Use of Tungsten as Anode in Electrolytic Cell

[pwm97128]

What are the limitations or downsides of using tungsten as an anode for electrowinning copper from precious metals waste solution.

There are cheap salvaged solid tungsten high voltage light electrodes available online. My uneducated research indicates that tungsten is little affected by HCl, H2SO4 or HNO3. My hope is that tungsten will be cheaper than Platinum and just as durable.

 

[Lino1406]

What are the limitations or downsides of using tungsten as an anode for electrowinning copper from precious metals waste solution.

There are cheap salvaged solid tungsten high voltage light electrodes available online. My uneducated research indicates that tungsten is little affected by HCl, H2SO4 or HNO3. My hope is that tungsten will be cheaper than Platinum and just as durable.

As tungsten will produce anodic film, it is assumed that voltage will need to be higher even if it permits electron conduction, and harder to control than with other metal, e.g. lead

 

[Lou]

It won't work very well.

It will end up forming yellow WO3 and just slough off in the cell

 

[pwm97128]

Thank you.
Many hours of work and frustration now avoided.

 

[Ultrax]

Tungsten readily oxidizes in the presence of OH(-) to WO3, but as I remember in alkaline solutions.

 

[Lino1406]

Tungsten readily oxidizes in the presence of OH(-) to WO3, but as I remember in alkaline solutions.

The same will occur with H2O, only at higher potential.

 

[Ultrax]

Found in my notes from [G. S. Kelsey, J. Electrochem. Soc. 124, 814 (1977)]:
Tungsten electrodissolution rate is under diffusion control by OH–ions, while limiting current densities of tungsten dissolution at high anodic potentials are proportional to the concentration of OH (-) in the solution independently on the presence of supporting electrolyte.

 

[Lino1406]

Found in my notes from [G. S. Kelsey, J. Electrochem. Soc. 124, 814 (1977)]:
Tungsten electrodissolution rate is under diffusion control by OH–ions, while limiting current densities of tungsten dissolution at high anodic potentials are proportional to the concentration of OH (-) in the solution independently on the presence of supporting electrolyte.

What standard redox table gives:
W + 3H2O = WO3 + 6H+ + 6e- at 0.0v
For acidic solution. So probably WO3 may stay as such

 

[D-dog]

I don't mean to high jack this thread. But can I use titanium as an anode?
I have a couple pieces of 1/4" tubing from when I was a machinist, making parts for chemical etching machines.

 

[Ultrax]

But can I use titanium as an anode?

Yes. In some cases. With potential between 5v and 10v.
Please, describe your goal. Do you want to use titanium anode for yielding what?

 

[olawlor]

I don't mean to high jack this thread. But can I use titanium as an anode?
I have a couple pieces of 1/4" tubing from when I was a machinist, making parts for chemical etching machines.

This did not work for me--the current through a plain titanium anode drops below milliamps in just a few seconds. Titanium grows a clear but insulating TiO2 layer in any oxidizing solution I've tried. (Anodized titanium's neat interference colors are directly related to the voltage used, and very stable and pretty though!)

Titanium is used as a substrate for other more conductive anode materials like platinum, perovskites, or lead dioxide precisely because it will passivate if the coating flakes off.

Folks looking for home anodes should try graphite: the 1/4" graphite rods in C, D, or 6V alkaline batteries work well as an anode for many weeks at a reasonable voltage, and slowly generate graphene oxide.

 

[D-dog]

This did not work for me--the current through a plain titanium anode drops below milliamps in just a few seconds. Titanium grows a clear but insulating TiO2 layer in any oxidizing solution I've tried. (Anodized titanium's neat interference colors are directly related to the voltage used, and very stable and pretty though!)

Titanium is used as a substrate for other more conductive anode materials like platinum, perovskites, or lead dioxide precisely because it will passivate if the coating flakes off.

Folks looking for home anodes should try graphite: the 1/4" graphite rods in C, D, or 6V alkaline batteries work well as an anode for many weeks at a reasonable voltage, and slowly generate graphene oxide.

Thanks much for the info.
I was wondering about the carbon battery electrodes too.
I understand that they make good electrodes for arc furnaces as well.

 

[D-dog]

Please, describe your goal.

In a silver cell to start with. To grow large silver crystals. I was thinking between 3 and 5 volts to start and change voltage to see what creates the biggest crystals.

 

[Lou]

This is why mixed metal oxide anodes were invented. Or platinum can be used as an anode.

 

[Ultrax]

Or a platinized titanium electrode. Not much worse, but much cheaper than pure platinum.
You can easily make your own from any platinum scrap.

 

[Lou]

Yes, he could make P salt from K2PtCl6 reduced to K2PtCl4 and then onward with nitrite and ammonia...

 

[D-dog]

Yes, he could make P salt from K2PtCl6 ---

Thanks much for the information everyone.
I'm not sure exactly how to do that. But I will endeavor to find out.
All of you are fantastic people to be willing to share your knowledge with the rest of us!
Thank you all again!

 

[ChopperGreg]

...snip

Folks looking for home anodes should try graphite: the 1/4" graphite rods in C, D, or 6V alkaline batteries work well as an anode for many weeks at a reasonable voltage, and slowly generate graphene oxide.

It is probably dependent, on the source of carbon rod, but I’ve seen some cases where the carbon rods used as electrodes start to erode as carbon sloughs into the working solution leaving you with a situation where you are left with bits of carbon floating around in it, needing to be filtered out.

 

[Nountaineer]

Is there any issues with using tig tungsten anode rods?

 

[Yggdrasil]

Is there any issues with using tig tungsten anode rods?

The same as noted above with forming WO₃, and of course the very small area of the 3.2 mm rods