Electrolytic de-plating of silver in sulfuric acid

[kaisernine]

Interesting, I never heard abot this. Wonderful information. This will take a long time to discover I planned to try some other electrolytes, but never even thought about sulfite

Do you use some arbitrary concentration of sulfite, or there is some "sweet spot" ?
And second question - does it produce some smelly sulfur compounds like SO2 or sulfane gas ?

Thank you guys for very useful information

I have never really tried to smell it, but I have never noticed anything, I'd still use a well ventilated area just due to possible hydrogen/oxygen gas build up. Anytime I use electrolysis I assume some gas is coming off of the anode/cathode.

Again I think Snail mentioned this many years ago now scrolling back through the forum and I believe a few members did videos on this as well owl tech I believe. Maybe someone can post a link if they know where it is to give credit where it is due.

Our shop used it as we got thousands of pounds of silver plated busbars from obsolete power equipment so we set up a tank to deplate this as we got the same scrap price stripped or not, think we ended up with around 30 pounds of silver in the end which was a lot of money we were giving away before we started...

Also if my mind serves me right I think snail is the one who picked up our left over chemicals when the shop took a different direction from plating and etching to machining .

 

[BGDOCK]

I have been using sulfuric aid and potassium nitrate and micro doses of nitric acid to go after silver plated items .
Five days in .
I used a spoon that was silver over iron as a test and it removed and cemented out the silver . I also have a question about this method .
The reaction had stopped and I pulled out the silver plated items to check how much was removed (80%}
I had allowed the silver sulphate to settle and then decanted off the liquid and added it to some of my rinse water and Then i had the red fumes ( nitrogen dioxide )
Does the water donate +H ions to reactive the nitric acid ? Why did the nitric acid reaction start again ?
I put the silver plated items back in to use up the acid and remove the rest of the silver and plan to use iron and weak sulfuric acid to convert the silver sulphide .
I find this method “ tricky” Im on the fence about using it .I had used KNO3 as an electrolyte And it worked ok but was really time consuming .

 

[orvi]

I have been using sulfuric aid and potassium nitrate and micro doses of nitric acid to go after silver plated items .
Five days in .
I used a spoon that was silver over iron as a test and it removed and cemented out the silver . I also have a question about this method .
The reaction had stopped and I pulled out the silver plated items to check how much was removed (80%}
I had allowed the silver sulphate to settle and then decanted off the liquid and added it to some of my rinse water and Then i had the red fumes ( nitrogen dioxide )
Does the water donate +H ions to reactive the nitric acid ? Why did the nitric acid reaction start again ?
I put the silver plated items back in to use up the acid and remove the rest of the silver and plan to use iron and weak sulfuric acid to convert the silver sulphide .
I find this method “ tricky” Im on the fence about using it .I had used KNO3 as an electrolyte And it worked ok but was really time consuming .

I am OK with sulfuric/nitrate or sulfuric/nitric method, not that bad if the acid is concentrated - copper is nicely stripped, however, you need to heat it to like 60 °C or more to get an OK reaction rate.

It also works with plain concentrated sulfuric acid, however, you need to heat concentrated sulfuric really hot... And that is obviously not very nice to do However, selectivity of this approach with copper base metal is very good.

 

[kurtak]

So far I have never found a solution that works better than sodium sulfite, unless you want the sulfuric/nitric strip for speed but it has a lot of hazards using and recovering from solution.

Sodium sulfite with a voltage lower than 1.8v is extremely selective, xrf tested every silver button at 95% or higher and that contamination was probably due to using my crucible I use for sterling melts.

Only downside to sodium sulfite it takes a several hours and it converts to sodium sulfate over time with oxygen present however you can use the solution for several days before it does this so if you prepared your silver items you can use it before it "spoils" if you want to call it that.

What are you using for your cathode - SS I "assume" ?

Kurt

 

[kaisernine]

What are you using for your cathode - SS I "assume" ?

Kurt

We have used other metals but generally stainless steel yes, cheap and readily available even if it were to get attacked.

Generally I think we used it in the case we wanted to acid wash it and remove any silver from it that was stuck to it, but don’t think we ever did as the majority sponges and falls off, wasn't enough left worth the acids.

 

[scrappyjoe]

Hello All.

Very interesting . i have been hoping to find something relatively safer , easy and cost effective. Hope to try it out on the weekend if i can procure some Sodium Sulfite. Seems a little hard to find and somewhat expensive. So . Here they come...

Where is a good source to purchase it ? is it available disguised as a different use product (along the lines of StumpOut, or various drain cleaners, etc)?

20 to 80 grams per liter ? thats a pretty big spread .... 50 liters of solution compared to 12.5 liters per Kg of powder. is there a " sweet spot" in anybody's experience that balances time/cost /efficiency/ etc ?

Same question relates to voltage as well. 1.8 volts was mentioned. Does a higher voltage increase speed at the cost of more impurities in the deposit on the cathode ? Does amperage play a role?

The cathode. What other metals could be used and are there any advantages? If not then stainless it is. 304 ? 316 ? any difference in performance?
Would there be an optimal ratio for surface area of cathode vs anode ? I realize the silver amounts to a small percentage of the plated pieces but my thinking is that you would want to keep replacing the anode pieces as they get stripped to best utilize your solution before it is "spent". Would you keep replacing or cleaning off the anode after each piece?

As your solution is deteriorating is it a steep decline in performance? Does the presence of the sulfates hinder the process or could you just keep adding sulfites until you reach some saturation limit in the solution? How do you know when it is spent ? Does the process just gring to a halt?
I am assuming the transition of the solution is caused by atmospheric oxygen binding to the sulfite. As most people use plastic totes nowadays for these processes , would putting its lid on and running it semi sealed not slow that process ? Perhaps with an airlock bubbler like they use for alchohol fermentations? Does this system produce hydrogen in amounts that could cause any risk ?

I know there is a lot to be learned from trial and error , and i am sure i will, but if others have succeeded before you , ti doesn't hurt to ask and save time , money, and grief.

Thank you in advance of any replies

 

[BGDOCK]

I am OK with sulfuric/nitrate or sulfuric/nitric method, not that bad if the acid is concentrated - copper is nicely stripped, however, you need to heat it to like 60 °C or more to get an OK reaction rate.

It also works with plain concentrated sulfuric acid, however, you need to heat concentrated sulfuric really hot... And that is obviously not very nice to do However, selectivity of this approach with copper base metal is very good.

Recovered close to 16 grams from 21 spoons , not a bad experiment .
Really need to get better at weighing item before and after.
Converted the silver using HCl and Al2
Didn’t boil the the powder in HCl to get rid of the Al . Lesson learned used three pinches of borax to get rid of the impurities silver shot looks ok . Food for the silver cell .

 

[anarxi]

Hello All.

Very interesting . i have been hoping to find something relatively safer , easy and cost effective. Hope to try it out on the weekend if i can procure some Sodium Sulfite. Seems a little hard to find and somewhat expensive. So . Here they come...

Where is a good source to purchase it ? is it available disguised as a different use product (along the lines of StumpOut, or various drain cleaners, etc)?

20 to 80 grams per liter ? thats a pretty big spread .... 50 liters of solution compared to 12.5 liters per Kg of powder. is there a " sweet spot" in anybody's experience that balances time/cost /efficiency/ etc ?

Same question relates to voltage as well. 1.8 volts was mentioned. Does a higher voltage increase speed at the cost of more impurities in the deposit on the cathode ? Does amperage play a role?

The cathode. What other metals could be used and are there any advantages? If not then stainless it is. 304 ? 316 ? any difference in performance?
Would there be an optimal ratio for surface area of cathode vs anode ? I realize the silver amounts to a small percentage of the plated pieces but my thinking is that you would want to keep replacing the anode pieces as they get stripped to best utilize your solution before it is "spent". Would you keep replacing or cleaning off the anode after each piece?

As your solution is deteriorating is it a steep decline in performance? Does the presence of the sulfates hinder the process or could you just keep adding sulfites until you reach some saturation limit in the solution? How do you know when it is spent ? Does the process just gring to a halt?
I am assuming the transition of the solution is caused by atmospheric oxygen binding to the sulfite. As most people use plastic totes nowadays for these processes , would putting its lid on and running it semi sealed not slow that process ? Perhaps with an airlock bubbler like they use for alchohol fermentations? Does this system produce hydrogen in amounts that could cause any risk ?

I know there is a lot to be learned from trial and error , and i am sure i will, but if others have succeeded before you , ti doesn't hurt to ask and save time , money, and grief.

Thank you in advance of any replies

Hello All.

Very interesting . i have been hoping to find something relatively safer , easy and cost effective. Hope to try it out on the weekend if i can procure some Sodium Sulfite. Seems a little hard to find and somewhat expensive. So . Here they come...

Where is a good source to purchase it ? is it available disguised as a different use product (along the lines of StumpOut, or various drain cleaners, etc)?

20 to 80 grams per liter ? thats a pretty big spread .... 50 liters of solution compared to 12.5 liters per Kg of powder. is there a " sweet spot" in anybody's experience that balances time/cost /efficiency/ etc ?

Same question relates to voltage as well. 1.8 volts was mentioned. Does a higher voltage increase speed at the cost of more impurities in the deposit on the cathode ? Does amperage play a role?

The cathode. What other metals could be used and are there any advantages? If not then stainless it is. 304 ? 316 ? any difference in performance?
Would there be an optimal ratio for surface area of cathode vs anode ? I realize the silver amounts to a small percentage of the plated pieces but my thinking is that you would want to keep replacing the anode pieces as they get stripped to best utilize your solution before it is "spent". Would you keep replacing or cleaning off the anode after each piece?

As your solution is deteriorating is it a steep decline in performance? Does the presence of the sulfates hinder the process or could you just keep adding sulfites until you reach some saturation limit in the solution? How do you know when it is spent ? Does the process just gring to a halt?
I am assuming the transition of the solution is caused by atmospheric oxygen binding to the sulfite. As most people use plastic totes nowadays for these processes , would putting its lid on and running it semi sealed not slow that process ? Perhaps with an airlock bubbler like they use for alchohol fermentations? Does this system produce hydrogen in amounts that could cause any risk ?

I know there is a lot to be learned from trial and error , and i am sure i will, but if others have succeeded before you , ti doesn't hurt to ask and save time , money, and grief.

Thank you in advance of any replies

Hello.
you should look at the information on the Russian segment of the Internet.
This method is very popular there.
I think using a translator you will understand everything.
For example, here is a forum similar to this, and the topic is dedicated to your question :

https://alhimika.net/forum/showthread.php?tid=31

 

[scrappyjoe]

Thank you. i will check it out next time i am at the library on a public computer, as my antivirus stopped me from opening the page for potential security concerns.

 

[kaisernine]

Hello All.

Very interesting . i have been hoping to find something relatively safer , easy and cost effective. Hope to try it out on the weekend if i can procure some Sodium Sulfite. Seems a little hard to find and somewhat expensive. So . Here they come...

Where is a good source to purchase it ? is it available disguised as a different use product (along the lines of StumpOut, or various drain cleaners, etc)?

20 to 80 grams per liter ? thats a pretty big spread .... 50 liters of solution compared to 12.5 liters per Kg of powder. is there a " sweet spot" in anybody's experience that balances time/cost /efficiency/ etc ?

Same question relates to voltage as well. 1.8 volts was mentioned. Does a higher voltage increase speed at the cost of more impurities in the deposit on the cathode ? Does amperage play a role?

The cathode. What other metals could be used and are there any advantages? If not then stainless it is. 304 ? 316 ? any difference in performance?
Would there be an optimal ratio for surface area of cathode vs anode ? I realize the silver amounts to a small percentage of the plated pieces but my thinking is that you would want to keep replacing the anode pieces as they get stripped to best utilize your solution before it is "spent". Would you keep replacing or cleaning off the anode after each piece?

As your solution is deteriorating is it a steep decline in performance? Does the presence of the sulfates hinder the process or could you just keep adding sulfites until you reach some saturation limit in the solution? How do you know when it is spent ? Does the process just gring to a halt?
I am assuming the transition of the solution is caused by atmospheric oxygen binding to the sulfite. As most people use plastic totes nowadays for these processes , would putting its lid on and running it semi sealed not slow that process ? Perhaps with an airlock bubbler like they use for alchohol fermentations? Does this system produce hydrogen in amounts that could cause any risk ?

I know there is a lot to be learned from trial and error , and i am sure i will, but if others have succeeded before you , ti doesn't hurt to ask and save time , money, and grief.

Thank you in advance of any replies

Personally we were not really trying to get all of it, this process just added "extra" revenue to our scrap so it was just a tank that we used before we processed our copper / brass - silver plated scrap.

We saturated the solution until it stopped dissolving in warm distilled water, there may be a ratio that is perfect for the process but for what we were doing it worked for us just saturating it.

We noticed when the solution went bad it would start to plate out copper and we would stop the process.

I believe it is possible to use the solution possibly to make copper sulfate after which could be used for other things. - someone else may know here with experience and can chime in, not something we needed to do but I am sure the solution can be used in some other process for refining.

We evaporated the solution and took left over waste to a chemical recycling facility at $50 a bucket to get rid of.