Platinum sponge from hydrazine sulfate

Hey guys,
I have been struggling to get platinum sponge using hydrazine sulfate. I understand that I could just calcine the ammonium platinum chloride salt to get the sponge, but I'm under the impression that it can be done quickly & efficiently with hydrazine and that's what i'm after.

Here's what I'm doing... Pt, Pd, Rh mix from cats was Reduced previously with zinc then redisolved in AR. Rh was then seperated out as greyish white powder leaving Pt & Pd in solution. The first time through I was curious to see how the metals would reduce so I increased the PH with ammonia and then sprinkled in some hydrazine sulfate, almost immediatly the solution darkened to a black color and within a min or two the particles began floculating. So now I was again left with the black powder that looked similar to the stuff that the zinc originally precipitated.

In a new batch I followed the same proccedure as before but this time I precipitated the platinum with NH4Cl. After filtering the orange-yellow salt I washed it a few times in the filter with NH4Cl solution. Fresh stannous chloride was showing positive results throughout all of my testing. After dissolving the Pt salts in water with a ph of about 6 at room temp. I got the same precipitant, a difficult to work with black powder.

My qustion is, how do I get the heavy, easy to work with, grey platinum sponge when reducing with hydrazine sulfate?

Any suggestions/corrections would be very much appreciated, I enjoy details!
Thanks for any help!
Greg

Try adjusting the ph with sodium hydroxide.

Greg,

I've never had any luck getting sponge from hydrazine, only black moss at best.

For a good sponge calcine the Pt salt and then sinister the sponge under hydrogen to a coherent mass. Or you can continue heating to fuse the Pt to a bead as seen on my Pt DVD.

Steve

Reduction of Ammonium Chloroplatinate to Platinum metal using Hydrazine hydrate

Add DI water to the Pt salts to yield 1 gram of platinum (which equals 2.3 grams of ammonium chloroplatinate) per 20 ml of water.
example 100 grams of ammonium chloroplatinate divided by 2.3 = 43.478 grams x 20 ml/g Pt equals 869.5 ml

Heat the water salt suspension th 45 degrees C and stir well

Prepare s solution of Hydrazine Hydrate by adding 4.1 ml of Hydrazine Hydrate (85%) to 50 ml of DI water.

Every 50 ml of the Hydrazine Hydrate solution will reduce 10 grams of platinum metal.

Allow the metal to settle and decant the solution, wash and dry the metallic platinum.

If you are torch melting this powder be careful as it is easy to blow away all of your hard work.

Thanks for the replys.

Steve,
If I eventually just can't figure it out I will most certainly be using the method you used in your pt/pd dvd, it's great btw! I'm just determined at this point to do it the hydrazine route

4metals,
Am I right in assuming the deionized water is helping it to flocculate better? Also, will I have the same results if I desolve hydrazine sulfate into some di water, or is it nesessary to be using the freebased hydrate form?


Thanks
Greg

4metals procedure does work, but I usually add about 50 mL of conc. ammonia per liter, with subsequent additions as needed. As you add your hydrazine sulfate solution, you'll see the evolution of nitrogen gas. If you're getting a finely divided black precipitate you're 1.) going too fast with the additions, 2.) your ammonium hexachloroplatinate is impure, 3.) you're too hot. You should get a heavy gray sand if done properly (this is with hydrazine hydrate, or its common salts). When you start adding you're reducing agent, be it zinc, hydrazine, formic acid, or whatever else you may be using, you will see a sickly green hue to the solution right before the metal begins flocculating. Also, make sure you boil you're solution after the last addition--doing so will help the particles agglomerate. IF you're still messing it up, add half a teaspoon of cornstarch when you boil, this will help it all settle. That can be removed with oxygen in a tube furnace, or burned away if you make casting grain.

Keep away from ammonium formate and borohydride--those two are the worst at giving super fine blacks that can take fire and take forever to filter. hydrazine hydrochloride + ammonia is the way to go if you're after sponge. No rinsing needed.

Any further questions, ask me! I've reduced platinum with many reducing agents, and hydrazine is my second favorite.

Lou wrote;

Any further questions, ask me! I've reduced platinum with many reducing agents, and hydrazine is my second favorite.

Click to expand...

And your favorite is?

Lou, how do you like formic acid? I can get formic acid at a very reasonable price from an apiary supply place.

A combination of careful heating and hydrogen gas done in a quartz tube with a removable quartz frit on one end in a tube furnace.

Doing it this way makes it much easier to remove all of the ammonium chloride (or chlorine gas if you start from a halide). A separate tube for Pt, Pd, Ir, Rh. No acids, no filtration, simply load the tube, set the PID to its preprogrammed ramp/cycle and open the regulator when at temperature, close the regulator after a certain amount of time (material & compound dependent), and open the valve to the vacuum as it cools back to RT. In a large 15 cm tube, one can reduce many kilograms of ammonium hexachloroplatinate, palladate, rhodate, osmate, etc. (it is general). The vacuum is applied as it is cooled to ensure that there is no hydrogen left adsorbed onto the surface. Several years back, I had rhenium sponge take light after opening the cool tube. Quite an experience! I've done the whole thing with just straight calcination. Works fine for platinum if you go nice and easy, and to a lesser extent Pd and Rh (I usually let them cool under a soft H2 flame).


There are the most minimal PM losses this way, and all the platinum group can be reduced cleanly and very cheaply. Mole for mole, hydrogen is very cheap. The quartz tube is several hundred dollars, the regulator several hundred dollars, the vacuum pump, a thousand, the T cylinder is three hundred or so, and $28 to fill, the rest of the glass (which may be borosilicate), several hundred dollars, and the tube furnace, several thousand dollars. For about ten thousand dollars, you can have a setup that can reduce EVERY platinum group metal (as well as produce their halides, oxides, and various other salts and compounds for a value-added product). The versatility is what makes it so useful. Hydrazine and its salts work great, but handling hydrazine gets old, and even the relatively benign sulfate is still irksome. I've long since grown tired of aqueous work with the platinum group. Beaker and flask are fine for ~10-20 oz, but anymore, and it's easier to do it in a tube furnace rather than get a sealed glass-lined Pfaulder kettle (and much less reagent intensive). Being frank, the oxidation is easier on scrap material too (especially for rhodium).


Formic acid works quite well for platinum, palladium, and to a lesser extent rhodium if the proper precautions and care is taken. I usually take whatever salt, dissolve it in a minimum quantity of water, and then add ammonia. The solution may be clear or turbid. I then heat, and add small (50 mL) portions of conc. formic acid. You will see ebullition as CO, CO2 and H2 gas is produced. It should be pH 6.5 or above to work correctly. Boil away (80-90*C) and go until all trace of green is gone (or light brown for Rh). It will be inky black when all is reduced , but will gray as you boil and the particles stick together. Filter on a quartz frit.* Filtering PGM blacks is a pain in the butt, so avoid them at all costs. They quickly clog the frits, and vacuum filtration goes quite slow especially if you have gallons of solution. Filtering with a vacuum setup and fritted glass is a proposition only for very high purity metals in 10-30 oz. quantities, any more than that, and a dry method using the tube furnace is preferred.

Ammonium formate solutions are old hat insofar as organic and inorganic chemistry goes...


*Quartz frits are somewhat of an investment, but when I do not want contaminants or extra steps, they are useful. They may be cleaned with aqua regia, or with conc. sulfuric acid, and you should have one for each metal, clearly marked (ask the glassblower) to avoid cross contamination).

Nice, no waste and no oxides. You're right if you end up with PdO you have to heat it to get rid of it anyway. I would have some serious reservations about having just any operator doing the reductions. In the refining of karat scrap the Pt and Pd is present in ounces per thousand ounces of scrap in most cases. For those quantities I think wet chemistry would be simpler.

Materials with high levels of PGM's are a different story. Versatility is nice.

I absolutely agree! If your game is karat scrap where they accumulate only slowly, by all means, aqueous methods are the best.

If, however, you're buying thermocouples, platinum compounds, spent research catalysts, and concentrates from catalytic converters, and your incoming purity is say 90% of a given metal, then this method compliments aqueous methods quite well insofar as reduction and conservation of purity are concerned. It's suited to an operation that strictly processes PGMs in high purity.

I needn't tell you that tube furnace processing of rhodium, osmium, rhenium and ruthenium is THE only sensible way to go. Putzing around with them in solution is a certain way to have them tied up in your waste stream effluent for weeks! Keeping them concentrated and purifying with selective gas phase chemistry is a way to keep down first pass losses.


Lou

Lou,

Your posts above have really got me inspired to get my tube furnace going full speed!

It's a shame I've had it ready to go for nearly a year and haven't reduced a single compound in it yet. As I mentioned to you before, I'm seriously lacking a proper place to set it up and put it to work. I know mine is only a 65 mm x 610 mm tube, but I feel it will be just right for me!

One note on this subject: Anyone thinking about the tube furnace will need the proper power source to run the thing also. I know it sounds obvious, but some people jump in head first the first time and don't realize all of the requirements of operating equipment like this.

I'm very interested in trying my hand at stripping gold plated scrap with it.

Hopefully one day very soon, I'll graduate to using the tube furnace exclusively!

Thanks for all of your guidance and wisdom Lou.

Steve

I sure would like to see what this tube furnace looks like.

Do you have a photo?

Here's one of it disassembled :



And here's the tube sections next to a fat marker for size comparison:



There is a bunch of other hardware and glassware that is not in the photos.

I had the tube fabricated from two 24" x 64 mm ID fused quartz tubes and two fused quartz 24/40 joints I purchased on eBay. I wish I had done it a little differently, but it should work and I was on a budget. Turns out the fabrication work cost five times what the glassware did, but it was done professionally and I feel good about that. One day I'll fed it some scrap catalytics and post the video.

Steve

LOL word of the day: ebullition
thanks Lou!

Steve, is that white fluffy cylinder a homebuild tube furnace? Care to share any details?

skippy said:

Steve, is that white fluffy cylinder a homebuild tube furnace? Care to share any details?

Click to expand...

Yes I built it myself.

The fluffy white stuff is the ceramic heater tube wrapped in koawool. The straps hold the wool in place around the ceramic tube. The tube assembly gets inserted inside the steel housing and the thermocouple is wired to the PID in the black control box.

The long fused quartz reaction tube gets inserted into the ceramic tube. The short fused quartz collection tube is attached to the long tube after the charge is place in the longer tube. The reaction tube is the one that is heated and the collection tube is the one where your values condense.

Search the forum for tube furnace for more details.

Steve

Steve, it looks good! Those two leads sticking out on the end, what are they? They look something like sheathed stove elements. I'm building a tube furnace too. I'll have to take some pictures when its done.
I'm looking to try the Quartz tube process too. I have a glass blower where I live who will work for $40 per hour, which is amazing, because I can't even get anyone to work on my car for that :lol:

skippy said:

Those two leads sticking out on the end, what are they?

Click to expand...

They are actually insulating ceramic tubing standoffs (1/8" ID x 1/4" OD) around the element wire. The wire is terminated into a straight brass coupling with set screws (Lowes electrical section) to hold the standoff in place and provide a convenient hook up for the element power feed.

Steve

Steve said;

The reaction tube is the one that is heated and the collection tube is the one where your values condense.

Click to expand...

A little clarification here please, I've calcined a lot of platinum salts in my day in furnaces without a reducing atmosphere. The values never volatilized and re-condensed and I wonder why they would in your rig?

I have never been a big fan of filling those finger shaped silica boats with metal salts for reduction. Plus there is a limited capacity in a small diameter tube. Factor in that I've become frugal in my old age and I have some ideas for building a atmospheric reducing chamber that will fit into my assay furnace.

I spoke to my glassblower and he can make me a 8" diameter 6" deep quartz glass chamber with the tubes I've sketched in the drawing. The top will have a tapered glass joint lid to open the top fully. I would mount this on a replacement door / shelf arrangement which I can slide into my assay oven. Once loaded with a silica tray full of salts it can be slid into place while the kiln door remains open and out of the way. Then I can hook up a vacuum to the top an a hydrogen cylinder to the bottom.

This will out-gas some nasty chlorine fumes so I'd use a venturi in a closed loop to pull vacuum and scrub the fume in the water at the same time. The top of the venturi tank can go to the exhaust. Now I can heat the oven and when it gets to temperature (around 200 C) turn on the hydrogen gas and evacuate at the same time with the vacuum.

This should work on both small and relatively large lots and since I don't need a tube furnace and controller, should be 4 or 5 thousand cheaper than Lou's estimate.

Opinions?