Electrochemistry Gold fizzer cell experiments

[bogarasjoe]

Dear All!

First of all, i would like to thank you all for the so nice instructions and guidelines, especially for Lazarsteve, GoldSilverPRO, Lou, Palladium, and everybody.
A few words about myself.... I am David, a hungarian PhD student. I finished my chemistry MsC in 2015. I am a synthetic chemist, I work on preparing new metal-organic framework structures. I also love organic chemistry, especially chiral compounds and highly strained compounds (for eg. cubane derivatives). And of course I love gold and gold refining so much. I started gold refining about 4 years ago from ceramic CPUs and E-scrap.
Until nowadays gold refining was just a hobby for me. But a few months ago, a hungarian jewelry factory conctacted me, to improve their gold refining technics. Unbelievable, but true! Of course, I kindly accepted their request.
I never did electrochemistry, I was a little bit afraid of it because I am an "organic chemist". But I found many brilliant patents, and descriptions wiith membrane electrolysis cells, and I became so interested in fizzer cell, Shor cell, etc... HCl (+peroxide) fizzer cell seemed to be reliable, effective, cheap and not so enviromental polluting method, so I started to do a lot of experiments.
Getting porous 0.5 microns (or less) porcelain cup is nearly impossible here in Hungary. Finally I found, that water purifying ceramic cartridges are so easy and cheap to get. Like this one here: http://aquafilter.com/en/product/2/4/fccer. It 's an aluminosilicate ceramic tube with 0.3 microns pore size and it costs about 10 Euros.. Unfortunately, it's a tube, not a cup, so I had to seal up to have a cup. I sealed it by polypropylene welding (welding a PP plate to the PP end cup). I stripped 10.27 grams of 0.8985 gold in about 20 minutes in my fizzer cell. I filtered the silver chloride and precipitated gold by adding SMB. We filtered the fine gold by vacue filtration, washed with water. Gold was smelted (with filter paper together). We got 8.23 grams of gold. Some gold was plated to the graphite anode . Fire assay gave 0.989 purity of gold. XRF results: Au 983; Ag 8.3; Fe 6.5 (!); Cu 2.4; and Pd 1.1.
So I have a lot of questions. First, why was some gold plated to graphite? Maybe the poor sealing of the ceramic tube? Or can too high Amperage result in passing gold trough the membrane?
The other… purity. According my current knowledge, SMB drops gold, silver, and Pd. But there are iron and copper. Is it the result of poor washing? Next time i would wash with a lot of water, ammonia and water again.
But silver cause problems. What about using an anion exchange membrane? You covered this idea in an other topic: http://www.goldrefiningforum.com/phpBB3/viewtopic.php?f=86&t=19258&p=198274&hilit=anion+membrane#p198274. So anionic gold complex would pass trough and plate to the catode, leaving the cationic metals in the anode part. No SMB need. But also copper, Pd could form (anionic) chloro complexes, right? Did anybody try fizzer cell experiments with anex membrane? GoldSilverPrO, I think you can help me. I see you did a lot of interesting membrane experiments…
An other idea. What about adding a little bit EDTA before dropping with SMB? Would it catch silver?
I would reach somehow 999 purity or better. I know, organic extraction can be an option. Ethyl acetate extraction seems to be reliable.
I also have a new plexy adapter (with silicon rubber sealings) for disposable 47 mm PTFE filter device, so next week I will try with 0.5 microns PTFE membrane.

Regards,
David

 

[Palladium]

Skip the ammonia and just wash with water and cold hcl twice.

 

[Palladium]

More information would help.
What is your voltage and amperage?
What is your salt concentration?
How are you attaching your anode bar to your wire?
How much do you need to process at one time?
Is your raw source of gold just jewelry?

 

[g_axelsson]

Instead of inventing a new method, why not having a detailed discussion about their current setup. Maybe we can find some things to improve on their current setup.

What exactly is their problem with the current setup?
What volumes do they refine? Source of the material, only in-house or scrap from external sources?
Is it only gold or do they run any other precious metals?

I don't think there are many members that run fizzer cells among our members and I can't recall anyone using one to refine a lot of gold. Will the membrane hold up over time or will it clog? How large lots can you run? Will some gold be lost due to absorption in the membrane?
There are a lot of unanswered questions and there isn't a lot of experience here(, at least not shared).

Göran

 

[bogarasjoe]

More information would help.
What is your voltage and amperage?
What is your salt concentration?
How are you attaching your anode bar to your wire?
How much do you need to process at one time?
Is your raw source of gold just jewelry?

Thank you for your fast replies. I also thought on washing with HCl. I know that ammonia can cause fatal accidents.
So I used a 100 mm x 10 mm x 1 mm "rolled" anode. So the surface was about 20 cm^2. Fire assay gave 0.8985 purity of this starting material.
The electrolyte was 10 % HCl solution (with catalytic amount of peroxide)
Voltage was 12 Volts, and (maximal) current was 8 Amperes. Maybe I applied too much current (to do fast) and that's why the gold plated on to cathode?
The anode was attached by crocodile clip simply, of course avoiding to contact the clip with the electrolyte.
The raw source is just from jewerly. It was "pre purified" with an other method to 0.8985. This method is also an electrolytic method, that dissolves base metals and leave gold.
The goal is processing kg-s of gold at one time. It was just a smaller scale "starting experiment" .

Regards,
David

 

[bogarasjoe]

Instead of inventing a new method, why not having a detailed discussion about their current setup. Maybe we can find some things to improve on their current setup.

What exactly is their problem with the current setup?
What volumes do they refine? Source of the material, only in-house or scrap from external sources?
Is it only gold or do they run any other precious metals?

I don't think there are many members that run fizzer cells among our members and I can't recall anyone using one to refine a lot of gold. Will the membrane hold up over time or will it clog? How large lots can you run? Will some gold be lost due to absorption in the membrane?
There are a lot of unanswered questions and there isn't a lot of experience here(, at least not shared).

Göran

Dear Göran!

Thank you for your kindly reply.
The current setup electrolyses out of base metals, leaving the gold in an anode bag. I really don't think, that we could reach the gold purity of 999 or better by this "weak electrolyte" system. So that's why I am trying to introduce other methods.
It is of course silver too, that we would like to also refine. And as final XRF result gave, it was a little palladium in it. I wondered that Pd also get in to solution by fizzer cell method (the Shor patent claimed that platinum metals left untouched by HCl electrolyte, but it seems to be not true for Pd). At this moment, the company deals only with Au and Ag refining, but I am planning to introduce platinum metals refining of course.
Maybe I would try NH4Cl electrolyte to do it. But I am not sure, that ammonium electrolyte is so safely... What about fulminating gold in the ammonium chloride electrolytic process (Shor's method)? Maybe the ammonium chloride process will be the last method I try...
The goal is processing kg's of gold a time. And yes, there are many good questions about membrane gold absorption, lifetime of membrane etc...

Regards,
David

 

[Palladium]

Explain your first process a little more please. What form is the gold in after the first process before your trying to clean it up?

 

[bogarasjoe]

Explain your first process a little more please. What form is the gold in after the first process before your trying to clean it up?

Dear Palladium!

I sent you a private message. Base metals were electrolysed out by a "weaker" electrolyte, leaving gold as anodic slay. Afterwards this gold was smelt and rolled to have an anode.

David

 

[bogarasjoe]

So the current method is so similar to the "weaker electrolyte" formula (HCl without peroxide) of Shor, that dissolves base metals, but leaves gold untouched. I am so sorry, but I am not allowed to write the formula down here, because it is a "top secret of the company". Also this current method gives an unpure gold. I don't think we could get 999 or purer gold by electrolysing base metals of from gold. So that's why I improve some new.

 

[nickvc]

If your clients are manufacturing jewellery the silver will matter little so long as they know the gold assay and silver assay as most alloys have some silver in them, it’s easy to over think some things, the main point to be aware of is to rid the final product of troublesome elements such as lead.

 

[Palladium]

Shore is nacl + h202 and not hcl. Basically the same as far as we need the cl ion for the work.
With hcl you are producing the chlorine you need at the anode and hydrogen at the cathode.
You have to use a concentrated solution of nacl. A concentrated solution will produce cl gas at the anode and will put your gold into solution. A weak solution of salt will make your gold anode into a hydrogen generator with the anode producing oxygen and the cathode producing hydrogen. A Small amount of liquid h2o2 is added at the beginning to overcome the voltage potential and kick it off.

 

[Palladium]

The shore design is based on the chloralkali process.
https://www.youtube.com/watch?v=1FDzt5VP50c&index=8&list=FL7MJW65g2CFT9wr0eUx4msg

 

[bogarasjoe]

Thanks all of your replies. Nick, I can agree with you, silver doesn't cause troubles in jewel, and we should get rid some troublesome metals, like Fe (that is actually present here), lead and tin. But we would like to refine gold to 999 somehow...
Palladium, thanks for the so useful replies so much. I know the chloro alcaline process, NaOCl also form when chlorine meets caustic solution. Also in larger batches, chlorine should scrubbed to NaOH solution.
Shor have a lot of lot of patents. I mentioned this patent of Shor: https://docs.google.com/viewer?url=patentimages.storage.googleapis.com/pdfs/US4612093.pdf
It claims, that also HCl, NaCl, and the mixture of NaCl and HCl works well (with catalytic amount of peroxide). In the electrolysis of NaCl, chlorine and caustic soda produced as you mentioned. I used a ceramic membrane. NaOH can damage ceramics, that's why I used HCl. But with my new nice PTFE filter adapter I can and I will use NaCl. How concentrated should the NaCl electrolyte be? Over saturated solution at higher temperatue?
I also thought over, that some contaminants could come from the graphite crucible while smelting... So the powder could be purer before smelting....
Regards,

David

 

[bogarasjoe]

This is the "weaker formula" I mentioned: https://www.google.com/patents/US4895626. It uses NH4Cl without peroxide. It dissolves base metals and leaves gold as anodic slay. Shor simplicity system uses a mixture of NH4Cl, NaCl and catalytic amount of peroxide, it dissolves gold and base metals too. This one: https://www.google.com/patents/US5009755
I also mention, that I dislike the idea of using ammonium compounds in the presence of gold...

 

[nickvc]

If you want or need better purity then simply take your recovered powders and refine in solvent of your choice.
There are plenty to choose from all detailed here on the forum, your process so far is a good recovery but not a refining process, whichever way you decide to go will involve more toxic chemicals, gold will not dissolve in harmless chemicals.

 

[bogarasjoe]

Yes absolutely right, that gold wouldn't dissolve in harmless chemicals. AR, chlorine (it's produced by chloride electrolysis like in this case, or int the HCl-bleach method) and all these chemicals are toxic...
Maybe more carefully washing, or solvent extraction (BDG, ethyl acetate) could help to get purer gold...

 

[bogarasjoe]

I think, this method gives a solution nearly equal to AR method... So I have a gold III chloride solution with some base metals. Gold selectively dropped out by precipitant like SMB.
Maybe two runs with fizzer cell can also improve purity...

 

[FrugalRefiner]

I think, this method gives a solution nearly equal to AR method... So I have a gold III chloride solution with some base metals. Gold selectively dropped out by precipitant like SMB.
Maybe two runs with fizzer cell can also improve purity...

Loewen discusses using a fizzer cell as an alternative to AR. It eliminates the need for nitric acid, and so eliminates NO_x fumes. You have some acid spray from the fizzing at the cathode, and you have hydrogen gas to vent. It's an idea that has interested me since I read about it, so I'm interested in your progress.

I'd lean towards one fizzer cell run, redissolve with HCl and H₂O₂, and drop with a different precipitant. It saves all the remelting into anodes and dealing with stub ends.

Dave

 

[bogarasjoe]

Thanks Dave so much!

I also find this method so interesting and useful. I think it's not so bad for a first experiment, to get 989 gold with a really poor washing. I hope we would reach bettter purity with more intensive washing and using new, unused graphite crucible for smelting.
It's a really cheap and easy method, and I can say it is so fast. No NOx fumes and no nitric need. Of course, we need current... But in the case of AR method, we also need some energy to heat the solutions (at least at the evaporating stage of nitric before precipitation)...
Of course I would share my results, we help each other!
With my new PTFE membrane adapter, I would try to do it with NaCl electrolyte, eliminating the acidic spray and reducing the costs of disposal.
So nice idea to refine it further with AP saving the cost of another melting of gold anode, thanks so much.
And last but not least, this method seems to be excellent for saving silver (in the form of AgCl) for further refining.

Regards,
David

 

[rickzeien]

Thanks Dave so much!

I also find this method so interesting and useful. I think it's not so bad for a first experiment, to get 989 gold with a really poor washing. I hope we would reach bettter purity with more intensive washing and using new, unused graphite crucible for smelting.
It's a really cheap and easy method, and I can say it is so fast. No NOx fumes and no nitric need. Of course, we need current... But in the case of AR method, we also need some energy to heat the solutions (at least at the evaporating stage of nitric before precipitation)...
Of course I would share my results, we help each other!
With my new PTFE membrane adapter, I would try to do it with NaCl electrolyte, eliminating the acidic spray and reducing the costs of disposal.
So nice idea to refine it further with AP saving the cost of another melting of gold anode, thanks so much.
And last but not least, this method seems to be excellent for saving silver (in the form of AgCl) for further refining.

Regards,
David

Bumo

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Sorry. Just trying to be notified of new post. Thanks for letting me look over your shoulders.

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