Getting Ag from AgNO3 using Cu powder

[HAuCl4]

The thing that interests me about this is the ease of treating the waste acid. In a formic reduction a complex is formed which is a pain to break causing extra steps and specialty chemicals to clean up the acid.

When treating old sterling silver it is not uncommon to find 0.5 parts per thousand of gold in the silver. In this method the lack of filtration before adding the copper would leave the gold in with the silver. Also any palladium, which can also be in old sterling, will be in the silver as well.

What I think Hrushi meant by adding hydrochloric was testing a drop of the blue acid in water containing a few drops of hydrochloric. Any silver still in solution will turn a cloudy white. I do not think he is adding hydrochloric to the silver nitrate.

Check Hoke's description of procedures for cementing/cleaning up the silver chloride at the Homestake mine after Miller processing. At the end there is a pretty thorough description of getting the silver crystals cleaned up with ferric chloride and washing with HCl. Those crystals are about the dirtiest cemented silver that can be had as feed by man or beast. And yes, there will be some AgCl at the end to deal with. I didn't learn it from there, but from trial and error. :shock:

From the video it seems the bucket on his left has HCl and leaves a little white cloud when added to the blue liquid.

Boy, am I glad that is Hoke claiming 9995-9997 silver and not me... :lol:

 

[HAuCl4]

When treating old sterling silver it is not uncommon to find 0.5 parts per thousand of gold in the silver. In this method the lack of filtration before adding the copper would leave the gold in with the silver. Also any palladium, which can also be in old sterling, will be in the silver as well.

Cementing the silver nitrate with silver foil or silver dust and filtration an option here do you think?. :?:

(Clarification: With the purpose of filtrating out all PMs except silver, before the silver drop).

 

[Platdigger]

You need a metal higher in reactivity than the metal you are trying to cement out.

 

[goldsilverpro]

When treating old sterling silver it is not uncommon to find 0.5 parts per thousand of gold in the silver. In this method the lack of filtration before adding the copper would leave the gold in with the silver. Also any palladium, which can also be in old sterling, will be in the silver as well.

Cementing the silver nitrate with silver foil or silver dust and filtration an option here do you think?. :?:

(Clarification: With the purpose of filtrating out all PMs except silver, before the silver drop).

I see what you're saying. It may work. However, the potential differences are so slight on the PM end of the EM series, PM cementation may be incomplete or not happen. Also, the EM series chart is based on pure systems and, in practice, things like contamination, acid strength, temperature, etc., can produce deviation from the ideal.

 

[Platdigger]

OK, I see it now also Chris.
When I first read it I thought he was suggesting cementing out silver on or with silver.

 

[goldsilverpro]

OK, I see it now also Chris.
When I first read it I thought he was suggesting cementing out silver on or with silver.

Me, too.

 

[Barren Realms 007]

Thought the same thing then I read between the lines and figured it out and let one of you answer that one.

 

[HAuCl4]

In theory it should work, in practice I can see problems filtrating the bulky solution and retaining the fines. When using a cell this is no problem since the mud gets retained and concentrated slowly in the anode bags, but here there maybe practical problems or the filtration may take a very long time. The cementing could take a long time too. Only an experiment will tell the tale.

 

[hrushi]

Well I had a long vacation now finally back at work
I would be answering all your doubts
I really appreciate all of you for your great study and experience in this field
I am totally new I hardly have experience of few years.
I am not technically sound as you people are.
I don't want to challenge any body or test anyone.
I would be posting all my replies based on my practical experience.
SO please don't feel offended.
I have learned a lot from all you guys.
Thank You all
Hrushi

 

[hrushi]

Although you'll never get 999 from a cementation process, I would think the purity would be less with Cu powder than with Cu bars, due to possible Cu entrapment. Of course, if you're purifying it further, it wouldn't make much difference.

Hello GSP
I would say every time I get 999+ Ag with the process.
Yes Cu entrapment is there but if we stir it well Cu entrapment is not there and slowly all Cu is dissolved.
Hrushi

 

[hrushi]

Are you adding a precise quantity of copper to stoichiometrically replace the silver?

No.
Firstly we have to thoroughly stir the sol.
It completely depends on how much thick is the AgCl spot appears after add HCl.
If AgCl spot is thick after good stirring then add Cu powder and don't add large quantity of Cu at a time add in small parts it is really helpful. Slowly AgCl spot will faint. And finally there would be no AgCl spot even after adding HCl all Ag will be cemented.
If after adding HCl if Dark or black spot appears then it indicates that we have added excess Cu no need to worry. Excess Cu can be removed by add some AgNO3 if we have or take 5lts of H2O add 250mL of H2SO4 and put in cemented Ag and stir it for some time you can do this for 1-2 times more.
Please be careful while adding Cu powder it is very important that we small parts of Cu powder.
Hrushi

 

[hrushi]

Hello GSP

This is a very interesting process and I see merit in it. The copper looked beautiful and pure and I would be very interested in knowing it's source and how you prepared it.

I recovered Cu from left over CuNO3 using Fe

If you are trying to maximize purity, any excess of copper would have a negative effect. Unlike copper buss bars, you can't pull out the excess copper powder and any remaining will contaminate the silver. Too little copper will leave silver in solution. You can't guess on this and there are no accurate visual clues. You need to know (a) The amount of free nitric in the solution and (b) The amount of silver in the solution.

(a) is easily solved by using less nitric than is necessary to dissolve all of the silver in the batch. In other words, when all of the nitric is spent (preferably heating the solution at the end), there should be some undissolved silver remaining on the bottom of the container. Only by doing this will there be essentially zero free nitric. A liter of nitric, diluted to 2 liters with distilled water, will dissolve close to 821 g of Ag or 240 g of Cu. I would use enough nitric yo only dissolve 90-95% of the metal.

(b) is solved by knowing exactly how much silver is in the solution. This is known by either knowing exactly how much silver was dissolved (difficult) or by analyzing the solution. The latter is cheap (about $100 setup cost), fast (5 minutes), and easy to do using the Volhard titration method.

Here's how I would do this for maximum silver purity:

(1) Use only enough nitric (plus distilled water) to dissolve 90-95% of the silver alloy. Heat at the end. If too much nitric is used and all the alloy dissolves, add enough more alloy until all the nitric is spent and some metal remains. Put the remaining metal in the next batch.
(2) Accurately measure the total volume of solution, analyze the silver content, and calculate the total silver in solution.
(3) Depending on how good you are at this, add enough Cu powder to cement between 95 and 99% of the total silver. It takes about .294g of Cu to cement 1g of silver. Instead of mixing by hand, use a stainless paint mixer (one with a chopping action) chucked in a drill or a small motor.
(4) When all the Cu has reacted, remove the stirrer and hang some Cu buss bars or clean pipe in the solution to cement the remaining 1-5% of the silver. Remove and clean off the bars.

Steps (3) and (4) are added because it would be very difficult to determine exactly the amount of Cu needed to cement 100% of the silver.

I doubt if all this will add more than 20-30 minutes of labor to each batch.

I do not follow any of above things
It is quite simple and very easy process believe me.
I really don't know amount of Ag present in sol.
And also I really don't how much Cu by WEIGHT I am adding in sol. Never did that.
I simply check that by adding HCl
Thank you
Hrushi

 

[hrushi]

Chris,

You have the copper and silver ratios reversed:

2 AgNO3 + Cu --> Cu(NO3)2 + 2Ag

2 *107.8 = 215.6 g Ag
1 * 63.55 = 63.55 g Cu

215.6 / 63.55 = 3.39 g of Ag per gram of Cu used.

So 1 gram of Cu precipitates ~3.4 g of Ag.

Steve

Hi Steve
got UR DVD the great you have taken tonnes of efforts on making them.
great calculation above they are very precise
Hrushi

 

[hrushi]

He had stated that he adds a little bit of HCL till he gets no white silver cloride reaction reaction and then he seperates the material and adds a copper bar to the liquid to finish the process.

Barren
No
I complete the process using Cu powder ONLY NO CU BARS ARE USED its quite simple.
Hrushi

 

[hrushi]

I wonder what hrushi's washing procedure is for the silver crystals and if he uses anything to leach the silver crystals after washing and before melting. An hour in ferric chloride with stirring cleans up pretty much any excess copper and leaves silver 999+ with iron traces as the main contaminant.

4metals formate method seems more straightforward though (haven't tried it yet).

edit: I just saw the video and his stirring tank is made of...steel, and he is adding HCl...voila ferric chloride is in there somewhere!. 8)

Iron traces can be removed at the time of melting bu adding flux. As Fe doesn't melt even at 1050C it can be removed bu using graphite rod. One thing is sure it needs good cleaning while melting.
Hrushi

 

[hrushi]

The thing that interests me about this is the ease of treating the waste acid. In a formic reduction a complex is formed which is a pain to break causing extra steps and specialty chemicals to clean up the acid.

When treating old sterling silver it is not uncommon to find 0.5 parts per thousand of gold in the silver. In this method the lack of filtration before adding the copper would leave the gold in with the silver. Also any palladium, which can also be in old sterling, will be in the silver as well.

What I think Hrushi meant by adding hydrochloric was testing a drop of the blue acid in water containing a few drops of hydrochloric. Any silver still in solution will turn a cloudy white. I do not think he is adding hydrochloric to the silver nitrate.

All cementation is done after filtration of solution so any Au or PGM is left behind.
I am adding HCl to AgNO3 Sol check amount Ag still present in sol.
Hrushi

 

[hrushi]

The thing that interests me about this is the ease of treating the waste acid. In a formic reduction a complex is formed which is a pain to break causing extra steps and specialty chemicals to clean up the acid.

When treating old sterling silver it is not uncommon to find 0.5 parts per thousand of gold in the silver. In this method the lack of filtration before adding the copper would leave the gold in with the silver. Also any palladium, which can also be in old sterling, will be in the silver as well.

What I think Hrushi meant by adding hydrochloric was testing a drop of the blue acid in water containing a few drops of hydrochloric. Any silver still in solution will turn a cloudy white. I do not think he is adding hydrochloric to the silver nitrate.

Check Hoke's description of procedures for cementing/cleaning up the silver chloride at the Homestake mine after Miller processing. At the end there is a pretty thorough description of getting the silver crystals cleaned up with ferric chloride and washing with HCl. Those crystals are about the dirtiest cemented silver that can be had as feed by man or beast. And yes, there will be some AgCl at the end to deal with. I didn't learn it from there, but from trial and error. :shock:

From the video it seems the bucket on his left has HCl and leaves a little white cloud when added to the blue liquid.

Boy, am I glad that is Hoke claiming 9995-9997 silver and not me... :lol:

True
but according to my experience when i recovered Ag from AgCl there are more losses, more efforts and even after melting some amount of AgO is present in ingots and more time I can recover near about 25 Kg of Ag( Sorry I am not used to pounds and Kg ratio) in just 25-30 min and of 999+ purity.
hrushi

 

[4metals]

First I would like to thank Hrushi for his follow up on this thread.

Although you are not adding a stoichiometric quantity of copper to the process vat by calculating the exact quantity of silver, in essence you are doing it by adding until the solution tests silver free to chlorides and adding extra silver nitrate if you overshoot it.

The powdered copper you use must be very fine, do you know what the mesh size is?

I do not know why you add the HCl to the process vat to test for silver instead of adding a few drops of the process solution to a HCl solution out of the process vat. Apparently the presence of a small quantity of silver chloride is converted into silver metal when melting the silver.

What analytical method are you using to determine the .999+ purity. Have you ever had it assayed by ICP?

Any more video's would be appreciated, you have an interesting setup. I would especially enjoy a video of the silver nitrate HCl testing step.

 

[teclu]

Hello Hrushi,
Have you tried before the Au cementation(from AR) with Cu powder?
It could be a reasonable alternative for remove Au from AR solution? AR solution which besides gold contains base metals(Cu, Ni, Fe and Sn)
Thanks!
teclu

 

[eeTHr]

How about a small, slow, motor, with a long shaft and a copper bar attached to the shaft as a stirrer blade? For faster results, make a bank of four motors with stirrers.

The motors would need to be sealed air tight, like motors used in explosives areas.

When the copper bar blades get too small, replace them, and re-process the old blades.

This would solve the "contact all the silver nitrate" problem, and the "too much copper" problem.

I would recommend gloves and eye protection, though. And strong exit ventilation behind the vat.