Dirty filter material from AP solution

[rodion]

Dear miner folks,

As an amateur radio hobbyist and IT worker, I have collected a few computers around me over the years.
From the separated scrap of the parts I started leaching the fingers of PCBs and RAM memory cards
(stripped of the IC's). To dissolve the base metals I use hydrochloric acid (30-33%) with
hydrogen peroxide (3%); substances that are readily available in my area and can be used relatively
safely. In addition to the gold foil and particles, the acid solution also loosens a lot of other material
that is in the coffee filter. The result is a small container with gold particles mixed with much other stuff
(leftover plastics, pieces of PCB board, soaked SMD components, oxides, etc.) Because I use the AP solution
more often (several batches), it is - albeit filtered - also getting more dirty. I leave the bucket with AP solution
and PCB material in the corner of the shed for about a week. At this moment the last PCB-material batch is
'soaking'. I have questions about how to proceed further. Before disposing the AP solution, I would like to
experiment with it by cementing copper. The previous solution ate a reasonable piece of an unknown metal relatively
eager and fast. Should the AP solution in this be diluted first to slow this down? and what cements other than copper
could be possibly made? The second question is whether it makes sense to further treat the 'dirty' gold foils with
another muriatic acid bath, some highly diluted nitric acid (5%) of perhaps concentrated sulfuric acid (36%), which is also
available here but more expensive.

Thanx in advance for any tips or information.

Kind regards,

Richard

 

[Yggdrasil]

Dear miner folks,

As an amateur radio hobbyist and IT worker, I have collected a few computers around me over the years.
From the separated scrap of the parts I started leaching the fingers of PCBs and RAM memory cards
(stripped of the IC's). To dissolve the base metals I use hydrochloric acid (30-33%) with
hydrogen peroxide (3%); substances that are readily available in my area and can be used relatively
safely. In addition to the gold foil and particles, the acid solution also loosens a lot of other material
that is in the coffee filter. The result is a small container with gold particles mixed with much other stuff
(leftover plastics, pieces of PCB board, soaked SMD components, oxides, etc.) Because I use the AP solution
more often (several batches), it is - albeit filtered - also getting more dirty. I leave the bucket with AP solution
and PCB material in the corner of the shed for about a week. At this moment the last PCB-material batch is
'soaking'. I have questions about how to proceed further. Before disposing the AP solution, I would like to
experiment with it by cementing copper. The previous solution ate a reasonable piece of an unknown metal relatively
eager and fast. Should the AP solution in this be diluted first to slow this down? and what cements other than copper
could be possibly made? The second question is whether it makes sense to further treat the 'dirty' gold foils with
another muriatic acid bath, some highly diluted nitric acid (5%) of perhaps concentrated sulfuric acid (36%), which is also
available here but more expensive.

Thanx in advance for any tips or information.

Kind regards,

Richard

Have you read C.M. Hokes book?
Have you read the Safety section of the forum?
Have you read the treating wastes section?
When you have done this, you will know enough to continue your studies.

You will need to take your containers to a well ventilated area preferably outside or under a fume hood.
The gases from HCl will start to destroy any exposed metal in its vicinity.
The AP solution(Copper Chloride etch) don't need to be disposed of you keep it for the next round of leaching.
Better use air bubbling in stead of Peroxide it will provide the needed air and sufficient stirring by itself.

When leaching fingers, we cut off the fingers from the board as tight as possible to the plated area.
This gives a very clean result.

 

[Martijn]

Welcome to the forum Richard.
You're not in a hurry to get the gold out as I understand.
And you have a lot to learn. Don't let it discourage you.
AP is not waste. Only when you have no more base metals to recover gold from. Or when it gets too dirty.

Do you use an air bubbler?

Do you understand the way the copper chloride leach revives itself by adding oxygen (air) and a slight excess of free HCl?

If you study dealing with waste you will understand how to cement copper out.
Cementing is a displacement redox reaction where a more reactive metal goes into solution, oxidizing, becoming an ion and exchanging an electron with lesser reactive metals in solution, which are reduced back to metal.
https://goldrefiningforum.com/threads/dealing-with-waste.10539/Take your time and answer our question as good as you can.

Giving the foils a HCl bath for while will clean it up a lot. Do not use nitric on it, you will create Aqua regia, dissolving the foils.
But put it aside for now and tell us more about where you learned this and how your setup is.

If you are responsible about dealing with waste and have a safe approach, you will get the help you need.
We don't just give instructions on how to get result fast, but we rather want to help you understand it all better and have a good plan and stop you getting in easily avoidable problems.

Martijn.

 

[Martijn]

By using H2O2 you could have dissolved some gold, which will have cemented out on the basemetals as brown powder, possibly inside pieces of PCB or components.

Cut everything but the gold plated parts off to avoid this. We like to say: trash in, trash out.
That means separate as much as you can mechanically and manually before going any chemical route and crwating a mess to clean up.

 

[rodion]

Dear Yggdrasil and Martijn,

I am indeed studying a copy of the book Hoke C.M. (1940) - "Refining Precious Metals Wastes" that may contain the best descriptions of how to separate precious metals from base metals and then refine them. Looking at a photograph of the metallurgist in the book, it turns out that Calm Morrison Hoke may have been an attractive lady as well. I also regularly read messages on the forum. For safety I wear acid-resistant gloves and protective respiratormask (with acidfume filter).

As mentioned, I leave the hydrochloric acid (30%) and hydrogen peroxide (3%) solution (ratio 2:1) with the PCBs in a small plastic bucket in the corner of the barn and stir almost daily - I don't use an air pump. After about a week all the gold foil has soaked off the PCBs and then it is filtered through coffee filters. Although I have cut from most PCBs only the fingers, I soaked many RAM plug-in cards as a whole (removed the ceramic RAM IC chips - those will be in the spring put on the grill). When filtering I use a plant sprayer with which the remaining gold is blown off the insert cards with a jet of water. I'm not in a hurry, but I do want to mess out the barn this year. Most of the material (computer cases, power supplies, etc.) has already been scrapped and I invested the money in safety gear, some tools and even laboratory glassware for the exciting refining part later this year.

My impression is that the AP solution is very useful for soaking most of the gold from the parts and components and I also would like to use it to remove gold from other materials such as parts from smartphones, gold-plated connectors pins from motherboards etc. The intention is to reduce the mass and concentrate the gold and possibly other precious metals before using nitric acid. When the time comes, I'll let you know. I have some clean but highly diluted nitric acid (5%) but in the spring I would try out some methods to make stronger nitric acid to complete the recovery process.

P.S. regarding cementation: according to a metal reactivity chart, with an iron or steel rod in the AP solution, the less active metals will take the place of the iron such as nickel, tin, lead, copper (and possibly silver, gold and platinum - of which it is obviously not desirable that these are dissolved in the AP). When I use a lead rod, there wil be mainly only cement copper, is this a correct conclusion?

Thanks a lot for the tips!

Kind regards,

Richard

 

[Yggdrasil]

Dear Yggdrasil and Martijn,

I am indeed studying a copy of the book Hoke C.M. (1940) - "Refining Precious Metals Wastes" that may contain the best descriptions of how to separate precious metals from base metals and then refine them. Looking at a photograph of the metallurgist in the book, it turns out that Calm Morrison Hoke may have been an attractive lady as well. I also regularly read messages on the forum. For safety I wear acid-resistant gloves and protective respiratormask (with acidfume filter).

As mentioned, I leave the hydrochloric acid (30%) and hydrogen peroxide (3%) solution (ratio 2:1) with the PCBs in a small plastic bucket in the corner of the barn and stir almost daily - I don't use an air pump. After about a week all the gold foil has soaked off the PCBs and then it is filtered through coffee filters. Although I have cut from most PCBs only the fingers, I soaked many RAM plug-in cards as a whole (removed the ceramic RAM IC chips - those will be in the spring put on the grill). When filtering I use a plant sprayer with which the remaining gold is blown off the insert cards with a jet of water. I'm not in a hurry, but I do want to mess out the barn this year. Most of the material (computer cases, power supplies, etc.) has already been scrapped and I invested the money in safety gear, some tools and even laboratory glassware for the exciting refining part later this year.

My impression is that the AP solution is very useful for soaking most of the gold from the parts and components and I also would like to use it to remove gold from other materials such as parts from smartphones, gold-plated connectors pins from motherboards etc. The intention is to reduce the mass and concentrate the gold and possibly other precious metals before using nitric acid. When the time comes, I'll let you know. I have some clean but highly diluted nitric acid (5%) but in the spring I would try out some methods to make stronger nitric acid to complete the recovery process.

P.S. regarding cementation: according to a metal reactivity chart, with an iron or steel rod in the AP solution, the less active metals will take the place of the iron such as nickel, tin, lead, copper (and possibly silver, gold and platinum - of which it is obviously not desirable that these are dissolved in the AP). When I use a lead rod, there wil be mainly only cement copper, is this a correct conclusion?

Thanks a lot for the tips!

Kind regards,

Richard

Copper will cement mainly precious metals, but also Mercury if it is in solution (highly unlikely).
But Iron will also cement Copper.
That is why we recommend the use of Copper when cementing.

Be aware that filter masks are not recommended for working with acids.
They are to be considered an emergency solution.

Miss Hokes book had a few unfortunate procedures regarding safety due to its age.
But if you are reading the one offered as download here on the forum it has been modified with respect to that.

 

[Martijn]

Here is a pdf i made to make the copper chloride circle visible.
Air revives the AP.

 

[andu]

I would cement any kind of metal from the solution, tin takes the silver along, gold is last metal i think of. Palladium for the matter gets dissolved by hcl alone, and also, like tin, sticks to silver. Nice to see this post given i'm also reaching my limit on pcb hoarding space and i'm still uncertain what approach to take.
Edit: I can't yet prove you wrong yggdrasil, thanks for the answer, however all research i done on google claims that hot concentrated hcl will dissolve pd, and i guess we can skip the hot concentrated part by the addition of 3% hp? It also contains some citric acid here, it wouldn't surprise me it works when you can oxidize and dissolve copper with vinegar and salt and/or bleach but not with hcl.

 

[Yggdrasil]

I would cement any kind of metal from the solution, tin takes the silver along, gold is last metal i think of. Palladium for the matter gets dissolved by hcl alone, and also, like tin, sticks to silver. Nice to see this post given i'm also reaching my limit on pcb hoarding space and i'm still uncertain what approach to take.

Pd don’t dissolve in HCl.
Nitruc will do the trick though.