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Author: Subject: Recover platinum from perchlorate cell electrolyte
Tellurium
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[*] posted on 25-3-2018 at 21:56
Recover platinum from perchlorate cell electrolyte


Hello,
yesterday I totally screwed up - I let my perchlorate cell run for too long because I cant get home and when I came back and looked at it the 1g of Platinum wire was gone because of low chlorate concentration.

So now I'm thinking about what to do.
Can I electroplate Ti with platinum out of this solution? If not: How can I recover the platinum anyways? What is actually the form of the platinum now? I suppose some kind of komplex?

Thanks in advance:)
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Thulium
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[*] posted on 25-3-2018 at 22:57


Hello Te,
Without knowing the specifics of your setup, I would first check to see that it's truly gone and not buried under precipitate at the bottom of the cell. I've had chlorine fumes corrode the alligator clip holding the electrode, causing the electrode to fall to the bottom and it's hard for me to imagine an entire gram of platinum corroding away in a day at any normal currant, regardless of chlorate levels.
If it's in fact gone, you have presumably managed to make a solution containing platinum cations (I would expect Pt4+ since Pt2+ halides tend to be insoluble. I can't seem to find any data on platinum perchlorate or chlorate though). There are a number of ways I could think to recover this. Most obvious is a single replacement reaction with just about any metal since platinum is at the bottom of the activity series and should precipitate out no problem. However if it's acidic, avoid anything above hydrogen on the activity series.

As for electroplating platinum onto titanium, I could imagine it working. I run my cell with two platinum electrodes and switch the anode and cathode every few days, the idea being any platinum lost from the anode should be plated onto the cathode. I don't know how big your cell is, but if it's not very large, the platinum ion concentration may be high enough to immediately attack the titanium with the single replacement reaction I described above. Even if it's very dilute, I suspect this may still take place to some degree, resulting in a less than ideal electroplating setup.

In any case, recovering platinum should easily be doable, although I will admit I have never actually tried this since I have never seen platinum dissolve :) If you go the single replacement route, I would be inclined to try copper. HCl, chlorate and perchlorate ions shouldn't affect it at all, but Platinum, in theory, is one of the few ions that can displace copper. I imagine this would progress with the copper slowly dissolve into a green-blue solution and precipitating out the grey platinum.
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Tellurium
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[*] posted on 25-3-2018 at 23:25


Hey Tm,
when I checked it this morning I wasn't able to see any Pt, which I also think to be pretty strange, but maybe I was just to tired at 4:30AM :o
The most strange thing is,that I ran the cell with only 2 Amps for test of the new Pt(because I was ripped of with another electrode beeing not Pt, but this one was legit producing KClO4).
I will take another look when I'm home, maybe you are right and just the copper connection(which was above the surface of the electrolyte) was etched away.

Are you using straight Pt for electrolysis or have you electroplated electrodes? Because I have some Ti-Sheets laying around and maybe it would be good etching the oxide layer away and electroplate them, because in this way I would have a lot higher surface area than with straight Pt.
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[*] posted on 26-3-2018 at 09:33


Hello Te,
Hopefully it's just sitting at the bottom, buried under precipitate. I had this happen once when I used wire and it was really hard to find since it's thin, dark and buries itself under any precipitate due to greater density. I don't know what wire you are using, but I know when I used Pt wire, 2A would have been an awful lot for a really thin piece of wire. It's possible it could have melted off as well. With these limitations of Pt wire, I switched to the "industrial" platinum plated titanium electrodes (the type used in jewelry plating). You can buy them at many jeweler equipment suppliers, or eBay.

It may be possible to plate your titanium sheets at home with Pt, but from what I've read, Ti is a very difficult metal to electroplate (you will recall it reacts with both nitrogen and oxygen). Furthermore the processes I've read about for plating with platinum seem to require molten hot cyanide salts which just seems like it's asking for trouble in a typical home setting. I suspect it could be done, but it's not something I personally would be much inclined to try and I'd happily pay for my electrodes to avoid working with large quantities of hot cyanides...
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[*] posted on 26-3-2018 at 11:59


Maybe you could start with a cheap platinized anode
https://www.ebay.co.uk/itm/5-x10cm-Mesh-Platinized-Titanium-...:P~sAAOSwQm9Zu7D4
and thicken the plating ?




CAUTION : Hobby Chemist, not Professional or even Amateur
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[*] posted on 26-3-2018 at 21:10


@Tm
You luckily were right, under a thick layer of KClO4 there was some Pt smiling at me :D
I also thought about the proplem of thin Pt wire not handling that much current , thats why I cut a platinum bar in something wire like with a diameter of 1-2mm.
I really didn't thought, that it will be that much of a pain to electroplate Pt. I thought I could just use some PtCl4 in solution and thats it:(

@Tm @Sulaiman
Yes I bought one of these cheap Pt coated Titanium electrodes before buying the Platinum bar, but I was ripped of with a nickel coated something and it seems like most of them are actually fake. My seller also had a fairly good reputation on ebay.
So its hard for me to find a reputable source, thats affordable;)
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[*] posted on 27-3-2018 at 23:39


Glad you found the platinum :)

I would avoid going through online sources since you're likely to get fakes from China. I was able to buy mine at a local jeweler supply company and pick them up in person. If you really can't find anything near you, I'd try ordering directly from such a company rather than eBay. It's a little pricier than eBay, but unlike eBay sellers, suppliers know they will see lawsuits if they try to scam customers...
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