Science project: Recovering gold from SIM cards

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Jon is right. Each additional process adds the risk that a detail does not work like you expected, that you do a mistake, that your professors ask something you have no answer to. It would be something else, if you had enough scrap and time to become familar with the processes from morning till evening. If you can, try to get 200g of clean cut fingers. This will yield +/- 1g gold.

Better be a little expert in one process, than a dabbler in many.
 
solar_plasma said:
Jon is right. Each additional process adds the risk that a detail does not work like you expected, that you do a mistake, that your professors ask something you have no answer to. It would be something else, if you had enough scrap and time to become familar with the processes from morning till evening. If you can, try to get 200g of clean cut fingers. This will yield +/- 1g gold.

Better be a little expert in one process, than a dabbler in many.
Click to expand...


That is a VERY good quote on this forum with limited time. 8)

I agree 100%

Dave
 
Frugalrefiner pm'ed me to tell you more about using SnCl2-test. I hope he will chime in and do it himself with his own words.

Just for the completeness I try to underline some points you have to understand:

the stannous test is your eyes and ears!
test your test with standard gold solution first!
In a clean, oxidizer-free gold solution you can even get a feeling of the concentration of gold, if you have several different gold standard solutions to compare
use it before and after leachings and precipitations
use it to be sure, no gold has been leached together with the base metal leach
use it to know, where your gold is
after precipitation you use it to know that all gold has dropped out

it will not only show gold (purple or black), but also Pd (green/brown) and Pt/Rh (orange)
it is very, very sensitive
testing coloured solutions you will need to use the spotplate method and look for purple stain
if you overdo SMB, the test will show false positive (maybe because SnCl2 reduces even SO2 to H2S (Wiberg, Inorganic Chemistry), which again will precipitate almost everything as sulfides)

with excess oxidizer the purple reaction disappears again
large excess of oxidizer might prevent the purple reaction (I am not sure about this)

Ag+ will (of course) give white AgCl precipitate with SnCl2
Though in high acidic high chloride matrix AgCl is soluble as complexes (that's why we dilute, settle and decant/syphon/filter before precipitating gold - syphoning or decanting after a day is the high art but takes its time, whereas filtering works as well, if you choose an adequate fine filter material)
before this, we have added a little SO4-- and cooled to drop lead

avoid to let dust fall into your gold solution while settling
Under the second refining:
use only beakers that haven't been used for anything else
they have to be extremely clean, don't touch the inside - dried gold would cling to the walls of the beaker if there are scratches or if you had touched its inside
the whole second refing can be done in that only beaker: precipitating, washing, drying

never "boil" solutions with dissolved values (and if you have to, then reflux in some way)

Ofcourse can I make mistakes, forget details, think/remember wrongly or mistype, - so everyone feel free to comment
 
Maybe you want to be able to tell your professors, why you have chosen one and not the other method. So, I will try shortly to mention some points about that. In fact you could write a book only about that issue:

Dissolving base metals (Cu, Ni):
your choice: nitric acid
advantage: availability, fast, simple chemistry
other options and no-options:
CuCl2/HCl system - cost effective, slow, advanced chemistry
FeCl3 - same, a little faster, lots of brown stains
persulfates - slow, more expensive, ammonium persulfate would add ammonium to the process and makes it necessary to treat the waste separated
dilluted forms of piranha - too dangerous (process not allowed and not necessary to discuss here), expensive, fast)

Dissolving gold foils:
Your probable choice:
Modified AR (=HCl enough to cover the gold and make the solution handy/only as much nitric as needed(see link given)) - fast, but excess nitric must be avoided and/or expelled, sulfamic acid or gold button method - usually AR is only used, if you have to dissolve massive items or leach fine insoluble powders that contain gold, otherwise the other methods are preferred - makes H[AuCl4] or AuCl3 (dilluted solution)
other options:
HCl/NaOCl or HCl/Ca(OCl)2 - strong enough to dissolve foils or powder, excess clorine can easily be expelled by heating, slower, more liquids=more dillute gold solution - makes Na[AuCl4] (could not find the reference)
HCl/H2O2 - works with foils or powders, slowest, no problems with excess oxidizers - probably it makes H[AuCl4]or AuCl3 (dilluted solution)
all other methods make a lot of liquid volume, are hard to control their complicated chemistry or are hard to treat their waste - many of them are applied in leaching ores (leaches)

Precipitating gold:
Your probable choice:
SMB and other sodium sulfites - easy handling, must not be overdone (potassium compounds work too, but could form insoluble PGM salts]
SO2 - easy handling, if you have it available
other options and no-options:
FeSO4 - I think it is preferred for dirty solutions, can be used for additional testing
oxalic acid - more complicated to do properly, often preferred for the second refining (I love it]
cementing is no option for the gold refining, only used for recovery from spent or messed up solutions
other options are not readily available, implicate unnecessary dangers and/or are not selective

A little specialty is the appliance of lquid-liquid extraction solvents. If you need it, I help finding the links, but I have no clue about it, other than it is a method to get high purity even from impure solutions.

No option:
Another specialty in recovery only for the completeness is cyanide leach of plated gold. It is very dangerous (of course), not allowed to discuss here, but in professional/industrial setups often applied due to its cost effectivity and (at least for those who know it to handle really professional) simplicity. - disadvantages: one little mistake=last mistake of your life, waste problematic
 
Okay thanks for the help. As a matter of fact I do need to write about alternative methods, I did write something about sulfuric acid (compared to dissolving base metals with nitric), and using FeSO4 instead of SMB for precipitation.

I need to know more about the chemistry behind the SnCl2 test, and the CuCl2/HCl seems interesting cause it's cost efficient , but I can't find any reliable literature for these methods.
He will definitely ask me about alternative methods... but I need to know the chemical background otherwise I'll have no answers if he asks in more detail.... like chemical reactions and so on..
 
Chemistry of SnCl2: have a look at Wiberg/Inorganic chemistry, you need to get the book at the library or buy it, there is a description of how and why SnCl2 is a reductant
Sn++ -> Sn++++ + 2e- (+0,154V)

but there are about 2 pages about SnCl2

About CuCl2 lazersteve has written a very nice text: http://goldrecovery.us/\goldrecovery\documents\CuCl.pdf

in fact CuCl2 works like a catalyst, so the reason why this method is cost-effective is, it works with HCl (low g/mol, cheap, would not oxydize Cu without this catalyst) and all HCl uses up effectively. I think saying it is reusable is chemically not correct, you still need to add HCl from time to time. Chemically it is a catalyst and under processing you get more and more of it.

also look at the bottom of his site (documents section): http://goldrecovery.us/site.asp

Search also your university library for extractive - metallurgy - gold - refining, since you need current scientific sources, books that are very (too) expensive to buy.
 
lesuth said:
I did write something about sulfuric acid (compared to dissolving base metals with nitric)
Click to expand...

Sulfuric is slower. If used with strong oxidizers, it is quite dangerous and the exotherm reactions need a consistent controlling. Further the controlling and the oxidizers would make the process more cost intensive. I think it is waste of labour, material and energy compared to the drop-and-forget-methods plus accidents are more probable.

Since this is not allowed to discuss, I want to underline, that this is only mentioned as a theoretical issue! The reader shouldn't even consider to use this!
 
I am not sure, but maybe here are some useful diagrams regarding CuCl2:

SKI Rapport 98:19
Pourbaix diagrams for the system
copper-chlorine at 5–100 °C

I am not a chemist, but (correct me if I'm wrong) I think at least it shows why sufficient acid and oxygen is required. Also it shows why and when the solution loses its corrosivity, what species are present under certain conditions and when insoluble compounds precipitate. As a bonus it shows the influence of temperature.
 
Lesuth, I sent my suggestion regarding stannous chloride testing to solar_plasma in a PM because I didn't want to be another voice adding to any confusion you might have felt here. Since he has asked that I post here on this thread, I will.

He's already done a good job of describing why we use it, and its importance. Once you dissolve your gold, stannous chloride becomes your eyes. It will tell you which solutions have gold in them and which solutions don't.

I think you can use this testing to great advantage as part of your demonstration. Once you have dissolved your gold and eliminated any excess oxidizer, remove a small sample of the solution. Put one drop in a spotplate well, and another drop in the next well. Add 9 drops of water to the second sample to create a solution with only 10% of the original concentration. Mix, and take one drop and put it in the next well. Add 9 more drops of water to create a 1% solution. Do this several more times creating increasingly more dilute solutions. Then add a drop of stannous to each to demonstrate how sensitive stannous is.

After you precipitate your gold, you can test the barren solution to demonstrate how complete the precipitation has been. This is the technique we use to determine if we've used enough precipitant. If the solution still tests positive, we know we need more precipitant. If it tests barren, we know we've recovered all the gold that was in solution.

It's a simple demonstration that can be performed in front of your professor.

I hope that helps.

Dave
 
Well said, Dave!

Lesuth, while I drove on the road I got another idea:

If you want and if you don't get confused, you could process the fingers parallel, each batch with 0,1-0,2g gold (like 12 RAM sticks), one in nitric, one in CuCl2, one in FeCl3 and so on.

When you have harvested the foils, you dissolve them together as one batch. For precipitation you can split it up again, one SMB, one FeSO4 and one oxalic.

It is hard to determine how much we can load onto your shoulders. If you feel safe with the basics of each process, this would make a nice show together with Dave's stannous sugestion. But I think it is necessary to have tried this before the presentation.
 
I think I would stay away from oxalic for now since he is new at this and trying to learn so much. It will be better for him to do one thing and do it good than three things and make a mistake somewhere down the process and damage his grade.
 
Some of the processors have aluminum heat sinks attached. This should be removed first either with a screw driver or a sharp knife. Makes no sense adding aluminum to the mix when it can be so easily removed by mechanical means.
 
Thanks a lot everyone. I'll finish up writing the... thing (don't know the term in English) today and next week we'll start the experiments. I'll keep you updated and If I have more questions I'll post here.
EDIT: By the way I'll probably stick to processing the rams with one method so I don't mess things up. I just wanted to know more about the theoretical side of the other methods so I can explain more if I'm asked about alternative methods.
 
Hey guys here is my update.
This week i treated the ram fingers with nitric and dilluted the solution and then filtered it. I put some more nitric to be sure that I got rid of all the base metals. Then I dissolved the gold foils in aqua regia there were some tiny green plastic from the ram fingers in the aqua regia I filtered them from the aqua regia. And the solution was light yellow and very clear.
I need to synthesize H4AuCl4 ( that needs to be the end product, not gold). So my initial plan was to precipitate the gold out of aqua regia and then redissolve it in aqua regia, then get H4AuCl4 by evaporation process. More specifically I'm gonna make anhydrous H4AuCl4 by using ethanol at the last step of the evaporation process.
So my question is how pure the compound would be if I don't precipitate the gold and go straight to getting H4AuCl4. Because there isn't much gold to precipitate.
EDIT will the precipitation be unsuccessful if there is very little gold in the solution.
 
35grams of RAM sticks
1ml of 15M nitric and 3.5ml 12M HCl, nitric is definately in excess, if I'm precipitating the gold I will probably evaporate it.
Hmm maybe i could neutrilize the excess nitric and calculate how much nitric is actually used to dissolve the gold and from there I could calculate the amount of gold. Well too late for that now.
 

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