Refinning Silver to get a purity of 999.9

[ashapura refinery]

Hello to all

We did a process for refining silver. We used nitric acid (72% concentration) and zinc of purity 998 for the silver recovery.

We did this process twice. The first time we did it the purity of silver was 998 and the second time we did it came 998.5.

Can anyone suggest on how to reach 999.9.

 

[nickvc]

Refine your silver in a cell, all the details for it are here on the forum.

 

[ashapura refinery]

Refine your silver in a cell, all the details for it are here on the forum.

Thank you for the reply. I am going through the information.

 

[kurtak]

Using heavy copper (electrical bus bars or copper pipe etc.) is a better choice then zinc for recovering your silver from nitric solution - it then needs to go to the silver cell to complete the refining

As Nick said - starting do some research here on the forum - all the info is here you just need to do some digging

Kurt

 

[4metals]

This thread had an interesting video with it using copper powder to drop silver.

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=50&t=8621&hilit=stoichiometric#p80549

 

[Westerngs]

Ashapura,

Actually, your first method may not be bad.

First, a question though? How did you ascertain the purity of the silver product? It may be that your assay method is not accurate enough to determine is your silver is 4 9's. Did you also assay a known 4 9's control sample to make sure you could determine 5 9's purity?

If assay method is good enough. Try with zinc again. Add zinc slowly with much stirring. Do not add enough zinc to precipitate all the silver, leave some silver in solution. Collect the silver and rinse very several times. Then soak in 10% hydrochloric acid w/v or v/v does not much matter. This will dissolve any unreacted zinc. Heating the solution will help. Rinse very well and melt.

The solution with some silver still in it can be recycled to the silver circuit.

 

[g_axelsson]

Unless your source of silver nitrate is very pure I would say that zinc is a bad alternative for cementing silver. Any copper contamination will cement with the silver and mix with the final product.
Even copper can cement unwanted contaminants and the most common one is palladium. If there is palladium in the source both zinc and copper will cement palladium which will mix in the final product.

If a metal grain is covered in silver then no washing can ever get it out of the final product. The only way to remove it is to run the silver in a cell.

Göran

 

[4metals]

Notice Westerngs said it may work, if the solution is clean enough to start zinc is fine. The question is what kind of chemical soup is he starting with.

Zinc is popular to reduce silver chloride to metal but when you start with silver chloride you can rinse it and start with clean silver chloride so the other metals are not even there to contaminate the resulting silver metal. Then removing the extra zinc with dilute HCl works great.

Zinc was commonly used long before copper. I had always preferred to drop a silver chloride and rinse it and reduce that with zinc.