Multiple streams of material.

[Dr_Code]

Lots of reading, a very small amout of doing, and a job that requires a lot of driving. So I have lots of time to think.

The time reading, and little doing also gives me time to remove and sort various types of gold containing scrap. The time to think gave me a question I wasn't able to answer by searching.

Once I gather an ample ammount of (I have some pretty good piles already) CPUs (ceremaic, intermediate, and fiber), fingers, touchpads and LCD boards, pins, flatpacks, boards with gold plating on them and traces, etc.

If I process everything else to the point of base metal removal except for the ceramic CPUs. Then I process the ceramic CPUs using the HCL/bleach method. Can I put the resulting somewhat pure gold, from the other processes, in with the CPU mix to disolve (adding some HCL/Bleach if needed to fully disolve things) and then drop it all out at once?

Or is this ill advised due to contamination, length of time to get rid of the excess Cl, some other factor I am not thinking of? Am I better off dissolving the results seperatly, droping the gold, and melting?

I realize doing this would not give me an accurate count on what I am able to recover from various parts using my techniques and skills.

 

[qst42know]

I don't see any problems combining recovered powders for additional refining. It's the recovery of the different types of materials you want to keep as simple as practical.

 

[Geo]

if its my material, i keep recovered gold that needs to be refined in a vessel by itself. it really doesnt matter what state the recovered gold is at that time,80%,90% or even nearly pure. if it needs to be further refined, it all goes together.

 

[butcher]

This is just my point of view here,

Different materials can have different contaminants, (and sometimes different methods used to recover), if you can process item's separately, you will have less trouble, it is usually better to save up the material until you have enough of that one type to recover a decent amount of values from them, working with very small batch's can add up those small loses of values.

Processing different types of materials separately can also make things more simple and less trouble, say if tin in one type of material becomes a problem, this problem would not be mixed with your other processing of material that do not have a problem with tin.

Recovered gold powders can be washed and dissolved together as long as you do not have conflicts in the previous acids used, in this case and incineration can help to remove the previous acid.

Say one process makes foils and another makes fine powders, and a third has some dissolved gold in solution with tin forming colloids, mixing these three together can be a problem, not only have you contaminated the other materials with tin now, but you have to either get all of the gold reduced out of solution, or else get all of the gold oxidized and dissolved into solution, before proceeding, filtering would become troublesome and now everything will be harder to recover, and proceed with.

Or if you can deal with the problems involved as they rear their ugly head, you can process different items together, it is up to you.

 

[Dr_Code]

With that I think it would be best to disolve and drop what I can from each process, combine the results, and then disolve and drop again? As long as I am liberal with the spray bottle there shouldn't be many PMs in the filters and such. Can I mix up a larger batch of HCl/bleach and only use enough to disolve the material I have, or will it go bad?

How low should I go in my seperation of material? Is a flatpack a flatpack? Should I seperate them into types? GPU, memory, other stuff I'm not really sure what it does? It seems it all has the same process to recovery - incinerate, remove base metals, and refine.

 

[butcher]

"Can I mix up a larger batch of HCl/bleach and only use enough to dissolve the material I have, or will it go bad?"

I am not sure what you mean here, you will only need enough HCl to make gold chloride in solution adding bleach in small increments to dissolve the gold, letting this sit or heating will drive off chlorine gas leaving a gold chloride solution that will not go bad.
If you are talking about premixing HCl and sodium hypochlorite that is not a good idea even without gold in the solution, it will generate chlorine gas which will fume off as gas , the solution will also raise the pH of your acid, and dilute it with water.

 

[Dr_Code]

Thanks for the replys.

You all are a wealth of information!

With butcher's responce, it looks like I will have to read more. I don't think I understad the process completly. Thanks again! Time to read more and take more notes. I'll post more later.

 

[butcher]

We are trying to make a gold chloride solution (dissolved gold ions)
To do this we need to remove electrons from the gold, to do this we must oxidize the gold.
Oxidize means to give up electrons.
(To reduce or reduction is a gain of electrons)
This is called a redox reaction.

gold is very low in the reactivity series of metals, (almost the bottom of the chart), this means gold is a very un-reactive metal we call a noble metal, it does not oxidize easily (does not give up its electron easy).

gold is below hydrogen in the reactivity series, this means it will not replace hydrogen from acid's like (HCl) hydrochloric acid, stated another way HCl will not oxidize gold (take away electrons from gold) or will not dissolve gold into solution, HCl is not strong enough of an oxidizer for this noble metal.

for something to be oxidized (lose of electron), something else has to be reduced (gain of electron),

Chlorine gas (already oxidized) it wants electrons, and will take electrons from the gold.
so in this reaction of gold and chlorine the gold gives up its electron to the chlorine (so we say the gold is oxidized and chlorine is reduced to chlorides (a salt of chlorine).

the oxidized gold in this solution missing an electron joins with the chlorides in solution (HCl) and depending on acidity and concentration, one gold ion joins with 3 to 4 chloride ions making gold chloride HAuCl4 or AuCl3, this is a salt of gold in solution.

metal + acid = salt of that metal

when we dissolve a metal in an acid we make a salt of that metal, some are soluble some are not,

For a better understanding see solubility chart,
And also study the reactivity series of metals,
Reading about redox reactions is also helpful.
To better understand the cementing of a metal from solution read about displacement reactions.


Excess HCl acid is not a problem in our solution of gold chloride; if we do not give enough oxidizer we will not dissolve all of the gold.

In this case chlorine gas is our oxidizer, we generate it in solution using household bleach NaClO (sodium hypochlorite) this bleach is a salt of chlorine, a base (opposite of an acid), it is wanting electrons to become chlorine gas, luckily our acid HCl is a strong enough oxidizer to oxidize the hypochlorite to chlorine gas (this oxidized chlorine gas now missing electrons will take them from our gold to dissolve gold in solution as gold chloride).

when we mix the NaCLO sodium hypochlorite with the HCl hydrochloric acid the chlorine gas forms in solution and begins to leave the solution (chlorine is a gas, and will not stay long in an acid solution, (heat will also hold less gas than a cold solution, so heating will drive chlorine out faster),

We need the chlorine gas to stay in the acid long enough with our gold to oxidize it (the larger the surface area the longer it would take, this is why we use this method for flakes or fine powder and not larger pieces of gold.

so when we add small increments of bleach to our acid with gold in it we generate chlorine to dissolve the gold into a chloride solution, by adding the bleach a little at a time we keep the chlorine in contact with the gold longer and are not wasting our chlorine gas.

also since the sodium hypochlorite is a base (opposite of an acid) with sodium hydroxide (to keep the hypochlorite in solution), when we mix this base with our acid we bring up the pH of our acid (we make the HCl acid less acidic and closer to being just salt water NaCl-H20), so here we see we do not want to add bleach to solution if it is not making chlorine and working to dissolve our gold.

Also the bleach is almost all water so adding bleach dilutes our acid tremendously with water.

Premixing the acid and bleach can form a less acidic salt water and chlorine gas not doing any work.

 

[kurt]

also since the sodium hypochlorite is a base (opposite of an acid) with sodium hydroxide (to keep the hypochlorite in solution), when we mix this base with our acid we bring up the pH of our acid (we make the HCl acid less acidic and closer to being just salt water NaCl-H20), so here we see we do not want to add bleach to solution if it is not making chlorine and working to dissolve our gold.

Butcher - First I want to thank you for the detailed explanation of the HCL/CL process - however I got lost where you make mention of sodium hydroxide in the above - can you explain whats with the sodium hydroxide a bit more?

Kurt

 

[butcher]

Quote from above:
Also since the sodium hypochlorite is a base (opposite of an acid) with sodium hydroxide (to keep the hypochlorite in solution), when we mix this base with our acid we bring up the pH of our acid (we make the HCl acid less acidic and closer to being just salt water NaCl-H20), so here we see we do not want to add bleach to solution if it is not making chlorine and working to dissolve our gold.

Basically bleach is Hypochlorous acid HOCl dissolved in water H2O and sodium hydroxide NaOH to form what we call bleach, sodium hypochlorite NaClO, the sodium hydroxide is a base (above neutral in the pH scale), (opposite of an acid), it is the sodium hydroxide keeping the solution basic which is keeping the chlorine in our bleach.

When we mix the basic bleach (basic =opposite of an acid), with our HCL acid (acid= opposite of a base). we are bringing the bleach more acidic which releases chlorine gas to react with our gold, but this also makes our acid less acidic bringing the pH of the acid closer toward neutral on the pH scale.

Base + acid = neutral solution
(Now we know the acid and caustic would have to be mixed in correct proportions to get a neutral salt or solution).
But adding one of these to the other changes our pH.

Since we add only small portions of the basic bleach to our HCl acid we are not quite neutral salt water, but less acidic than if bleach was not used and if we just reacted the chlorine gas or bubbled chlorine gas into solution with our HCL to dissolve gold.

Bleach is mostly water so it will also dilute our solution with a heck of a lot of water, we cannot evaporate this water easily or very far as it begins to form salts. Which settle out of solution.

Basically:
Premixing the acid and bleach can form a less acidic salt water and chlorine gas not doing any work.