CuCl2 (AP) Process Chemical Formulas... Need help figuring out where I went wrong~

[LT_golden]

Hi folks,

My chemistry background is only like a couple of classes taken in high school, and those were the science-related classes in which I got the worst grades in, primarily because I couldn't balance the chemical equations.

I've been working on processing some e-waste for the first time. It's not possible to get nitric acid here without government scrutiny and monitoring my family and my for the rest of my life, so I'm going with the CuCl₂ (Acid Peroxide) method. I've been successful in recovering gold foils, but I'd like a deeper understanding of what's going on and attempt some stoichiometry for the amount of HCl needed.

The reaction equations I have for dissolving copper are the following, with notes.
[1] 4 Cu + O₂ -> 2 Cu₂O (Cuprous Oxide). This oxygen can come from dissolution at liquid-air interface, an air bubbler, or hydrogen peroxide.
[2] 4 HCl + Cu₂O -> 2 CuCl₂ + H₂O. This HCl is of course the thing we add.
[3] CuCl₂ + Cu -> 2 CuCl. Cupric Chloride goes to work on solid copper metal to form Cuprous Chloride. This is happening along with [1].
[4] 4 HCl + 4 CuCl + O₂ -> 4 CuCl₂ + 2 H₂O. This is the regeneration reaction.

Based on reactions [2] and [4], we need 2 and 1 molecules of HCl to process each atom of copper metal, respectively. Based on standard atomic weights, the weight ratio of a HCl molecule to a copper atom is (H(1.008)+Cl(35.45)) / Cu(63.546) = 0.5737, meaning theoretically that to dissolve a given amount of copper, exactly 57.37% of its weight in pure HCl molecules is needed.

Suppose I have 20% HCl (usually this is concentration by weight, right?), and have 100g of non-magnetic pins to dissolve. Let's assume that the 100g is all copper. The HCl acid density at 20% concentration is 1.098g/mL (from Wikipedia).

100g x 57.37% = 57.37g of HCl molecules needed to dissolve the 100g of copper.
57.37g / 20% = 286.86g of the aqueous HCl (hydrochloric acid now, no longer just gas molecules) needed to dissolve the copper.
Weight of the acid divided by density = 286.86g / 1.098g/mL = 261.26mL of 20% HCl needed to dissolve 100g of copper.

In practice though, this isn't even close to being enough. Why? I know I made some mistake and/or made insufficient or erroneous assumptions (eg. incorrect reaction formulas, not enough reactions, etc.). I'd like to be able to get a better estimate for how much HCl I would need. Call it a compulsion, but this is just for understanding... In real-life, these calculations would be estimates to give me a starting point.

It's sort of like the discussion in this thread. The theorists come up with new things that the hands-on folks use to apply to existing processes or create new ones, while the hands-on folks discover what works and what doesn't from their hands-on experience that the theorists use to improve their understanding and perhaps generate new ideas; I think it's a benign, generative cycle and is how progress is made.

Thanks a lot for any help or insights!




EDITED to correct [3] [stt]2 [/stt]CuCl₂ + Cu -> 2 CuCl

 

[g_axelsson]

Without tracing every step in your calculations I assume that the end product in your calculation is CuCl. This is a white solid that is weakly soluble in water and that in the presence of oxygen and HCl turns into CuCl₂. This step alone is doubling the amount of HCl needed.

But to get a working liquid you need excess of HCl to dissolve the CuCl as it is soluble in strong HCl solutions. So HCl is both consumed and used as a solvent. Evaporation of HCl will also take it's toll on consumption.

Göran

 

[LT_golden]

The reaction equations I have for dissolving copper are the following, with notes.
[1] 4 Cu + O₂ -> 2 Cu₂O (Cuprous Oxide). This oxygen can come from dissolution at liquid-air interface, an air bubbler, or hydrogen peroxide.
[2] 4 HCl + Cu₂O -> 2 CuCl₂ + H₂O. This HCl is of course the thing we add.
[3] CuCl₂ + Cu -> 2 CuCl. Cupric Chloride goes to work on solid copper metal to form Cuprous Chloride. This is happening along with [1].
[4] 4 HCl + 4 CuCl + O₂ -> 4 CuCl₂ + 2 H₂O. This is the regeneration reaction.

Hi Göran,

If I’m not mistaken, did you mean this reaction above in blue?

But that’s still 1 molecule of HCl for each copper atom (actually cuprous chloride molecule) right?

I always cover my beaker with plastic food wrap to greatly reduce evaporation, but that isn’t a tight seal so air bubbler gas will still escape. This should work, right?

Am I missing anything else?

Thanks.







EDITED to correct [3] [stt]2 [/stt]CuCl₂ + Cu -> 2 CuCl

 

[g_axelsson]

CuCl₂ is two Cl per Cu. (Cu atomic weight is 63.5 Cl 35.5 which gives about equal amounts of Cu to Cl in mass.

20% HCl is about 20% Cl in mass so 5 times that in hydrochloric acid, 100g Cu would take around 500 ml HCl 20% to dissolve at a minimum. Not counting using it as a solvent and evaporation losses. Bubbling air through HCl will lead to losses, how much this is I have no idea.

Göran

 

[nickvc]

As I pointed out on another thread theoretical chemistry and practical day to day chemistry can be two totally different fields, if you are using any form of nitrates in a reaction then knowing the amount needed helps to avoid problems when it comes to precipitation.
The other point to remember is that if you have other metals and or elements in the mix or are not using heat or using strong agitation this can and will also make any theoretical calculations a waste of time in my opinion but understanding the process your using and knowing what’s going to happen or could happen are a much more useful pieces of information to have to process the scrap you are working with.
The beauty of the AP process is that it’s forgiving, if you dissolve some gold then the simple solution to recover it is to add some more copper based material to cement it back out of solution, if it stops working then add a little more Hcl and it’s off and going again.
Virtually all the problems associated or encountered using it have been covered and fully discussed here on the forum, it’s a simple workaround process that many many members use to great effect that avoids the use of other much more dangerous or hazardous chemicals and or processes.

 

[LT_golden]

Hi Nick,

Thanks for the reply.

As I pointed out on another thread theoretical chemistry and practical day to day chemistry can be two totally different fields, ...
...
The other point to remember is that if you have other metals and or elements in the mix or are not using heat or using strong agitation this can and will also make any theoretical calculations a waste of time in my opinion but understanding the process your using and knowing what’s going to happen or could happen are a much more useful pieces of information to have to process the scrap you are working with.

I do see your point... theory vs. application and all that. This happens with electrical engineering too, which is what keeps my family and me fed.

I'm mainly posting the question to try and understand the chemistry of it, since it's all so new to me. In addition to learning from all the valuable experience that you and so many others have shared, I'd also like to better estimate how much HCl is needed, at least theoretically. :lol:


--Luke

 

[LT_golden]

Hi Göran,

CuCl₂ is two Cl per Cu. (Cu atomic weight is 63.5 Cl 35.5 which gives about equal amounts of Cu to Cl in mass.

You know, your reply made me go back and check my math... It seems like the idea was correct, needing 3 HCl to process every atom of Cu, but where I messed up was forgetting to multiply by that 3 in the Excel sheet I made!

That's just a stupid, careless mistake. This is very embarrassing. So the new calculation comes out to be theoretically about 783.78mL of 20% HCl plus some air to dissolve 100g of copper... There's some double-counting since Reactions [2] and [4] are happening simultaneously, but I can live with that, for now.

:shock:

--Luke

 

[g_axelsson]

Now you thinking too hard again, equation 1 and 2 is only active in the start. When you have a steady process the only parts that happens is equation 3 (etching) and 4 (regeneration).

What you have is :
Cu + 2 HCl + some O₂ -> (some magic happens) -> CuCl₂ + some H₂0

That's only two Cl per Cu.

I'm running my CuCl process by look and feel, any white copper chloride? What is the color of the solution? Is the process advancing? Adding HCl according to what I feel is correct, not based on a formula.
It takes some experimenting but it's not a hard process to master.

Göran

 

[ChemGeek]

I've been working on processing some e-waste for the first time. It's not possible to get nitric acid here without government scrutiny and monitoring my family and my for the rest of my life, so I'm going with the CuCl2 (Acid Peroxide) method. I've been successful in recovering gold foils, but I'd like a deeper understanding of what's going on and attempt some stoichiometry for the amount of HCl needed.

Peroxide method is expensive.

Try this:

Battery sulfuric acid (36%) - 100mL
ammonium nitrate ---------- 12g (instead of ammonium nitrate you may use 15 g of sodium nitrate)

This mixture at 50-60*C will dissolve *minimum* 10 g of copper within 5-24 hrs.
Filter off undissolved parts including golden foils while warm, above 40*C and allow blue solution to cool down to 5-10*C.
Most of copper sulfate will crystallize, so you won't have too much troubles with waste disposal.
You will just filter it off and dry. Remaining solution should be subjected to electrolysis to separate rest of copper. You need 100-200 A @ 3-4V PSU to make it a fast process of few kg scale. It is possible to adapt welder for such a task. Anode is made of graphite block, cathode might be of copper sheet.
By doing so you will avoid damaging environment, particularly if you are going to do reprocessing for profit.

Wash well undissolved bits with water before further processing.

 

[LT_golden]

Try this:

Battery sulfuric acid (36%) - 100mL
ammonium nitrate ---------- 12g (instead of ammonium nitrate you may use 15 g of sodium nitrate)

This mixture at 50-60*C will dissolve *minimum* 10 g of copper within 5-24 hrs.
Filter off undissolved parts including golden foils while warm, above 40*C and allow blue solution to cool down to 5-10*C.
Most of copper sulfate will crystallize, so you won't have too much troubles with waste disposal.

Hi ChemGeek,

Sweet, thanks for the tip. I’ve thought about using sulfuric acid to make nitric acid before, but didn’t think that this gentle heating would be enough (I’m a little paranoid about hot sulfuric acid after being on this forum). But this is just warm...

Ammonium nitrate... I’m only able to get impure fertilizers with around 30-6-0 ratio and with nitrates content at >=14 (whether this is a percentage, I don’t know.

Sodium nitrate... this is another very restricted thing here, even though it’s also used as a meat additive during processing. I had to look for a while to even find sodium nitrite (which is useless in gold recovery, but just to show how hard it is here to find such stuff).

Potassium nitrate... I’m able to get a purer form of this in a fertilizer, it’s basically all potassium nitrate (they say >=99%, but I take that with a grain of salt).

I’m thinking my best bet would be the potassium nitrate here? But how would you recommend that I deal with the white solid potassium sulfate? Should I make the mixture, gently heat as you prescribed, filter first (and throw the potassium sulfate at my plants), and then dissolve the copper/kovar pins? My next and last batch of pins is all kovar...

And if I were to scale this up, would I just for example double the same ratio of materials?

Thanks a lot for your help.

 

[ChemGeek]

@LT_Golden,
Regarding "hot sulfuric acid".
If we are talking about hot *concentrated* sulfuric acid then yes - it is dangerous and can cause horrible burns in no time at all. This didn't stop me to work with tens of liters of it in industry in the past though and no burns on my body.
Warm battery acid (36%) is a piece of cake. Don't wash your hands in it and keep it away from eyes (safety glasses) and you will be fine. An odd small mishap won't do much as long as you wash your hand with water fast.

Regarding fertilizers, one of 34% of total *nitrogen* content is a reasonably pure ammonium nitrate.
You must evaluate products available on your market. Some fertilizers contain insoluble ballast like calcium or magnesium carbonate. All what you would need to do is leach nitrate into water, filter off insolubles and evaporate water to small volume, then leave in fridge to crystallize pure nitrate, filter off and dry in dessicator over solid sodium or potassium hydroxide.

Potassium nitrate (KNO3) you can use as well. You will need 15g to replace 12 g of ammonium nitrate.
Learn about *molar proportions* if you didn't do it by now, it is easy and this will make calculations self evident.
For now I will say that 80g of NH4NO3 contain as much of nitrate as 101g of KNO3.

You may also use calcium nitrate, Ca(NO3)2 hexahydrate (another fertilizer or an agent helping cement to set in low themperatures).
If you got this one I will write you exactly what to do as approach is marginally different.

Finally, there *are* ways to use nitrites but it is a bit more advanced though scaleable but if you can buy potassium nitrate, you don't need to worry.

Finally reaction of sulfuric acid with potassium, sodium or ammonium nitrate will give hydrogen sulfate, not neutral one as a by product.
eg.
H2SO4 + KNO3 ---> HNO3 + KHSO4.
You do not need to worry about this by product. At 50-60*C it will stay in solution and if it crystallided before or during filtration to contaminte your treated components, just boil them with water, it will dissolve, filter off components and wash with warm water.

Alternatively first prepare mixture of acid and KNO3 at 50-60* C (all must dissolve), cool it down to RT, leave it overnidht (best in fridge but not essential). Filter off crystals and wash with small amount of cold water, about 1/10 of original acid volume and resulting solution of acids free of most of by product use for processing. This is just more work and no obvious benefit.

Do not throw this material (KHSO4) on plants. It is acidic and will damage them.

 

[g_axelsson]

Making nitric acid from nitrates and sulfuric acid has been described several times before, it's all here if you search for it.

I have collected a few links at the bottom of this page.
http://goldrefiningwiki.com/mediawiki/index.php/Making_nitric_acid

ChemGeek, if you are going to use nitrates for making nitric acid you don't need to crystallize the nitrates, just use the right amount of water that is used in the process of making nitric acid, then you could go straight from filtering to making nitric acid.

Welcome to the forum, both of you!

Göran

 

[ChemGeek]

ChemGeek, if you are going to use nitrates for making nitric acid you don't need to crystallize the nitrates, just use the right amount of water that is used in the process of making nitric acid, then you could go straight from filtering to making nitric acid.

Welcome to the forum, both of you!

Göran

Hi,
I was commenting on nitrates/carbonates mixtures present in some fertilizers.
In such situation I would leach nitrate to water and filter off insoluble carbonate (Magnesium or calcium) and only then add sulfuric acid.
I agree, there is no need to recrystallise commercial nitrates of reasonable quality.

 

[Shark]

Sodium Nitrite has a good use in gold refining. It may not be widely used, but has it's use's. It is useful for many who live in areas that has a harder time in finding certain chemicals, as well it gives us another option in how to do things. I recently ask the very question on using it for my self.

http://goldrefiningforum.com/phpBB3/search.php?keywords=sodium+nitrite

 

[LT_golden]

Hi Göran, ChemGeek, and Shark,

Now you thinking too hard again, equation 1 and 2 is only active in the start. When you have a steady process the only parts that happens is equation 3 (etching) and 4 (regeneration).

What you have is :
Cu + 2 HCl + some O₂ -> (some magic happens) -> CuCl₂ + some H₂0

That's only two Cl per Cu.

Sh*t... Thanks for the tip... You know, I seem to often have this problem, and I really don't know how to fix it. I don't think that "thinking too hard" is the issue here; it's "thinking in the wrong direction", which I think is much worse than thinking "too hard" or "too much"...

@LT_Golden,
Regarding "hot sulfuric acid".
If we are talking about hot *concentrated* sulfuric acid then yes - it is dangerous and can cause horrible burns in no time at all. This didn't stop me to work with tens of liters of it in industry in the past though and no burns on my body.
Warm battery acid (36%) is a piece of cake. Don't wash your hands in it and keep it away from eyes (safety glasses) and you will be fine. An odd small mishap won't do much as long as you wash your hand with water fast.

ChemGeek, your post gave me some courage to try this out. Part of the fear of sulfuric acid stems from hearing horrible stories as children from our parents about "bad people" throwing sulfuric acid on people and disfiguring them...

I got my KNO₃, my battery acid after weighing seemed to be some 43% concentration, so I adjusted the volumes and weights of the input materials. After fully dissolving the chunks of KNO₃ (no heat was released; endothermic), I added the pins and applied heat only to get reaction started. And when it ran for a few minutes, the familiar-from-YouTube orange fumes started coming out, the solution turning blue. Holy sh*t, I made nitric acid! (Could you tell that I was excited, after weeks and batches of slow AP? :lol I had a tube hooked up to the reaction flask and into a bottle of water to catch and reduce the fumes going into the air. I stuck a litmus paper to the lip of the water bottle and in the morning it was only very slightly orange.

I left the reaction going on outside overnight; no additional heat was applied but it was like 20 deg. C warm outside. In the morning I saw that only about 10% of the pins remained. Fantastic. And the foils looked like floating "sleeves" of the original pins.

A nice thick layer of clear solids has formed at the bottom of the flask. I will follow your procedure to try and get things cleaned.

Molar proportions... Yes, thank you. I've been looking into stoichiometry, which was the reason I started this thread, to practice and learn from you guys.

Now that I got KNO₃ working, since the potassium nitrate was not expensive, I would probably stick with it until I find an inexpensive, easily-acquired NaNO₃. However, I'm interested in learning about processing with calcium nitrate. If you please, could you still tell me about how you run that process? I will still do my own homework as well for comparison.

Making nitric acid from nitrates and sulfuric acid has been described several times before, it's all here if you search for it.

I have collected a few links at the bottom of this page.
http://goldrefiningwiki.com/mediawiki/index.php/Making_nitric_acid

...

Welcome to the forum, both of you!

First of all thank you for the welcome message. Actually I've been here for a little while now (like... 2 months?), but mostly just reading.

I've read some discussions on making nitric acid with sulfuric... but the ones I read, almost always talked about using concentrated; battery acid was scary enough for me (paranoia based on childhood stories). In one of his posts I believe butcher mentioned that battery acid could be used but the discussion was centered around using concentrated acid. Admittedly, it is likely that I didn't look hard enough, but the only clear instruction on using battery acid safely was what ChemGeek had given me.

Sodium Nitrite has a good use in gold refining.
...

Kool, thanks for the info. I just didn't know it was used in recovery as well.

 

[ChemGeek]

LT_Golden,
Here is a method based on calcium nitrate:
Ca(NO3)2 + H2SO4 ---> 2 HNO3 + CaSO4
CaSO4 will precipitate out of reaction mixture, solution of HNO3 (nitric acid) is to be decanted from precipitate of hydrated CaSO4 (calcium sulfate also known as gypsum).
Commercial calcium nitrate also known as calcium salpetre of formua Ca(NO3)2 is often a tetrahydrate or a trihydrate, sometimes a hexahydrate which is a wet slush. Description below will serve all of these:

1. Preparation of solution of nitric acid:

Calcium nitrate hydrate ------------------236 g (approx. 1 mole)
Battery (36%) sulfuric acid ---------------300 g (approx. 1.1 mole)
Water ----------------------------------------50 mL

Place sulfuric acid in 1L beaker and warm it to 50-60* C with stirring. You may use a thermometer, a glass or teflon rod for stirring. Lacking that wooden stick will do, albeit acid sometimes gets discolored this way.

Now in separate beaker place 236 g of hydrated calcium nitrate add 50 mL of water and warm to 50-60*C as well.
This salt is very well soluble in water so all should dissolve at stated temperature. Stirr it well.
Solution may be dark due to imurities present in calcium nitrate, there may be a tiny amount of undissolved impurity present but it does not matter.

Now slowly add this solution to stirred sulfuric acid. You will observe white precipitate forming while addition is in progress. When all is added stirr for 5 minutes more, then cover beaker with plate and leave to cool overnight at 20-30*C. Cooling to lower temperature is not necessary due to unusual solubility profile of by-product.
Next day carefully decant your nitric acid solution from precipitate. You may also wish to filter off precipitate, perhaps with suction (under reduced pressure) for a reasonable recovery.
If you *do* use filtration with suction, then press well your precipitate with a bottom of 50mL beaker or something similar so there is a solid mass in your funnel and air is not drawn via cracks in it, then wash it with 50 mL of water and reapply suction.

Your nitric acid is approximately 30%, its density is about 1.26 and 1L contains ~6 moles of nitric acid. Additionally it contains small amount of sulfuric acid and 5-15 g/L of dissolved calcium salts, but it is suitable for your task.
It can be stored in glass or good quality polyethylene/polypropylene bottle with good seal indefinitely.
Spilling it on your hands will turn them yellow (and this color may last for a week or two) but not much more than that is going to happen, as long as washed with water away within 30 seconds or preferably faster. Longer contact can cause blisters/acid "burns". Work in rubber gloves (and of course with eye protection) will spare you these niceties in any case.

2. Dissolving copper:

Prepare mixture of 100 mL of batery (36%) sulfuric acid and 25 mL of your 30% nitric acid for every 10 grams of copper to be dissolved and proceed as before at 50-70*C.
You may find this process a bit faster than with former methods.
Avoid inhalation of nitrogen oxides produced. These brown fumes are reasonably toxic but 1 or 2 whiffs of gas mixed with surrounding air won't kill. Headache might result. Fume cupboard or working outside is the way to go as repeated exposure is not good at all.

You have written that you have stopped heating towards end of process. I would carry on with heating to the end, because it helps most when not much acid is left, eg towards end of process, when reaction slows down.
Heating also prevents crystallization of copper and other salts from solution and this helps with work up.

In larger scale, say 100-200 g and more of copper, it is wise to assemble equipment allowing to pass liberating gas *together with* stream of air or much better oxygen via large flask with batery acid cooled in ice. This way nitric acid is produced back, base on weight increase you will know how much you got and then you don't need to add much of nitric acid to your next batch as most is already there.
For good source of oxygen you can buy second hand oxygen concentrator, also used by lung cancer patients. They are cheap enough, will work well for years and have many other uses as well.

Reaction has few stages but overally it goes as below:
4NO + 3O2 + 2H2O ---> 4HNO3

One remark regarding sulfuric acid:
If your work in the future is going to be done for profit you will wish to learn how to work with concentrated acid for this very reason: profit.
Purchasing concentrated acid and diluting it is much cheaper than equivalent of battery acid and considerable money can be saved in large scale operations (eg. 5 - 50kg and more of copper).

Hope, these help.

 

[LT_golden]

LT_Golden,
Here is a method based on calcium nitrate:
Ca(NO3)2 + H2SO4 ---> 2 HNO3 + CaSO4
CaSO4 will precipitate out of reaction mixture, solution of HNO3 (nitric acid) is to be decanted from precipitate of hydrated CaSO4 (calcium sulfate also known as gypsum).

Hi ChemGeek,

Whoa...! These definitely help! Thanks very much! Man... first of all, I really appreciate you and the time that you take out to help me and other newbies in the forum. I hope that you have somewhere you could just copy-paste these instructions/info from and not having to type it all out each time I ask a question...?

I’ve been on a business trip for a little bit so I haven’t really done much or been able to reply here... but here’s what I got.

Calcium nitrate hydrate... thank you for this info. Simply because you told me about it, and not because I need to or anything, I will be trying this out when I get my hands on some calcium nitrate. This is great!

Profit... Well, since I seem to be progressing along (despite messing up here and there along the way — no real disasters, just time-consuming), after I get my first gold button assayed and seeing what kind of price I might be able to get for it, I think I’ll be researching a bit to get a bunch of “black top” chips to process. I couldn’t imagine myself doing this on a larger scale beyond the amateur level, since I couldn’t bring myself to disregard the environment, and any recovery & refining plants of any scale here either uses large-scale incineration or just dumps massive amounts of chemical wastes down any nearby body of water with no waste processing (regulations vs. enforcement and all that). In addition to personal ethical considerations, I would have no way of competing with those entities who have the officials all bribed up so they could continue operating with almost complete disregard to the environment or relevant regulations.

So yeah, I would only do it on a small, personal/home-level scale (not literally inside my home, of course), for a small but hopefully regular profit.

But I will never sell my first button.

Heating towards the end of the dissolution... actually I stop the heat because I don’t feel safe leaving the thing running in the workshop overnight; I think it’s my wife’s OCD affecting me. I do heat it again for a bit to try and dissolve some of the salts before filtering though.

Oxygen concentrator and the recovery of nitric acid... Wow, this innovation/improvisation/creativity is just so awesome. I took a quick look and there were a few second-hand oxygen concentrators for senior folks for sale for around the equivalent of USD$50-100. I’ll definitely consider this when I find a good, reliable source of e-waste materials to process.

So as I filtered the batches of blue solutions... I found that this translucent thing as a byproduct (yeah I see your point about heating to prevent crystallization of the copper sulfate):







I think this looks like Stannic (Tin[iv]) Oxide? Nitrate...? Does Tin actually form nitrates? Seemingly insoluble in water (tried spraying it down but had no appreciable effect, unlike the pretty copper sulfate(?) crystals), and since this was all dissolved with nitric acid and there are still foils in there, I haven’t tried applying HCl to it to check. I think this must’ve come from pins which were pre-treated with tin, and Hoke did say that it would be annoying when dissolving with nitric... but I suppose at this point I shouldn’t do anything other than just let the filtering sit overnight?

Another question... I have like around a dozen filter papers from stuff dissolved via the AP method, this poor man’s nitric acid, and even some vinegar-salt solutions. Some of these filters also have bits of copper powder and other metals in them. I wasn’t wise enough to separate all the filter papers by the solutions that passed through them (major newbie...). I suppose when I start processing them, I should first add very dilute (10-20%) HCl to the whole pile, let the copper powder cement out all the gold that might be dissolved by the dilute aqua regia, and then proceed to wash filter paper + foils with hot water, then HCl, before dissolving the foils with Poor Man’s Aqua Regia? Does this sound like a viable and correct process?

On a different note, how’s this for thoroughly cleaning the glassware before the actual refining of the gold? I was thinking boiling key beakers/flasks with HCl, brushing, then hot water and brushing, then dilute ethanol and brushing, then sodium hydroxide solution and brushing, and then soaking in RO water (we have a small RO water system) overnight? Would this clean the glassware to laboratory-level clean and theoretically be safe for food (though of course I wouldn’t ever actually do that)?

Hey ChemGeek, thanks for all your help. If I ever get this small home-level operation set up, I’ll be asking for your PayPal account so I could send you some money. :lol: It wouldn’t be a lot but I just really wanted to show my appreciation.

 

[ChemGeek]

Hi LT_Golden,
At some point in the future, particularly when you are handling larger quantities of gold or other PM you will probably wish to use proper aqua regia, eg one made of salts free nitric acid. Small quantities (like 1-2 L) of this acid of arbitrary concentration can be made at home but it is best to develop some more skills before attempting that.
Standard 65-70% HNO3 is about as dangerous as concentrated sulfuric acid.
From 1 L of such acid you can make enough of aqua regia to dissolve ~0.3 kg of gold powder, wires or foils.

Profits - this should come as long as you concentrate on securing cheap chips. I have secured my first deal for $ 0.3 per laptop motherboard and will collect about 100-200 of them from computer service shop within 2 weeks. Can't wait...
I am new to gold refining as such but well versed in chemistry and for a while at work I was recycling industrial catalysts containing platinides on a resonable scale. So I was recovering lots of 300-500g of Pd or Pt and also Rh or Os albeit in lots not exceeding 100g per go. I had to design and then execute procedures because composition of many catalysts was variable and deviations from established SOP-s were often called upon.
So I am profit oriented.
Now I no longer work in industry and have picked this subject for fun. Damaged jewelery of my wife went on first fire and 60+ grams of pure gold was reclaimed and used for custom made new jewelery.
Wife is Chinese and gold greedy so now she supports my activities very much.
But reclamation from electronics is an interesting challenge.

Regarding Tin, yes your stuff looks like that (Hydrated SnO2, probably nitrate complex of it).
Tin is a sh*t for refiner. Outright nuisance.
There are several ways to deal with metastannic acid, all with their drawbacks.
Best advice is not to produce it at all and keep your solution tin free, before applying oxidants.
So for example treat all parts with conc HCl for few days before further processing.
Unfortunately there *are* electronic elements like some pins made of phosphor bronze (eg Cu/Sn/P) alloy and there is no way to remove tin from these without oxidative workup.

Existing remedies are as follows:
1. Preventing precipitation of metastannic acid.
There are plenty of additives which even in small quantities can delay precipitation of said acid by keeping it in washable and filterable zol form. Within few days to few weeks precipitation will still start but meantime you will get your gold out.
Many of these are listed in patent literature like USP 3,986,970 Oct. 19;1976.
Sulfuric acid systems with co-oxidants other than nitric acid are discussed there but base on my knowledge most of additives *should* work with nitric acid as cooxidant as well.
Addition of sodium tetrafluoroborate NaBF4 (or fluoroboric acid) in quantities 1-5 g/L of your "copper dissolving acid" appears to be particularly promissing. Will test it myself.
Mind you, these reagents will not redissolve metastannic acid once precipitated.

2. Converting material into zol form easier to treat further. Reductive incineration followed by hydrochloric acid treatment, oxalic acid and hydroxide solution have been tried by members of this forum. It is somewhat tedius but in their opinion works.
http://goldrefiningforum.com/phpBB3/viewtopic.php?f=52&t=20477
https://goldrefiningforum.com/phpBB3/viewtopic.php?t=15324

3. Forcing metastannic acid to solution.
- one few occasions not related to gold reclaiming I had this trouble and stannic mess was first dried well and smelted for 1-2 hrs with sodium hydroxide above 320 *C. Steel or better stainless steel crucible can be used (but not glass or aluminium alloys!!!), obsolete pot would do but smelted NaOH *is* dangerous, about as corrosive to your body as boiling concentrated sulfuric acid, but otherwise nice to work with (no suffocating fumes etc).
Proper protective clothing, face/eyes protection mandatory. Thinking forward and decent setup construction as well but surely can be done. Melted mix must be cooled to rt and leached with water to dissolve resulting sodium stannate.
Results are very good.
- it is reported that boiling stannic mess with 40-57% hydriodic acic at 120*C for few hours will dissolve it by conversion to H2SnI6.
Hydriodic acid must be Iodine free (or gold will dissolve as well) and this can be secured by adding 0.5% of sodium hypophosphite or hypophosphorous acid or some other additives like TiCl3.
Colour of Iodine must disappear or turn pale yellow before proceeding further.
Hydriodic acid is not cheap and available only from specialist suppliers. It likes to corrode all metals around much more than HCl and it is a bit more dangerous than concentrated HCl.

Finally, here you have reference to a decent work dealing with tin, nitric acid and resulting mess:
Monatsh., 1918, 39, 149-178.
With time you will find that work of older generations of chemists from first 5-7 decades of XX century is somehow more realiable than recent publications. For me it is one of many signs of pending decay of intellect observed around.

Regarding treatment of filter papers:
I always tend to wash them with water, dry them and finally burn to ashes before further work. Amount of ashes is negligible and they can be filtered off together with other unreacted material after acid treatment.

Regarding washing glassware.
We are working in gold refining, not in analytical laboratory. Washing with appropriate brush, water and detergent usually does the trick, organic mess (if present) is to be washed with acetone.
Some chemicals like solution of sodium hydroxide upon long contact or at higher temperatures will etch glass slightly and make it looking ugly for good, but that does *not* make it any less useful. Don't worry about it.
On very rare occasion aggressive mixtures like one made of 10-20 g of CrO3 or dichromate in 1L of concentrated sulfuric acid are used (followed by wash with water) but you are unlikely to ever need it in this class of work.
If your tap water is of poor quality, with plenty of dissolved iron and other salts then in *final* stages of your refining process distilled water might have some merits, albeit it is rather for those meticulous peoples aiming at 99.99+ product or working with mixtures of platinides. Otherwise forget it.

 

[anachronism]

If you're getting laptop boards that cheap then trust me - sell them for a good profit and buy something worth refining - something you actually stand a chance of getting all the value from. 8) 8)

Refining boards as a home refiner is a mug's game.

Jon

 

[ChemGeek]

If you're getting laptop boards that cheap then trust me - sell them for a good profit and buy something worth refining - something you actually stand a chance of getting all the value from. 8) 8)

...If I only know, are they working or not...
I am not a computer dork equipped in all sort of stuff necessary to test them. Neither I have a necessary knowledge or patience.
Of course there will be some picks for re-sale for example if some collectable ceramic processor is spotted or if I got gold plated circuit borad or one which comes from some famous and respected past model no longer in use.

What to do with the rest?
There might be 2-5 kg of different chips there, mostly "flatpack" type. I even cannot estimate as it will be my first kill.
How much chips in your opinion I might get from 100 laptop motherboards?