Waste treatement electrolysis

[Swissgoldrefiner]

Hello
I tryed to treat some copper nitrate mixed wast with electrolysis.
In theory, the copper and other metal should go to cathode and i will stay with nitric solution.
No way...it dosent work. Nothing apear in cathode.
I use titanium anode and cathode. The current is very low. So, i tryed to add some sulfuric acid. It get higher current.
But even at 12V, i dont have anything on cathode.
There is some Chlorine, as when i add AgNO3, i see some cloudy AgCl.

What's the explaination?

 

[Yggdrasil]

Hello
I tryed to treat some copper nitrate mixed wast with electrolysis.
In theory, the copper and other metal should go to cathode and i will stay with nitric solution.
No way...it dosent work. Nothing apear in cathode.
I use titanium anode and cathode. The current is very low. So, i tryed to add some sulfuric acid. It get higher current.
But even at 12V, i dont have anything on cathode.
There is some Chlorine, as when i add AgNO3, i see some cloudy AgCl.

What's the explaination?

Of course when you add AgNO₃ to chlorinated liquids AgCl will form.
As to the reason why the waste metal do not deposit, I'm not sure.
It may have to do with some kind of passivization or surface area vs Voltage.

 

[Swissgoldrefiner]

Of course when you add AgNO₃ to chlorinated liquids AgCl will form.
As to the reason why the waste metal do not deposit, I'm not sure.
It may have to do with some kind of passivization or surface area vs Voltage.

Maybe there is some passivation, but dont think...I will try with graphite and silver as anode.

 

[nickvc]

I’m not sure it will work at all as when you run a refining cell the anode is made of the metal you wish to deposit on the cathode , the metal ions in solution move to the cathode as the metal at the anode goes into solution.
I will admit I’m not sure of my thoughts but to me it makes sense.

 

[Shark]

Just rambling thoughts here but….

At times when running plating cells if the parameters are off the solution starts to loose the metals to the part being plated. Leaving a diluted solution. Too much or not enough voltage or amps. Wrong size anode or cathode. Distance between the anode and cathode.

 

[Martijn]

Maybe there is some passivation, but dont think...I will try with graphite and silver as anode.

This might be an interesting thread for you.
In it he says:

I processed the sterling bar using electricity (12V 10A battery charger) and and electrolyte of left over copper nitrate from previous inquartations and cementing reactions(see on my website).

Thread 'Processing Sterling Silver without nitric acid' Processing Sterling Silver without nitric acid

 

[Swissgoldrefiner]

I’m not sure it will work at all as when you run a refining cell the anode is made of the metal you wish to deposit on the cathode , the metal ions in solution move to the cathode as the metal at the anode goes into solution.
I will admit I’m not sure of my thoughts but to me it makes sense.

It should work. As in the solution i have already metal in form of ion.

 

[Swissgoldrefiner]

So, i change the anode. As Yggdrasil suggest and as it was what i suspect, titanium make some passivation.
I had an old graphite crusible and i use it as anode. As you can see in the picture, it start to deposit copper.
However, it s too slow and there is some thing strange. The amp is around 3.5 [A] and voltage around 4.0 [V].

My calculs: 3.5 amps is 3.5*6.28*10^18*3.6*10^3 = 7.91 *10^21 electron in 1 houer.
We need 2 electron to change Cu++ to Cu°. So we need 1.2*10^24 electron to get 63.5 gram of Copper.
Which means i need 15 houer to get 63.5 gram of copper.
In practive i may have 10 gram after 24hour. So, the explainations should be:

- Off curse, maybe some electron react with other element. For example it react with Cl- to give Cl°.
- The voltage is maybe too high and it mainly electrolyse water.
- There is another effect, that i dont know, which avoide the deposition of Cu.

I will try to decrease the voltage and maybe change the anode to a platinum one.

 

[nickvc]

If it’s a nitrate solution you could try stainless steel as the anode and I believe there are calculations to determine the anode to cathode size for optimizing the process which unfortunately I do not know but I’m sure someone will.

 

[BGDOCK]

Hello
I tryed to treat some copper nitrate mixed wast with electrolysis.
In theory, the copper and other metal should go to cathode and i will stay with nitric solution.
No way...it dosent work. Nothing apear in cathode.
I use titanium anode and cathode. The current is very low. So, i tryed to add some sulfuric acid. It get higher current.
But even at 12V, i dont have anything on cathode.
There is some Chlorine, as when i add AgNO3, i see some cloudy AgCl.

What's the explaination?

Did you evaporate the copper nitrate solution to reduce the volume ?
Six moles of CuHNO3 / 1.7-1.9 Specific gravity
Graphite Anode / stainless steel Cathode
The copper should start plating on the cathode ,

 

[Swissgoldrefiner]

If it’s a nitrate solution you could try stainless steel as the anode and I believe there are calculations to determine the anode to cathode size for optimizing the process which unfortunately I do not know but I’m sure someone will.

I will try stainless...but it's mixed with HCl...so it will probably react...I may try with silver, but i am curious to see what happen. As there will be AgCl formation.
This morning all the anode broken/dissolved. As the graphit break.

 

[Swissgoldrefiner]

Did you evaporate the copper nitrate solution to reduce the volume ?
Six moles of CuHNO3 / 1.7-1.9 Specific gravity
Graphite Anode / stainless steel Cathode
The copper should start plating on the cathode ,

Dont want evaporate it. I want a way to make it easier than cimentation with Iron or using hydroxide way.

 

[BGDOCK]

Sounds like you got it

 

[Swissgoldrefiner]

So, I tryed another setup and it looks very nice.
I used as anode platinum 999.5 ingot and as cathode titanium grade 2.
Voltage = 6.1 [V] and Current = 2.3 [A]. The solution that i use was blue, same as befor, and i let the setup overnight.
In the morning the solution become clear! All metal gone to cathode.
pH = 2. I will try to see if there is any chlorine left with adding some AgNO3. So, it must be mainly nitric acid.

Few pictures are better than 100 words.

 

[BGDOCK]

Looks like it removed the copper that’s a better setup than my copper wire mesh cathode / found stainless steel anode good job seriously

 

[snoman701]

Have an analytical balance? Is your Pt losing mass?

 

[Swissgoldrefiner]

Have an analytical balance? Is your Pt losing mass?

Pt dont loose any mg...it was shiny ingot befor and after the process.

 

[4metals]

So to summarize you had a copper nitrate solution remaining from cementing out spent silver nitrate electrolyte and you used a pure Platinum anode and a titanium cathode. Do
You know the areas of the anode and cathode so we can work out a current density? I wonder if this will work with a platinized titanium anode?

 

[4metals]

The Platinum bar is about 1.5" x 1" and since only 1 side faces the cathode that makes the amperage you used about 220 Amps/sq ft.
That is a lot of power.

 

[Swissgoldrefiner]

So to summarize you had a copper nitrate solution remaining from cementing out spent silver nitrate electrolyte and you used a pure Platinum anode and a titanium cathode. Do
You know the areas of the anode and cathode so we can work out a current density? I wonder if this will work with a platinized titanium anode?

I have wast, which comes from processing gold, silver, etc... which should contain Cu, HNO3, HCl and other metals and probably some Au, Pd, Pt.
Usually i was using cimentation or hydroxide way. But, it take too long and need to pass it trought filter press.

The area is even smaller than what you suggest. As i didnt introduce whole platinum ingot. Let's say it was around 1cm inside the solution. I agree that the current density should be very high. Actually the water was warming. I think it should work with platinazed titanium. I think best would be to use Ir plated one.

What i would like to try as well to see if there is anything left in my copper. I may melt the copper and electrolyse with sulfuric/CuSO4.
But first i want scale up the process.