Aurum197-5,
I see a lot of base metals there, in the one picture of salts, the blue copper salts, the purple in your description of colloidal gold (gold reduced by tin salts), or silver salts, in the one beaker I suspect iron in solution, and a large volume of base metal salts.
In the title it states fantastic at recovery (is your goal is to recover trash of every metal?).
Horrible at precipitating (you done a pretty good job of precipitating most of those base metals).
I agree with the others, you started in the lab, before you should have, you need to study more to get a better understanding of the principles of recovery, and then also of refining.
Even without you describing everything you have done up to this point, I can see you have done everything wrong, first you are working with dangerous acids and metals before you spent the time needed to understand the safety and what you are doing, you may have read a little and understand a few things, and seen a few videos, but you have no understanding of the basics or the processes of recovery or refining.
I suggest you do the study before you continue to lose your gold, I know you are working on that, continue with your study of Hoke's, dealing with waste, safety, and the forum.
At this point your lab work should include dealing with the waste from this mess, and doing the getting acquaintance tests as Hoke's book suggests.
Aurum, basically you just made the same mistakes many of us beginning make, recovery and refining have certain principles that you need to understand, these principles are subtle but very important, you learn these basic principle's from study, Hokes and the forum. Not from trying to recover your lost gold from a toxic mess of acids and metals.
Hoke's book covers these principles in her book, but it is not obvious to the reader as he reads the book the first time, the forum also covers these principles, but to the new member learning the processes, these principles seem elusive to him.
It is something hard to describe, but as you keep studying these principles become more clear to you.
In the chemistry of metals, reactions of every batch of scrap is different, each type of scrap material will be different, and will need different treatments accordingly, each metal can react differently in solution, and most of the time each metal can react differently with each acid. Metals in solutions with each other one metal can affect the other metal in solution. Chemical reactions can get more complex the more metals in solution, and the more chemical reactions going on in a solution, add organics grease oil from the circuit boards, or your fingers, plastics or other trash and we add more complication.
In recovery our goal is to remove the trash (organics), and base metals from our values, basically separating our gold from everything else, including metals that will cause problems.
This is done using several methods, mechanical and chemically.
Putting gold into solution with base metals is a big mistake, some base metals like tin will not only give trouble filtering, but will rob you of gold, undissolved base metals with gold in solution can also take your gold. With electronic scrap materials these base metals like copper can be hidden up under layers of circuit boards solder mask or between the fiberglass layers, or deeper down inside the CPU's...
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Trouble with precipitation, lets look here at why that may happen.
In this example I will try to describe a mess.
The real trouble here begins with our recovery methods, or lack of, improper mechanical separation, lack of incineration, basically many of the finer details and lack of understanding of many of the principles important to the recovery and refining processes.
We have organics, from dirty materials, oils from hands, grease from electronic materials (heat sinks...), plastics, dirty vessels, or a variety of other sources.
we also have base metals, like iron, copper, lead, tin, and you name it.
In this example: We have some of these base metals in areas very hard to reach, or to be able to tell if all of the metal is consumed (under layers of circuit board or down under layers of CPU's...
We make the common mistake of beginners and do not remove all of the base metals before we put our gold into solution.
We mix up a solution of aqua regia, or in this case poor mans solution, HCl with a nitrate salt, (note here even this solution can cause trouble later if principles are not understood).
Adding this to our material we begin to dissolve metals into solution, reactive base metals deplete our solution of acid as they form hydrogen gas, other toxic and dangerous gases evolve NOx gases and chlorine gases.
Metals begin to go into solution with our gold, and the gold is also cemented back out of solution onto base metals like copper, as the copper goes into solution (some of these metals may be under layers of circuit boards or inside the CPU hard for the acid to reach as the gas tries to escape from the hidden areas it can block access to fresh acid, plating gold onto the copper also making it harder to remove the base metal from these hidden spots.
Tin from any solder in solution gives us a gelatinous mess of tin salts, metastannic acid (acidic tin salts oxidized by the nitric in solution) giving us problems later with filtering , and stannous chloride which will reduce our gold in solution to colloidal gold making testing or getting our gold back out of solution almost impossible.
We are getting a real mix or mess in solution of metals and organics.
Copper in solution also forms nitrates and chlorides.
Many of the other base metals in solution also react making dissolved salts of these metals in solution.
Lead or silver may precipitate some white salts of lead chloride PbCl2, and of silver chloride AgCl, while a percentage of these metals will remain in solution as lead nitrates Pb(NO3)2, and or silver chloride of a higher oxidation state (AgCl2).
Gold as we know will not form nitrates, gold will not react with nitric acid alone, gold will not react with HCl alone, but in an aqua regia solution the gold atom can be oxidized with nitric in solution and form a dissolved salt of gold chlorides with the HCl acid solution, giving us a dissolved metal salt of yellow gold chloride solution.
As we know base metals in the elemental state (having all of their electrons will gladly give up electrons to the dissolved gold in solution, as these base metals give up the electron to the gold ions, the gold cements from solution as elemental gold metal in brown powders or is plated to the remaining base metal, as the base metal is dissolved into solution as ions.
Pure gold dissolved in a solution of Aqua regia is a pretty yellow color. some base metals do not give much color to the solution, dissolved copper is a metal which colors solutions easily, copper being a strong coloring agent to solutions, a little copper in solution can give a strong color to the solution. If just a little copper is dissolved with gold it will color the solution, giving it color from blue, green, dark brown, to black as more copper is in solution.
Just a tiny amount of copper in solution (very small amount) with our gold we can deal with, with very little copper in solution our gold will precipitate leaving copper in solution, but as the copper concentration increases so will our problems to the point of making de-noxing and precipitating our gold difficult or impossible.
Too much copper can cause problems when we try to de-nox the solution, basically giving us problem trying to remove the free nitric acid or nitrates from solution (more discussion on this later).
As the copper in solution increases we also have more problems with precipitating the gold pure (more drag down) or even being able to precipitate the gold at all when the copper in solution becomes too great as the gold clings to the copper chlorides in solution (organics just increases these troubles).
Lets look at our aqua regia solution, before we can test the solution for dissolved gold, to see if gold is in solution, we have to have removed the oxidizer (free nitric acid from solution), other wise our stannous chloride cannot reduce the gold to the purple (violet) gold metal colloidal solution we recognize as a positive results, the gold will be oxidized right back into solution, or never reduced to metal in the first place.
Another problem here we covered some above, it that if we only have a little gold in solution, and we had tin in solution (our mess), the gold in this solution is already reduced to metal as colloidal gold, so here again our stannous chloride will not show a positive in the test, although we have gold in this dirty solution, because the gold here in solution as colloids is already in a reduced state, and our stannous chloride only works by reducing gold in solution, the stannous chloride test solution cannot reduce gold that already contains all of its electrons.
So from this we can see that even if we have gold in solution that we may not know, because our stannous test will not work in these instances, and with the tin in our solution and where it has reduced the gold to gold colloids it can be easy to throw out our gold with the bath water, losing our gold without knowing it (working blindly).
When de-noxing an aqua regia solution with pure gold, if we worked smart we would have limited the amount of nitric used, and would have reacted most or all of the nitric acid in dissolving the gold, in this case we would not have much or very little nitric to evaporate off making the chore a breeze, even if we use a little more nitric than we needed we can use the fact that the water, then nitric gases will vapor off of the solution faster than the HCl will, the process of the first evaporation can take a lot of time, as we do not want the solution boiling but just hot enough to vapor off the gases. As the solution evaporates mostly water comes off at first, then nitric acid, (the nitrates, hydrochloric acid, metal chlorides and metal nitrates concentrate with our gold chlorides), as the solution concentrates more free nitric acid vapors off as NOx gas, (there comes a point in concentration where these will try to evolve in one big boil-over if the worker is not careful), then HCl will evaporate.
Sulfuric acid or sulfates will not leave solution at these temperatures, as gases, this is where Hoke's suggestion of adding the few drops of Sulfuric come in handy making it more difficult to cook the gold salts dry if the evaporation process is carried too far.
Also it should be noted that the separation of the acids and gases is not a complete separation, although mostly water evaporates at first it is mixed with some of the other gases, but the majority being water.
Now lets look more at evaporating a solution in this case we will discuss our mess.
In particular nitrate salt, which could come from poor mans aqua regia, over use of nitrate salts (un-reacted into nitric acid in the solution of poor mans aqua regia).
But another place these nitrates can form is with our pure aqua regia (in using pure HCl and pure HNO3) to dissolve gold, here is where copper or other base metals can give us troubles in de-noxing the solution as we mentioned above.
As we mentioned above copper in solution of aqua regia (with our gold chloride solution), can form dissolved salts of copper in solution with our aqua regia, copper chlorides and copper nitrates in solution with our gold chloride.
Many of the metal nitrate salts can be evaporated to crystals, copper nitrate is one of these, if we took a solution of pure copper nitrate and evaporated it, the free nitric acid would vapor off, but the copper nitrate could be dried to copper crystals, retaining the nitrate, unless these dry copper salts were heated strongly they would not produce NOx gases forming copper oxides.
Also if we took these copper nitrates salts and added back HCl to wet them we basically, make a solution that will dissolve fine gold back into solution.
So we can see here where nitrate salts or even copper in our aqua regia solution (of gold chlorides) can become a problem in the evaporation process, even before we get to the precipitation process.
Recovery and refining although it seems like a simple tasks or following a simple process, it is by no means simple, there is so much to the chemistry involved in these metals and their reactions, although you do not need to understand all of the chemistry involved to be able to recover and refine these metals to a high purity, you do have to understand the basic principles, this is where Hoke's book and the forum will help you gain that understanding, you will not learn it from making messes and losing your gold.
Changed word nitric to sulfuric (my mistake)
Hello,GRF...I am a beginner/intermediate "backyard" alchemist who is recovering all types of e-waste (RAM, Green board, Ceramic/Non-Ceramic CPU Chips, pins...etc) I use a Muriatic and Sodium Nitrate mixture (~Aqua Regia). I've been exceedingly successful thus far pushing gold into solution. My stannous chloride (SnCl2) tests prove black within 1-2 seconds, however, I cannot seem to precipitate Au out of the solution I create, for the life of me.
