# cementing pm with copper



## ericrm (Sep 29, 2012)

does someone know if when you cement pm with copper in a aqua regia solution, if all gold fall to the bottom. i know that all pm will cement out of solution if done correctly. but my main concern is about small particle just flotting aroud.

so if i have 1g of gold in solution and i cement it with copper, i will have 1 g out of solution... but will i have 1 g at the bottom in a 24 hour standing period ?


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## Geo (Sep 29, 2012)

if you start with one gram of gold, there will be more than 1 gram cemented out. the rest will be contamination. usually copper. gold is heavier than the solution, given enough time, all solids will settle to the bottom.


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## ericrm (Sep 29, 2012)

but Geo will enuf time will be in the 24 hour period? a years ago when i was using that way to recover my gold(mostly because i didnt know what i was doing)i was leaving by batch for week before siphoning...

i realy wanna make sure that i wont endup with half of my material floting around. the solution on witch i intend to use it, is very dilute, less than half a gram liter but very voluminous (like a stock pot), but this isnt a stock pot where your happy to manage to get something because you already made your money and it just gravy... ,i wanna use it on one of my recovery process and i want to make sure it is practicaly bullet proof and constant.....


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## Geo (Sep 29, 2012)

evaporate the solution down very low. make sure the PH is low even if you have to add some acid. after evaporating, filter the remaining solution in case some base metal fell out of solution. put your copper in and heat the solution to steaming. it will help put copper into solution. as copper goes in, PM's come out.


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## ericrm (Sep 29, 2012)

i cannot evaporate it down, there is way to much solution(10-20 many liters at the time). hoke's talk about using zinc shaving (it would be usefull because the solution would be clear but i would be stuck to recover my gold a second time ...

my concern is very much about the pm "attitude" how long that powder take to settle when you want 99% of that same powder back. is 24h ok ? one week? this is what i realy need to know ,i need to have some certitude about that gold powder "way of acting"


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## NobleMetalWorks (Sep 29, 2012)

Are you using copper because it's difficult for you to get SMB? You can also use Ferrous Sulfate, or if you want to spend the money you could use other things.

You are right about zinc turnings, it will precipitate everything lower on the reactivity scale. You are also right that you will have drop all metals, and have to refine further to get 24k. However, if you did do it that way, then digested the resulting material in HCl, then washed, incinerated so that you insure you have no more free HCl in solution, then you could digest in Nitric Acid, which would digest Pd, Cu, Ag, etc. If you have no other PGMs associated with your solution, you should be left with mostly Au. However, even after all that, there will still be other contaminants associated with your AU.

Where are you from? There are off the shelf products you can also use to selectively precipitate your Au out of solution, I believe some people use Stump Out, although I have not yet tried it myself.

If SMB is difficult for you to come by, I could send you some, you just live in Canada, correct?

Scott


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## ericrm (Sep 29, 2012)

SBrown said:


> Are you using copper because it's difficult for you to get SMB? You can also use Ferrous Sulfate, or if you want to spend the money you could use other things.
> 
> You are right about zinc turnings, it will precipitate everything lower on the reactivity scale. You are also right that you will have drop all metals, and have to refine further to get 24k. However, if you did do it that way, then digested the resulting material in HCl, then washed, incinerated so that you insure you have no more free HCl in solution, then you could digest in Nitric Acid, which would digest Pd, Cu, Ag, etc. If you have no other PGMs associated with your solution, you should be left with mostly Au. However, even after all that, there will still be other contaminants associated with your AU.
> 
> ...



this is a very generous offer, thank you very much, but it wont be needed. i have acces to very clean smb. in a process that im working on right now, i endup with a huge volume of ar solution with very little gold in it (just like a regular stock pot), but since this solution come from a recovery process and not a regular stock pot, i want to make sure that i could use the cementing gold with copper way without worry about loosing value and for that i need to know how long cemented gold will take to settle...


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## NobleMetalWorks (Sep 29, 2012)

I understand now, I think zinc turnings would be best for what you are talking about, because you have so little Au in solution, precipitating it out with the other metals, then decanting, washing the resulting precipitated values, incineration, HCl soak on a heat pad to warm the solution so that it digests most of your base metals, then wash, incinerate again to insure there is no free HCl, then soak in Nitric to remove Ag, Pd, Cu, etc. You will then have very little solution and should be able to recover the Au from that point forward.

The reason I would use Zinc Turnings is that you probably already have Cu associated with your values, cementing that out with your other values will only make them easier to collect initially, and because I suggested the Nitric Acid wash to remove Pd and Ag, that will remove your Cu as well. So in the end you will have the same purity, but initially it would be easier, I think, to collect the values with the base metals as well.

Just my thoughts...

Scott


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## quisno (Dec 9, 2013)

urea is a good material to make the gold drop out of the AR solution
We have ore we table use nitric to remove the silver and one pgm this keeps you from making an explosion


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## Smack (Dec 10, 2013)

How so? :shock: Have you used urea to precipitate gold from Aqua Regia before?


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## moose7802 (Dec 10, 2013)

Yes I'm quite curious about that? :roll:


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## niteliteone (Dec 10, 2013)

quisno said:


> urea is a good material to make the gold drop out of the AR solution
> We have ore we table use nitric to remove the silver and one pgm this keeps you from making an explosion


Have you read where "Urea" added to AR with gold in solution *can* decompose into explosive compounds :shock: 
Learn a little more and you will know that.

PS. Urea is NOT a good precipitant and actually has little use in recovery or refining other that testing for excess nitric. Nothing more.


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