Path: utzoo!hoptoad!pacbell!pyramid!decwrl!labrea!husc6!yale!Ram-Ashwin
From: Ram-Ashwin@cs.yale.edu (Ashwin Ram)
Newsgroups: alt.aquaria
Subject: Re: what does carbon in a filter do? (AND) Re: "Brown and smelly"
Message-ID: <28713@yale-celray.yale.UUCP>
Date: 9 May 88 16:29:14 GMT
References: <9178@agate.BERKELEY.EDU> <4268@super.upenn.edu> <28329@yale-celray.yale.UUCP> <419@bacchus.DEC.COM>
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Reply-To: Ram-Ashwin@cs.yale.edu (Ashwin Ram)
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Organization: Computer Science, Yale University, New Haven, CT 06520-2158
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In-reply-to: reid@decwrl.dec.com (Brian Reid)

In article <419@bacchus.DEC.COM>, reid@decwrl (Brian Reid) writes:
> In article <28329@yale-celray.yale.UUCP> Ram-Ashwin@cs.yale.edu (Ashwin Ram) writes:
> >You can't regenerate activated carbon.  How often you need to replace it
> >depends...
> 
> Sure you can. You just bake it in an oven. Chemistry labs all over the world
> regenerate it all the time. I haven't got the reference book in front of me
> here, but a call to my friend Peter who used to be a chemistry professor got
> me the instructions to bake it at 450 for 20 minutes or so, in a glass baking
> dish. He says that the trick is to drive the adsorbed molecules out, leaving
> behind the activated carbon structure.

[This is probably an academic discussion since this stuff isn't expensive enough
to worry about, but here goes anyway...]

450 what?  Activated carbon is manufactured at 900 Celsius, and regenerated in
chemistry labs by baking it at 400-450 Celsius in anerobic conditions (no
oxygen, otherwise you end up with burned charcoal).  This is considerably higher
than most household ovens will let you get (which is about 550 Fahrenheit).

Lower temperatures drive out gases that are adsorbed, but not everything.
Probably depends on the boiling point of the impurity.  This may be sufficient
to regenerate carbon for aquarium purposes.  I'm not a chemist, so I don't know
for sure.  Wish I'd stayed awake during those chemistry classes... :-)

-- Ashwin.

ARPA:    Ram-Ashwin@cs.yale.edu
UUCP:    {decvax,ucbvax,harvard,cmcl2,...}!yale!Ram-Ashwin
BITNET:  Ram@yalecs