Mixed Black PGM Powders

[lazersteve]

When purifying the Pd I have never seen any reason to drive off the excess ammonium hydroxide. I simply add enough HCl to acidify the mix and reform the yellow Pd salt.

The orange salt may be Pt, check a sample with stannous chloride to see.

Steve

 

[kadriver]

I filtered the precipitate to remove the liquid and washed multiple times with cold distilled water.

 

[kadriver]

Once all the liquid was gone from the filter, I removed the filter and placed on some paper towels to dry for calcining later on.

 

[kadriver]

I also had some palladium dissolved in ammonia from another extraction of the flesh colored precipitate from earlier in this post.

If you look back in the post, you will see where there was some flesh colored precip that did not completely dissolve during the ammonia treatment.

I added more ammonia (this time 10% ammonia from Ace Hardware), more stirring and more heat.

I noticed that more of the flesh colored precip had dissolved after these additional treatments.

This is the liquid from those additional treatments - it has already been filtered to remove any solids.

 

[kadriver]

I heated the solution for about an hour to drive off excess ammonia, filtered again, then added hydrochloric acid to form the bright yellow precipitate.

I then filtered off the liquid and removed the filter with the precipitate and set it out ot dry for calcining.

 

[kadriver]

Here's the results of todays work.

Probably about a grams or a gram and a half of palladium (after calcining).

Not all that much metal, but a great learning experience for me.

I learned that the flesh colored precipitate, if fresh ammonia is added, will yield more yellow powder (filter paper on the left).

And I learned how to recover the yellow powder from the DMG scavenged precipitated dissolved in ammonia (paper on the right).

I did notice that the DMG side (right) has a two toned color to it - as opposed to the single solid color of the yellow powder on the left.

Thanks for looking - any critique or comments are welcomed - kadriver

 

[kadriver]

When purifying the Pd I have never seen any reason to drive off the excess ammonium hydroxide. I simply add enough HCl to acidify the mix and reform the yellow Pd salt.

The orange salt may be Pt, check a sample with stannous chloride to see.

Steve

Steve - I'll remember this next time I do this. I did remember to use cold water to rinse the yellow powder this time.

It worked perfectly with no visible yellow powder dissolving after adding cold distilled water.

The first time it did this part, I used hydrochloric acid to rinse the yellow powder - I did not realize that the yellow powder was somewhat soluable in HCl.

I did save the filter with the orange precip, I'll test it to see if it is indeed Pt.

Thank you - kadriver (Kevin)

 

[kadriver]

Here's some posts on Rh testing:

Rh Test Results Stannous

Rh Test Results Sulfuric Acid

Steve

Steve:

I have never performed any testing for rhodium - Lou mentioned that sulfuric acid is a good qualitative test for rhodium earlier in this post

From reading the procedure for doing SnCl test for rhodium, it looks like I will need some rhodium in solution to perform the test (with no gold, platinum or palladium).

The only way I can see to get the Rh in solution is with hot concentrated sulfuric acid.

I'll take about .1 gram of the rinsed and dried black powder and carefully boil it in concentrated sulfuric acid in a test tube to get the rhodium (if any is there) to go into solution.

Then I will do the test on the sample to see if I can detect the presence of Rh with stannous chloride (SnCl).

I looked at the link for the sulfuric acid test - it showed a picture of a tube with a redish brown colored liquid, but I did not see a procedure for performing the test.

After the rhodium tests are complete, then I think I am ready to do a platinum extraction using HCl & H2O2 with the remaining black powders.

I believe that I have gotten all the Pd that I can at this point from the repeated nitric acid treatments of the original black powders that I started with in the beginning of this post.

I have begun to use distilled water for doing the rinses - tap water is sure to allow residual chlorides - this may cause a slight bit of AR to be formed when the nitric is added for the palladium removal step.

This would explain (at least partially) why some of the platinum dissolved during the nitric acid treatments - platinum is not supposed to dissolve in hot nitric - theoretically speaking.

Thank you for all the help provided - you guys are great!

kadriver

 

[kadriver]

I dried the washed powders of all moisture, then added 50ml of hydrochloric acid and 50ml distilled water.

 

[kadriver]

I moved everything outdoors and added some hydrogen peroxide - about 5ml - to the dilute hydrochloric acid.

This is my first time using HCl/H2O2 to dissolve platinum black powders - I expected some fizzing or bubling - but the reaction was practically non-existant.

Probably due to the small amount of material in the beaker.

 

[kadriver]

After about an hour I could see that some of the black powder had dissolved, the liquid looked deep red colored.

I added three drops from the beaker to the spot plate. Also three drops of platinum standard test solution.

 

[kadriver]

I added three drops of distilled water to each cavity containing the Pt solution from the beaker, and to the Pt standard test solution to dilute a little.

Then I added 1 drop of stannous chloride to each cavity.

I looks very dark red color - the camera does not show what it looked like in person.

I would say that it is a positive test for Pt, but I have never tested a concentrated Pt solution so I can not say for certain.

 

[kadriver]

I added 3ml more of H2O2 to the beaker, then set the beaker under a plastic bucket and put a weight on top.

I held it up to the light after adding the 3ml H2O2 and I could see tiny bubble being generated by the reaction.

I'll let it set overnight and check it in the morning.

Hopefully, only the Pt will dissolve, and all that will be left in the Rh (if any).

Thanks for looking - comments and critique welcomed.

kadriver

 

[kadriver]

Today I drew off the dissolved platinum to a clean beaker and placed it on the heat to evaporate excess liquid in preparation to precipitate the orange platinum powder with ammonium chloride.

 

[kadriver]

I evaporated the solution by about half.

I added ammonium chloride to about 200ml of hot water.

I kept adding the ammonium chloride and heating until no more would dissolve - it surprised me how much it took.

I did not keep track of the amount I added - I knew that it would be saturated when no more would dissolve.

 

[kadriver]

I slowly added the saturated ammonium chloride to the concentrated solution

[youtube]http://www.youtube.com/watch?v=2vkipKcZbTw&feature=plcp[/youtube]

 

[kadriver]

The color of the precipitate was not what I expected.

 

[kadriver]

I did not know how much ammonium chloride to add, so I added until no more precipitate appeared to form.

Then I filtered the precipitate out of the solution - I used the ammonium chloride to rinse the precip from the beaker into the funnel.

Edited once to add a photo

 

[kadriver]

I was surprised to see the filtered liquid was quite dark.

I was expecting the liquid to be nearly clear.

 

[kadriver]

I tested with stannous and got a positive for Pd - I was not expecting that!

I thought I had removed all the palladium with nitric acid treatments.

I tested with DMG and discovered that the solution was loaded with palladium.