Ram-Ashwin@cs.yale.edu (Ashwin Ram) (05/03/88)
In article <9178@agate.BERKELEY.EDU>, ephram@violet writes: > The store I used to go to placed nylon bags full of > carbon in the tank. When asked the proprietor would mumble something about > helps clean the ... I went to another store and heard much the same think > "It cleans the water". > > All of this has been very unsatisfactory, so I ask, What does charcoal do > in 1) a external box and floss type filter? and 2) in tandem with my U-G > filter? I'll take 2 first. If you mean the little filter plugs that go on the outlets at the top of the UG lift tubes, probably nothing except reduce the flow of water. But 1 is a different story: Activated carbon (or activated charcoal) is produced by the carbonisation of plant matter. It's good as a filter medium (if prepared properly) since it adsorbs coloids (e.g., proteins, dyes, organic acids, water-soluble drugs), and gases such as chlorine and ozone. Will not adsorb ammonia, nitrite, nitrate. (Adsorption is the adhesion of gases/dissolved substances to the surface of a solid body without a chemical reaction.) Activated carbon filters must be cleaned regularly. Spent filters begin to release poisonous fission products and ions which eventually begin to creep back into the aquarium. Also, spent filters contain oxidisable substances in high concentrations, which tend to remove the oxygen from the water. In article <4268@super.upenn.edu>, levine@eniac (Jonathan M. Levine) writes: > I have just a 10 gallon with a box filter...and I've been changing the floss > every time it gets brown and smelly. Is this not what I'm supposed to do? > How often is one supposed to change the charcoal/floss in a box filter? You can't regenerate activated carbon. How often you need to replace it depends on how many fish you have, how large (and dirty) the tank is, and so on. Once every 2-4 weeks is a good estimate. One way to test whether the adsortivity has reduced is to put a drop or two of a dye that the carbon would adsorb (such as methylene blue) right behind the filter cartridge. If you see blue trickling out with the water on the other side, you probably need to replace the carbon. As a rough guide, try turning the flow rate on maximum and check if all the water passes through the filter. If the filter is clogged, the water will accumulate on the input side and begin to trickle back into the tank without passing through the filter medium. (Depends on the design of your filter.) -- Ashwin. ARPA: Ram-Ashwin@cs.yale.edu UUCP: {decvax,ucbvax,harvard,cmcl2,...}!yale!Ram-Ashwin BITNET: Ram@yalecs
reid@decwrl.dec.com (Brian Reid) (05/04/88)
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. Also he says that activated carbon and activated charcoal are the same thing except for the physical shape of the granules.
Ram-Ashwin@cs.yale.edu (Ashwin Ram) (05/09/88)
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