PGM recovery with AR leaching. pics

[kjavanb123]

All,

After a succesfull Pd refining. I tried to estimate the amount of Pd or Pt in following honeycomb belongs to Peguet 406 I believe, French made car. Here is the picture show for it. followed by my questions.

Here is the 2-piece honeycomb, no sign of Pt though


After adding HCL and heated for few mins, dropped in few ml of HNO3 on top of honeycomb, fizzing started.


I added more drops of HNO3 till I saw no signs of fizzing or bubbling, so I stopped. Here are the stannous result throughout the heating in AR


After filteration, some soda ash is added, nothing happened, no white residues


Zinc addition also did nothing,


Now, what did i do wrong? I am guessing I should have evaporated the nitric first, before adding soda ash and zinc? Objective here, to produce the mixed black powder then AR digestion and the rest.

Any tips in this method of leaching would help.

Thanks
Kev

 

[lazersteve]

The process is not as straight forward as add one item to the next like making a cake.

You have to run each step to completion.

It looks like you performed the dissolving step correctly.

The stannous test is not conclusive, you need DMG to get the Pd out of the way so you can test for Pt.

The soda ash step can be gauged by pH measure, pH 2-3 is fine. If you don't have a way to check pH then skip the soda ash.

You messed up when it came to the zinc. Zinc is added, a little at a time with stirring, until the solution changes from the original color of the leach (red-orange or green) to gray black. The color will change as the zinc saturates the solution and pushes the PGMs out. Here's what a solution properly zinced looks like:

Notice the color of the liquid is clear/gray. Add zinc, let it dissolve with stirring, and add more if your color has not changed. Continue until the color changes.

Steve

 

[HAuCl4]

Do you like zinc better than copper for this job Steve?.

 

[lazersteve]

Do you like zinc better than copper for this job Steve?.

Yes, PGMs tend to stick to solid copper, plus copper is much slower to react and harder to clean out of the resulting mixed PGMs powder.

Zinc is quick, easy to clean up, and gives a more desirable precipitate.

Steve

 

[HAuCl4]

Cheers Steve. 8)

 

[lazersteve]

Kev,

One last note on the zinc reduction. Make sure you have some free HCl acid in the solution. If you add the zinc turnings and they do not start to fizz within a few minutes then add 10 mL of HCl.

Steve

 

[pgm]

Kev,

listen to what STEVE has just said....add a little acid and then keep on adding zinc small amounts and plenty of mixing....when adding zinc you should get a reaction....keep adding until there is no reaction and the colour will change...you will see..please put up pictures they really help

 

[pgm]

Kev,

One last note on the zinc reduction. Make sure you have some free HCl acid in the solution. If you add the zinc turnings and they do not start to fizz within a few minutes then add 10 mL of HCl.

Steve

Steve this reminds me when i started, i asked you for help.....funny how it looks so simple now....lol, i have just finished my leach today 5kg, i am also re-using my acids and getting good at it. i have done quite a few leaches now with honeycomes, i could setup a production line......only if i had the room.. thanks again steve....

 

[kjavanb123]

All,

Thanks for your advise on this, I have completed zinc percipitation and Pd percipitation, here are the pics and some questions.

Zinc percipitation completed. Checked the solution with stannous and no color.


AR digestion of mixed black powder. There was some gray color residue at the bottom. Rh maybe?


PGM solution filtered, ready for Pd percipitation. I tested the gray residue with stannous and i got very dark red first, and dark emerald green after
few mins. Is there anyway I can test this gray powder if it is Rhodium?


Pd percipitation. I had some spillage accidently dropped in two pieces of sodlium chloride


Pd salt rinsed from filter paper into beaker with saturated ammonium chloride. I was trying to get the most of the Pd salt from the paper, now I have Pd salt and as you can see some ammonium chloride, Is this gonna mess up with Pd purifying? If it does, how can I get rid of the ammonium chloride solution without losing more Pd salt?


Also one more question, how do u keep your ammonium chloride saturated solution clear all the time? with mine, after boiling and dissolving the 38g of ammonium chloride, it hardens after few mins or so and clugged the hose which i rinse the PGM salt with. Any suggestion?


Thanks
Kev

 

[lazersteve]

First, your filter:

You should rinse the filter with diluted ammonium chloride solution (10-15%) until all of the color is out of the filter and only the gray powder remains. Yes, the gray powder is likely Rh. Lou and I have both post the test and results for dissolving the Rh powder. It's dissolved by boiling concentrated H2SO4 into a red-brown solution as seen in the Rh test post in the General Reactions list.

Next, you are using way too much ammonium chloride. This is why you are getting these thick salts. Rinsing is done with diluted ammonium chloride as water dissolves the colored powdered. Lou has spelled all of this out for you in the separation procedure he posted in the other purifying Pd thread. Adding water a few drops at at time with swirling will help digest the excess NH4Cl and leave the Pd salt in the liquid. Too much water will dissolve all of the Pd salt.

Once you had the colored Pd salt in the filter it should have been rinsed with water into a beaker and digested with an excess of NH4OH, then filtered, and the resulting solution gets acidified with HCl to precipitate the clean bright yellow Pd salt. This is all covered in the Purifying Pd powder thread.

Excellent job on completing the zinc process. You are learning one step at a time, but you are forgetting what you have already learned about cleaning the Pd. Remember that the processes have to be followed in order as spelled out, to completion before moving on. It seems that every time you post you have jumped two steps ahead, causing yourself more work in the process.

I'm confident you will put all of what you have learned together into one continuous process start to finish soon enough. You are making it a little further down the line with each batch.

Don't give up and you will meet with success.

Steve

 

[kjavanb123]

Steve,

Per your helpfull instructions, I got the following;

Rh percipitant being rinsed with dilute ammonium solution.


Rh percipitant dried.


Now, I did some search in forum on Rh, information varied, some suggested digesting this gray mud into hot sulfuric acid, then filter, and drop the Rh using zinc? incinerate, then melt?

Also, added few drops of hot water to excessive ammonium solution with Pd salt. this is what it looked like after almost 3 ml of water addition over few times.


After filtering the Pd salt, rinsed it to a beaker using ammonia, and got the following orange flesh color.


I have to read the post about the pinkish mud from Pd purifying process, as I think i am getting it. other than that it went smoothly. more pics coming up.


Thanks
Kev

 

[kjavanb123]

Here are some updates from last steps of refining, I haven't touched the Rh yet, as I am not clear how to refine it or is it clean enought to be melted as this gray mud. But for the Pd this is what I did.

Pd contaminated dissolved in ammonia after 24hrs with some pink residue.


I followed Lou advise, filter the tinted yellow solution, and added some ammonia to pinkish residue, 1.2x water stirred, and heated


To be sure all the Pd dissolved in ammonia, checked with stannous and as you can see the left swap looks almost no color change, right part darkend.


After dropping HCL into the ammonia solution, got the canary color Pd salts, which was rinsed to quartz dish to avoid any losses. I am gonna pour some of water out, the rest would be evaporated while incinerating, is this correct?


Filtered solution from above still have yellow color to it, so i added HCL, but didn't see any canary powder, tested with stannous and minor color change.


Kev

 

[lazersteve]

You are doing fine now.

A few comments:

1) Be sure to clean your dishes between each batch. I have noticed that your canary powder seems to contain some odd debris or residue of some sort. Not sure what it is or where it's coming from. My second precipitation for Pd is always nice and clean without debris or large chunks of odd colored stuff in it.

2) The left over solution most likely contains iron impurities from the dark brick colored Pd you precipitated. Iron is a common contaminate in catalytic converters. Neutralize a 5 mL sample of the yellow liquid with sodium hydroxide and see if the liquid clears and you get a pasty brown precipitate.

3) Be sure to test any left over solids from the ammonia reaction before proper disposal. All liquids should be made acidic before stock potting or disposal.

4) Adding a clean shiny copper bus bar to the left over acidic solution for a few days will ensure no PGMs get tossed out.

Steve

 

[kjavanb123]

Steve,

Thanks for your tips. Debris you see in Pd canary salt are actually left over Pd metals from my last incineration which was stuck to the quartz dish. I am a lil unclear on processing Rh. Based on my reading here, I dissolve the gray mud in boiling concentrated sulfuric acid, filter, then drop the Rh using ammonia hydroxide? Rh and acid should be concentrated solution like Pt or Pd in AR? I have 25% ammonia, do i get ammonia hydroxide by mixing ammonia with water. what is the ratio of water and ammonia to get the ammonia hydroxide used to drop the Rh from solution?

Thanks
Kev

 

[lazersteve]

Debris you see in Pd canary salt are actually left over Pd metals from my last incineration which was stuck to the quartz dish.

Quartz cleans up easily with a little warm AR after each incineration. Save the wash solutions for PGM recovery later.

I am a lil unclear on processing Rh. Based on my reading here, I dissolve the gray mud in boiling concentrated sulfuric acid, filter, then drop the Rh using ammonia hydroxide?

No filters when working with concentrated sulfuric acid. Also you need to be well protected from the fumes and random spills or splashes as this stuff is nasty. Most likely not all of the Rh will dissolve on the first run, so you'll have to repeat the process and combine the results. Use only enough acid to get the Rh dissolved and no more. Work with small amounts to dissolve the Rh powder in steps. This is safer than handling large volumes of hot concentrated sulfuric acid.

When the Rh is all in the sulfuric acid solution and you have diluted it with water (add acid to water only, not water to acid!), allowed to settle, and poured off the liquid into a fresh beaker:

1) Add Lye (NaOH) until the pH is 2.
2) Add dry baking soda (NaHCO3) to bring the pH to 3-4.
3) Heat to just below boiling and slowly add small increments of NaHCO3 until the pH reaches 6-7.
4) Allow to heat for an additional 5-15 minutes and verify the pH stabilizes at 6-7 without further carbonate additions.
5) A yellow powder Rh(OH)3 forms after another 30 minutes of heating at near boiling temperatures.
6) Cool and Filter the yellow powder as Rh(OH3).
7) Heat in a hydrogen flame to reduce to the metal.

Rh and acid should be concentrated solution like Pt or Pd in AR?

No need to concentrate the Rh solution.


Steve

 

[kjavanb123]

Steve,

I got your post AFTER I went ahead and did process both Rh and Pd, here is the following

Rh,
Added it to 95% sulfuric at first it was this color


After 20mins of boiling, it got to this color which i am guessing dissolved most of Rh, but i could still see some gray residue at the bottom.


So i added more sulfuric to solution and let it boil, but the color changed to more gray looking again, I tried to filter that, as you can see in pic below, everything went black, even swap would turn black..


So i left it as it is so i can know what to do from here on.

Pd salt,
Yesterday, i had rinsed the canary powder to another beaker using water, and had left it there till today, i went to pick it up but the solution has turned yellow, with some canary left at the bottom, the solution on top tested postive for Pd, so i went ahead added some ammonia and HCL nothing happened, had to filter the canary powder, zinc the left over solution, and AR the black powder and the whole nine yard.
as for the left over solution from yesterday which u suspected it might have iron, I added sodium hydroxide and no brown percipitant appeared, so i zinced and filtered that one.
I was on impression that canary yellow Pd salts are insoluble in water, or is it HCL?

Thanks steve

 

[lazersteve]

Kev,

Your solution with Pd was most likely still slightly basic before it sat over night and redissolved some of the yellow powder. You should make it acidic with HCl and vacuum filter out the yellow powder.

Let me know what happens with your Rh test.

Steve

 

[kjavanb123]

Steve,

I went ahead with Rh refining, but instead of baking soda I added soda ash, is this bad? I can still see stannous resulted positive for existance of Rh in solution, I am gonna try to do it with baking soda tommorow.

Here are some pics
Rh solution from the night before.


Rh solution after addition of lye.


Rh solution after soda ash addition.


Stannous result for Rh in solution.


I will post more photos tommorow once I added baking soda to the solution.

Kev

 

[Lou]

Baking soda isn't bad.


Actually looks like a dilute Rh solution. Good work so far.

 

[kjavanb123]

Lou

so i start the step 6 on Steve procedure? near boiling heating for 30 mins till the yellow powder forms?

Thanks
Kev