extra gold and palladium

[arthur kierski]

i have a lot of spent powder from which i extracted gold , palladium ,silver by the tradicional methods--
as this time of the year i have less work then usual, i decided to make a ssn leach in some of this powder---not knowing if i had pms in the solution and curious of how long it takes to leach this powder (first time that i did this experiment)----after 2hours of leaching,itook some of the liquid and tested with stanous chloride ----the result was fantastic,deep ,almost purple black collor in the spot plate-------at the same time i was happy,and frustrated because i did not extract all the pms using the traditional methods(ar,hcl-clorox,hcl-h2o2)--
question:did any member of the forum uses or used this ssn method?if so how one knows how long it takes to put all the metals in solution?-----
thanks for any remarks----anyhow i will have some extra gold,pd and perhaps later dissolve the agcl from the powder with nh4oh
Arthur

 

[skippy]

Did you add iodine to it ? That can mess up stannous tests I believe.
Have you figured out what precious metal(s) are in your solution yet? I wonder if SSN dissolved rhodium residues that AR couldn't.

 

[arthur kierski]

Skippy,thanks for asking-----i did not add iodine to the ssn leach---the only iodine is from the table salt(nacl)----it is infinitessimal----as for rhodium(i do not know if this special powder had it initially)--- i read that this leach dissolves platinum metals----as rh is a pt metal,it might dissolve---from the stanous test(by experience) it is mainly gold-----what i do not know is how long i must keep this powder leaching to dissolve all the pms----up to now ,i know that i have gold---i have not the faintest idea of the quantity--- i used around 5kilos of powder----i have over 500kilos of this powder
regards,
Arthur

 

[butcher]

arthur kierski,
I have not used this leach and cannot give details, but it seems to me to be a poor mans aqua regia:

NaCl + 2HNO3 --> HCl + HNO3 + NaNO3

Saturated salt (NaCl) and nitric acid (2HNO3) gives hydrochloric acid (HCl) nitric acid (HNO3) and sodium nitrate (NaNO3)
I do not know for sure if these ratio's of chemicals are right in the formula above, (weight's or moles), I have read before 7 parts saturated brine (saturated salt water) to 1 part nitric acid used as ratio in the SSN leach,(7:1 / brine: nitric ratio),

What I do note from the above equation above is you will create some unused sodium nitrate in solution (I would think adding a little HCl acid would help react this to make leach go further:
2HCl + NaNO3 --> HNO3 + HCL + NaCl

Also seems to me you will have an excess of NaCl just about any way you do this, when evaporating and denoxxing the salts will form easy, I would add a few drops of sulfuric acid when evaporating off any excess HNO3, so your salts do not bake out to dish as easily.

(A double-edged sword here: in first equation if NaNO3 salts unused in solution with H2SO4 would form some more HNO3 in solution to evaporate (adding earlier in process of denoxxing may help).

But If you did add HCL as in second equation above the sulfuric and sodium chloride would just form more HCl in solution when evaporating and may give less salts in bottom of dish when concentrating to drive off any free nitric acid)

What would be nice is if we could calculate mole of each ingredient and come up with a better leach by figuring correct proportions and acid to perfect this poor man aqua regia leach.

I would like to further calculate and look into the math and calculations (moles) of this leach further, and figure the best amounts of ingredients (Salt water and acids to add) and formula to use, I think I will put this on the to do list.

Being an aqua regia (substitute) I believe leach time would be very similar (maybe just a bit slower than aqua regia), also you very well can have nitric acid to eliminate before precipitating gold (depending on proportions used in equation above).

Again I have not used this leach and have not studied it, and the equations or advice above is just me doing some thinking here.

 

[arthur kierski]

thanks Butcher for all your thinking and the equations ----today i will do some more research on this matter-----as you read the formulae is 2gallons water plus 6lbs nacl+1liter nitric------in my first experiment,i used half the formulation and added 5kilos of spent powder-----to have an idea of what i have,i will take (filtrate) 1liter of this material and divide in 2parts----to 500ml of the solution i will add zinc powder to see what precipitates------to the other 500ml i will denox it and then smb to precipitate gold and to the liquid left i will add dmg to see if yellow pd salt precipitates-----as for adding more hcl to reinforce the formation of nano3 and eliminating nitric, or h2so4---i will leave for another time----because the author of the article about this leach says:it is one of the stronger and most effective leach that is used----he also says that no pms will precipitate without denoxing the leached solution-----i will mantain you informed of what i am doing so that you can give me more help on what to do
thanks again
Arthur

 

[arthur kierski]

Butcher,when denoxing i will add some h2so4 ass you cleverly mentioned-----
regards
Arthur

 

[butcher]

arthur kierski,
Arthur you stated: the formulae is 2gallons water plus 6lbs nacl+1liter nitric.

What I read was the salt was added to boiling water to saturate (excess salt added), then cooled letting excess salt settle from brine (no temperatures mentioned but Nacl solubility if I remember salt solubility is not that much more different from cool to warm solutions). They then took 7 quarts of solution of brine saturated salt water, and added one quart of HNO3, for a ratio of 7:1.

Did you follow this formula, saturating with boiling and cooling removing excess salt before adding nitric?




Just a thought since this is an aqua regia, you may try leaching your powdered material in several batches,

I would pre-treat the metal powders, {Incinerate powders materials to be leached, grind and classify with screen to size, boiling hot HCl wash, then boiling water, decanting hot, to help remove things that may give you trouble later, like tin, lead, and aluminum).

Using a several batch leach I will call upgrading batch leach.

Container #1 leach:
Use more metal powders than leach will hold, leach dissolving base metals and some values, letting most of values cement back into remaining undissolved metal powder, using heat and excess metal powders to help lower the excess nitric in solution.

(Stannous chloride, or other spot plate tests can tell you if have values in solution or where they are)’

Move the decanted solution from leach #1 to leach #2 container,
In leach # 2 we will cement out any values that may have been carried over from leach #1 solution, this will also pick up some base metals in leach #2.

Leach #1 we add fresh SSN leach solution, and again picking up base metals in this first leaching container, and trying to leave as much values behind in leach #1 as possible, then solution is transferred to leach#2 where any values that did get dissolved cement out and dissolve some more base metals from leach #2.


We can also have more leach batches (leach 3 or 4) if wanted,

Stannous chloride tests will be your eyes as to what is happening in this process of upgrading leaches.

The leaching and most all of the process could be done using corning ware dishes on hot plates, liquids and rinses are transferred with suction bulbs and jars, powders remain in dish on hotplate and are not transferred back and forth throughout most of the process, except when using an acid resistant plastic screen to separate larger pieces of metal from fine powders.


Basically leach #1 will be cleaned up of most base metals,
Once I was close to having most all of the base metals removed from the leach #1,
I would rinse remaining powders well in boiling water, lower heat and letting settle, but decant hot to help remove lead and base metals, repeated till no color in rinses.
Boil powders in a dilute solution of sodium hydroxide (NaOH) and water, using this caustic soda solution to neutralize remaining powder.
Rinsing out salts formed well in boiling hot rinses.
Dry powders.
Incinerate powders red hot.

{This step may not be needed if you pretreated the powders, but if you had trouble filtering solutions, then treat to remove the trouble
Boil in HCl let settle decant, boiling hot water rinses.
If you did the wash in HCl above re-incinerate.}

Treat powders with nitric acid, and rinses.
Then dissolve gold in aqua regia.

And so on.

 

[arthur kierski]

Butcher----i am dealing with powders that was already incinerated----already passed thru nitric to eliminate base metals and already passed thru ar or similar to extract gold ,pd pt etc----these powders in my mind were bare (no more pms) ------i prepared the leach solution as described by you in the thread and added these suposed bare powders ---i was startled when a few hours later when doing a stanous test ,the solution indicated gold predominantly----
today i took 500ml of this solution and precipitated with zinc powder-----it gave 1,15grams of precipitate that gave after ar ----0,78grams of gold-----in other words, at the moment this 500ml gave 0,78grams of gold-----as my leach have 4,3liters ,it might give at least 6,7grams of gold----it is a lot of gold when i expected none-----6,7grams of gold in 5kilos spent powder----

the advice you gave me as what you would do is excellent for fresh powders---if in the future i choose to adopt this leach method----tomorrow i will filtrate and extract the gold from the 3,8liters left----perhaps pms will stay behind in the twice spent powders because i do not know the time needed to leach these powder----tomorrow will be 48hours-----
thanks again and i will continue to inform you----by the way i have over 300kilos of this spent powder and not 500as i mentioned before
Arthur

 

[glondor]

Arthur, How do effectively rinse the leach from the powders with out having copious amounts of rinse water? Could it be that previous rinses were not as effective as you hoped?

 

[arthur kierski]

Glondor , i have a big vacuum filter pump----buchner type---the filter paper have a diameter of 50cms and the liquid deposit holds 50liters of liquid----i throw the solution with the powder in this filter and in a few minutes the liquid is in the deposit----i wash(rinse) the powder with a hose until the liquid in the deposit is clear---even liquid with tin paste is filtrated(of course it takes more time to filtate)----regards
Arthur

 

[skippy]

Arthur, How do effectively rinse the leach from the powders with out having copious amounts of rinse water? Could it be that previous rinses were not as effective as you hoped?

That would be my inclination, to suspect that during one or more extractions that lead to the accumulation of this material, something was missed. Whether by not enough rinsing, or insufficient oxidizer, or not enough stirring. I think SSN chemistry is subtley different than AR, and there may be an extra degree of potency achieved by saturating the solution with chloride ions, but I can't see how gold wouldn't dissolve in AR or HCl-Cl2 or HCL-H2O2, and then dissolve in SSN just on virtue of the formulation.

 

[arthur kierski]

probably the rinses were (as you mentioned) not so effective----but all liquids were and are tested with stanous chloride and dmg(pd)always-------but i have to agree with you that-pms were held in the powder---i said in the initial thread that i was surprised,frustrated and happy for discovering the extra pms with this leach method-------as i do a lot of powder monthly,i will continue to do what i used to do until today---only that the spent powder will be thrown into a ssn leach solution----

with this i improved my extraction methods
regards
Arthur

 

[skippy]

Arthur, I know you run a variety of different materials, and it seems that sometimes it might be hard to predict exactly what is in there and how long it will take to dissolve.
Running everything through another leach (SSN) may be good insurance to be sure you've got everything.

 

[arthur kierski]

Skippy,thanks for understanding my reasons---any how,with these mistakes , i think that only with the gold i became 20thousand dollars richer-----regards
Arthur

 

[arthur kierski]

continuing-----the leached material was precipitated with zinc powder----the precipitate was washed with dilute h2so4 until no more reaction-----the powder left was put in ar and gold went to the solution and was precipitaded with smb normally---the gold result was what i expected---around 0,75 grams per kilo of this leached powder-------------fine------

remarks: 5kilos of spent powder;after leaching ---left 8grams of material precipitated with zinc----this 8grams gave with ar dissolution 3,75grams of gold and remained in the filter paper around 4grams of a greysh powder(this is a powder that always remains in my work and i wrote for help in other threads)-------this powder may be some agcl?
thanks for following and regards
Arthur
ps:this 5kilos was leached during 48hours-----i am doing another 4kilos leach and 3kilos leach separatedely that will leach for more then 96hours---until monday----

 

[TXWolfie]

Maybe I am wrong but I thought I read somewhere that paltinum will also give off a deep purple almost blackish toned color with stannous.

 

[arthur kierski]

txwolfie, the spent powder tht i used for the leach,did not have pt in its original stage--------------next week i will try this experiment with fresh (not spent) car catalysers and then i will obtain pt,pd and perhaps rh----if the results (yealds)will be good then perhaps i will find a cheap way to extract these pmgs-------from catalysts---i am trying to this for many years (extracting pmgs from catalist) but the method used were too dificult- too much work-by these way i will have only 2stages----eliminating carbon and then leach the powder-----
regards
Arthur

 

[Harold_V]

Maybe I am wrong but I thought I read somewhere that paltinum will also give off a deep purple almost blackish toned color with stannous.

Not to my knowledge. A heavily concentrated solution might yield a coffee color, but it is never black or purple. If you have such an experience, allow the test (which SHOULD be conducted in a spot plate) to stand for a few minutes. Rinse the solution to your stock pot, and check the cavity to see if it has a purple stain. If it has one, you have gold present, which will readily override a platinum display when tested with stannous chloride.

Harold

 

[arthur kierski]

continuing this strange adventure: i did the ssn leach and from the liquid i extracted the gold and the pd------the powder left after water rinsed---perhaps not so well and perhaps not for the exact time(which i still do not know) i added nh4oh (50%nh4oh-50%h2o) and filtered (repeated this many times)---the alkaline amonea solution was red in collor-- to the solution i added hcl and imeddiatelly a lot of agcl was formed ----i filtered ,and to the now yellow chloride (the red became yellow) solution i did a stannous test that gave the pink gold indication----i xtracted this gold with smb ----- tired i went home ----monday i will reduce this solution and test for more pd!!!----

i am happy and glad that i did not dispose of the (300kilos) of the spent powder---but i must agree with other members that i must have done a very bad work with this powder before(the nitric and then the ar or hcl-cl leach)----- i extracted around 80% of the au and pd (i think) and now i am extracting the 20% left plus all the silver------
thanks all and a happy new year
Arthur

 

[glondor]

Arthur. I do not think you did a bad job on anything. New processes and procedures being developed always need evaluation, refining and modification. It is all part of the art of learning. Do not dismiss what you have accomplished to date so easily. Keep up the good work and good luck with further recovery. 8) Mike