Hi everybody. I have a green palladium solution. I took a sample of it and I added a DMG and sodium hydroxide solution to the green pd solution. It precipitated green powder. I read in some forums that I should filtrate the powder and wash it with cold water until it gets yellow pdDMG powder. When I washed it it got white color. Am I doing something wronge? Or I didnt make the DMG solution correctly. I tested the green solution with Stannous chloride before and after adding DMG solution. Before it was positive after adding it got negative with the green precipitate. What should I do?
Palladium precipitation
- Thread starter Rem123
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Geo
Well-known member
You may have neutralized all of the acid and made the solution basic. Any copper or other base metal that forms a green salt would drop out.
I took a sample of the precipitate and dissolved it in AR and stannous tested it and it was positive for palladium. When I added sodium hydroxide a brown precipitate settled on the bottom. Is this palladium hydroxide and should I add formic acid to get the pd sponge?
Geo
Well-known member
Convert the palladium to an oxide with sodium hydroxide first. I've seen it done with sodium carbonate but I don't understand it that well. Allow the palladium oxide to settle and decant the spent solution. I try to rinse with distilled water. If you have enough time, it best to let it settle and siphon. Add water to cover the salt and heat until the beaker is slightly too hot to touch with your fingers starting out. Add the formic acid in small doses and let it react while stirring. Repeat until you add formic acid and it does not react. The conversion will be complete. It's best to do this in a fume hood or wearing a respirator. Wear gloves and all other appropriate PPE's.
Thank you Geo. My second problem is with another palladium AR solution. It color is green. The stannous test is positive for palladium. When I add a drop of DMG/sodium hydroxide solution the color gets red and blue but no precipitate. The red I think is for nickel but why the palladium doesnt precipite. The solution is acidic so the nickel only drops in alkaline solution. When I continue adding DMG the color gets yellowish but still red with no precipite. What should I do?
Rem123 said:
I am far from an expert on PMGs, but why are you adding a "DMG/sodium hydroxide solution" for testing? I agree the red (or pink) is indicative of nickel, but that's in an ammoniacal or basic solution. For testing purposes, I dissolve as much DMG in distilled water as possible (It's very limited). No un-needed NaOH that could change the pH.
How do you know the solution is acidic? Did you test before or after adding the "DMG/sodium hydroxide solution"?
Might there be enough NaOH in your test solution to push the tested sample to basic?
I'm just guessing in hopes of helping you sort it out.
Dave
Geo
Well-known member
The cheap DMG coming out of Russia dissolves better in a solution of sodium hydroxide.
All DMG dissolves better in a solution of sodium hydroxide. It depends on your intended use.
For testing, I have never needed to use hydroxide. The amount of DMG that dissolves is tiny, but for testing it works just fine.
If you're using it to precipitate palladium to separate from other metals, then hydroxide will allow you dissolve a lot more DMG in a given volume of solution, keeping the overall volume of solution lower.
My comment, and question, above was specifically regarding testing.
Dave
For testing, I have never needed to use hydroxide. The amount of DMG that dissolves is tiny, but for testing it works just fine.
If you're using it to precipitate palladium to separate from other metals, then hydroxide will allow you dissolve a lot more DMG in a given volume of solution, keeping the overall volume of solution lower.
My comment, and question, above was specifically regarding testing.
Dave
Hi thank you for your comment. I realised that when I make a solution of DMG and sodium hydroxide the solution geta acidic and thats why a red precipitate forms from nickel. Because the pH gets above 7 and the solution is alkali. But you said that I can precipitate palladium with sodium hydroxide and DMG solution but in that case the nickel will precipitate again because it is alkali. Or should I add just a little but sodium hydroxide to dissolve DMG without getting the solution alkali and test the pH?
You can use less hydroxide when mixing the DMG, and you can also add some HCl to your solution to maintain an acidic pH.
Dave
Dave
That's kind of like asking how much a rock weighs. What kind of rock? How big a rock? There is far too much variety to make a guess. I've really never processed much ewaste, so I'm not the one to answer.
Dave
Dave
