Ammonia Soluble Hexachloropalladates (IV)

Gold Refining Forum

Help Support Gold Refining Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

kadriver

Well-known member
Joined
Oct 25, 2010
Messages
1,830
Location
United States
I have had this beaker sitting on one of my shelves for months containing Palladium dissolved in nitric acid.

The palladium came from mixed black PGMs, I extracted the Pd using dilute nitric acid, then evaporated it to remove most of the liquid.

I did a stannous test and it is loaded with palladium, the standard test solution on the left contains 100mg Pd dissolved in 100ml liquid

The spot on the right is a sample from the beaker that I am going to try and process to get ammonia soluble brick red [(NH4)2PdCl6] Ammonium hexachloropalladate (IV).
 

Attachments

  • P1250090.jpg
    P1250090.jpg
    874.3 KB · Views: 570
I began by filtering the liquid to remove any mixed black PGMs (and any other solids) that may have made it into my Pd nitric acid extraction.
 

Attachments

  • P1250097.jpg
    P1250097.jpg
    746.8 KB · Views: 569
This is what filtered out of the Pd/nitric solution - I'll wash this back into the mixed black PGMs as it may have traces of Pt and Rh and add the filter to my PGM paper storage.
 

Attachments

  • P1250110.jpg
    P1250110.jpg
    1 MB · Views: 568
I transferred the filtrate to a 1 liter beaker and added zinc turnings to cement out the Pd.
 

Attachments

  • P1250105.jpg
    P1250105.jpg
    838.3 KB · Views: 567
  • P1250104.jpg
    P1250104.jpg
    822.6 KB · Views: 567
  • P1250103.jpg
    P1250103.jpg
    833 KB · Views: 567
Here is a shot of the Pd that cemented onto the zinc turnings (beaker held up to the light and the photo shot from below). This was only about five minutes after adding the zinc - the Pd cemented out very quickly.
 

Attachments

  • P1250109.jpg
    P1250109.jpg
    840.5 KB · Views: 566
This is as far as I got with this new project.

I covered the beaker and left my fume hood running until tomorrow morning.

Tomorrow I'll clean the cemented Pd black powder with dilute HCl to remove any zinc that remains, wash to remove all traces of nitric, and then dry and weight the Pd.

My goal is to end up with some pure palladium sponge for use with other PGM refining experiments.

kadriver
 

Attachments

  • P1250111.jpg
    P1250111.jpg
    502 KB · Views: 561
Kevin,

Make sure that there is no trace of nitric acid(water washes and Ph neutral) before washing the Pd black with dilute HCl,otherwise some of the Pd black would again go into the solution.
 
RaoOvious said:
Kevin,

Make sure that there is no trace of nitric acid(water washes and Ph neutral) before washing the Pd black with dilute HCl,otherwise some of the Pd black would again go into the solution.

I Always keep a small Al rod in my Pd nitrate solution; If any slips back into the solution it would directly cement back; And Nitric acid does not attack Al so it has prefrence over Zn in a nitrate solution.

What would the optimal Ph be for cementation? and what base do you advice to use for increasing the Ph of a Pd solution without forming any complex Pd salts?
 
RaoOvious said:
Kevin,

Make sure that there is no trace of nitric acid(water washes and Ph neutral) before washing the Pd black with dilute HCl,otherwise some of the Pd black would again go into the solution.

Rao - I plan to rinse this over and over until the pH is neutral to avoid forming AR.

When I got to the shop this morning the supernatant was crystal clear and colorless with some left over pieces of zinc
 

Attachments

  • P1250116.jpg
    P1250116.jpg
    719.9 KB · Views: 515
I used a pipette to remove all the clear liquid from the beaker after testing the liquid with stannous chloride.
 

Attachments

  • P1250119.jpg
    P1250119.jpg
    733.9 KB · Views: 515
  • P1250118.jpg
    P1250118.jpg
    722.9 KB · Views: 515
After the liquid is drawn off, I use a pair of plastic tweezers to remove the larger pieces of zinc left over that did not get dissolved.

I put the pieces of zinc in the small beaker containing the liquid that was drawn off from the large beaker.

If they are taken out and left in the air they get an oxidized coating, putting them in the liquid will help preserve them for use on another batch.

Having these pieces of zinc sit overnight in the solution with the Pd black powder will also help ensure that the nitric acid is used up.
 

Attachments

  • P1250129.jpg
    P1250129.jpg
    670.8 KB · Views: 514
  • P1250128.jpg
    P1250128.jpg
    809.5 KB · Views: 514
  • P1250126.jpg
    P1250126.jpg
    623 KB · Views: 514
I then added some more distilled water to do another rinse.

Then I checked the drawn off liquid for PMs with stannous chloride - the test was negative which means all the metal has been cemented out of the solution.
 

Attachments

  • P1250134.jpg
    P1250134.jpg
    770.2 KB · Views: 514
  • P1250131.jpg
    P1250131.jpg
    743.8 KB · Views: 514
I waited all day for this second rinse to settle completely and it never did.

The liquid is a slight grey color after settling for about 8 hours.

I removed the liquid with a large 125ml pipette with a rubber bulb on the top to draw a vacuum.

Then I switched to a small disposable 3ml pipette to get that last few ml of liquid from the container.
 

Attachments

  • P1250175.jpg
    P1250175.jpg
    752.1 KB · Views: 514
  • P1250172.jpg
    P1250172.jpg
    635.8 KB · Views: 514
  • P1250171.jpg
    P1250171.jpg
    585.2 KB · Views: 514
  • P1250170.jpg
    P1250170.jpg
    644.7 KB · Views: 514
  • P1250169.jpg
    P1250169.jpg
    664.1 KB · Views: 514
I added more distilled water for the another rinse and set the beaker aside with a cover to keep trash out.

Then check the pH of the previous rinse water - got a pH of 5 so the acid is fairly week which means the zinc destroyed most of the nitric acid.

This is as far as I got today - thanks for looking and as always critical comments are welcome.

kadriver
 

Attachments

  • P1250178.jpg
    P1250178.jpg
    688.7 KB · Views: 513
  • P1250176.jpg
    P1250176.jpg
    669.7 KB · Views: 513
Is there a flocculant that I can use to get this to settle quickly and not interfere with the reactions?

If yes, then where can I get some?

Thanks!

kadriver
 
Heat to a boil and let it cool back down.
Things tend to settle faster when the solution is hot.
 
Kevin,

Top notch post, great job as usual for you.

You can quickly clear the gray solution by packing a glass (or plastic) conical funnel neck with a small rolled up section of Charmin tissue and vacuuming the liquid thru the moistened Charmin plug. The plug will contain the suspended gray material and can be incinerated to recover the suspended material later. Don't pack the funnel neck too tightly or the filtration will take a long time. One to two drops per second is a good drip rate that will afford a clear solution under vacuum. Test the packed funnel under vacuum with water before adding the gray liquid. Try for the fastest drip rate that will produce a clear solution. Once you have the drip rate correct, add the gray liquid.

The filtered solution should be 100% clear and free of suspended particulate.

Steve
 
9Kubby9 wrote

"What would the optimal Ph be for cementation? and what base do you advice to use for increasing the Ph of a Pd solution without forming any complex Pd salts?"

Ph of around 2-3.Use filtered concentrated solution of Sodium Carbonate or Bicarb.

Kevin, as Sam said,heating would make flocculation faster and easier but in case of even traces of nitric acid some black might get dissolved in the process so making it neutral first and then moving ahead seems efficient.
 
Back
Top