What is the best extract method for converters?

[Bobplatinum]

Hello,
I wonder what the best and most effectful method to refine the platinum from converters?

I´ve watched steves DVD fundamentals of platinum and palladium, and in the first part extract he dissolve the platinum with muriatic acid and bleach.

I wonder if I can crush the honeycomb and use aqua regia to dissolve the platinum from the converters instead.
I think it will go faster with concentrated agua regia what do you think?
Why use agua regia diluted with water?

/Thanks

 

[butcher]

Either would work to dissolve platinum (aqua regia would be stronger and could tolerate the needed heat easier.

Why water to dilute aqua regia short answer is to keep acid working instead of leaving as unreacted fumes.

My attempt at a longer answer:
One reason to dilute the aqua regia is to keep the acids reacting instead of fuming off, platinum is not very reactive even to aqua regia, it takes heating for long periods of time to dissolve, keeping the solution dilute keeps the acid in solution.

during heating some acids react slowly with metals and also the gases from the reaction and from heat evolve, water leaves the solution first, then the nitric, then the HCl, these leave the heated solution as unreacted acidic gases, (HCl acid is 32% HCl dissolved in 68% water), 68% nitric acid is 32% water, once the water from these acids are gone from heating the acid fumes off, but if there is water in solution the gases tend to stay in solution where they will keep or reform acids to attack metals.


Let’s look at heating a dilute nitric acid, say 50% solution, no metals in solution or other acids to complicate things, the solution if not heated too strongly will have a vapor forming from the acid, this vapor will contain mostly water until the solution concentrates and reaches 68%acid, at this point the vapor will contain 68% of our acid as fumes until it was all gone and the pot was dry,
but if we add water to solution (again mostly water would fume off of this solution) and the NOx gases that would leave the solution if concentrated now stay in solution with the water, and now mix with the water and stay in solution reforming acid, and water vapors off leaving our acid being heated in the reaction vessel, (where if we had metals this acid would do work making salts instead of fumes), (also metals reacting with acid produce gases from the acid and metal reactions, having water in solution these reacted gases mix with the excess water in solution to reform acid instead of leaving solution as gases, to again attack more metal).

I hope you can understand this better than I can explain it.

 

[AndyWilliams]

Either would work to dissolve platinum (aqua regia would be stronger and could tolerate the needed heat easier.

Why water to dilute aqua regia short answer is to keep acid working instead of leaving as unreacted fumes.

My attempt at a longer answer:
One reason to dilute the aqua regia is to keep the acids reacting instead of fuming off, platinum is not very reactive even to aqua regia, it takes heating for long periods of time to dissolve, keeping the solution dilute keeps the acid in solution.

during heating some acids react slowly with metals and also the gases from the reaction and from heat evolve, water leaves the solution first, then the nitric, then the HCl, these leave the heated solution as unreacted acidic gases, (HCl acid is 32% HCl dissolved in 68% water), 68% nitric acid is 32% water, once the water from these acids are gone from heating the acid fumes off, but if there is water in solution the gases tend to stay in solution where they will keep or reform acids to attack metals.


Let’s look at heating a dilute nitric acid, say 50% solution, no metals in solution or other acids to complicate things, the solution if not heated too strongly will have a vapor forming from the acid, this vapor will contain mostly water until the solution concentrates and reaches 68%acid, at this point the vapor will contain 68% of our acid as fumes until it was all gone and the pot was dry,
but if we add water to solution (again mostly water would fume off of this solution) and the NOx gases that would leave the solution if concentrated now stay in solution with the water, and now mix with the water and stay in solution reforming acid, and water vapors off leaving our acid being heated in the reaction vessel, (where if we had metals this acid would do work making salts instead of fumes), (also metals reacting with acid produce gases from the acid and metal reactions, having water in solution these reacted gases mix with the excess water in solution to reform acid instead of leaving solution as gases, to again attack more metal).

I hope you can understand this better than I can explain it.

I can safely say that I am getting more and more of your wisdom every day. Thanks for a great explanation Butcher.

 

[BJL1984]

there is a nurd rage video on you tube of dissolving a platinum bar in aqua regia, check it out it will give you a good idea of the amount of time it takes to fully disolve the platinum, reciantly a friend helped me start doing the two cats i took out of my subaru, Platinum is a very intresting and resiliant metal,

 

[butcher]

Aqua regia begins reacting as soon as the two acids are mixed, these two acids will react with each other even if metals like gold or platinum are not involved, to form NOCl nitrosyl chloride and Cl2 chlorine gas, the acids and these gases react with metals and produce other volatile gases, keeping these gases in solution, is important to keep the solution reactive to dissolve our noble metals, these gases are hard to keep in solution as they are volatile and want to vapor out of solution, heat actually will drive these gases out of solution faster, but heat can also help our solution to work faster or in the case of platinum heat is needed for the acids and gases to be strong enough to dissolve the platinum, this is really a double edged sword, we need the heat, but the heat also drives out what we need in solution to work, we discussed dilution to help lets look at some other things.

I feel one way to help is to use closed reactors, (some pressure if possible would even be better as pressure can keep gases from leaving a solution), pressurizing a reactor can be dangerous, and for most of us this is not an option, but a some what closed system or refluxing the gases back into solution is an option many of us can use easily and safely, something as simple as a watch glass cover will help, as water vapors and these gases condense and drip back into solution from the watch glass, we will still loose a lot of these volatile gases and water vapors, but can get some to drip back in helping our cause. a reflux condenser would even be better here much more of the gases would condense with the water and drip back into solution, something else I believe that can help, beside having the metal we are trying to dissolve in as small of particles as possible, is to not to add all of the aqua regia at once in the beginning of the reaction, but adding fresh mix of aqua regia as the reaction proceeds (this can be a bit harder in a closed system but can be done), in open containers with a watch glass adding fresh solution can be much easier, I believe giving this dose of fresh aqua regia gives a fresh dose of NOCl and chlorine to solution, helping to make up for the lost volatile gases while heating, again concentration of our solution is important, some water is in these acids, and some forms in the reactions of these acids, but if prolonged evaporation or boiling in a relatively open system we may need to add some water also, with refluxing we would need less water than in a container with a simple watch glass.

 

[Dirtdiggaler]

You should put the media in sulfuric acid, filter, then put what is left in A/R. I saw it at a big refiner, They do that for platinum from the oil refinery media.

 

[jimdoc]

You should put the media in sulfuric acid, filter, then put what is left in A/R. I saw it at a big refiner, They do that for platinum from the oil refinery media.

What the "big refiners" can do safely and at a profit varies greatly from what the backyard refiner can do safely and at a profit.

Jim

 

[kurt]

You should put the media in sulfuric acid, filter, then put what is left in A/R. I saw it at a big refiner, They do that for platinum from the oil refinery media.

Working with sulfuric is "very" dangerous business to start with so you best know what you are doing - also filtering sulfuric requires special filtering - "paper" filters will not work - also "hot" sulfuric will not work with most plastics it will turn the plastic to carbon (seach wet ashing) its not as simple as suggested in the above quote.

If you are going to suggest such a process you need to be more specific in your instructions - the "big refiners" know what they are doing & have the right equipment --- many beginners & new members that come to this forum have little or no experience &/or knowlege &/or proper equipment concerning working with sulfuric --- simple telling them to "put mrdia in sulfuric, filter" - is setting them up to cause them harm &/or a big mess.

Kurt

 

[Gratilla]

Consider SSN (Saturated Saline, Nitric acid).

I realize that at least one of our forum members refers to this as "poor man's AR" <And we all know who you are! :mrgreen: >, but I believe from the Pourbaix diagrams in "Leaching With SSN" by the American Society for Applied Technology (links to the pdf elsewhere on the forum), SSN acts differently. Also, although AR (ie rich man's) will dissolve Platinum, when hot, it will not dissolve Rhodium or Iridium. SSN will. For the pH/Eh conditions refer to the doc above.

 

[skippy]

I can confirm that SSN is pretty effective, especially when you consider how inexpensive it is. I still don't think it is competitive with plasma melting though.
Sulfuric acid won't work on honeycomb/biscuit converters as the sulfuric wont dissolve all of the cordierite. Probably because of the silica component.
It might work on bead converters but the same caveats apply as previously mentioned of course.

 

[goldsilverpro]

Gratilla,

I remember this idiot named Lasley that was associated with ASAT - he was maybe the founder. He posted totally worthless articles in the California Mining Journal for several years. Nothing he said was ever definite. It was all mysterious, lots of alchemical crap. Garbage. I wouldn't trust anything that came out of ASAT.

 

[skippy]

I agree that the paper is dressed up to look more scientific than it is. I still say that SSN is surprisingly effective for what it is. The extra salt in the solution does make a difference from what I've seen. I made it up with HCL and NaNo3 carefully balanced to provide correct molar ratio and then saturated the solution with salt. Adding the salt dramatically increased the reaction. It does a decent job of cat honeycomb, but it still wasn't effective enough that I could make a go out of it. You are maxed out with aqueous techniques at 90-95% platinum recovery and about 80% rhodium recovery.