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Author: Subject: Extraction of rare earth metals from CFL lamps
ficolas
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[*] posted on 9-2-2018 at 09:37
Extraction of rare earth metals from CFL lamps


I recently had the idea of extracting the rare earth metals from CFL phosphors. And to my surprise, there seens to be more oxides per light bulb than I expected, almost a gram. Out of wich arround 50% is Ytrium oxide, what would leave me one step closer to makimg YBCO at home.

Ytrium oxide seems to be soluble in alcohol, so my plans are crushing the glass, dissolving the powder in ethanol, filtering and precipitating the ytrium oxide.

Contents of CFL bulbs source:
https://www.google.es/url?sa=t&source=web&rct=j&...

I cant seem to find much information about the solubilities, or the rest of the contents of the powder tho.
I'd also like to know how hazardous this can be. Ytrium oxide isnt toxic acording to what I have read, mercury vapour should be in very small amounts, so i'll just do this outside, and maybe leave the area when I break the bulbs, just in case.

Anything i'm missing?
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elementcollector1
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[*] posted on 9-2-2018 at 12:47


This paper does say that about 60% of the phosphor is rare earth compounds, but it doesn't mention what the balance is.

Rare earths are notoriously hard to separate from each other, but can easily be separated from iron and alkalis by reaction with excess oxalic acid and hydrogen peroxide (All RE oxalates are insoluble, but alkali oxalates are soluble and iron oxalate complexes with the excess oxalic acid and hydrogen peroxide). Oxalates can then be carefully calcined to the oxides in a furnace (or, in my case, a stovetop worked too).

I'm not so sure about yttria being soluble in alcohol - can you provide a reference for that?




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ficolas
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[*] posted on 9-2-2018 at 16:30


The paper says betwen 46.9% and 51.2% is ytrium, while only like 6-7% is europium and terbium, thats why my idea was recrystalycing.
I only found the ytria being soluble in alcohols in wikipedia, and wasnt able to find any literature about it. In chemspider, it says its insoluble in water and in dilute acids, but doesnt say anything about alcohols, so its probably a mistake.
Would the other ~40% of the phosphor be iron and alkalis tho?

I cant seem to find any better composition online. I'd guess different color of lamps would use different compositions, but from what I have seen all CFLs contain yttrium oxide, wich is what i'm after. Other than that, they also contain, barium aluminate or chloroapatite (?) for the blue color, and calcium tungstate or lanthanum phosphate for the green color. (yttrium oxide gives the red color)
This does not seem to be something easy to separate at all.
The more I look, the more compounds I find they can contain, luckly yttrium oxide seems to always be there.

Now, another question, how would I know if I indeed have yttrium oxide, and its not contaminated with anything else? What tests can I run to tell if it is, and how bad is it?

[Edited on 10-2-2018 by ficolas]
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Melgar
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[*] posted on 9-2-2018 at 16:46


I thought that the greenish blue color was copper-doped zinc sulfide? The same stuff that glow-in-the-dark stickers are made from? If you adjust your eyes to the dark, then cover them, then turn on a CFL for a few minutes (with your eyes covered and shut), then turn the light off, then look at it (with your eyes adjusted to the dark) you'll see it glows greenish blue.

If that's true, the yellowish "warm" lights would be better for rare earths. I think that there are mainly three different phosphorescent complexes in fluorescent lights, and the color temperature (3500K, 5000K, or 6000K IIRC) determines their ratios.




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[*] posted on 9-2-2018 at 17:04


Quote: Originally posted by Melgar  
I thought that the greenish blue color was copper-doped zinc sulfide? The same stuff that glow-in-the-dark stickers are made from? If you adjust your eyes to the dark, then cover them, then turn on a CFL for a few minutes (with your eyes covered and shut), then turn the light off, then look at it (with your eyes adjusted to the dark) you'll see it glows greenish blue.

I have seen that effect, but yea, as I said, the more I look it up, the more compounds I find that can be used for it
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