Cu-Zn-Au alloy separation

[kjavanb123]

All,

I have produced this alloy from smelting gold finger cards, after some reading here, I noticed copper or zinc electrolysis requires 95% plus purity of metals at anode, but my anode is 58% Cu, 38% Zn. I searched for electrolysis of brass on internet and couldnt find any help, also this alloy shows 3200 ppm gold, please advise.

Best regards,
Kj

 

[nickvc]

Kevin by melting the material together you have caused yourself problems. If you could have dissolved the zinc first in hydrochloric acid and then melted the material you could possibly have run the remaining material through a copper cell and collect the values from the slimes, failing that traded the bars through a large copper refiner if you have the volumes needed.

 

[9kuuby9]

The cheap way would be to add copper until it's <95%, But then you will have to deal with the Zinc.

An other way would be to add zinc until it's <95% in Zinc, then get it trough a Zinc Cell.
Collect all the sludge, add copper until it's <95%, remelt and get it trough a Copper sulfate Cell.
This method is far more efficient and cheaper in the long run. Because you fully recover Zn and Cu, But requires more investment in equipment and metals (Cu and Zn). And also don't forget that it's on a much bigger scale than usual.

Then you would be left with PM sludge with some other base metals.

 

[kjavanb123]

Thanks guys, so to recap evereything, I add zinc to the alloy to reach 96% zinc, then from what I read st the following link, use copper sulphate mixed with 60 ml nitric with agitation, he metioned first to remove copper, using cathode sheet, then drop Cu left in electrolysis using zinc powder, then change anode to lead anode, and aluminum cathode with the same electrolysis from the copper refining, at 140 A/sq ft and 4 V, to drop zinc.

Here is the link for an old document regarding electrolysis to separate copper and zinc from brass,
http://digitalcommons.mtech.edu/cgi/viewcontent.cgi?article=1086&context=bach_theses

Best regards,
Kevin

 

[solar_plasma]

Just an idea that maybe could help....

Since you will need ZnSO₄ for the electrolyte, you could dissolve some of your brass, save the gold sediments and cement out any copper with zinc metal. The sulfuric shouln't be more expensive, than buying ZnSO₄ and you have less metal to process in the cells.

 

[butcher]

Kevin,

I have broken down brass as an anode in a copper sulfate cell.
The brass was silver plated, my goal was to try and recover the silver.

The whole experiment was ran for many months, it worked but was found a very expensive, and time consuming way to recover very small amounts of silver.

I tried several electrolytes CuNO3, CuSO4 and others, I found CuSO4 to work the best, as the cell ran I would have to adjust the pH of the electrolyte back towards an acidic electrolyte, as the cell would become more basic after many hours of operation, the copper would not plate out to the cathode worth a darn, would form a copper sludge on the cathode that after building up would fall to the bottom of the cathode of the cell (eventually copper in the electrolyte was replaced by zinc, As zinc would build up in solution, (as zinc in solution also will push copper out of the electrolyte solution)so after many hours I would have to replace the electrolyte with a fresh CuSO4 electrolyte (this CuCO4 saved as a byproduct from a process I use to make nitric acid), Basically what I would have was the anode dissolved, the copper was the majority of the fluffy metal sludgy with some silver powders, most of the zinc stayed in the spent electrolyte (copper was cemented from this waste solution, as part of the treatment process, I had no desire to try and recover Zn).

That part of the process to recover the silver plate was fun watching the electrolysis and always trying to figure out what was going on in solution and when things started to go south trying to figure out what the problems were.

Then I had a fluffy pile of copper sludge with a very tiny amount of silver, I used mostly used copper II chloride solution to convert this copper sludge to CuCL2, leaving AgCl powders, but even using the used solutions for doing most of this work (CuSO4 for electrolyte, and CuCl2 to dissolve copper sludge), I still had to use new acids, keeping pH of the electrolyte healthy, and to regenerate the CuCl formed back to CuCl2 (regenerating the copper II chloride leach), and then acid to wash the silver chloride and reagents to convert the silver.

Basically I learned a lot, after months of working on this project, but it cost me, I paid dearly for that little bit of silver metal, after this experiment was done, I did get some silver but it really cost me a lot, so basically I paid for an education.

I do not see an easy way to do this, and economically recover the gold from your brass. It would be better not to make brass in the first place, Upgrading your material to 95% copper and running a copper cell would be the best option, but cost of fuel, reagents, and time and trouble of running the cell could still prove to be costly for that bit of gold.
Recovery of the zinc I would forget unless you wished to make a zinc sulfate and you had a market for it.

Adding copper in the beginning of your process of the circuit board materials, of the original smelting process, fluxing this original melt to help oxidize the zinc and other base metals to get them into the slag as much as possible (a high oxidizing flux could put some of your copper into this slag) to upgrade the copper content of your Dore bars.

Although you could try run these copper Dore bars yourself to try and recover gold, through electrowinning the copper, I cannot see this as economical, I think it would be difficult, very time consuming, and costly on a small scale, (even costly on a very large industrial scale, a very big learning curve...
Selling the 95% copper Dore bars, to a copper refiner who would pay for your gold although he would take a portion of your gold, you would still most likely come out money and time ahead.

PS. I would probably have fun playing with it as a hobby, and to learn But if I was trying to make money at it I would try to look at it differently.

 

[freechemist]

Hi Kj,

The composition of the alloy, you are working with, is not far away from the one (brass) cited in your old document:

Rolled commercial brass containing sixty-two percent copper, thirty-five percent zinc, and three percent lead was used for making anodes.

In addition it contains 3200 ppm gold (=0.32% gold). That means: 1000 g of your alloy contain 580 g Cu, 380 g Zn, and 3.2 g gold, corresponding to an approximate value of roughly 120 - 150 $. Such an alloy should be easily dissolved completely in HCl/Cl₂, using H₂O₂ or NaClO₃ as the oxidant and excessive HCl as the solvent. In terms of 32% HCl, using 4 moles HCl each per gram-atom of Cu and Zn, this corresponds to a total of 6.6 liters 32% HCl. To these 3.3 liters of water have to be added, in order to minimize losses in gaseous HCl, if mixtures have to be heated.
Dissolved gold, as [AuCl₄]^-, can be absorbed on strongly basic anion-exchange resin (quaternary ammonium type, chloride-form), just by adding the needed quantity of resin-beads to the metal solution and stirring for several hours, or by letting pass the solution through a column, filled with resin-beads. The fully loaden resin can contain 10% and even more of it's dry weight in gold. This absorbed gold can be recovered by completely burning and incinerating the loaden resin.

An appropriate small-scale-experiment could be like this:

- Take 10 grams of your alloy and put it in ca. 70 ml of 32% HCl. Add 35 ml water.
- Stir constantly (magnetic stirring bar) and heat to 70-80^oC. Add dropwise the solution of 7 g NaClO₃ in 25 ml water.
- After complete addition, continue stirring and heat to boiling, until no more Cl₂ escapes. Let cool down and filter, if necessary.
- Test the clear solution with SnCl₂. Gold should be detectable.
- Add 1 gram of strongly basic anion-exchange-resin-beads, previously washed with several small portions of 1 M HCl and stir for several hours. Test from time to time with SnCl₂.
- As soon, as no more dissolved gold is detectable, filter the loaden resin-beads into an ashless filter, wash with water, dry and incinerate completely.
- A residue of ca. 30 mg metallic gold (as a small sponge) should be obtained.

 

[niteliteone]

This material seems to resemble (sound like) the "Gold Drops" they sell on ebay, when they melt gold plated pins.
How much tin from the solder ended up in the dore drops :?:

 

[kjavanb123]

This material seems to resemble (sound like) the "Gold Drops" they sell on ebay, when they melt gold plated pins.
How much tin from the solder ended up in the dore drops :?:

Hi,

For assay report for the alloy please follow the following link,

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=33&t=19447

Best regards,
Kevin

 

[kjavanb123]

Hi Kj,

The composition of the alloy, you are working with, is not far away from the one (brass) cited in your old document:

Rolled commercial brass containing sixty-two percent copper, thirty-five percent zinc, and three percent lead was used for making anodes.

In addition it contains 3200 ppm gold (=0.32% gold). That means: 1000 g of your alloy contain 580 g Cu, 380 g Zn, and 3.2 g gold, corresponding to an approximate value of roughly 120 - 150 $. Such an alloy should be easily dissolved completely in HCl/Cl₂, using H₂O₂ or NaClO₃ as the oxidant and excessive HCl as the solvent. In terms of 32% HCl, using 4 moles HCl each per gram-atom of Cu and Zn, this corresponds to a total of 6.6 liters 32% HCl. To these 3.3 liters of water have to be added, in order to minimize losses in gaseous HCl, if mixtures have to be heated.
Dissolved gold, as [AuCl₄]^-, can be absorbed on strongly basic anion-exchange resin (quaternary ammonium type, chloride-form), just by adding the needed quantity of resin-beads to the metal solution and stirring for several hours, or by letting pass the solution through a column, filled with resin-beads. The fully loaden resin can contain 10% and even more of it's dry weight in gold. This absorbed gold can be recovered by completely burning and incinerating the loaden resin.

An appropriate small-scale-experiment could be like this:

- Take 10 grams of your alloy and put it in ca. 70 ml of 32% HCl. Add 35 ml water.
- Stir constantly (magnetic stirring bar) and heat to 70-80^oC. Add dropwise the solution of 7 g NaClO₃ in 25 ml water.
- After complete addition, continue stirring and heat to boiling, until no more Cl₂ escapes. Let cool down and filter, if necessary.
- Test the clear solution with SnCl₂. Gold should be detectable.
- Add 1 gram of strongly basic anion-exchange-resin-beads, previously washed with several small portions of 1 M HCl and stir for several hours. Test from time to time with SnCl₂.
- As soon, as no more dissolved gold is detectable, filter the loaden resin-beads into an ashless filter, wash with water, dry and incinerate completely.
- A residue of ca. 30 mg metallic gold (as a small sponge) should be obtained.

Freechemist,

Thanks for your info, please kindly elaborate on resin-beads, what are they?

Best regards,
Kevin

 

[freechemist]

Hi Kevin,

Here some probably useful links.

The first one, http://www.lenntech.com/Data-sheets/Ion-Exchange-for-Dummies-RH.pdf leads to a general introduction about composition, functioning, chemistry of different types of cation- and anion-exchange resins. Emphasis is mainly on water purification, deionization and separation of impurities from diverse process streams. If one regards anionic complex anions of precious metals as impurities, dissolved in fairly concentrated aqueous HCl, containing in addition significant concentrations of base metal cations, these resins can well be used, to absorb selectively certain dissolved PMs as anionic chloro complexes, liberating equivalent amounts of absorbed chloride ions into solution. These PM-chloro-anions are: [AuCl₄]^-, [PtCl₆]^2-, [IrCl₆]^2-, [PdCl₆]^2- and [PdCl₄]^2-.
The following links lead to data sheets for such resins.

Amberlite IRA402 Cl: http://www.lenntech.com/Data-sheets/Amberlite-IRA-402-Cl-L.pdf
Amberlite IRA410 Cl: http://www.lenntech.com/Data-sheets/Amberlite-IRA-410-Cl-L.pdf
Amberlite IRA900 Cl: http://www.lenntech.com/Data-sheets/Amberlite-IRA-900-Cl-L.pdf
Amberlite IRA910 Cl: http://www.lenntech.com/Data-sheets/Amberlite-IRA-910-Cl-L.pdf

The last link leads to Sigma Aldrich who sells these resins in lab quantities, included the one, Amberlite IRA-400 Cl, which I used in my first PM-recovery/refining experiments in an industrial lab. http://www.sigmaaldrich.com/catalog/product/aldrich/247669?lang=en&region=



Kind regards, freechemist

 

[kjavanb123]

Freechemist,

Thanks a lot for your detailed explaination on the sibject. I am just curios is this method feasible for lab scale operation or could it be used for more commercial operations?

Thanks and regards,
Kevin

 

[MarcoP]

If the resin beads can hold 10%, or more, of its own weight in gold means that 100g of beads should hold at least 10g of gold. Can those be partially used, stored and reused again till fully loaded? If used beads can be stored, is a good water rinse all they need before storage?

Marco