Recovery of Iridum from iridium coated Titanium Mesh

[IBJ]

I have titanium mesh which has a coating of Iridium on it. As far as I have researched, it seems as so the coating is of iridium oxide. The mesh is entirely made of titanium, about 99.5%
Thus far, I have tried cutting the mesh in small pieces and throwing it in concentrated HCL and made the solution boil. This turns the solution purple after a while and a black powder sits at the bottom of the beaker. I dont know what to do with this black powder because it is not pure.
If anyone has a better way to get iridium metal recovered from this please help

[AustralianPyromaniac]

Interesting problem. What is your use for the iridium? And what's the need to extract it from these electrodes? Do you need iridium or are you extracting it for profit or for interest?

If these are standard MMO electrodes such as used in pools and chlorate cells, the coating contains more than iridium, at least some titanium dioxide is present, along with other noble metal oxides - manufacturer-dependent. 

It sounds like your current experiment has dissolved away the titanium dioxide in the hot HCl which destroyed the structural integrity of the coating, letting the noble oxide fall to the bottom. This may be your best option for recovering only the noble metal, as you can filter this powder and then dissolve it separately in boiling aqua regia.  

If you have to dissolve the whole coating off, I think your best bet would be hot aqua regia. Which would dissolve the iridium oxide, but would also dissolve the titanium dioxide, and may also dissolve the other oxides (although not platinum). Maybe this is a problem, but may not be depending on your use case.

Titanium (substrate) is said to be resistant to aqua regia, but it may be attacked when hot. Titanium is an extremely reactive metal, but the oxide coating is so strong that it behaves highly as a highly unreactive metal in normal conditions (once the oxide forms). The oxide is what makes it resistant though, any compound able to destroy the oxide coating should also be able to destroy the much less resistant metal beneath. 

You may have to just dissolve everything and then separate out the desired compound/s with further processing. 

[Arthur]

Youtuber "Sreetips" has lots of videos dealing with silver and gold recovery, then there are gems where he recovers the rarer platinum group metals etc. Go search his videos for all the metals you think that you have. There may be Tantalum there too. Your lab work will have to be perfect to recover the minimal quantities of valuable metals unless you have many kilos of destroyed electrode. Sreetips will happily refine gold and silver and put the rest of the precious metals aside until he has enough to bother with. It's nothing for him to have ounces of gold in solution but only parts of a gram of platinum group metals. No-one will give you money for PGMs in sub gram amounts

[IBJ]

On 7/5/2024 at 3:09 AM, AustralianPyromaniac said:

Interesting problem. What is your use for the iridium? And what's the need to extract it from these electrodes? Do you need iridium or are you extracting it for profit or for interest?

If these are standard MMO electrodes such as used in pools and chlorate cells, the coating contains more than iridium, at least some titanium dioxide is present, along with other noble metal oxides - manufacturer-dependent. 

It sounds like your current experiment has dissolved away the titanium dioxide in the hot HCl which destroyed the structural integrity of the coating, letting the noble oxide fall to the bottom. This may be your best option for recovering only the noble metal, as you can filter this powder and then dissolve it separately in boiling aqua regia.  

If you have to dissolve the whole coating off, I think your best bet would be hot aqua regia. Which would dissolve the iridium oxide, but would also dissolve the titanium dioxide, and may also dissolve the other oxides (although not platinum). Maybe this is a problem, but may not be depending on your use case.

Titanium (substrate) is said to be resistant to aqua regia, but it may be attacked when hot. Titanium is an extremely reactive metal, but the oxide coating is so strong that it behaves highly as a highly unreactive metal in normal conditions (once the oxide forms). The oxide is what makes it resistant though, any compound able to destroy the oxide coating should also be able to destroy the much less resistant metal beneath. 

You may have to just dissolve everything and then separate out the desired compound/s with further processing. 

Thank you for the response. I have to recover the iridium for profits, and I do not care about removing any other metal, also, what would happen when I dissolve the black powder in aqua regia? My main goal is just to get iridium in a state of 70+% purity and yes the electrodes are standard MMO electrodes. Would putting the black powder in a furnace remove the impurities? According to a precious metal tester gun, the powder is majority light elements and has some percentage of ruthenium in it, I will attach the report below. Your help will be really appreciated, thank you!

[a_bab]

Firstly, Ir is not soluble in AR. This is how it was discovered in fact, as a black redue left from natural Pt dissolved in AR.

Secondly, the Ir you get from MMO is in very small amounts. You probably need around 50-100 kg of mesh to reclaim one gram of Ir.

Thirdly, Ir is not very saleable. You will likely be paid 50% from the spot value and you need lots of grams to even start thinking about a transaction. The buyers are not numerous like in the case of gold.

And finally, you'd better sell the MMO as it is. You surely make way more this way.

[Arthur]

Iridium and Ruthenium are each several dollars per gram when pure, BUT how much do you have at 5 and 3 percent, percent of how much. Given a kilo of your tested powder 8% is valuable and 8% of a kilo is 80 grams - it's worth the work. If you have 1 gram of powder then 8% is only 80 milligrams so recovery is probably a waste of time -keep it til you have more.

DO you have a precious metal recovery company in your country? Someone who would take your Black waste powder and recover the PGMs for you and give you a price for the metals. It's likely cheaper to engage a contractor than too learn and practice the whole chemistry  of PGM recovery buying all the reagents.

Should you engage in chemistry with PGMs read carefully any noted hazards in the literature, some PGMs have catalytic properties and some PGM compounds are powerful irritants to skin.

Remember that your test gun will tell you percentages, BUT only you know what that's a percentage of. 

Sreetips has pulled some interesting metals out of old jewelery.

 

[IBJ]

50 minutes ago, a_bab said:

Firstly, Ir is not soluble in AR. This is how it was discovered in fact, as a black redue left from natural Pt dissolved in AR.

Secondly, the Ir you get from MMO is in very small amounts. You probably need around 50-100 kg of mesh to reclaim one gram of Ir.

Thirdly, Ir is not very saleable. You will likely be paid 50% from the spot value and you need lots of grams to even start thinking about a transaction. The buyers are not numerous like in the case of gold.

And finally, you'd better sell the MMO as it is. You surely make way more this way.

Are you absolutely sure of the fact that there is a little amount of iridium on the mesh? I have attached a photo below of the mesh and the report of the mesh. 

[IBJ]

9 minutes ago, Arthur said:

Iridium and Ruthenium are each several dollars per gram when pure, BUT how much do you have at 5 and 3 percent, percent of how much. Given a kilo of your tested powder 8% is valuable and 8% of a kilo is 80 grams - it's worth the work. If you have 1 gram of powder then 8% is only 80 milligrams so recovery is probably a waste of time -keep it til you have more.

DO you have a precious metal recovery company in your country? Someone who would take your Black waste powder and recover the PGMs for you and give you a price for the metals. It's likely cheaper to engage a contractor than too learn and practice the whole chemistry  of PGM recovery buying all the reagents.

Should you engage in chemistry with PGMs read carefully any noted hazards in the literature, some PGMs have catalytic properties and some PGM compounds are powerful irritants to skin.

Remember that your test gun will tell you percentages, BUT only you know what that's a percentage of. 

Sreetips has pulled some interesting metals out of old jewelery.

 

I managed to recover 6 grams of powder from 400g of mesh today, and I am not aware of any recovering companies in my country, cannot find any on the internet, but could you please tell me how I can seperate out iridium oxide from the black powder? 

 

[AustralianPyromaniac]

There are a few papers/ forum posts indicating decent solubility of the oxide in hot AR, so I do think it’s a viable route. Although as a_bab said the metal itself, not already oxidised, cannot be oxidised by AR and is highly resistant to attack. AR is really the only route available to you.

You have to get the coating into solution somehow to process it further, but the exact steps you need to take we cannot tell you. It depends what contaminants you have, what scale you’re working at, and what chemicals you have access to. People here also are not experts in these subjects, you need to speak to someone in the field of precious metal refining. 

[IBJ]

2 minutes ago, AustralianPyromaniac said:

There are a few papers/ forum posts indicating decent solubility of the oxide in hot AR, so I do think it’s a viable route. Although as a_bab said the metal itself, not already oxidised, cannot be oxidised by AR and is highly resistant to attack. AR is really the only route available to you.

You have to get the coating into solution somehow to process it further, but the exact steps you need to take we cannot tell you. It depends what contaminants you have, what scale you’re working at, and what chemicals you have access to. People here also are not experts in these subjects, you need to speak to someone in the field of precious metal refining. 

Lets say the Iridium Oxide does get dissolved in AR, the other two oxides of Ruthenium and Titanium will not dissolve. I plan on adding ammonium Chloride in the AR to form a precipitate of Iridium, and then putting the precipiate in a furnace to get iridium metal, so if the oxides of titanium and ruthenium do not dissolve, how will I seperate the black powder and the new iridium precipitate?

[Arthur]

So you have 6g at 2.6% = 0,15g which is about £1

you've likely spent more than that on reagents to do the recovery. Maybe look to see what you have and what it's really worth.

The screenshots of the XRF can be confusing because they say different things. 

No-one is going to offer you money for single gram quantities, because they have to spend time and money doing assays on your item before adding it to their stock.

[Arthur]

There will be a precious metal dealer who trades in your area, even one that trades platinum group metals (PGMs). HOWEVER they will likely not advertise because simply they do not want queues of robbers (etc) at their door. ONLY by becoming known to jewellery makers and sellers as a responsible person ill they share their contacts (remember that every jeweller buys in broken items that may get recycled or remanufactured).

[Richtee]

Quit fishing for free advice on a hair-brained idea. And crapping up a pyro forum.

[AustralianPyromaniac]

Lead oxides are soluble in boiling HCl, titanium oxides are soluble in boiling H2SO4 and ruthenium oxide is soluble in boiling HNO3. A three-step process in that order would yield a solution of ruthenium nitrate and powder of the iridium oxide out the other end. Ru nitrate then reduced to something insoluble however you would like, and both Ru and Ir compounds can be reduced to metal with hydrogen gas at 1200 C. You will spend more in reagents than your product is worth. 

[Arthur]

Remember that this metal has NO VALUE if you cannot find a buyer. If you have ruthenium and iridium oxides present  then sell the whole lot to a precious metal dealer who will give you a price for the PGMs and ignore the base metal. Alternatively find someone locally who wants a MMO electrode for it's usual obvious purpose in pyro. Remember that the black cladding is probably one thousandth of the mass of the mesh and this will ultimately contain almost no PGMs so despite the cost of PGMs the amount and value of PGMs present will be minimal.

PGM -platinum group metal.

[IBJ]

56 minutes ago, Arthur said:

Remember that this metal has NO VALUE if you cannot find a buyer. If you have ruthenium and iridium oxides present  then sell the whole lot to a precious metal dealer who will give you a price for the PGMs and ignore the base metal. Alternatively find someone locally who wants a MMO electrode for it's usual obvious purpose in pyro. Remember that the black cladding is probably one thousandth of the mass of the mesh and this will ultimately contain almost no PGMs so despite the cost of PGMs the amount and value of PGMs present will be minimal.

PGM -platinum group metal.

Your point is valid Arthur, but I come from a third world country and the dynamics work a little differently in here, finding a buyer is not a problem, and selling the MMO electrode directly is not really a good idea but yes thanks for the advice.

[IBJ]

1 hour ago, AustralianPyromaniac said:

Lead oxides are soluble in boiling HCl, titanium oxides are soluble in boiling H2SO4 and ruthenium oxide is soluble in boiling HNO3. A three-step process in that order would yield a solution of ruthenium nitrate and powder of the iridium oxide out the other end. Ru nitrate then reduced to something insoluble however you would like, and both Ru and Ir compounds can be reduced to metal with hydrogen gas at 1200 C. You will spend more in reagents than your product is worth. 

Thank you, that sure does sound helpful. Also I live in a third world country and reagents are dirt cheap here, and yes you may be correct that product is worth less than the cost of reagents but trying sure doesn't hurt!