# Rhodium in cats question



## steeranoff (Apr 2, 2009)

gthe grey mud from processing cats using Lasersteve's method,
Can it be converted to fairly pure metal by melting in a flux
And cuppelling out? 
Oh by the way, thanks Lasersteve I've gotten 1.65 ounces
Of platinum sponge so far and an impressive amount of 
Palladium salts that haven't been calcined yet! I love my 
New hobby and I couldn't have done it without your video
And teaching.


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## lazersteve (Apr 2, 2009)

Depending on the purity of your zinc and how clean your processing habits are, you should get fairly pure Rh just by melting. To properly refine it you will need to dissolve, filter, and precipitate before melting.

Steve


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## steeranoff (Apr 2, 2009)

Thanks, lasersteve. Can you tell me what to dissolve it
In and what to use as a precipitant?
Thanks,
Steve[/u]


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## lazersteve (Apr 2, 2009)

Steve,

Read this thread and you will better understand working with the various forms of Rhodium:

Dissolving Rhodium

Hopefully Lou will post a comment as he has lots of experience with Rhodium.

Once in solution you can precipitate with ammonium hydroxide (yellow salt) or with an excess of potassium hydroxide and alcohol from a hot solution. The rhodium metal from the potassium hydroxide and alcohol reaction precipitates as a black powder.
*
Here's a photo of a positive Rh test using boiling concentrated H2SO4 on the residual gray powder:*







*and positive test of Rh (left vial) and Pt (right vial) in solution using heated stannous chloride:*






I'm gearing up to demonstrate a small scale gas phase extraction of honeycomb material soon. I'll post my results when I have them.

There are many ways to get Rhodium into solution, most are not 100% efficient nor easy to do. 

Steve


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## Lou (Apr 2, 2009)

In the case of rhodium, it is almost always preferable to precipitate it as an ammonium salt of some form. Unless you have highly efficient filter apparatus, and your rhodium was extremely pure to begin with, reduction with alcoholic KOH (K methoxide) is NOT advised. You do not get rhodium sponge from this, you get rhodium black, a very fine powder that does not want to settle, and will not filter well.

You are far better served to calcine the material and get Rh sponge. Rhodium is rather stable to gas phase transport phenomena so it is hard to mess up the reduction.


As for the gas phase route Steve, I can now assume you have acquired a tube furnace? If you have any troubles with your setup, I'd be glad to assist you and recommend you to suppliers for the quartz apparatus (one is close to my house, and offer a great product for cheap). Furthermore, if you need help setting up a temperature ramp via a PID, I can probably help you out there as well.

Steve, I believe you mentioned you have H2? Have you considered the vastly superior method of reducing your salts with hydrogen at high temperature? 

Also Steve, considering the small scale with which you will attempt this, might I suggest you consider the synthesis of SO2Cl2. I have found through my own research that it decomposes in situ quantitatively to SO2 and Cl2 at the temperatures employed. It is an easy, high yield synthesis from SO2 and Cl2 using activated carbon or camphor as the catalyst. Very simple, and very convenient as the product is a liquid which may be stored.

I make this suggestion based off of my assumption that you do not have tanks of Cl2 or SO2 to use, and you would be generating the Cl2 from TCCA as per Len's method on sciencemadness, and the generation of SO2 would be from any acid plus any sulfite. Making sulfuryl chloride instead of independently generating the reactants will make life easy when it comes to 1.) controlling flow rates, 2.) controlling reaction rates, 3.) less glassware intensive, 4.) less concern of suck-back of gas stream (unless you use N2 carrier, which I suggest as a diluent). There are other conveniences which would no doubt become obvious if you proceed further.


I am convinced the most superior way to process rhodium and high rhodium alloys is via the gas phase method.

Aqueously, you will find it....inconvenient.


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## lazersteve (Apr 2, 2009)

Lou,

I'm finishing up the reconstruction and upgrade of my 18" Long x 3" OD tube furnace. I found a sweet deal on two 24" quartz tubes for $40 each. I need to get a coupling sleeve to join them so I can easily remove the condensation tube once the chlorides cool. I plan on a system that has 24" of hot tube coupled to a second removable 24" tube for condensation.

I also need to have some quartz glass work done on the tubes to add inlets and outlets for the the gas if required using your SO2Cl2 idea. Currently the tubes are in the form of over sized quartz test tubes (65mm x 609.6 mm each). Your advice on the proper modifications to the tubes would be greatly appreciated.

You are correct in your assumptions that I was pursuing the generation of SO2 and Cl2 separately, but now you have my undivided attention with your suggestion on SO2Cl2 synthesis. I love the idea of handling a liquid as opposed to the cumbersome apparatus needed for gas generation.

I'm very keen on the idea of speedy extractions and reductions of all PGMs that I handle.

I also have acquired an inexpensive, but nice PID with thermocouple and SSR for the furnace. I will definitely need your expert advice on the ramp timings and any other tips you may have. With my initial setup I was considering extracting the Pt and Pd first, then cleaning out the condensation tube, and finishing up by raising the temperature to get the Rh out. Any insight here would be welcomed also.

I feel that demonstrating this technique to the forum members will shed a much needed light on an alternative to aqueous PGM extractions for everyone. If nothing else my PGM waste stream will be greatly reduced.

Steve

[edit]PS: I have performed the methoxide reduction a few times and it did produce a very fine black powder. The powder took several days to settle then I siphoned the liquid, washed and stored the Rh black in powder form. I'm glad I didn't try filtering it.  [/edit]


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## Lou (Apr 3, 2009)

Yes, you will find this method greatly amenable to scaling. It works on the scale you propose, and also in a 6" diameter tube that's 6' long. 

The idea about the SO2Cl2 is that it's a liquid, so you can store it in a bottle. I can send you a bottle that will store it well (it's an exceptionally nice bottle too, it is made of FEP with a tefzel cap, it is rated for 3 bar as well).

Making this compound is easy--you generate both the Cl2 and the SO2 and run both of them into a tube (like an Ahlin condenser) that has its bulbs filled with activated carbon that is supported by glass wool. 

Alternatively, and quite easily, you can use camphor as the catalyst-- bubble SO2 into the container until the camphor forms a liquid and then bubble Cl2. According to Brauer, large quantities of SO2Cl2 may be synthesized from this nigh quantitative, smooth reaction. 

The point here is that you spend a day generating a liter or two of this liquid so that you don't have to worry about regulating two separate gas streams, either of which may suck back (thus requiring traps to prevent suck back, and also a drying train for the gases all on an already complex system). Short of doing what I do and using a manifold and cylinder supply, using the liquid reactant is the easiest method and will be the least problematic in practice. By making the SO2Cl2 separately, you can have much more convenience in controlling the flow rate.

The easy thing to do is to setup a boiler of sorts for the SO2Cl2 and sparge with N2. The N2 will carry the SO2Cl2 vapors into the reactor, where it will immediately disproportionate upon hitting the hot alumina. 
Make sure you recirculate your effluent gas to save on reagent.


As for KOMe, I'm glad that you back me up in how fine that powder is. It's great for a catalyst, but it's bad, bad, bad when you're trying to have the rhodium processed quickly. I envy the time scale on which you refine.


Lou


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## lazersteve (Apr 3, 2009)

Lou,

Thanks for the synth on the SO2Cl2. I did a little research last night and found that Sigma-Aldrich sells 95% SO2Cl2 for around $65 per kilo plus shipping. I'm thinking it may be easier just to buy some already made. I didn't really shop around, but the price seems reasonable to me.

What kind of suggestions can you provide for the tube modifications? As I mentioned above, they are just two really big quartz test tubes for all practical purposes right now.

Steve


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## Lou (Apr 3, 2009)

Steve, have you ever placed an order from Sigma Aldrich? 


As for modifications to the quartz tube, I can send you an email with some specifications.


Lou


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## lazersteve (Apr 3, 2009)

Lou,

I have not ordered from them before, but I have ordered from several other large chemical companies without any problems. I have a legitimate business license and have a good reason to order the item.

Why? Do you foresee a problem with me placing an order?

Steve


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## Lou (Apr 4, 2009)

I've heard that ordering from Fisher, VWR, and Alfa are all a breeze. Even with a business license and legitimate use, you might find that they still may refuse to sell to you.

Lou


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## skippy (Apr 10, 2010)

I'm putting this in this thread because it seemed like a good place. 

http://www.springerlink.com/content/a51010856k75456k/
This article mentions putting rhodium into solution with sulfuric acid and barium peroxide.
The peroxide and the sulfuric acid makes a version of 'piranha solution' (piranha solution is very dangerous and can decompose violently, it can also turn organic matter into unstable explosive peroxides and melt your flesh - if you're particularly careless it could probably do all those at once :shock: )

I just thought I'd put this out there as I'd never heard of Rhodium dissolved like this before and maybe someone knows something more about this, or is feeling brave and would like to give it a try.


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## Oz (Apr 10, 2010)

Rh will go into boiling sulfuric without the need of H2O2. The H2O2 does speed the process to a point, depending on its concentration it can also water down your sulfuric.


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