AgCl to Ag+AlCl3

[David Frederick]

I’m trying to figure out an effective way to chemically separate Ag from AgCl. Currently I’m experimenting with aluminum. I’m running into an issue with the Ag forming a shell around around untreated AgCl. This is how the boss wants it done but I’m struggling to make it work.
The current process is removing Ag from nitric acid using HCl, rinsing and collecting the AgCl. Placing 50lbs of the AgCl into a cement mixer and adding water. Once blended slowly adding fine aluminum until roughly 2.5 pounds has been added, always keeping the temperature below 120 F. If anyone has any tips, tricks, or completely new processes I’m open to all suggestions.

 

[Martijn]

Welcome to the forum.
Agitation is key imo. Try a sharp blade stirrer to cut it all up in the solution.

Have you considered not converting to AgCl and cementing AgNO3 directly on copper? Or the lye and sugar conversion.
Martijn.

 

[snail]

A method that has received considerable comment here is to use dilute Sulfuric (about 10%) in a cement mixer with heavy iron punchings or short pieces of rebar.

The pieces of iron help break down the pieces of silver chloride. Iron contamination tends to not alloy into the silver when melting.

 

[Lino1406]

Aluminum has a major drawback, producing aluminum oxide which is hard to get rid of

 

[David Frederick]

Welcome to the forum.
Agitation is key imo. Try a sharp blade stirrer to cut it all up in the solution.

Have you considered not converting to AgCl and cementing AgNO3 directly on copper? Or the lye and sugar conversion.
Martijn.

I just did a small sample of the lye and sugar method and it came out really well. About 99.2%, but I’m getting resistance from the boss since we’ve never done it that way before.
I have not tried the silver nitrate method…would you elaborate on that please? I know nothing about it.

 

[David Frederick]

A method that has received considerable comment here is to use dilute Sulfuric (about 10%) in a cement mixer with heavy iron punchings or short pieces of rebar.

The pieces of iron help break down the pieces of silver chloride. Iron contamination tends to not alloy into the silver when melting.

The sulfuric and iron method is how we originally processed Ag and I think we may need to go back to that.

 

[Alondro]

I just did a small sample of the lye and sugar method and it came out really well. About 99.2%, but I’m getting resistance from the boss since we’ve never done it that way before.
I have not tried the silver nitrate method…would you elaborate on that please? I know nothing about it.

The lye + sugar method works phenomenally and is cheap. When the lye is added, warm and agitate it until the powder looks evenly dark brown-black and is only small particles. Clumps that don't stir apart still could have a core of AgCl remaining unconverted. You can use Karo corn syrup for the sugar, which is high-dextrose, the ideal reducing sugar, and very cheap to buy in bulk.

There are no other metal in those reagents, so the only contaminants after the completed reduction and washes will be those found in the AgCl itself.

 

[Martijn]

You have silver nitrate.
When you make the nitrate, leaving a piece of silver undigested, using up all excess free nitric, filter and put a piece of clean copper in the solution.
Silver will be displaced from solution as metallic silver, trading electrons with the copper, which goes in solution. The silver can be washed and melted.
Basically the same as:

https://goldrefiningforum.com/threads/when-in-doubt-cement-it-out.30236/Based on the reactivity series.

This can result in 99% pure silver or better.
Further refining can be done in the electroytic silver cell.
You will be left with copper nitrate with traces of silver, get that last bit out with HCl.

Martijn.

 

[David Frederick]

I appreciate everyones feedback, I think I’ve got enough information to move forward anyway. I’ve got about 3300 lbs of AgCl to process, but I may come back to you all if I can’t get ratios right or have any other questions. Thank you again!

 

[Alondro]

I appreciate everyones feedback, I think I’ve got enough information to move forward anyway. I’ve got about 3300 lbs of AgCl to process, but I may come back to you all if I can’t get ratios right or have any other questions. Thank you again!

Ah, you're doing true industrial scale refining. Yes, the NaOH and sugar method will work best for such quantities. With any method using a metal to displace the silver from the chlorine, you risk heavy contamination unless it's a process you're innately familiar with and know all the little crucial details to make it work.

You'll be buying bulk amounts of lye and sugar, which will make those reagents even cheaper per pound than for those of us who just buy a bottle of lye and a bag of sugar/bottle of corn syrup from the store for our few ounces or pounds of silver.

 

[snoman701]

Are you using a plastic tub cement mixer? I don't understand why the sulfuric iron method was abandoned.

It's the easiest by far, my biggest issue is the filtration. It's a lot of work.

 

[David Frederick]

Are you using a plastic tub cement mixer? I don't understand why the sulfuric iron method was abandoned.

It's the easiest by far, my biggest issue is the filtration. It's a lot of work.

I am using a plastic tub cement mixer. Even though the sulfuric and iron method was working for us, my boss is a chemist. We had a ready source of Al and according to his calculations the Al would have been more efficient and save some time. I was having a lot of trouble getting it to work so I got desperate and came here for wisdom.

 

[David Frederick]

Ah, you're doing true industrial scale refining. Yes, the NaOH and sugar method will work best for such quantities. With any method using a metal to displace the silver from the chlorine, you risk heavy contamination unless it's a process you're innately familiar with and know all the little crucial details to make it work.

You'll be buying bulk amounts of lye and sugar, which will make those reagents even cheaper per pound than for those of us who just buy a bottle of lye and a bag of sugar/bottle of corn syrup from the store for our few ounces or pounds of silver.

To make sure I understand what I’m doing with the lye and sugar: I would need to add the AgCl and water, then the lye until I bring the Ph back to neutral then add the sugar until there is no more reaction, rinse and be done?
I did a very small sample in a five gallon bucket, but I think I added to much caustic soda because the silver turned black, but it was still 99.2% so I didn’t think much of it.

 

[Alondro]

To make sure I understand what I’m doing with the lye and sugar: I would need to add the AgCl and water, then the lye until I bring the Ph back to neutral then add the sugar until there is no more reaction, rinse and be done?
I did a very small sample in a five gallon bucket, but I think I added to much caustic soda because the silver turned black, but it was still 99.2% so I didn’t think much of it.

Silver chloride is supposed to turn black when lye is added and mixed up well, because it's turning into silver oxide. That's step 1. Then it needs a wash to remove the bulk of the lye, and then add the sugar and mix more. After a little while, it should turn light silvery-grey. That's the reduced and very pure silver.

 

[David Frederick]

Perfect! So my attempt is about half right, I need to rinse it, mix it up well, and then add the sugar. With that being said, if I were to melt the silver oxide would it just burn the oxygen out leaving me with metallic silver? I’m trying to learn this stuff on the fly so I really appreciate all of this information!

 

[silver1]

Perfect! So my attempt is about half right, I need to rinse it, mix it up well, and then add the sugar. With that being said, if I were to melt the silver oxide would it just burn the oxygen out leaving me with metallic silver? I’m trying to learn this stuff on the fly so I really appreciate all of this information!

Add the NaOH and sugar together. No need to wash the NaOH away before sugar addition. This will lead to more problems. The NaOH helps break down the sugar. Yes you can melt the silver ox straight, but washing and filtering can be a p.i.t.a.. Sugar is cheap and completes the process.

 

[silver1]

https://goldrefiningforum.com/threa...via-naoh-and-karo-question.14618/#post-147115

 

[snoman701]

I feel like NaOH and Karo syrup at that scale is just ASKING for an ant infestation!

 

[Alondro]

I feel like NaOH and Karo syrup at that scale is just ASKING for an ant infestation!

Eh, we get swarms of those Argentine ants everywhere even without it. We have BILLIONS of them hiding under every rock, inside every pipe, under bark, under siding, in mailboxes, under leaves... basically any sheltered space with a little slit for an entrance is full of the damned things.

I actually use a mix of sugar and borax to at least keep the ones that come pouring into the house in spring under control.

 

[David Frederick]

I’m taking it really slow while adding sugar (I only have granulated sugar from the break room because I’ve been told to stop but I’m not giving up on it lol) and I am starting to see the silver in the bottom. Would you happen to have a good starting ratio so when I try a larger batch next time I’m a little closer to my goal? I’m also using caustic soda because I don’t have any dry lye, will that make any difference?