Get silver from sulfuric acid solution. How?!

[refineag]

Hi
I have some silver dusts. I wash them with sulfuric acid first to remove impurities like copper, iron, zinc,... and residue that remained is silver.
But I think a little of silver dissolve in sulfuric acid(Right?). Can I drop a copper bar in sulfuric acid solution to cement out silver ?
Is it necessary to neutralize solution before cementation ? If yes how ?

Thank you

 

[IdahoMole]

I use a dilute (5%) sulfuric acid to remove flux from poured silver bars. When the solution starts looking dirty I hang some copper in it to cement the small amount of silver that has dissolved. If you have a concentrated solution I would guess that the excess acid should be neutralized or you will use a lot of copper to over come the acid. I do not know the best way to do that.
That's all I got, I hope it helps.

 

[Topher_osAUrus]

An excellent point was raised.
How concentrated is your sulfuric acid?
How hot was the leach when you were using it?

You can cement on copper, or iron -which would be much better and faster if the sulfuric was dilute.

Ive also read (never tried) dropping as a chloride with salt.

Reduction from solution by adding ferrous sulfate to the sulfuric loaded with silver. (Which is interesting, as that is a way to reduce silver sulfate crystals as well)

If its a heavy concentration, you can remove the silver in its sulfate or bisulfate(less desirable) form by dilution. In the books they use steam added to the sulfuric to precisely get the specific gravity correct. Just so they would stay away from the "mushy" bisulfate crystals.

Cementing sounds easiest to me

 

[Lino1406]

The maximal concentration of silver sulphate in concentrated sulphuric acid is around 5%. To recover - dilute with water and convert the precipitate to silver oxide with adding cautiously NaOH solution. Also dissolved silver sulphate remnants can be recovered using same.

 

[refineag]

Thank you
As I said there are some impurities like zinc, copper, iron and ... in solution so cementation is best way
But There is very very little silver in solution. Can I get all of my silver with cementation ?

An excellent point was raised.
How concentrated is your sulfuric acid?

It is dilute with a little acid

 

[Topher_osAUrus]

Eventually, yes.
So long as all of the silver ions in solution contact the copper metal, it will remove them all.
It may take a day. A week, a month. I dont know. But, I do know that it is a function of surface area (of the copper) and movement/agitation of solution. So the more copper in there, the better, and the more you stir the solution or agitate it with a bubbler, the faster the silver will cement out.