# Any better options than copper for dropping silver?



## ssharktu17 (Feb 9, 2022)

Are there any better options? I saw some website mention SPC "silver precipitating crystals" though no idea what they are talking about.


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## Martijn (Feb 9, 2022)

No. Nothing better. Copper is closest to silver in the reactivity series. Except for tungsten and mercury. 
And i think the precipitating crystals is just the silver that is precipitated out on the copper. Or some more reactive metal than copper. Which is no good.


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## Martijn (Feb 9, 2022)

It could also be NaCl crystals. Table salt to get AgCl.


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## Lino1406 (Feb 10, 2022)

Adding H2O2 to silver nitrate solution will drop the silver


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## Yggdrasil (Feb 10, 2022)

Lino1406 said:


> Adding H2O2 to silver nitrate solution will drop the silver


Will it drop silver as metal or a salt?


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## orvi (Feb 10, 2022)

ssharktu17 said:


> Are there any better options? I saw some website mention SPC "silver precipitating crystals" though no idea what they are talking about.


Depends.
Firstly, we must clarify what you expect the substitute for copper as precipitating/reducing agent should do better.
Lower the cost ? Improve the purity ? simplify the procedure ?
There are several variables to consider. And as it is any time, all comes with cost.

You can use NaCl or HCl to precipitate silver chloride and get it very, very clean - thus improving the purity over silver cementing on copper. However, turning AgCl to elemental silver is more time intensive and messy. But if you have decent other metals in solution, you could make sharp separation on these - which is helpful in some cases.

You can use selective precipitants for silver, like sodium formate, to produce very high purity silver from relatively dirty solutions. But it also come with the higher cost of reagents, labor intensity and procedure difficulty.

These are the two other most common methods employed. Altough no one of these beat the simplicity of hanging copper bar to the jug of silver nitrate solution 

There are more methods, mainly variations of these above. And also many more, regarding selective precipitation of silver from solution, but reducing agents used are often quite expensive.

These 3 methods profiled over time as most reliable, cost effective and replicable


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## ssharktu17 (Feb 10, 2022)

orvi said:


> Depends.
> Firstly, we must clarify what you expect the substitute for copper as precipitating/reducing agent should do better.
> Lower the cost ? Improve the purity ? simplify the procedure ?
> There are several variables to consider. And as it is any time, all comes with cost.
> ...


Looks like I will be sticking with copper. I might research the HCL method a bit just to compare them. More steps = more work though haha.


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## ssharktu17 (Feb 11, 2022)

What’s the best copper to use? Copper Busbar?


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## Gsracer (Feb 11, 2022)

I cast my own Copper bars from scrap and hang them in the silver nitrate with 316 stainless wire. 

In between runs I hang the copper bars in my stock pot. Then when I go to use them again. Brush the oxide off with a stainless wire brush and reuse.


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## Lino1406 (Feb 11, 2022)

Yggdrasil said:


> Will it drop silver as metal or a salt?


2Ag+ + H2O2 = 2Ag + H2O +


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## Yggdrasil (Feb 11, 2022)

Thanks Lino


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## Lino1406 (Feb 11, 2022)

2Ag+ H2O2 = 2H+ + O2 + 2Ag


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## cejohnsonsr1 (Feb 11, 2022)

I’d have to say no. Cementing on copper is cheap, fairly quick and the purity is pretty good.


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## orvi (Feb 11, 2022)

Lino1406 said:


> 2Ag+ H2O2 = 2H+ + O2 + 2Ag


This is first time I´m hearing about this reaction. Strange to look at it - oxidant reducing other "oxidant"  
But from the potential point of view, yep... I must try this out sometime on my own, just look so unfamiliar I have to do it to convince myself throughly


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## Lino1406 (Feb 11, 2022)

orvi said:


> This is first time I´m hearing about this reaction. Strange to look at it - oxidant reducing other "oxidant"
> But from the potential point of view, yep... I must try this out sometime on my own, just look so unfamiliar I have to do it to convince myself throughly


E(Ag)o= 0.8v E(H2O2)r< 0.8v


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## Yggdrasil (Feb 11, 2022)

Lino1406 said:


> E(Ag)o= 0.8v E(H2O2)r< 0.8v


So if you add Hydrogenperoxide to Silver nitrate, you get silver and Nitric?
Or it used under other conditions?


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## Lino1406 (Feb 11, 2022)

Ag and nitric acid, by electrochemistry


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## Gsracer (Feb 11, 2022)

Forgive my ignorance, as i have never heard of this before. Wouldnt the silver begin to go back into solution? Is the nitric reusable. I think im missing the point, or the process, or both. Id be really interested to know more. Thank you!


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## ssharktu17 (Feb 11, 2022)

Lino1406 said:


> 2Ag+ H2O2 = 2H+ + O2 + 2Ag


But wouldnt it drop copper too? or you would have to get the ORP just right?


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## Lino1406 (Feb 11, 2022)

No, (copper)Eo<. ( H2O2)Er


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## ssharktu17 (Feb 11, 2022)

Lino1406 said:


> No, (copper)Eo<. ( H2O2)Er


hmmmm sounds great to me. Do you do it yourself?


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## Lino1406 (Feb 11, 2022)

I did once


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## Gsracer (Feb 12, 2022)

I found this on the web referencing Hydrogen peroxide precipitation from an xray film solution, looks like the silver precipitates as a sulphide.
Recovery of silver from X-ray film processing effluents by hydrogen peroxide treatment​Author links open overlay panelA.D.BasE.Y.YaziciH.Deveci
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Abstract​In this study, recovery of silver from X-ray film processing effluents by precipitation was studied. Hydrogen peroxide was used as the precipitating agent. A full factorial design (42) approach was adopted for the study. The results have shown that precipitation process is highly exothermic in nature with the evolution of copious amount of heat apparently owing to the concomitant oxidation of thiosulphate. The precipitation of silver by hydrogen peroxide is a fast reaction, which is almost complete within minutes. It is also an acid consuming reaction with the tendency of pH to increase towards neutral/alkaline conditions. The concentration of hydrogen peroxide was proved to be statistically the most significant factor affecting the precipitation process. High silver recoveries (≥ 95%) from the waste solution (1.1 g/L Ag, 113 g/L S2O32 −) were obtained only at high levels of H2O2 (≥ 37.6 g/L). Over the reaction period, a substantial increase in the concentration of sulphate was noted indicating the consumption of H2O2 mainly by the oxidation of thiosulphate. Increasing pH was found to have a beneficial effect on the recovery of silver noticeably at low H2O2 concentrations. The addition of ethylene glycol (0.5–10 mL) enhanced the recovery of Ag (by 1.3–18.7%) presumably due to its stabilising effect on H2O2. SEM–EDS and XRD analyses of the precipitates have revealed that silver is present mainly as fine silver sulphide. These findings demonstrate that the waste photoprocessing solutions can be suitably treated by hydrogen peroxide to recover silver and remove thiosulphate.
Highlights​► Hydrogen peroxide can be effectively used for treatment of photoprocessing effluents. ► Precipitation of silver by H2O2 is complete within minutes. ► H2O2 concentration profoundly affects the recovery of silver. ► Addition of ethylene glycol as a stabiliser improves the effectiveness of H2O2. ► Silver precipitates mainly as silver sulphide.


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## Gsracer (Feb 12, 2022)

also found this 






Recovery of silver from waste silver chloride for the MEO system (Technical Report) | OSTI.GOV


The U.S. Department of Energy's Office of Scientific and Technical Information




www.osti.gov





stating that hydrogen peroxide can reduce silver chloride to silver metal.


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## Gsracer (Feb 12, 2022)

and yet another interesting read, patent application regarding using hydrogen peroxide during nitric digestion which claims to not produce nitrogen oxides or at least minimize them. 



https://patentimages.storage.googleapis.com/pdfs/65897df1e37781736f29/EP0568259A1.pdf


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## orvi (Feb 12, 2022)

Gsracer said:


> I found this on the web referencing Hydrogen peroxide precipitation from an xray film solution, looks like the silver precipitates as a sulphide.
> Recovery of silver from X-ray film processing effluents by hydrogen peroxide treatment​Author links open overlay panelA.D.BasE.Y.YaziciH.Deveci
> Show more
> Add to Mendeley
> ...


In this particular publication, silver sulfide is produced, which is slightly different than elemental silver. But still very interesting work. Mainly how the sulfide is produced in oxidizing media. And silver valence is unaffected.


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## ssharktu17 (Feb 13, 2022)

maybe going from AgCl would be best


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