Problems in platinum recovery

[Yggdrasil]

Chlorox is Hypochlorite

More specifically Sodium Hypochlorite.
Anything else you want to inform us about?

 

[4metals]

You started out by saying this,

I precipitate PGM's and base metals out of Aqua Regia with an Alloy of Aluminum and Magnesium, then I selectively leach different base metals out

and followed that up by saying this,

In my experience, I find Palladium chloride and Silver chloride co-precipitate when you add Salt to the Aqua Regia

The 2 processes you have mentioned will produce different, if not questionable results. I am afraid that anyone trying to follow this thread will be thrown off without clarification.

In your second quote you mention dropping the Palladium with salt. then later on you said;

Now filter the Silver Chloride out of the Aqua Regia Solution, and wash this with clean water until the water becomes clear. Now Filter the water away. Leach the water-free Silver Chloride with Hydrochloric acid/ Chlorox , you will find that the leach will turn orange, meaning that Palladium is extracted from the Silver Chloride.

While I do not understand the mechanism for just table salt dropping the Palladium I will concur that Silver Chloride is notorious for dragging down other metals with it and possibly, in your case, Palladium is dragged down.
The rinsing and addition of hypochlorite (or bleach, choose your terminology) can possibly reduce any Palladium the Silver Chloride may have dragged down.

How are you sure there is not additional Palladium in the mother solution, given the salt precipitation is not a well documented process and it may have only caused some of the Palladium to drop as a salt?

I realize you type slow, I too type with 2 fingers (with the thumb helping on the space bar) but I guess I can do it faster than you. I am not trying to pull out any guarded secrets from you but you did mention some process steps that can be questionable and I do not want to cause any members reading this to take it as doctrine without it being discussed fully.

There are too many missing parts to this for me. Nothing about what the starting material is or other PM's recovered and for now, until you clarify, it is just too big a pill for me to swallow.

 

[100tific]

in my experience, I find Paladium chloride and Silver chloride co-precipitate when you add Salt to the Aqua Regia

maybe you mean that they co-precipitate when you add salt to the solution of Pd and Ag in nitric acid (not in AR). I seem to remember that it also happened to me on one occasion.
thank you very much kurt and 4metals.
There were some things I didn't know like not using AR if PGMs are not the main metal, or that PGMs don't precipitate well in dilute solutions. Also the silver 10 times higher than the Pt so that it drags everything towards the silver part.
You are not aware of what a tremendous pleasure it is to read and learn from you.
I will reconsider everything you have told me and see again what path to take.
I come across platinum tunings more often than I would like and sometimes I don't understand why sometimes it turns out well and other times not so much.
So thanks again for providing your vision.
I take this opportunity to ask another question. I have noticed that sometimes the precipitate after adding ammonium chloride is yellow, other times orange, and even once I recovered it from a solution that had iridium it came out red. From what I have read, this depends on the temperature at which it is formed. But as I understand it, iridium precipitates black. The red I got was carmine red, it didn't look like a mixture of the orange powder and black. I leave a photo of the normal one, and that red that I tell you about. In case you can provide some valuable information through your experience.
Thanks guys

all images are ammonium hexachloroplatinate

 

[4metals]

When refining platinum I always start with a concentrate made by cementation. The gold from all of the solutions containing Platinum is dropped with ferrous sulfate and the accumulated Platinum is processed in bulk. This is possible by paying for the metals in customer bars by assay and only processing the PGM's when they are in larger quantities. The method I always used was to mix up a super saturated solution of ammonium chloride in a volume equal to the volume of Platinum solution I have to treat. The Platinum solution I am treating is heated in a vessel large enough to contain the extra volume of adding all of the ammonium chloride solution, which is also hot.

The Platinum comes down quickly and after about 30 minutes I filter it off and rinse it in a solution of distilled water with 15% ammonium chloride added (W/V). That keeps any of the ammonium chloroplatinate from dissolving in the rinse. (ammonium chloroplatinate has a slight solubility in water). The Platinum salt I recover is always the yellow color as @100tific shows in the bottom (third) photo.

I have no doubt @Lou can shed some light on possible causes for the varying shades of yellow/red you have pictured as Lou deals extensively with PGM's.

 

[Lou]

I should point out that you really should not be drying the ammonium hexachloroplatinate like that. It is best to always handle it damp, with full PPE and preferably in a filter box. Then take a shower after!

That admonition aside, the color of the ammonium hexachloroplatinate you have shown and talked about indicates contamination. It's highly suggested to either dissolve the salt in aqua regia (or otherwise remove the ammonium cation) and complete a hydrolytic refining from oxidizing conditions, as described in 4metals other thread titled Bromate Hydrolysis. You do not need to use bromate, chlorine and caustic soda are use industrially. Bromate just happens to give a better result.

the iridate salt, which comes down substantially completely with the platinum from highly oxidized solutions, will darken your platinum precipitate orange to red. Palladium can also do this, and is far more likely.

 

[4metals]

When treating the solution with ammonium chloride it should be noted that platinum will come down first and then iridium will fall a short time later without you doing anything else to the reaction. This is why I mentioned 30 minutes. I typically siphoned off the majority of the liquid as soon as it settles and filter the rest. I have had success waiting as long as 30 minutes but if you let it go overnight any Iridium will be mixed in as well.

Please pay particular attention to Lou's advice about handling the powders, Platinosis is a serious illness which you can find information about HERE