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Author: Subject: methanol/ionic liquid electroplaing of metals
semiconductive
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[*] posted on 3-5-2021 at 07:40
methanol/ionic liquid electroplaing of metals


I'm trying some experiments in methanol, to see how it compares to water electroplating.

Iron, for example, rapidly turns a water bath brown and rust forms during electo-deposition of metal. Rust sludge falls to the bottom of a water bath. Only certain acids seem to be able to plate iron from water, and the results aren't very useful in most manufacturing settings.

So, I decided to try iron deposition from a methanol bath to see if I can control the rust issue and get more crystalline iron to plate out. I also wanted to see if more electropositive metals, such as strontinum and calcium, could be electroplated from a bath containing methanol or methanol salts.

I made potassium acetate from potassium carbonate and white vineagar; and then re-crystalizzed it twice to get rid of most impurities. This, I mixed with methanol and began electrolysis between two steel electrodes.

An orange colored solution forms at the anode, and it diffuses into solution well.
If any solid forms, just a gentle shaking causes it to dissolve.

A dark colored deposit forms on the cathode. I expect this is iron monoxide, and I think there is probably a small amount of moisture in the potassium acetate. If that's the case, the deposit could possibly turn grey or silvery in a day or two after the traces of moisture are destroyed.

What I am curious about, though, is how likely am I to get either acetate or methoxide embedded in the iron as it plates? Is there a theoretical way to estimate the percentage I should get?

The cathode voltage is the most negative (reducing) of all reaction sources, and any potassium that plates out will want to go back into solution as potassium acetate or potassium methoxide. So, I don't expect significant potassium to end up in the deposit because there is excess methanol present as a solvent. K is too reactive to build up when liquid methanol is present.

That brings me to a second experiment with more electropositive metals, which rapidly react with methanol. Alkaline alkoxides are generally solids, and can interfere with electrodeposition of more metal. Calcium acetate, when mixed with methanol, will also form a gel; and I don't know if that would be conductive or not.
So, I want to avoid the gel.

I want another solvent that is not likely to react with calcium or strontium, but would tend to dissolve acetates. This will dillute the methanol and reduce the rate it attacks an electropositive metal and hopefully prevent gel formation.

For my first attempt, I tried a methanol-acetate ester. I'm just thinking acetate and acetate ... are likely to dissolve each other since they are alike'. I assume the ester will be relatively inert or at least slow reacting around calcium metal, but I'm not sure. Please advise.

Next, I made calcium acetate (a solid) and mixed it with the ester.
No obvious dissolution happened.

I added a few drops of methanol to the solution and applied voltage to a carbon anode and iron electrode. No current flowed at all. So, I added a very small amount of ethylene carbonate.

Then the reaction started. It requires more than 3volts for significant current to flow. Ethylene carbonate is advertized as having a 4v working window before it will participate in side reactions. So, I think it's possible for calcium metal to be reduced at the electrode, and be re-dissolved by the methanol present.

Is my choice of solvent (ethane-acetate ester) likely to react with calcium ions or metal or not?


[Edited on 3-5-2021 by semiconductive]
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[*] posted on 3-5-2021 at 08:05


I don't think methanol is going to work for either group of metals, as you suggest . I think you will need an aprotic polar liquid such as an organic carbonates, dioxane, ethylene-diethers such as glyme etc. I think you would reduce DMSO so that no good.

The tradition method of preparing alkaline earth metals was to use a mercury cathod and then distill off the mercury but that probably rather risky.

As for iron it should be possible since there is a commercial process used to electrowin zinc for hydrometallurgical solutions. This process is used commercially in at least one mine I know of. I am not sure of the exact conditions but I am sure a google search will yield a link.
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[*] posted on 3-5-2021 at 08:07


Quote: Originally posted by semiconductive  
I'm just thinking acetate and acetate ... are likely to dissolve each other since they are alike'. I assume the ester will be relatively inert or at least slow reacting around calcium metal, but I'm not sure. Please advise.

That would be a poor assumption. An ionic acetate is nothing like an ester of acetic acid, and one will not be soluble in the other. Esters have much lower polarity than alcohols, and are poor solvents for ionic compounds.

Ethylene carbonate is much more polar, and is likely to be a better solvent for what you are trying.




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[*] posted on 3-5-2021 at 13:08


try Ethylene carbonate or propylene carbonate with iron perchlorates. Ethylene carbonate can be prepaid by urea and antifreeze with good vacuum pump and ZnO as catalyst. try youtube.



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[*] posted on 4-5-2021 at 19:42


Quote:

That would be a poor assumption. An ionic acetate is nothing like an ester of acetic acid, and one will not be soluble in the other. Esters have much lower polarity than alcohols, and are poor solvents for ionic compounds.

Ethylene carbonate is much more polar, and is likely to be a better solvent for what you are trying.


I agree, from experiment it's not good solvent for the calcium acetate even though the metyl group of acetate and the methyl group of the ester are the same for half the molecule. so, it's not like soap where half a molcule helps it dissolve in non-ionic, and half helps the ionic.

But, I'm more interested in the reactivity and some weirdness. Would the ester react wth calcium metal or hydroxide, or potassium metal or hydroxide?

This is why I ask: ethylene carbonate goes into ethanol-acetate ester after running electricity through the bi-layer for several days with even a tiny amount of methanol in the solution (to make it conductive). Methanol appears to make ethylene carbonate soluble in ethanol-acetate ester. The solubility increases rapidly as metal ions are dissolved; and that seems opposite of what you suggest. For metal in solutions should be ionic, and decrease the solubility in the acetate-ester. Correct?

Here's what I did:
I added a chunk (2CC's and around 30%) of solid ethylene carbonate to the ester; and two drops of methoanol, along with potassium cabonate. The cabonate stayed solid on the bottom.

I ran electricity through it the bi-layer with an iron cathode inside the ehylene-arbonate, and a carbon anode in the ester above. I wanted to make a small amount of the potassium go into solution and wasn't trying to dissolve iron yet.

After a few days, I had a liquid and no more solid ethylene-carbonate at the bottom.
This disappointed me, because I was hoping the two would stay separate and help me isolate different molecules which might prefer one media to the other. But, I guess I'll need a semipermiable membrane to do anythng like that.

I tried to evaporate the ester off, but the last 2cc's mostly stayed liquid even after cooling. I got less than 1/4cc of solid which was darkened by the iron of the cathode. (The anode was carbon fiber, and perfectly clean.)

There was very little gas formed at the carbon anode, and almost all gas came from the cathode.

So, I'm wondering if the ester reacted with the etyhlene-carbonate, or the metal ions, ??

Why would the carbonate stay liquid after I tried to evaporate the ester off, especially when alkalai methoxides are gnerally solids?
Is this a Eutectic issue, or a chemical reaction issue.
How might I design an experiment to tell?

The test tube was sealed, so no moisture was entering during the multiple days.
It had gas pressure when I opened it, so there should be hydrogen and perhaps carbon dioxide in the tube preventing moisture from working it's way in. The potassium carbonate is suppoed to be dry, reagent grade. So is the Ethylene cabonate. I was getting a 2.7 V back voltage after disconnecting power , which generally means there couldn't be much water in the electrolyte or the 'battery' voltage would decay in seconds rather than in hours.

[Edited on 5-5-2021 by semiconductive]

[Edited on 5-5-2021 by semiconductive]
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[*] posted on 4-5-2021 at 20:25


Quote: Originally posted by rockyit98  
try Ethylene carbonate or propylene carbonate with iron perchlorates. Ethylene carbonate can be prepaid by urea and antifreeze with good vacuum pump and ZnO as catalyst. try youtube.


Why perchlorates? Wouldn't that be explosive and rust causing?

I've tried electrolysis on KCl, before I bought reagant grade potassium carbonate. I thought I would drive off the chlorine as gas in KCL, (and produce cheap potassium hydoxide.) Then I could that would react with my methanol to make a methoxide.

But, I got a very strong oxidizer ... as in INSTANT rust. I'm thinking it might have been potassium perchlorate, but I'm usually wrong. So, I'll just let someone smarter answer.

But -- I'm wondering: wouldn't an iron perchlorate be prone to making rust?
I've been trying methanol over water, because the methyl group has a much stronger bond to the oxygen than hydrogen does. I'm hoping the methyls will prevent the iron from absorbing the oxygen.

What's the supposed advantage of using iron perchlorate?
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[*] posted on 5-5-2021 at 12:53


Small update .... The Iron in methanol with potassium acetate plates organ-metallic. It has a significant amount of grey iron in it ... but it is spongey and mostly dark. Though, it's an actual deposit and not a sludge that falls off the electrode. The deposit is metallic enough to make a very thick deposit overnight of several millimeters..

I added the ester to the electrolyte to see how soluble the iron ions were in ester. About 40% of my mixture (approximately the amount of methanol present) misced with the ethanol-acetate ester making a dark orange liquid. After that, the liquids separated into two layers and the orange condensed into a smaller space on the bottom of the test-tube. So, I assume the iron acetate is nearly insoluble in ethanol-acetate ester. I'm merely extracting methanol out of the electrolyte with the ester.

The deposit is promising. Solid but spongey deposits in water based electrolytes usually means too high of an electroplating current.
So, I'll fiddle with it. Maybe reduced current will produce a better deposit in a non-aqueous electrolyte as well.
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[*] posted on 5-5-2021 at 17:32


If you mean ethyl acetate, say ethyl acetate, not "ethanol-acetate ester". The iron may plate out of your methanol solution, but it's not organometallic.



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[*] posted on 6-5-2021 at 19:52


I lookued up organometallic. Are you objecting because the oxygen an oxygen likely present? eg: it's not organometallic even though an organic acid or methly group is still attached to the iron?
The iron is soft, and that's not because its spongey ... but because not all the acid/alcohol bonded to the iron leaves the surface as it plates. The result is iron that still has acid attached to it, and possibly methanol.

Iron methoxide is called "organo-metallic" by american elements and others that sell it. I think that's a likely contaminant in the plating.

I assume you don't know if ethyl-acetate will react with sodium or potassium since you haven't answered, now, twice?

If so: I'm going to assume it doesn't react, because I can apply 12V to pure ethyacetate ... and no detectable current flows. Even with distilled water, a little current will flow. So, I think the ester would be pretty stable in the presence of alkali metal. If it does react, I'm going to assume (for now) that it probably is a slow reaction.

I added Ethyl-carbonate and ester, and will run it until the methanol (just a few drops was all I had in this vial) is chemcially exhausted. Perhaps the plating color will change.

I think Ethyl carbonate dissolves slowly in ethyl acetate; at least when in the presence of metal ions. I'm going to hypothisize that Ethyl carbonate is unlikely to release all the ethy acetate in a drying process, and that's why I end up with liquid when I try to drive off the ester with heat.

Today's plating is much harder and denser (at lower currents) than before; but it's also very rough and dark grey to black. It's not plating smoothly, either. That could be because of the large amount of potassium that is present.

I don't think there's much organics adhering to this deposit. It turns brown on exposure to air, though. So, maybe a small amount of the methanol is breaking down and releasing oxygen?

The solution varies between yellow and dark red depending on dillution; The red liquid sinks to the bottom of the vial. There's no brown color ... so I'm fairly confident that I have iron tri-acetate as the major constituent. I'm not sure what the yellowish color is, but maybe that's just very dilute iron tri-acetate. Iron tri-acetate doesn't dissolve well in the ester.
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[*] posted on 6-5-2021 at 20:15


Quote:
I lookued up organometallic. Are you objecting because the oxygen an oxygen likely present? eg: it's not organometallic even though an organic acid or methly group is still attached to the iron?
The iron is soft, and that's not because its spongey ... but because not all the acid/alcohol bonded to the iron leaves the surface as it plates. The result is iron that still has acid attached to it, and possibly methanol.

You've got iron. Maybe it's rusty, maybe it's dirty, but it's iron, not an organometallic iron compound.

Quote:
Iron methoxide is called "organo-metallic" by american elements and others that sell it. I think that's a likely contaminant in the plating.


It does not contain an iron-carbon bond, so it is not organometallic, despite what the salespeople say.

Quote:
I assume you don't know if ethyl-acetate will react with sodium or potassium since you haven't answered, now, twice?

If so: I'm going to assume it doesn't react, because I can apply 12V to pure ethyacetate ... and no detectable current flows.


That doesn't say anything about whether ethyl acetate will react with either metal- it just means it's a nonconductor. There's no ions in the solution,so why should it conduct?

If there is even a trace of moisture present, then the sodium or potssium hydroxide formed will hydrolyse the ethyl acetate pretty quickly.





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