1st Attempt at AR on Ceramic CPUs

[cejohnsonsr]

I made my 1st attempt at the AR process on ceramic CPUs yesterday. I used what I learned from Sam & lazersteve's videos. I had 1 Pentium Pro, 1 AMD K5 & a handful of assorted old Pentiums. I broke them all up into small pieces. Not as fine as I would have liked, but much smaller than in Sam's video. Maybe about 1/2" or a little smaller. I put it in a 1000 ml beaker & added 200 ml water & 200 ml HCl. I Placed the beaker on my hotplate in a catchpan & allowed it to warm up. It was set to a very low heat (Dial is weird. Reads from min to 6. I set it on 2 to begin & increase heat gradually because I'm still just a little bit afraid of boiling acids.) There was a little bit of bubbling as soon as I put the beaker on the plate BEFORE I added any Nitric Acid. Not much. Just a few bubbles. After a few minutes I added the 1st Nitric. Only 6 or 7 drops from a long pipette. I got a little reaction that ended in just a few seconds but no red cloud. The 2nd time I added about 2 ml & got a pretty good reaction & a red cloud, but again, it ended in only a couple of minutes. 3rd addition of Nitric was about 3 ml. This time I got a very vigorous reaction & a red cloud that lasted quite a while. I continued the Nitric additions as needed using gradually smaller additions which took longer to finish. Total time of reactions was a little over 3.5 hours. Last addition was a few drops which produced no reaction so I added 100ml of HCl & waited about 5 more minutes before I removed the beaker from the heat. When it was cool I poured the solution into another vessel with some ice cubes. I noticed then that the solution was a VERY dark green. Almost black. After the white sediment (silver salts?) had settled I gravity filtered twice & allowed it to sit for several hours. After sitting I discovered even more white sediment in the bottom so I filtered again. I now have a 1000 ml measuring cup with a lot of white sediment in the bottom. Maybe 25 - 35 ml in 100 ml of rinse water. And a 1000 ml beaker with the VERY dark green (almost black) diluted AR solution. It's not yellow like it should be & like I expected. Stannous test is negative for gold. I'm really at a loss as to what went wrong. I read everything I could find about processing ceramic CPUs before I started. (1 thread is 17 pages long.) Everything proceeded as expected except for the color of the final solution & the negative stannous test. I can't help thinking I used too much Nitric Acid somehow. Even after all the reading & studying, if that's it, I'm still not quite sure how to get rid of it except to add some gold (which I can't do) or evaporate (which I can do). If evaporation is the answer, does that mean to just let it sit or should I put it back on a very low heat? Any help is appreciated.

Thank you,

Ed

 

[cejohnsonsr]

My 1st miscalculation. I didn't have 400 ml equal parts water & HCl to begin with. I had equal parts water & HCl which, combined with the volume of the broken ceramic chips, equaled 400 ml. So I'm fairly certain I used too much Nitric Acid even though I added decreasing quantities until there was no more reaction. I also think I had the solution too hot & mistook boiling for reaction.

I searched the forum a little more & found some posts on "denox". Specifically, evaporation. Thank you, again, butcher & Harold. I had to divide my solution again. My largest beaker is 1000 ml & after filtering & rinsing I have almost 800 ml of total volume. I put 4oo ml in a beaker & put that on a very low heat to begin evaporation. I don't know how long it will take, but I guess that's what I'm going to have to do. I'm also not certain about how this works. Hcl boils at about 176F(?). Water boils at 212F. Nitric Acid boils at 248F. I really wish I understood the mathematics of chemistry much better.

Still welcoming any advice, help &/or edification,

Ed

 

[Kevmau5]

Although I've never done any refining myself, I'm sure I remember seeing posted on the forum that excess nitric acid will show negative for your stannous tests. So you may have too much nitric.

 

[Barren Realms 007]

My guess is that you processed the gold plated covers with the batch. If everything is off of your chip's there is a good chance your gold is in your filter paper.

 

[Palladium]

It could be cemented in the copper tungsten heat spreaders.

 

[cejohnsonsr]

Barrren Realms 007: I did process everything. I don't think anything is left in the filter paper. I washed it all down thoroughly when I rinsed off the white sediment.

Palladium: If I did cement the gold into the spreader, what do I do now? I'm determined to learn this & NOT lose my gold. I've read a little about the tungsten, but not being a chemist, I apparently didn't get it.

What I've done so far is to begin evaporating at a little below boiling. I can only see the color of the solution around the meniscus because the solution is so dark. It was green. After several hours on the heat & after reducing the volume by about 100 ml, the color is now a yellow brown. I don't know if that's a good sign or not. Beginning to rain here in Joplin & I can't stay with it all night so I turned the heat off. I'll continue in the morning.

Thanks for any help. I truly appreciate it.

Ed

 

[Geo]

dont toss or discard any solids. look at the processors carefully. where the legs were. is the ceramic base flat with little round green dots or is the surface rough and bumpy? the copper tungsten heat spreader will soak up some gold but it shouldnt have removed all the gold from solution. take a 10ml sample of the solution and put it in a container and add 10ml hcl. this should lighten the color so you can do a proper test. use a spot plate or plastic spoon.place 1-2 drops of the lightened solution in the test vessel and add 1 drop of stannous. look closely as the drop of stannous comes in contact with the solution. what was the reaction. did it lighten or did it sort of darken and then lighten quickly? in either case, add a heavy piece of copper metal to the solution and allow it to sit for several days to reclaim any values in the solution. be sure to use a small brush to brush the copper off back into the solution when you pull it out.
take the left over material from the CPU's and add about a 100ml of hcl to it and add a couple of doses of chlorine bleach in 10ml increments. allow the solution to sit on the material for about a minute and decant into another vessel. dont worry about filtering yet. test this solution with stannous chloride. a positive means there still gold in the material.

 

[cejohnsonsr]

Thank you Geo. I haven't thrown anything away. I'll do everything you suggested later today. I'll take careful notes & try to get some pics so I can answer your questions accurately. My hard drive died so if I'm a little slow answering that's why. I'm working on a borrowed laptop when it's available.

I should also mention that I had 5 old (early 90's) Apple/Mac CPUs in the batch too. As of this morning, the beaker that I've been evaporating is back on the heat. I tested with stannous again. The liquid is still very dark & green on a q-tip. Stannous turns a VERY light purple after a few seconds. It's hard to see because of the green, but I'm sure it's positive. The remainder of the liquid is in a 1000 ml measuring cup. The liquid in the measuring cup has cleared to a very pretty emerald green. On the q-tip it looks a little bit yellow green. Stannous turned almost blue but then changed to the same color as the liquid in the evaporating beaker. I can also see a little bit of some kind of "scum" floating on top of the emerald green liquid. It may be gold. I've seen some pics where gold floated this way. There is also some more sediment in the bottom of the measuring cup. I'll have to decant to see if it's the same white sediment as before. If so, there must have been a lot of it. I'm guessing it's silver chloride(?).

 

[cejohnsonsr]

I did as you suggested, Geo. Since I had 2 containers I took 2 samples. You can see the stannous tests on the spoons. 2 drops turned almost blue. I could see the change as the green changed color. 2 more drops finished it. Both samples reacted exactly the same. The spoon on the right is from the beaker that I had been evaporating. The solution was a darker shade of green. About the same difference as the shades of blue seen in the pic.

I really hadn't looked at the leftover pieces until now. I was surprised at what I thought I saw. Some of the legs were still there but I didn't think there was any gold left. Stannous proved there was. Those pics are included also. After the stannous test I put the HCl Cl back on the material. I figured I might as well let it dissolve as much as it could.

I bought a solid copper split bolt (like the kind used for a big ground wire). I put it in a beaker & then added all of the solution.

I know I have to wait a few days for any values to drop from the solution. What do I do after that? Try to remove everything except the gold with Nitric? Then dissolve the gold & proceed as it was supposed to the 1st time?

Thanks for the help. I really appreciate it.

Ed

 

[butcher]

It looks like most of the gold is still on the ceramic CPU's, there may also still be base metals like copper in them I do not know, much of your gold could have plated back onto the remaining copper, your stannous test does show some gold in solution but it does not look like much to me, most of your gold still looks like it is on the CPU's.

I am not sure what originally happened with your aqua regia, how much acids you used, if you used homemade nitric, or if they were very dilute, cold, or what, but you did not put all your gold into solution, did you use enough HCl for the amount of gold you had, and what strength? If you did not have enough HCl for the amount of metals you could have used up all of the HCl, if there was enough HCl did you stop nitric acid additions too early? If you had unreacted HCl and enough HNO3 it would dissolve the gold, if either of these acids are consumed the gold will not dissolve, although if acid solutions were very dilute it would take much longer, Heat is another factor, in a cold solutions acids are not as strong, the nitric may look consumed and seem to quit reacting (no visible reaction noticed), and if this same solution was heated the acid would still dissolve a lot of metals, dilution can also play a big part in the time it takes or how fast a metal may take to dissolve.

Acids with metals can the reactions be very vigorous at first, then slow down and look like nothing is happening, but they can still have a lot of action left in them, if heated or concentrated with the metal, sometimes it will surprise you how much more metal they will dissolve.

If your solution is slightly acidic you should be able to see fairly quickly if gold is going to cement out, but still let it sit overnight or longer, you should see it trying to plate to the copper, several factors like having the solution at least slightly acidic, if the solution is too concentrated it seem to slow the cementing process down, temperature play a big role here also, and since this is a contact reaction stirring solution is also important.

I do not expect much gold to cement out of the solution, but then again I can be surprised, the gold may be hard to see if not much of it, also a little may stick to the copper buss bar, even after your brush it off into solution, I normally do not worry about that little bit because I rinse and dry my copper buss bar and store it in a plastic bag, any gold on it I will get back later.

I do not know if anything I have had to say here will help or not.

 

[Geo]

theres no need in using hcl/Cl on that material. start over with fresh acid using the same material. the gold is still with the CPU's. what is your source of nitric? is it nitric acid or sodium nitrate? finish the dissolution of the metal on the CPU's. in the future, ALL the metal on the CPU batch MUST be dissolved (not just the gold plating). be sure to heat the reaction below the boiling point of water. continue the dissolution until all the metal is dissolved and the ceramic bodies have little round green dots where the legs used to be.

 

[cejohnsonsr]

Ok, it seems I need to start over. Let me start by answering some question.

butcher, I did the whole process with heat. I thought just enough to make it react, but now I think I may have had it too hot. I'm not certain exactly how much HCl, water & Nitric. I should have measured better & kept closer track of how many additions of Nitric.

Geo, it's supposed to be 67% Nitric Acid from ArtChemicals. I wasn't terribly happy with their service. I won't buy from them again & I don't recommend them to anyone else either.

Now my questions:

Can I use the 100 ml of HCl I used for the test by heating until the Cl is driven off, or should I start over with all fresh HCl?

I've seen a couple of recipes for AR. The first one uses equal parts water & HCl + Nitric Acid equal to 1/3 - 1/4 of the HCl added in small increments until there is no more reaction.The second doesn't use water. I used the first one. Is that the one I should have used?

My Revised Plan For The 2nd Attempt:

The starting material was 5 Apple/Mac CPUs weighing 131.64 gr, 1 Pentium Pro, 1 AMD K5 & several Pentium & AMD CPUs weighing 288.29 gr + 33.34 gr of CPU pins for a total weight of 453.27 gr. In a 1000 ml beaker the material was around 300 ml in volume. I had originally expected to recover around 3 gr of gold.

Assuming the 1st AR recipe is the correct one to use, I'll measure 200 ml of water & 200 ml of HCl. Now here's where it gets tricky. According to the General Reactions List provided by lazersteve:

Hoke states 4 fluid ounces HCl + 1 fluid ounce HNO3 dissolves 1 troy ounce gold. This is equivalent to 3.8 mL HCl + .95 mL HNO3 per gram of gold.

So if I expect 3 gr of gold AND with the understanding that there are also base metals to be dissolved, 200 ml of HCl should be more than enough & Nitric Acid should be at least 3 ml but not more than 50 ml.

Is there anything glaringly wrong with this? Am I missing anything? I'm in no hurry so I'm going to wait for input/confirmation before I start again.

Thanks for helping me with this, guys. I promise it won't be wasted effort.

Ed

 

[cejohnsonsr]

I put a piece of copper in the failed AR solution for several days & got a little bit of black "sand" in the bottom of the beaker. It dissolves in HCl/Cl so I'm hoping it was gold. If it is, it's not much. Maybe 1/4 gr. After I removed the copper I hung a piece of shiny steel in the solution. I was amazed to see cementing for the 1st time. The shiny piece of steel looked like a piece of copper after only a few minutes. After an hour it looked like copper was "growing" on the steel. I have the original ceramic CPU material soaking in a 50/50 mix of HCl + H2O until I can try AR again. I combined all of the HCl/Cl from the tests & black "sand". Once the Cl evaporates I'll drop with SMB just to see what I get.

Ed

 

[cejohnsonsr]

The ceramic chips (pieces) have been sitting in a solution 50/50 solution of HCl/water since the last post. All of the legs have dissolved. Nothing left but the little green bumps Geo mentioned. I stirred it up & can see gold in the sediment in the bottom. I'm wondering if it will be ok to just heat this up & add Nitric to make AR again or should I drain off the solution & use fresh HCl/water? I don't have my computer (it died) so I'm working from memory & with what I can find here. My guess is that the current solution has dissolved most of the base metals & the gold remains in the material & that I should drain it & start over with fresh solution.

Ed

 

[Geo]

the legs are Kovar (iron based). test it with stannous chloride. if the test is negative (be careful of a false positive), decant being careful not to pour out any solids and rinse with distilled water and start with fresh hcl. let all solids settle before decanting rinse or solution. remember to test every step you do.whether its a rinse or a chemical solution, test when moving liquids off of the solids.

if the test is positive (which it shouldnt be with all that base metal), decant into a container and cement values on clean copper. rinse the solids and go from there.

 

[cejohnsonsr]

Thank you, Geo. I thought that would be the proper thing to do. The solution these chips have been sitting in has turned green. I'm pretty sure copper will turn that color. Does iron/steel/kovar cause that as well? I'll be trying to cement again as soon as I can. I tried it on another batch of "spent" AuCl & got a surprise. Apparently my "copper" split bolt was alloyed with tin. At least that's what I think. I'm posting pics of the result on the thread, http://goldrefiningforum.com/phpBB3/viewforum.php?f=49.

Ed

 

[cejohnsonsr]

Well I have managed to get everything else caught up & out of the way. Now I'm ready to try to finally finish this batch of ceramic CPUs. I sorted through the larger pieces of ceramic material & removed any that didn't have any gold left on them. Most were where the legs had been. Only green dots where they had been. Some of the pieces were where the dies had been. Nothing discarded. I just set them aside to make the rest easier to work with. What I now have is mostly a ceramic sludge with gold mixed in & some larger pieces of ceramic where the gold didn't completely come off. This material is in a 1000 ml beaker. I covered it with 200 ml of water to keep it wet. Total volume in the beaker is about 300 ml.

If I understand correctly, 3.8 ml HCl + 0.95 ml HNO3 will dissolve 1 g Au. I had originally expected to recover around 2.5 - 3 g Au. Since I didn't recover anything from the 1st attempt, I think I should still get that much. My question now has to do with the acid solution. In the videos I've watched (lazersteve & sam) the solution was 50/50 H2O + HCl with HNO3 added in small increments. Steve's General Reactions List, however doesn't include H2O in the formula for AR. So I'm wondering how to proceed. Should I:

Add 200 ml HCl, heat & then add HNO3 in small increments?

or

Add HCl + HNO3 to the current amount of water in the ratios above?

or

Remove as much water as I can & add the HCl + HNO3 in the ratios above?

I'm thinking I should probably go with the 3rd option. Just enough water to cover the material, then add 4 ml HCl + 1 ml HNO3 & heat. Wait until the AR has consumed as much Au as possible (about 1 gram). Then add another dose to consume another gram (hopefully). Then if there appears to be more gold left, add the HCl & only a drop or 2 of HNO3.

Hope someone can tell me if I'm on the right track here. The 1st attempt was such a failure that I want to make double sure what I'm doing before I proceed.

Thanks,

Ed

 

[butcher]

Water is not needed, and the acids already contain water (which will usually need evaporated off at some point), if heating a solution sometimes water is helpful.

HCl / NaClO bleach is much easier to deal with than aqua regia, either would work here.

If you do use aqua regia, I would not add water, add expected amount of HCl , if acid does not cover material a little excess HCl will not hurt (or you can add a little water to increase volume, warm the solution till vapors form, add your calculated nitric with a pipette in increments waiting between additions for reaction to cease, this will concentrate solution as you dissolve the gold, when all of the gold is dissolved finish concentrate the solution, add several drops of H2SO4 and finish concentration, if solution was yellow (copper not coloring the gold solution) you should see the gold chloride solution turning a darker orange color as solution gets concentrated, add just a little HCl to re-wet back towards yellow, evaporate back to orange, do this one more time, turn off heat let insoluble material settle, add a little sulfamic acid I add just a pinch of powder, decant solution to clean vessel add 3 time water to dilute cover and let sit so silver and lead precipitates, overnight, filter solution and precipitate your gold.

If using HCl/NaClO you will not need much heat, a good warm day is fine, dissolve gold , again adding you bleach sparingly, after gold dissolves, heat solution till vapors form, fill a cap full of ammonia hold it next to the vapors of your gold solution if you still have chlorine you will see a white cloud when vapor of ammonia and chloride forming a white smoke of ammonium chloride, when you do not see white smoke you have removed chlorine, dilute, let sit overnight for insoluble to settle, filter solution before precipitating gold,

 

[cejohnsonsr]

Hi butcher. Here's what I did. I kind of split the difference with the water. I removed 100 ml of water & added 100 ml of HCl. I then warmed it up a little & added 1 ml of Nitric Acid. After about an hour & 2 or 3 stirs the reaction had slowed to almost nothing but I could still see gold in the material. I added another 0.5 ml Nitric Acid & continued for another hour, stirring 2 or 3 more times to make sure all the material was well exposed.

It was at this point that I had to go get my grandson from school. The reaction had almost completely stopped again. I turned the heat off & left the beaker covered & everything just as it was. My plan is to turn the heat back on in the morning & continue.

Right now the solution is yellow with a hint of green. Really mostly yellow. There is a fine sediment covering all the ceramic material & I imagine there is still quite a bit of fine sediment from the original material in the bottom. Stannous test VERY positive.

After it heats back up I'll give it a stir to make sure all the Nitric Acid is used up. Then I'll add a few drops of Sulphuric Acid & stir it up again. This is where I need to make sure of what I'm doing. It's at this point that I begin concentrating the solution. Right? And I don't remove the ceramic material or decant yet. Right? I just boil it down until it starts turning orange, then add HCl & repeat 2 more times. Then decant while still hot & allow to cool over night while the silver/lead (if any) settles. Then I can filter & drop with SMB. Right?

Edited to add this:I don't have sulfamic acid. I don't think I've heard much about it so far. Can you tell me what it's for?

Thanks,

Ed

 

[butcher]

Ed,
I actually have gotten to where I concentrate or do my first evaporation as I dissolve my gold, it is not necessary, but I find it helpful and a time saver.

But you need to understand some principles, volatile gases may be the first to leave solution, then water vapors off before acid, HNO3 will be next and then HCl, sulfuric is almost impossible to vapor off from solution, its boiling point and azeotrope is so high.
Heating can help to make the acids react better, water can be vaporized off with no problem, but when the acid solutions concentrates we do not want the solution so hot we are just vaporizing off our nitric before it has a chance to oxidize the gold, but heat can help it to react better, after water is vaporized off the HCl will react better with the gold, but also as the solution concentrates and azeotropes we will also loose HCl to fumes (so the goal is to get most of the gold reacted before the acid concentrates too much, this is normally not a problem as the HCl is about 68% water any way, and then as it reacts it can also form some water from the reaction, I try to use most of the nitric before the solution gets too concentrated, as the solution is concentrated further it can dissolve more gold without the additions of HNO3 or very little maybe just a drop or two at a time, so being close to a concentrated solution with either all of the gold dissolved or just a small amount left I can then concentrate it down further to finish my first evaporation, here I add the few drops of sulfuric acid (sulfamic acid could be added here as an alternative as it will form H2SO4 in the reaction and help to remove nitric acid, help with keeping from making salts if you make a mistake and evaporate too far, and it can also help to form lead sulfates later just like sulfuric acid does), we do not want to boil the solution just heat it so it vapors and concentrates, after concentrated the first time we add back a little HCl (remember this is 68% H2O and we do not want to dilute much as it will just need vaporized off), the HCl give more HCl acid to the gold (we have vaporized off, it can also acidify nitrate salts so we may see brown fumes of NOx gas from free nitric,again we will concentrate to drive off water then nitric and get the solution to a concentrated gold chloride, we will do this one more time to insure we vaporized off any free HNO3.

DO NOT BOIL it would result in gold solution leaving the vessel.

Sulfamic acid (I buy it at home depot store where they sell floor tile it is used to clean tile grout), sulfamic acid destroys the nitric acid from solution, the byproduct of that reaction is a little sulfuric acid is formed, which is actually helpful with what we are trying to achieve here.

There are other choices beside sulfamic acid to help remove nitric, like leaving a little undissolved gold, or adding a gold button during the evaporations to help use up HNO3.

Actually we only need one method to use up or remove nitric acid:
Minimum amount HNO3 added.
Three evaporation method.
Leaving some undissolved gold.
Adding a gold button.
Sulfamic acid.
But I have found it much better for me if I use several of these methods simultaneously to insure I have no free nitric when I go to precipitate the gold.

Remember to use your stannous chloride tests, not only are the great at indicating gold in solution, but it is also helpful to see that oxidizers are removed where gold can be reduced back to metal when you go to precipitate the gold back out of solution.