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topic 6262

Silver refining problem: Removing copper from silver nitrate


A discussion started in 2000 but continuing through 2018

2000

Q. In the process of refining pure silver, we end up having a lot of copper in the electrolyte (silver nitrate). The efficiency of the process diminishes as the copper concentration increases in the bath. I am wondering if there is a process where I can regenerate the electrolyte (AgNO3) by removing the excess copper from the solution.

I would greatly appreciate anybody's help.

Thank You.

Ajit Menon
- Alden, New York, USA


2000

A. Dear Ajit,

Selective removal of copper from AgNO3 can be performed by ion-exchange, provided the pH is not below 1.5. The key will be to minimize silver loss by extensive wash of the resin or by use of a continuous counter current ion-exchange system (ISEP).

Ruud Gerritsen
Recomet B.V. - Simpelveld, Netherlands


September 16, 2012

Q. I noted the suggestion of Mr. Gerritsen to use a counter current ion-exchange system (ISEP). I have refined 80/20 Ag/Cu for a while in a AgNO3/HNO3 bath, but I think I have got to the point of copper contamination of the electrolyte, like the original poster. Is there a way to electrically remove the copper and keep the AgNO3?

Thanks,

Tom, who just started this stuff and finds it fascinating.

Thomas Schmidt
- Tuckahoe, New York


(2002)

A. Have you thought of precipitating the Ag with HCl and resmelting with Borax [linked by editor to product info at Amazon] and flour to obtain about 95% Ag which you can redissolve in HNO3 to get your electrolyte?

Edmund nkrumah
- Accra, Ghana



Moebius cell technique leaving impurities in refined silver

(2002)

Q. What could be the cause of having impurities in refined silver using the moebius cell technique, when crystals obtained have been thoroughly washed with deionised water?

Edmund Nkrumah
- Accra, Ghana



Only achieving 50% silver recovery; need 90-95%

May 8, 2009

Q. We are facing the problem of silver recovery from silver and copper mixture. We are refining the silver metal as silver chloride and copper as copper cathode, by electrolyzing process.

We get silver chloride from the electrolytic solution by addition of HCl. Rinse we filter the silver chloride from the solution, After the many water wash, we melt the silver chloride by addition of borax and carbon powder. But we are getting the silver recovery only 50%.

Please help me to get about 90 to 95 percent recovery of silver metal at least.

Please reply us as soon as possible.

Thanks.

Digant Ashra
hobbyist - Rajkot, Gujarat, India


November 8, 2014

A. If your silver nitrate solution gets saturated with copper, cement the silver nitrate out onto copper, you will get elemental silver, and one could get the copper nitrate out by cementing onto iron (after washing and separating from the cemented silver), you're left with iron nitrate and copper oxide, I believe, but the cemented silver is clean enough TO MELT and make new electrolyte again. DON'T put the cemented powder back into nitric. Nitric reacts explosively with metal powders, because of the large surface to act on!

Cementing onto copper:



wikipedia
Silver Chloride

I'm not an expert in refining, merely a student of this interesting science, but that's what I would do to get rid of silver electrolyte saturated with copper. Copper is close to silver on the reactivity series, =>
with only mercury and tungsten in between. Pt and Au will not be in a nitric solution, so pretty pure Ag is to be expected. Why bother making AgCl first and having to melt and waste borax?

Use this info (and everything else you find on internet, for that matter) AT YOUR OWN RISK!, it's purely for theoretical purposes, be educated and sure of what you do.
read MSDS! be safe!

wikipedia
Reactivity Series

Melting silver chloride will produce chlorine as well =>

Martijn Ehlers
- Zeeland, the Netherlands


January 30, 2015

A. To recover silver from silver nitrate solution I prepared a reagent which is directly added into silver nitrate solution. No need to precipitate as silver chloride. It works nicely and the purity of Silver is 9999.

Daulat Bhosale
- Bangkok Thailand


February 13, 2015

Q. Daulat,

Dead keen to know what your reagent is -- organic?

AG

Andrew Gowans
- Fairfield, Australia


February 15, 2015

A. Yes. The reagent is a mixture of three organic compounds. Watch the video on you tube. Recovery of silver from silver nitrate solution.

Daulat Bhosale
- Bangkok Thailand



June 14, 2018

Q. Can anyone tell me the how should I calculate the ratio of copper powder (red) to separate the 99% silver from copper nitrate (solution of impure silver + 70% nitric acid)?

dee kay
Dk Assay - mumbai,india


June 25, 2018

A. Theoretically, 1 gram of copper will cement (reduce, precipitate) 3.4 grams of silver from a silver nitrate solution. However, if there is any free nitric acid in the solution, copper will be dissolved by the nitric until the nitric is all consumed, before cementing any silver. It takes about 4.15 ml of 70% nitric (15.7 molar) to dissolve 1 gram of copper.

With copper powder, you must use an exact amount, which is difficult to predict, especially if any free nitric is present. Any undissolved excess of copper powder will co-mingle with, and contaminate the cemented silver powder.

The best copper to use is scrap, un-plated, clean, copper buss bar, with no solder on it, cut into pieces long enough to protrude up out of the solution, so they can be easily removed. Heavy, solid copper wire can be used, but, here again, the pieces should be long enough so they can easily be removed. Copper tubing can also be used, but, since the silver will also cement on the inside of the tubing, most people flatten it before use.

Chris Owen
- Benton, Arkansas, USA


July 31, 2018

Dee Kay,
Use of copper for silver refining is costly; there are several processes you can use for silver precipitation.

Bhupesh Mulik
CAC admixtures - Mumbai,india


September 20, 2018

Dear Ajit,
Once you have dissolved the all the silver into Nitric acid and your concentrated Nitric acid solution is ready, just add twice the amount of Distilled water to this solution & let cool for some time.
Next Filter the solution once, & then add HCl to get white Chloride until the color of the solution shows yellowish during addition. Stop at this stage and mix thoroughly the solution.
Wash this solution thoroughly, several times with distilled water till the pH paper shows mildly acidic and drain the water.
Next add 10% Sodium Hydroxide solution prepared with Distilled water and the white silver chloride turns blackish during addition of Sodium Hydroxide. Mix very very thoroughly & keep adding Sodium Chloride till the entire solution turns blackish & there are no white particles of Silver left in the solution.
Make a solution of 10-15% Hydrazine Hydrate with the distilled water and add gradually to the Black solution, the solution will fizz and you will see the Pure Silver rising to the surface. Keep adding 10-15% HH to the solution until the fizzing stops. Let Cool and start washing until the pH paper shows very mildly acidic.
Dry and heat to convert to Powder, and once dry Melt in Induction melter by adding a pinch or two of Boric Powder to get Pure 999.99% silver.
Please make sure you use all the clean consumables & utensils for this process ... try with a small batch first to be safe. This will surely give you good results.
All the best.

prakash pai
- mumbai, maharashtra, INDIA



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