precipitating pd from an ar solution wth copper

i tested the solution with sncl2 crystals----the colour of the test was strong yellow------
then i added a cu bar to the ar solution and black precipitates appeared---then i tested the ar solution again,and the collor continues yellow(not so strong)-----this indicates that there is still pd in solution------how can i accelerate the precipitation?
i thought of adding some bleach to the ar solution and then the copper bar---could this be done ?or the bleach would redissolve the black ppt. formed?
thanks for remarks and help
Arthur

Are you sure about the test? DMG gives yellow precipitate, SnCl2 should get green as far as Pd is not masked by something else.

Nevertheless, when you get a black cement on copper you have obviously something precious.

Nevertheless, when you get a black cement on copper you have obviously something precious.

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Or mercury.

I agree DMG is the definitive test.

Solar Plasma,i am not sure if it is pd---i even thought that might be pt ---even the possibily of having some au also passes through my mind---
what i know is that copper precipitates black pms----
i am doing these experiments under difficult circunstances(do not have dmg,and other material with which i could precipitate yellow pd(if it is pd)----so i am trying to obtain the black powder with copper precipitation and then see which pms do i have--
thanks for reminding me about the sncl2 crystals tests--
regards
Arthur
ps :the question remains---would bleach help to precipitate black powder from ar with copper?

never thought of HG(mercury)-----i hope not
Arthur

Arthur,

Copper cementation of PGMs is very slow. I leave copper hanging in the vessels for couple of weeks or until stannous shows no reaction and the solution becomes blue. The only way to speed it up is keeping it in warm place. Normally, I collect PGM solutions in 10L jag until its full, than move to bucket with hanging copper. I use the same copper piece until it fully dissolves as it is practically impossible to wash black precipitate from copper without loosing values. It falls off itself when crust is thick enough.

Thanks Alentia for your reply------i know that it takes a long time----that is why i am thinking of adding bleach to the ar solution--i think that doing this i add cl to the already chloride salts present in the ar solution
regards
Arthur

Arthur,

Cementation depends on the ions in solution coming in contact with the copper. You can speed it up by keeping the solution in motion. Stir it often, or add an automatic stirrer.

I can't see how adding bleach would help. Assuming you had an excess of HCl in your AR, I think adding an oxidizer like bleach would redissolve the metal you're trying to cement.

Dave

I don't know if it helps, but i found this link about the yellow reaction: http://goldrefiningforum.com/~goldrefi/phpBB3/viewtopic.php?f=37&t=17457

What material did you process?

Arthur,

Get some DMG powder, at least for future deals. If you're dealing with Pd, you must have it. Also, it's a great way to test for nickel. It's cheap. A gram will do at least 500 tests if you take care of it. Try to dissolve 1 gram in 100ml of boiling distilled water (see Hoke), with occasional stirring, maybe for an hour or 2. It probably won't all dissolve. Don't worry about it. Let it cool and settle as much as you can and pour off the solution (or, filter it). Put a drop of your sample on a spot plate or a white plastic spoon. Add a drop of DMG. A yellow/orange, fluffy precipitates proves the existence of Pd. If the solution is too dark to see, add a drop or two of water. With very small amounts of Pd, I have had to use an eye loupe to see the yellow stuff on the bottom. To test for nickel in an acid solution, add a drop of solution, a couple of drops of ammonia, and a drop of DMG. With nickel, it will turn red.

Note: It is much easier to dissolve the DMG in alcohol or an NaOH solution than in water. However, the water solution is best for testing because it's more sensitive than the others.

I'm no chemist but, since you're trying to reduce those metals, it wouldn't be good to add an oxidizing chemical. It seems to me, it would be a tug of war, the copper trying to reduce the gold, etc., out of solution, and the chlorine trying to re-dissolve it.

goldsilverpro said:

Note: It is much easier to dissolve the DMG in alcohol or an NaOH solution than in water. However, the water solution is best for testing because it's more sensitive than the others.

I'm no chemist but, since you're trying to reduce those metals, it wouldn't be good to add an oxidizing chemical. It seems to me, it would be a tug of war, the copper trying to reduce the gold, etc., out of solution, and the chlorine trying to re-dissolve it.

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Right on both accounts GSP - In fact your Pd will stay &/or go back into solution without the oxidizer the HCL alone is enough to keep/put back the Pd into solution

HCL will not dissolve a solid piece of Pd metal but when it is finely divided HCL alone will - I found this out when processing CATs - the Pd (or at least some) would go into solution as soon as I added the HCL to the combs & before I added the CL (oxidizer)

Also I just got done working on recovering the PMs from last years anode slimes (this was my first go at anode slimes)

After I incinerated them I did a nitric leach to get the remaining silver & of course some Pd went with that which I dropped with DMG (prepared with NaOH)

The next leach was AR (hot) to get the Au & PGMs with the plan to use copper to cement out the values to then be refined - what happened was interesting

I put the AR on the hot plate & turned it up to setting 4 - when it got relatively warm I dropped in my copper & the Au & PGMs started to come down out of solution - as expected - so I let it sit on the hot plate to do its thing for about 4 or 5 hours --- at which point I came & did a stannous test which showed there was still some Pd (kind of a lite to mid green on the swab) along with a trace of Pt (just a bit of orange) & the solution was showing good blue with just a hint of green --- so I left it on the hot plate & came back to check on it about 1&1/2 hours later - my solution had gone back to a blue/green & my stannous test showed heavy Pd green - almost black

I had my Au & at least most of the Pt in the bottom of the beaker & crusted on the copper --- but the Pd (& likely some Pt) had gone "back" into solution

That's when it dawned on me (from my CAT leaching experience) you can't really cement Pd from a solution that has HCL in the mix - The HCL puts the "finely divided" Pd back into solution --- & because HCL also does not dissolve copper

So (at least the best I can figure based on this out come) is that with AR - when you first start to try to cement PGMs using copper they will come down out of solution as long as the ion exchange with the nitric is taking place (copper going into solution - PGMs coming out) but once the nitric is saturated with copper the HCL goes back to work on the Pd putting the Pd back into solution

So what I did was filtered the Au & Pt from the AR that was once again loaded with Pd (as well as Cu & likely some Pt) was cement it with zinc --- because this of course was heavy in copper I then treated it with "hot" nitric - & because I am low on DMG instead of dropping the PD out of a nitrate solution with DMG I cemented it with copper which needs to be done hot other wise the Pd will passivate the copper & slow the ion exchange way down

So at this point of working on my anode slimes I have my silver removed (& most other base metals) - have parted the Au out (nice little 11 gr bar) & have my PGMs recovered (about 57 gr PGM black) that of course is contaminated with Cu & trace ? base metals

Kurt

I would like to point out one more thing being as how it came up --- be CAREFUL when using DMG prepared with alcohol on silver nitrate solutions

It is one thing to use it to "test" Ag nitrate for Pd --- but DO NOT use it to precipitate Pd from an Ag nitrate solution

Adding alcohol to silver nitrate is how you make silver fulminate which is a VERY pressure sensitive highly explosive compound

A drop of DMG prepared this way added to a couple ml of Ag nitrate (for testing) is not a real problem --- but precipitating on a large scale is

I prepare all my DMG with NaOH for this very reason

From wiki ----

Silver fulminate (AgCNO) is the highly explosive silver salt of fulminic acid.

Silver fulminate is a primary explosive that has very little practical value due to its extreme sensitivity to impact, heat, pressure and electricity. The compound becomes progressively sensitive as it is aggregated, even in small amounts; the touch of a falling feather, the impact of a single water droplet or a small static discharge are all capable of explosively detonating an unconfined pile of silver fulminate no larger than a dime and no heavier than a few milligrams. Aggregation of larger quantities is impossible due to the compound's tendency to self-detonate under its own weight.

Silver fulminate can be prepared --- " " " unintentionally" " ",--- when an acidic solution of silver nitrate comes in contact with alcohol

Kurt

Arthur,

From other posts I know, that you are working a lot with automotive catalysts, leaching the precious metals contained therein. Thus, your SnCl₂-test lets me suspect, that the examined solution contains mainly platinum.

Adding some bleach to the AR-solution could help indeed, but in a most different sense. It 1.) will keep the platinum dissolved as Pt (IV); [PtCl₆]^2-, and 2.) will slowly oxydize Pd(II) to Pd(IV); [PdCl₆]^2-. Both complex anions will be absorbed strongly by anion-exchange-resin beads; strong base, quaternary ammonium type, chloride form. The resin takes up [PtCl₆]^2-- and/or PdCl₆]^2--ions, setting free equivalent amounts of Cl^--ions into solution. To absorb 1 gram of Pt/Pd about 10 grams of resin-beads are needed. Solution and resin-beads are stirred together constantly at room-temperature (usually a few hours). The loaden resin-beads are filtered, washed, dried and incinerated cautiously to metallic Pt/Pd, in the final step at ca. 900^oC, preferably under exclusion of air.

thanks,Freechemist---in this case,it is not car catalyst ,but you are right---the yellow collor is pt,i dropped with nh4cl-----forming( nh4)2ptcl6--salt----------
the material is a mixture of many metalics powder----sometimes a batch have more au,others,pt and pd and others lots of ag---it is over 200kilos ,and was given to me freely-by a person whom i taught some recuperation tricks --this person was just after cherry pics,and left these metallic powders materials behind----
at the present moment ,i used only 3kilos from the 213kilos he gave to me
thanks and regards
Arthur

ps :the platinum salt is very dangerous to me---it gives me lung trouble as soon as it is dried

Very sorry to hear that it makes you ill.
You've worked too long (and perhaps too carelessly) with the Pt(IV) salts. That is a shame. Not just the yellow powder, but chloroplatinic acid will get you too.

My friend, I suggest that you quit while you're ahead and walk away from PGM recovery. Every day longer you work with them you will become more and more sensitized. I say PGM, not just platinum, because most scrap encountered with the other PGM metals has the platinum as well. So even when you precipitate palladium salts, the trace platinum impurities can also cause a reaction--it does not take much.

Pt(IV) is so allergenic that there is no exposure level recognized as not contributing to respiratory sensitization. I believe the US OSHA PEL is 2 micrograms/cubic meter, and that still is thought too high, as quite a number of people working with it on a daily basis become sensitized--sometimes in a year or two, sometimes in twenty, sometimes never if an individual lacks the genetic predisposition.

Thanks LOU,for your concern---you are right about pt salts---i noticed this alergy 3years ago and from that moment on,i avoided working with scrap containing pt---now i am 71years old and retired (since june 1913) ---- i still do some research,but as a hobby--- i still have my lab(since i am the owner of the property) and i go there once a week ,when i do some research---
this material(213kilos) is in the lab and i did some experiments with 3kilos----------------------

thanks and regards to you
Arthur Kierski