Starting Over... Slowly

[maynman1751]

Looks like another oversight. I have been using 70% nitric acid with no water. All the water in my lab (I like the sound of that) has been distilled arrowhead. I don't see how any hcl could have contaminated my nitric solution. I assume the contamination is from the board itself when the green film lifted off exposing the glue or whatever was holding it on. Everything was fine till that happened. I have taken out the boards and set them aside, they were coated with slime. Is that slime tin or is it tin+gold?

Joe! You need to do some more reading and studying. You are making way too many mistakes and compounding your problems.
I, myself, am fairly new to this , but through reading and researching the forum, I will tell you what I see (my opinion).
1. I would not do entire boards.
2. I would not use Nitric to remove base metals when HCl/Peroxide will work just fine (but slower) and is much cheaper.
3. If you are going to use Nitric it should be diluted 50/50.
4. The full strength Nitric may be the reason that the green film (solder mask) has come loose and exposed large amounts of copper trace that is being dissolved unnecessarily in the reaction therefore exhausting your acid needlessly.

These are just a few things that I thought that I would point out. I believe most of them have already been covered by other members already. If I am wrong on any of these points I'm sure that I will be corrected. Continue to let Butcher guide you through this stage and then, if it where me, go with the AP, HCl/Cl processes until you get better acquainted with what you are doing. I am by no means an authority on this. Just trying to give some friendly advice.
Read the forum daily. The mistakes that you are making are discussed here on a daily basis. Learn from the others mistakes to avoid making the same ones yourself. Don't be discouraged. Just work smarter!

 

[butcher]

The nitric should have been diluted, by using concentrated acid more nitric is used to make the brown NOx gas, this nitric wasted as gas, could have been used to form more nitric acid in solution and thus dissolve more metals.

Concentrated acids can act differently from dilute acid.

If you cannot dissolve any more copper with the solution, I would put the solution in a casserole dish on an electric hot plate (solid cast iron burner top or add sheet of metal between dish and the coil type burner, I would also add some water to dilute solution some, add more copper while using heat, seeing if more copper dissolves into solution, nitric acid has a way of slowing down in reaction, and you can still have much free nitric in solution. It may or may not dissolve quite a bit more copper.

If gold dissolved into solution, (and there was for some reason chloride in the nitric solution) this gold will at some point cement out onto the copper, or be pushed out of solution by the copper.

When adding whole circuit boards in a solution that dissolves gold you can have copper the gold can cement onto in places that may be very hard to get to this copper to dissolve (like under solder mask, or copper in the center layers if the circuit board on some types of circuit boards), some types of circuit boards have traces of copper sandwiched inside under and in-between the layers of fiberglass, if the gold solution comes into contact with this copper the gold could cement there, acid can also have a hard time getting to this copper to dissolve it of free this gold., Also bubbles of gas escaping from where the acid might gain access to this sandwiched copper may keep new acid from entering and dissolving the copper or freeing the gold from this copper.

Tin from solder and its problems as we have already discussed,

I would make sure the nitric will not dissolve any more copper after adding water and heat, basically to will have to saturate the solution with copper, use up the free nitric acid.

You can also take a small sample of the hot solution, in a spot plate or white spoon, add a prill of urea, watch for fizzing, if so you have free nitric acid, then test this same solution with stannous chloride for gold.

 

[megaplow]

Okay,
After researching and some experimenting, things are looking up. I added some distilled water, heat and a thicker piece of copper to my solution. As the solution heated yellow smoke came off it, I assume this was the nitric acid working on the copper. Some time after the yellow smoke stopped I let the solution cool. The next day my solution had a dark layer of mud on the bottom topped with a lighter one. I added one ball of urea to the solution and it didn't react. I added a pinch of SMB and that too had no reaction. At this point I am comfortable that there is no nitric acid left in my solution.

I decanted the fluid leaving wet mud and the clear solution. The decanted solution does not test positive for gold. Adding SMB to the solution precipitates white powder.

I took a portion of the mud and added HCL to it. The light mud dissolved leaving black powder.

Are these the right next steps?
1) Add HCL to all my mud.
2) Use HCL + Peroxide to dissolve it.
3) Precipitate the gold with capperas

Joe

 

[maynman1751]

I took a portion of the mud and added HCL to it. The light mud dissolved leaving black powder.

Are these the right next steps?
1) Add HCL to all my mud.
2) Use HCL + Peroxide to dissolve it.
3) Precipitate the gold with capperas

When you added HCl to the mud and the light mud dissolved, what color did it make the solution?
Depending on your answer to that, yes you could 'wash' the mud in HCl to rid it of unwanted materials. I would do this in a heated solution and decant while hot to remove tin in solution. Somewhere in here you should also incinerate your powder and rinse in HCl again. Then rinse powder in water until clear.
To dissolve use HCl/Cl not peroxide. Add a few drops of sulfuric to remove lead and filter.
You can precipitate with copperas or SMB after ridding the solution of Cl.

You may want to wait for a more definitive answer, but that is how I would proceed.

 

[nickvc]

A few points.
1. you are using stannous to test your solutions and not just relying on the fact no gold precipitated out of your solution ?
2. By not incinerating between using nitric and hydrochloric acids you could well have made a weak AR which could redissolve your gold.
3 I really think you should just cement any values on copper, seal up your containers and do some studying, by keep experimenting without knowing what your doing your wasting chemicals, time and effort.

 

[butcher]

Joe,
I agree with Nickvc, you are putting yourself right back into trouble, the troublesome metals and inorganic materials need an incineration to oxidize the tin and other base metals, and also to rid the nitrate salts from the metal salts, before a good boil in HCl, then slight dilution before decanting solution hot to remove tin and other base metals, hot water rinses at this point will also help to remove the lead chloride (insoluble in cold water but soluble in hot water.
And if you were going to do a nitric leach after this and did not want to dissolve the gold powders you would incinerate again to rid the metals of chloride salts.

Since you missed this step you still could have the trouble from tin in solution, and since you did not incinerate it is possible to have dissolved some gold, you can test for dissolved gold with stannous chloride.

Here is the double edged sword, if you do have gold in solution, and tin in solution, in this chloride solution you have made stannous chloride that reduces the gold to colloids, this gold you cannot test for in solution with your spot test of stannous chloride testing, it will not precipitate as it forms colloids that will not settle out, they repel each other keeping each other in solution, the tin in solution is also very hard to filter, and if you do you could possibly see the violet color from the purple of cassius reaction in your filter.

 

[megaplow]

Thanks for all the responses,
This morning I realized I forgot to add incineration to my possible next steps. All my tests thus far have been done with stannous. I will do a small incineration test and report back.

Joe

 

[maynman1751]

Well I almost got it right! Parts of it anyway. That's why I said to wait for a better answer. :|

 

[megaplow]

Hey All,
After reading Butchers instructions on incineration I needed to schedule some time before moving forward. Last night I completed my first reduction, rince, re reduction and incineration. The powder is still giving off smoke so I need to keep them on a little more heat. I havent added hcl yet. Just an update.

Joe

 

[butcher]

During the incineration the powers will smoke as long as there are organic materials or acidic salts, if the metals are high in acidic base metals sometimes the powder will dry when heated, then fuse into a syrup type material at higher temperatures, more heat they will dry again before you can get them red hot, keep crushing the material when dry (i will try to crush just before completely dry so it is not so hard, you want to have it in fine powder to get the metals exposed to heat and air, make the powders glow red with heat, and hold this heat for a while, stir often to expose to air.

Do not breath the acidic and metallic fumes.

 

[CASACEO]

Okay,
After researching and some experimenting, things are looking up. I added some distilled water, heat and a thicker piece of copper to my solution. As the solution heated yellow smoke came off it, I assume this was the nitric acid working on the copper. Some time after the yellow smoke stopped I let the solution cool. The next day my solution had a dark layer of mud on the bottom topped with a lighter one. I added one ball of urea to the solution and it didn't react. I added a pinch of SMB and that too had no reaction. At this point I am comfortable that there is no nitric acid left in my solution.

I decanted the fluid leaving wet mud and the clear solution. The decanted solution does not test positive for gold. Adding SMB to the solution precipitates white powder.

I took a portion of the mud and added HCL to it. The light mud dissolved leaving black powder.

Are these the right next steps?
1) Add HCL to all my mud.
2) Use HCL + Peroxide to dissolve it.
3) Precipitate the gold with capperas

Joe

Hi Joe, I too am new to the refining processes. From what I understand of your process, and I had to read it a couple times to make sure, you have already neutralized the nitric in your solution. SMB is naturally a white precipitate. The thicker piece of copper you added to spend the remaining nitric precipitated your gold for you. At this point in your process you could clean your gold first with water (tap or distilled is up to you) then with hcl (edited by CASACEO). After you are satisfied with your washes is when you would decide if you want to re-refine or test a small amount of gold or burn it into a button.
If it were me I would dry it, weigh it and re-refine it.

As for your first batch, you do not have Pd in or on your boards. Pd is found in the brownish capacitors that your boards do not have. It looks to me like the boards were never populated, so that is good news. All they are is Cu Au and plastics. I would recommend separating solids from fluids, rinsing the solids off into the fluids. You will need to further dissolve your base metal, Cu, off the boards to recover the Au. AP (c II c) should do the trick now that you know a little more about it. Test the fluids for gold with SC. The copper should have cemented any values out of the solution but testing is never a bad thing.

To reiterate, I am a newbie myself and I have very little experience. To me it sounds like you are learning the craft well and beat yourself up too much. You are doing much better then I did the first and second go at it. The first time I dumped out my solution and the second time I ended up with 1/2oz of 12k. The third time I prematurely cemented my waste with steel and I have been having a horrendous time trying to recover my PMs from that... I expect you will succeed, if not now then eventually.

 

[Harold_V]

At this point in your process you could clean your gold first with water (tap or distilled is up to you) then with hcl and a small (like a couple drops per wash) amount of 3%H2O2

I question the logic in using H2O2 at all. Not much different from using a drop of nitric, is it?

Your objective should be to wash the gold without risk of dissolving any.

Harold

 

[CASACEO]

At this point in your process you could clean your gold first with water (tap or distilled is up to you) then with hcl and a small (like a couple drops per wash) amount of 3%H2O2

I question the logic in using H2O2 at all. Not much different from using a drop of nitric, is it?

Your objective should be to wash the gold without risk of dissolving any.

Harold

You are right Harold, in some respects. They both are oxidizing reagents and they contain some of the same elements for construction. But I disagree about the difference between the two being not much. The chemical composition of each varies enough that it's like comparing apples to oranges, yes they are both fruit but have distinct differences that cannot be ignored. HNO3 vs H2O2 the key difference the N. Aqua Regia is not made with HCL and H2O2, it needs the N. I'm not going to waste time or materials making a 3% nitric to make an equally balanced scientific comparison.

There is a possibility for gold to dissolve, but thinking you're going to be able to get every nanogram of gold in the first try off computer electronics is a little out of logic to me. Copper precipitates gold when the solution is saturated and just about all the metals in a board are copper with gold plate. This is why we keep a stock pot of waste solutions for refining later, isn't it? The reason we rejuvenate a AP (cIIc) solution?

But using H2O2 in addition to HCL is most likely just a waste of peroxide and ultimately money (a couple drops a few thousand times will add up to a significant amount of money). Additionally allowing the few molecules of peroxide to work their magic is not going to prove efficient time management (unless you like watching reactions for hours upon hours instead of tv). I hope I explained my logic without offending you. Ultimately, I see why you didn't understand my logic... Few people do. :shock:

 

[Geo]

the gold will not precipitate out on base metal if theres no base metal left. when you use AR like that, you have to proceed with the digestion until all the base metal is consumed. then it really doesnt matter how contaminated the solution is, it will hold the gold until a precipitant is used to to drop it out.

hcl/H2O2 will act in the same way, just not as aggressively. the "trick" to all this is to keep the gold in a recognizable form one way or another so that you dont misplace it. if you know your going to dissolve gold, then dissolve it all to be sure you got it all. if your not dissolving gold in a process, dont dissolve any of it for the same reason. when your not expecting to dissolve gold and you do anyway, you may reclaim it in the stock pot but why tie up values when you dont have to.

 

[Harold_V]

In regards to washing gold, when base metals have been eliminated, for all practical purposes, the addition of ANYTHING that will oxidize some gold isn't a great idea. It serves no real purpose, as the second refining will provide the needed purification without risk of dissolving values when that isn't the objective.

I may have misinterpreted your comment, thinking that you were discussing the washing of precipitated gold. In that case, assuming that's what you meant, I strongly advise that you NOT post advice to add an oxidizer---as it serves no purpose aside from creating problems.

I took note that you are new to the forum, and new to refining. It is preferred, by far, that people such as you NOT DISPENSE advice. You should have enough wisdom to read the forum and understand what is acceptable here, so you don't create problems. Others who may not understand your lack of experience may assume that your recommendations are acceptable. That, then, has the potential to create a new wave of readers that have foolishly followed less than acceptable advice (it's called misinformation on this forum--and is strictly prohibited), creating yet more problems that must be resolved, and small fires to stamp out. None of us have time for that foolishness.

Harold

 

[CASACEO]

In regards to washing gold, when base metals have been eliminated, for all practical purposes, the addition of ANYTHING that will oxidize some gold isn't a great idea. It serves no real purpose, as the second refining will provide the needed purification without risk of dissolving values when that isn't the objective.

I may have misinterpreted your comment, thinking that you were discussing the washing of precipitated gold. In that case, assuming that's what you meant, I strongly advise that you NOT post advice to add an oxidizer---as it serves no purpose aside from creating problems.

I took note that you are new to the forum, and new to refining. It is preferred, by far, that people such as you NOT DISPENSE advice. You should have enough wisdom to read the forum and understand what is acceptable here, so you don't create problems. Others who may not understand your lack of experience may assume that your recommendations are acceptable. That, then, has the potential to create a new wave of readers that have foolishly followed less than acceptable advice (it's called misinformation on this forum--and is strictly prohibited), creating yet more problems that must be resolved, and small fires to stamp out. None of us have time for that foolishness.

Harold

Thanks for restating points I covered in my posting. It is clearly apparent that you misinterpreted my comments as a whole, or didn't read ALL of them (possibly both). Yes I know I misspoke and that was addressed three times in total after the fact. Others who 'may' not understand my lack of experience wouldn't have read my postings at all, it was clearly stated at the beginning and end of my first posting in this discussion. I would like to apologize for any confusion I have created and would like to thank you and 'geo' for clearing up the confusion that members 'may' have.

To Joe: If you followed all that your 3 steps are incorrect. If you are washing do not dissolve (no oxides of any type), if you are dissolving don't waste your time and chemicals washing.