Unable to Precipitate silver from Nitric Acid

[Jakes.vdv]

Dear Refiners

I’ve been scrapping various kinds of metal for some time now, and recently started looking into recovering silver from plated items.

My approach has been to reverse electroplate Silver plated items using a salt solution in a stainless steel bowl as the negative cathode, and the silver electroplate items as the cathode, using a glass separator to keep the silver items from touching the stainless bowl.

I then connect it to my 1.6v power supply, and it slowly chugs away at between 1.2-1.7 amps reverse electroplating plating the silver from the plated items onto the stainless bowl.

It’s a slow process, but speed isn’t a priority for me at this stage, for now I just want to get to the point where I can actually smelt down some metallic silver.

The reverse plating seems to work well, as much of the silver has been removed from the plated items, and is deposited onto the stainless steel bowl.

There is a orange reddish sludge that floats at the top of the liquid during the process.
Once a day I switch off the power, and the sludge fairly quickly drops to the bottom of the bowl. I then stain the salt water electrolyte, collecting the sludge and moving it into a glass container.
Every time I do this, I notice a blackish deposit growing on the bowl’s surface, which I stand to be corrected, but I think is some reverse plated silver.

After transferring the orangey sludge to a glass container, I add diluted nitric acid (30%) to it. The nitric goes to work on the sludge quickly, and before you know it, most of it dissolved into the now blueish green liquid.

I then strain this liquid into another glass container, assuming that it has some (maybe not much, but some) Silver nitrate in it.

I then proceed to add a saturated table salt solution to the strained nitric, with the hope of precipitating silver chloride from the nitric acid solution... but I’ve had no joy this far.

I figured that it may be one of two things. Either the Ph isn’t suitable, or there just isn’t any or perhaps not enough Silver nitrate in solution to be precipitated.

Unfortunately I don’t have a Ph testing kit, so I can’t really tell if the nitric solution is too basic, or too acidic. My understanding is that it should be between 1-2 if the precipitation of Silver nitrate by sodium chloride is going to work.

So I slowly added some diluted bicarbonate of soda to the mix, in order to make the solution more basic, and added more salt solution. I nearly danced for joy when I saw the blueish liquid change from clear to a more milky blue... and slowly I could see some curdling inside there. But then about half an hour later, I noticed the curdled stuff that dropped to the bottom of the jar. It was a more yellow orange colour, while the liquid remained milky blue. I figured that by making the solution more basic, I was simply undoing what the acid had done; turning the dissolved matter into solid matter again.

Well after another 30 minutes or so I started seeing very fine white as snow dust settling on top of the yellow orange particles. I thought this was silver, but then I made the solution more acidic again to get rid of the orangey stuff, but it dissolved and I just kept going around in circles with no joy in precipitating any silver chloride from the solution.

Could it be that there simply isn’t any silver in that solution and that everything is collecting onto the stainless steel bowl? Or is there something I should be doing differently to get a better result.

I’m planning on getting a ph testing kit. But is it really necessary?

Your feedback would be so very much appreciated. Thanks everyone.

 

[Martijn]

Reverse plating water cell creates silver oxide, which is black. it is not 'deposited' on stainless steel bowl, that is done with nitric. it just stick to it or settles there, i imagine.
In a salt water cell, you will create silver chloride. Silver chloride does not dissolve in HNO3.
So adding table salt to a solution without silver nitrate will not form any AgCl. silver chloride does reduce back to oxide at the cathode, I believe, but am not sure.

By raising the pH with soda, you create metal hydroxides, first to appear is iron, that partially turns to rust, orange. Blue is probably copper traces.

Salt water electrolysis creates NaOH, which converts AgCl into AgO, which is black. Freeing some Cl from the AgCl, which will form more AgCl with fresh released silver at the anode. Lots of things going on there.
Most use a stainless bowl as cathode for a silver nitrate cell, and a glass bowl with a silver plated piece as anode and cathode... (edited:.. for the tapwater stripping cell)

 

[Jakes.vdv]

Reverse plating water cell creates silver oxide, which is black. it is not 'deposited' on stainless steel bowl, that is done with nitric. it just stick to it or settles there, i imagine.
In a salt water cell, you will create silver chloride. Silver chloride does not dissolve in HNO3.
So adding table salt to a solution without silver nitrate will not form any AgCl. silver chloride does reduce back to oxide at the cathode, I believe, but am not sure.

By raising the pH with soda, you create metal hydroxides, first to appear is iron, that partially turns to rust, orange. Blue is probably copper traces.

Salt water electrolysis creates NaOH, which converts AgCl into AgO, which is black. Freeing some Cl from the AgCl, which will form more AgCl with fresh released silver at the anode. Lots of things going on there.
Most use a stainless bowl as cathode for a silver nitrate cell, and a glass bowl with a silver plated piece as anode and cathode.

Hi Martijn. I really appreciate your response, and value your input. I realised I still have lots to learn regarding all of this. I’ll go back to the drawing board, and perhaps start afresh with a nitrate cell instead.

 

[Yggdrasil]

Hi Martijn. I really appreciate your response, and value your input. I realised I still have lots to learn regarding all of this. I’ll go back to the drawing board, and perhaps start afresh with a nitrate cell instead.

Nitrate Cells are not suited to remove Silver plating from objects.

 

[Jakes.vdv]

Ok. What do you suggest I do?…Apart from taking a course on chemistry .

 

[Martijn]

Continue stripping silver plating with tap water. Not salt water.
Or if you want to use salt water, convert all dirty silver chloride to silver oxide with NaOH before thourough rinsing and leaching with nitric. Do not raise pH during stripping.
You could also directly smelt the silver oxide/chloride mix with a flux, to run in a silver nitrate cell, but others will have to jump in here.

 

[Yggdrasil]

Ok. What do you suggest I do?…Apart from taking a course on chemistry .

Read Hokes book, that should be done anyway.
Besides that, read and study the forum.

 

[Jakes.vdv]

Continue stripping silver plating with tap water. Not salt water.
Or if you want to use salt water, convert all dirty silver chloride to silver oxide with NaOH before thourough rinsing and leaching with nitric. Do not raise pH during stripping.
You could also directly smelt the silver oxide/chloride mix with a flux, to run in a silver nitrate cell, but others will have to jump in here.

Ok great. Thank you very much!

 

[Jakes.vdv]

Read Hokes book, that should be done anyway.
Besides that, read and study the forum.

Cool. I’ll do that.

 

[Akragon]

Dear Refiners

I’ve been scrapping various kinds of metal for some time now, and recently started looking into recovering silver from plated items.

My approach has been to reverse electroplate Silver plated items using a salt solution in a stainless steel bowl as the negative cathode, and the silver electroplate items as the cathode, using a glass separator to keep the silver items from touching the stainless bowl.

I then connect it to my 1.6v power supply, and it slowly chugs away at between 1.2-1.7 amps reverse electroplating plating the silver from the plated items onto the stainless bowl.

It’s a slow process, but speed isn’t a priority for me at this stage, for now I just want to get to the point where I can actually smelt down some metallic silver.

The reverse plating seems to work well, as much of the silver has been removed from the plated items, and is deposited onto the stainless steel bowl.

There is a orange reddish sludge that floats at the top of the liquid during the process.
Once a day I switch off the power, and the sludge fairly quickly drops to the bottom of the bowl. I then stain the salt water electrolyte, collecting the sludge and moving it into a glass container.
Every time I do this, I notice a blackish deposit growing on the bowl’s surface, which I stand to be corrected, but I think is some reverse plated silver.

After transferring the orangey sludge to a glass container, I add diluted nitric acid (30%) to it. The nitric goes to work on the sludge quickly, and before you know it, most of it dissolved into the now blueish green liquid.

I then strain this liquid into another glass container, assuming that it has some (maybe not much, but some) Silver nitrate in it.

I then proceed to add a saturated table salt solution to the strained nitric, with the hope of precipitating silver chloride from the nitric acid solution... but I’ve had no joy this far.

I figured that it may be one of two things. Either the Ph isn’t suitable, or there just isn’t any or perhaps not enough Silver nitrate in solution to be precipitated.

Unfortunately I don’t have a Ph testing kit, so I can’t really tell if the nitric solution is too basic, or too acidic. My understanding is that it should be between 1-2 if the precipitation of Silver nitrate by sodium chloride is going to work.

So I slowly added some diluted bicarbonate of soda to the mix, in order to make the solution more basic, and added more salt solution. I nearly danced for joy when I saw the blueish liquid change from clear to a more milky blue... and slowly I could see some curdling inside there. But then about half an hour later, I noticed the curdled stuff that dropped to the bottom of the jar. It was a more yellow orange colour, while the liquid remained milky blue. I figured that by making the solution more basic, I was simply undoing what the acid had done; turning the dissolved matter into solid matter again.

Well after another 30 minutes or so I started seeing very fine white as snow dust settling on top of the yellow orange particles. I thought this was silver, but then I made the solution more acidic again to get rid of the orangey stuff, but it dissolved and I just kept going around in circles with no joy in precipitating any silver chloride from the solution.

Could it be that there simply isn’t any silver in that solution and that everything is collecting onto the stainless steel bowl? Or is there something I should be doing differently to get a better result.

I’m planning on getting a ph testing kit. But is it really necessary?

Your feedback would be so very much appreciated. Thanks everyone.

It would actually be easier IF you just grabbed some sterling silver and tossed it into some nitric... don't waste your time with plated stuff. I had to learn this the hard way.... just wasted time and frustration. Unless you have pounds of it, its pointless.

 

[Martijn]

Ok. What do you suggest I do?…Apart from taking a course on chemistry .

You need to have some basic knowledge of chemistry, different reactions of the metals and acids you intend to use for tried and proven processes before you start serious recovery and even refining. Hoke's acquaintance tests are great for this.

Experimenting should only be done on a very small scale: to gain experience, and to avoid big problems to clean up or worse. A small poof or testtube boil over can be somewhat controlled, a warehouse full of ammonium nitrate going boom can not be controlled.

But which processes and chemicals should you use? Depends on which material you want to process, which chemicals and tools you can get your hands on, how much time you have to complete the task, how much waste it creates, how well you can deal with the dangers and safety aspects of certain processes or materials and how good you can perform certain processes.

Next challenge: there are a lot of ways to get the same end result from the same source material. So which one is best for you and your material? Many of us started out watching a random Youtube video, throwing an bunch of random gold bearing materials, regardless of all the other components and compounds in there in HNO3, or even worse, in AR. That's how they ended up here. I did.

But how will you know all this before you start out? What to choose? You can't! But you want that shiny gold! NOW! darn..

Now to avoid this checken / eg paradox, we really want you to read Hoke. Why?, she is one the few or the only one who explains chemistry on a normal understandable level. Much of it will still be way over your head, because it still is quite complex. That's why we ask you to read it again, and again.
If refining is anything for you, you will understand and love it in time.
And you don't have to read the whole book, but those chapters that contain info on the metals you plan to encounter, are a must read!
The rest is only adding to your knowledge.

No-one knows it all, and you have to start somewhere.
So how?
First is the reading, then there are the acquiantance tests, to be performed in a safe location!! (fume hood or outside, but no gas mask) Best is performing them yourself, or looking up the reaction on you tube to see what to expect before you perform them.

Next, with every new material you will receive, you will have to study, do research, ask us, or test it. Small scale first to find the best suitable proces for this material in your particular situation. This will never change.

And before you, as a novice refiner, try out something for the first time, just present your plan here, with all the details you can think of, and we will ask and warn you about the rest you forgot or did not know about.

One more thing: junk in junk out, meaning separate as much as you can mechanically or with simple and cheap chemicals before you dissolve everything in nitric or AR.

Take it slow, have fun and stay healthy!

Martijn.

 

[Jakes.vdv]

Thanks everyone for all your input. I’m busy reading the copy of Hoke provided on this site. Thanks for pointing me to that recourse.

I noticed that if I add just Hcl to the orange sludge, it does precipitate silver. But the silver precipitate is accompanied by undissolved base metals that will need more treatment.

The hcl has done well in doing this accompanied with some heat. I might use a bit of nitric acid to dissolve any remaining base metals before washing. But my concern is dissolving metallic silver in the process…which will have to be precipitated. I’m not so sure how that will work.

So for now I’m more interested in getting educated, especially on the safety side of things, rather than further experimentation.

Thanks everyone!

 

[Yggdrasil]

Thanks everyone for all your input. I’m busy reading the copy of Hoke provided on this site. Thanks for pointing me to that recourse.

I noticed that if I add just Hcl to the orange sludge, it does precipitate silver. But the silver precipitate is accompanied by undissolved base metals that will need more treatment.

The hcl has done well in doing this accompanied with some heat. I might use a bit of nitric acid to dissolve any remaining base metals before washing. But my concern is dissolving metallic silver in the process…which will have to be precipitated. I’m not so sure how that will work.

So for now I’m more interested in getting educated, especially on the safety side of things, rather than further experimentation.

Thanks everyone!

No metals will precipitate by adding HCl.
Insoluble salts like AgCl will though.
If you are going to precipitate any product you want from a solution it is wise to filter first to keep unwanted solids out of it.
The Nitric will dissolve Silver, Copper and more. To get The Silver back add HCl or table salt and then treat the Silver Chloride to get metallic Silver.

Edit to add:
Or cement it with Copper directly

 

[Jakes.vdv]

Yes. That’s what happened. The salt solution turned some of the metallic silver into silver chloride, as Martijn mentioned earlier in the thread.

I should never have added nitric to the first batch of sludge.

Which is more...I threw out about 5 litres of salt water that was used as electrolyte, which most likely had a bunch of silver chloride in it...I should’ve checked with hcl first. Live and learn

 

[Yggdrasil]

Yes. That’s what happened. The salt solution turned some of the metallic silver into silver chloride, as Martijn mentioned earlier in the thread.

I should never have added nitric to the first batch of sludge.

Which is more...I threw out about 5 litres of salt water that was used as electrolyte, which most likely had a bunch of silver chloride in it...I should’ve checked with hcl first. Live and learn

You need to study more. You don’t make much sense.
Metallic Silver will not turn into Chloride, at least not in any amount worth worrying about.

Nitric will dissolve most base metals.
And the Silver, just filter and drop with table salt or HCl.

If you threw out 5 litres of waste liquid.
I hope you treated the waste as it should have!!
Next, if it had no solids, there was no Silver.

 

[Jakes.vdv]

You need to study more. You don’t make much sense.
Metallic Silver will not turn into Chloride, at least not in any amount worth worrying about.

Nitric will dissolve most base metals.
And the Silver, just filter and drop with table salt or HCl.

If you threw out 5 litres of waste liquid.
I hope you treated the waste as it should have!!
Next, if it had no solids, there was no Silver.

You probably didn’t read the initial message in this thread.
The waste liquid is basically salt water…how do you suggest I treat that? I actually figured it would make good mineral rich fertiliser.

As for the ag turning to agcl, my understanding is that if you use a sodium chloride (table salt) cell to reverse plate silver onto a suitable cathode, there will be some silver chloride in the mix.

But, yes, you’re right…I do need to study more

 

[Yggdrasil]

You probably didn’t read the initial message in this thread.
The waste liquid is basically salt water…how do you suggest I treat that? I actually figured it would make good mineral rich fertiliser.

As for the ag turning to agcl, my understanding is that if you use a sodium chloride (table salt) cell to reverse plate silver onto a suitable cathode, there will be some silver chloride in the mix.

But, yes, you’re right…I do need to study more

Anything we have used in refining will need to be treated properly, just in case. There will be Copper and what not in the mix.
Ag will not dissolve in this setting but some may be converted to Silver Chloride which is insoluble in any acid and most other liquids.
Please use proper denomination of the elements. It is Ag and AgCl.