and maybe just stick to what’s known to work or learn how to change the processes to succeed.

 

[FrugalRefiner]

Indeed! There is a reason we promote the "tried and true" processes here. It's because they work almost every time, even for inexperienced refiners. Once you gain experience in those processes, you can start to experiment with other methods.

Dave

 

[hammerdown]

Thank you guys! I really did think that there was a more in-depth good reasoning that I had not yet run across in research, otherwise that's what most would do now, but thought I'd ask to clear up my understanding of what "on the surface" didn't make sense of extra steps. Now I better understand why. I didn't realize there could be any tin with cleaned material, nor was I aware of possible multi-layer substrates / etching to the PCBs. AP / CuCl2 leach I am pretty much comfortable doing since I've done quite a few runs with it at this point. I haven't gotten to the point of trying to check for & drop any possible PM's in the CuCl2 solution yet, nor to neutralize the solution once saturated & done with for proper disposal... in due time though. Again, thank you guys for the more in-depth reasonings as to why not straight to AR by passing AP for clean boards & fingers. I prefer to do as proper "tried & true", but can't help but ask why this or why not that on occasion, just to better understand when I can't seem to fully piece together the answers on my own from researching.

As far as what Yggdrasil mentioned about some just using nitric, I do believe I saw or read somewhere before about someone really jumping the gun for a quicker turn around time by doing something like that with card fingers. But I have 0 experience with nitric as of yet, therefore experimenting with nitric as a "off the beaten path" method is definitely out of the question for me until I'm more experienced with proper methods of use with it. My first use of nitric will most likely be via AR at some point.

 

[nickvc]

I think it’s fair to say that asking questions is what the forum is about and if it helps you or anyone else that’s all to the benefit of the forum.
There are many ways to recover from most materials and recovery is really the most important part and can be the hardest to understand or master, as most members work with e scrap that can and does contain many metals and materials that can make a real mess if not processed properly it’s the recovery that makes the refining easier. We have had many many posts from people who just got a load of scrap and dumped in reagents and then can’t fathom how to get their values back from the gloop they have created because they didn’t understand what the results of their actions would be.
An example from not too long ago from me. I was asked to refine about 100 kilos plus of old connectors still in the plastic, they were copper based pins so we tried nitric to remove the copper and leave the gold and plastic, seemed logical, but surprise the solution boiled over as the plastic was an old type and reacted to the nitric causing a boil over, the world of recovery is full of surprises some of which will leave everyone scratching their heads and with a what to do now expression.

 

[goldenchild]

I've processed fingers in AR before and the short of it is it's messy. At least for me it was. The problems I came across were vessel space, material coverage and acid depletion.

Fingers take up alot of space fast. That is if you want to situate them in a way where the acid can reach them. If laid flat for room efficiency then the acid won't be able to touch all surfaces to work on. Even if you lay them out randomly you usually still have to stir up the material for all surfaces to be exposed. Not fun doing that with hot AR.

Then you have to come up with a way to cover all the material using the least amount of acid. That is unless you have access to nitric and HCL real cheap. So then you have to mess around with adding water to the AR, enough to cover everything but not enough to dilute it where the acid won't work. That can be a pain.

And lastly is acid depletion. There's really no way to gauge the total amount of metal on the fingers. So you kinda have to just guess and hope you don't use way too much acid. That combined with the dilution with water is also not that easy.

So unless you have access to acids on the cheap I wouldn't do it this way. If you want to try it though I would say do it in small batches. You'll need plenty of containers as well. One to perform the reaction. A second to hold the next batch. One that you'll put the digested fingers in for rinsing when your entire stock is processed. The last vessel to hold your pregnant solution. So the operation would be digest one batch. Put another batch into another vessel. Pour the acid from the first batch onto the new batch (this is to ensure acid depletion). Put the processed fingers into your vessel that will hold all the digested fingers. When acid is depleted add the solution to your pregnant solution vessel. Keep juggling like this until all material is done. Then rinse all the fingers and add it to your pregnant solution.

It's alot of work.

 

[jarlowski1]

I've processed fingers in AR before and the short of it is it's messy. At least for me it was. The problems I came across were vessel space, material coverage and acid depletion.

Fingers take up alot of space fast. That is if you want to situate them in a way where the acid can reach them. If laid flat for room efficiency then the acid won't be able to touch all surfaces to work on. Even if you lay them out randomly you usually still have to stir up the material for all surfaces to be exposed. Not fun doing that with hot AR.

Then you have to come up with a way to cover all the material using the least amount of acid. That is unless you have access to nitric and HCL real cheap. So then you have to mess around with adding water to the AR, enough to cover everything but not enough to dilute it where the acid won't work. That can be a pain.

And lastly is acid depletion. There's really no way to gauge the total amount of metal on the fingers. So you kinda have to just guess and hope you don't use way too much acid. That combined with the dilution with water is also not that easy.

So unless you have access to acids on the cheap I wouldn't do it this way. If you want to try it though I would say do it in small batches. You'll need plenty of containers as well. One to perform the reaction. A second to hold the next batch. One that you'll put the digested fingers in for rinsing when your entire stock is processed. The last vessel to hold your pregnant solution. So the operation would be digest one batch. Put another batch into another vessel. Pour the acid from the first batch onto the new batch (this is to ensure acid depletion). Put the processed fingers into your vessel that will hold all the digested fingers. When acid is depleted add the solution to your pregnant solution vessel. Keep juggling like this until all material is done. Then rinse all the fingers and add it to your pregnant solution.

It's alot of work.

I agree it definitely is a pain that way. I am always afraid that the pcb will soak up some of my pregnant AR trapping Au chloride. I'm paranoid that way... Even though I would rinse the fingers throughly I still don't want to risk that. So needless to say I never have pcb boards in with my gold while its in solution. Just my take on it.

 

[hammerdown]

I've processed fingers in AR before and the short of it is it's messy. At least for me it was. The problems I came across were vessel space, material coverage and acid depletion.

Fingers take up alot of space fast. That is if you want to situate them in a way where the acid can reach them. If laid flat for room efficiency then the acid won't be able to touch all surfaces to work on. Even if you lay them out randomly you usually still have to stir up the material for all surfaces to be exposed. Not fun doing that with hot AR.

Then you have to come up with a way to cover all the material using the least amount of acid. That is unless you have access to nitric and HCL real cheap. So then you have to mess around with adding water to the AR, enough to cover everything but not enough to dilute it where the acid won't work. That can be a pain.

And lastly is acid depletion. There's really no way to gauge the total amount of metal on the fingers. So you kinda have to just guess and hope you don't use way too much acid. That combined with the dilution with water is also not that easy.

So unless you have access to acids on the cheap I wouldn't do it this way. If you want to try it though I would say do it in small batches. You'll need plenty of containers as well. One to perform the reaction. A second to hold the next batch. One that you'll put the digested fingers in for rinsing when your entire stock is processed. The last vessel to hold your pregnant solution. So the operation would be digest one batch. Put another batch into another vessel. Pour the acid from the first batch onto the new batch (this is to ensure acid depletion). Put the processed fingers into your vessel that will hold all the digested fingers. When acid is depleted add the solution to your pregnant solution vessel. Keep juggling like this until all material is done. Then rinse all the fingers and add it to your pregnant solution.

It's alot of work.

Yea... from what other's have mentioned that I wasn't aware of being possible & probable headaches, and from how you described how to do it if one were to try it... it does seem quite possibly more troublesome in the end than doing it the proper way of AP then AR.

 

[hammerdown]

I've processed fingers in AR before and the short of it is it's messy. At least for me it was. The problems I came across were vessel space, material coverage and acid depletion.

Fingers take up alot of space fast. That is if you want to situate them in a way where the acid can reach them. If laid flat for room efficiency then the acid won't be able to touch all surfaces to work on. Even if you lay them out randomly you usually still have to stir up the material for all surfaces to be exposed. Not fun doing that with hot AR.

Then you have to come up with a way to cover all the material using the least amount of acid. That is unless you have access to nitric and HCL real cheap. So then you have to mess around with adding water to the AR, enough to cover everything but not enough to dilute it where the acid won't work. That can be a pain.

And lastly is acid depletion. There's really no way to gauge the total amount of metal on the fingers. So you kinda have to just guess and hope you don't use way too much acid. That combined with the dilution with water is also not that easy.

So unless you have access to acids on the cheap I wouldn't do it this way. If you want to try it though I would say do it in small batches. You'll need plenty of containers as well. One to perform the reaction. A second to hold the next batch. One that you'll put the digested fingers in for rinsing when your entire stock is processed. The last vessel to hold your pregnant solution. So the operation would be digest one batch. Put another batch into another vessel. Pour the acid from the first batch onto the new batch (this is to ensure acid depletion). Put the processed fingers into your vessel that will hold all the digested fingers. When acid is depleted add the solution to your pregnant solution vessel. Keep juggling like this until all material is done. Then rinse all the fingers and add it to your pregnant solution.

It's alot of work.

I agree it definitely is a pain that way. I am always afraid that the pcb will soak up some of my pregnant AR trapping Au chloride. I'm paranoid that way... Even though I would rinse the fingers throughly I still don't want to risk that. So needless to say I never have pcb boards in with my gold while its in solution. Just my take on it.

To be honest, I've often wondered my self about if any PCBs could be soaking up solutions to some degree of loss if left in for too long or just by some physics that I'm not privy to yet.

 

[hammerdown]

I think it’s fair to say that asking questions is what the forum is about and if it helps you or anyone else that’s all to the benefit of the forum.
There are many ways to recover from most materials and recovery is really the most important part and can be the hardest to understand or master, as most members work with e scrap that can and does contain many metals and materials that can make a real mess if not processed properly it’s the recovery that makes the refining easier. We have had many many posts from people who just got a load of scrap and dumped in reagents and then can’t fathom how to get their values back from the gloop they have created because they didn’t understand what the results of their actions would be.
An example from not too long ago from me. I was asked to refine about 100 kilos plus of old connectors still in the plastic, they were copper based pins so we tried nitric to remove the copper and leave the gold and plastic, seemed logical, but surprise the solution boiled over as the plastic was an old type and reacted to the nitric causing a boil over, the world of recovery is full of surprises some of which will leave everyone scratching their heads and with a what to do now expression.

Exactly why I try to research as much as I can, and then ask questions if I'm having trouble finding the answers... or at least the answers in ways that I comprehend... before I attempt to do anything. That's why after about 5 years I am only still doing Lye baths to remove solder masks, Acetone to remove glues and AP for "simple" clean boards & fingers recovery, while hoard stashing other materials for later on eventual processing. I will be trying my first go at solder removal from cleaned boards that still have the solder on them here soon hopefully.

 

[Shark]

What has already been mentioned is sound advice. Plus you have the additional headaches of filtering such a dirty mess. It isn't quite as easy as having a nice clean AR to filter out. Then you need to figure out which precipitant to use on that dirty solution. Will SMB work better than copperas? Or maybe ascorbic acid or sodium nitrite, or the myriad of other possible precipitating chemicals. The chance that the gold powders you drop being dirty are fairly high so you need to be pretty good at washing your gold powders as well. It is possible, and like some of the others I have done it as well, it just isn't as easy as it sounds for the beginner. It does make a good learning experiment and can help to teach some of the little oddities of refining.

 

[hammerdown]

What has already been mentioned is sound advice. Plus you have the additional headaches of filtering such a dirty mess. It isn't quite as easy as having a nice clean AR to filter out. Then you need to figure out which precipitant to use on that dirty solution. Will SMB work better than copperas? Or maybe ascorbic acid or sodium nitrite, or the myriad of other possible precipitating chemicals. The chance that the gold powders you drop being dirty are fairly high so you need to be pretty good at washing your gold powders as well. It is possible, and like some of the others I have done it as well, it just isn't as easy as it sounds for the beginner. It does make a good learning experiment and can help to teach some of the little oddities of refining.

Which is why I asked before attempting and I'm very appreciative of the warnings advice instead of some saying "go ahead and do it then come back here with how it worked out for you"

 

[goldenchild]

From what I recall I never had an issue with tin or lead when using this technique. I will say though that I think you shouldn't even bother with a selective precipitant using this technique. You are better to take your final solution, acidify it a bit with HCL and use copper to drop anything under copper in the series. Then you should filter the solution and melt EVERYTHING that's in your slimes. This way you'll keep everything, even what you don't want. The melting will have the added benefit of removing alot of junk that can't stand up to the flame. It's much easier to work with a small button of mixed metals (even if containing lead and or tin) than solutions using selective precipitants.

 

[Shark]

From what I recall I never had an issue with tin or lead when using this technique. I will say though that I think you shouldn't even bother with a selective precipitant using this technique. You are better to take your final solution, acidify it a bit with HCL and use copper to drop anything under copper in the series. Then you should filter the solution and melt EVERYTHING that's in your slimes. This way you'll keep everything, even what you don't want. The melting will have the added benefit of removing alot of junk that can't stand up to the flame. It's much easier to work with a small button of mixed metals (even if containing lead and or tin) than solutions using selective precipitants.

I have noticed that some drops just seem to stay dirty and don't wash well. I also found that melting some of them would speed things up quite a lot, and have started melting more often as a pre (acid) refine step at times. Cementing a dirty solution is a great way to recover it as well, especially if there is a chance of other pm's along with the gold. Just shows there is still a lot out there I need to learn as well, and why I enjoy this type of threads.