Activated Carbon Question

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I understand running Activated Carbon is good for water clarity and for absorbing certain inorganic compounds.

I would really like to know how does the Carbon clear the water ?

Does Carbon react with every inorganic compound or does it just go after the bad ones ?

What sort of reaction is going on between the Carbon and the water column ?
 
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Yup, this is a good question, and I will try to answer how I understand the process to work - just keep in mind that I'm not a chemist or activated carbon "boffin", and could be totally wrong (if so, then whoever knows better must please correct me...)

What sort of reaction is going on between the Carbon and the water column ?
Activated carbon works like a very fine mechanical sieve. The interior (and exterior, obviously) is full of microscopic holes and tubes/channels, and as the water passes through these channels the larger molecules become physically trapped in them - this is called adsorption (with a "d"), as opposed to absorption (with a "b") which is the chemical process of binding something to something else (such as a phosphate "sponge").

Does Carbon react with every inorganic compound or does it just go after the bad ones ?
No, it "reacts" with all molecules large enough to become trapped in the microscopic tubes/channels.

I would really like to know how does the Carbon clear the water ?
As I understand it, the substances which cause the water to become yellow are large-chain organic molecules, and because of their size they become trapped rather quickly, and are thus removed from the water. Because the carbon does not chemically bind the trapped molecules, and they can (and do...) become dislodged quite easily, and can thus be returned to the water. This is the main reason why it is recommended to only use activated carbon for a few days and then to discard it. Also, as the channels become blocked with these large molecules the water-flow is restricted, and the carbon loses it's ability to filter rather quickly.

Hennie
 

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Thanks hennie, then the activated part?
Yes that's why when carbon is "full" it can leech back
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dallasg

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from wikipedia
Activated carbon, also called activated charcoal or activated coal, is a form of carbon that has been processed to make it extremely porous and thus to have a very large surface area available for adsorption or chemical reactions. [1] The word activated in the name is sometimes substituted by active. Due to its high degree of microporosity, just one gram of activated carbon has a surface area of approximately 500 m², as determined typically by nitrogen gas adsorption. Sufficient activation for useful applications may come solely from the high surface area, though further chemical treatment often enhances the adsorbing properties of the material. Activated carbon is usually derived from charcoal.
Activated carbon - Wikipedia, the free encyclopedia
 
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yip those explanations are pretty spot on.
just as a matter of intrest, malaysia, india and indonesia are the worls best manufacturers of activated carbon , they are cleaner with regards to carbon fines / dust and even more pourous as they made from heat activated coconut shell
 
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it depends.......high grade carbon can be used for about 4 weeks before needing to be replaced.
one must be carefull when buying carbon, some suppliers sell anthricite as carbon (very very low grade carbon) that can only be used for a few days before it needs to be removed
 

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yip very short because its so effective, i once had the pleasure of being a virology lab and they use it for air and water filtering
 

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I have also found that the "most common" and mostly "fresh water use" carbon, are made of burnt bones. This also leaches phosphates back into the water.
Whereas the activated carbon, made from burnt coconut, does not - and these are the one's that we should prefeably be using in our marine tanks....
 
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it depends.......high grade carbon can be used for about 4 weeks before needing to be replaced.
one must be carefull when buying carbon, some suppliers sell anthricite as carbon (very very low grade carbon) that can only be used for a few days before it needs to be removed
Marco, I use your product, what would be an indication that the Carbon needs to be replaced ?
 

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its brilliant for air filters :)
 

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Aquarists often ask how much activated carbon should be used in the aquarium. Some carbon products give recommendations while others give no indication at all. Independent research has shown that “more is better” when using activated carbon. When filtering municipal water or aquarium water a greater quantity of carbon will work faster and longer than a lesser amount. A rough guide would be two U.S. cups (480 c.c.) per 55 gallons (280 L.) of aquarium water. Some aquarists use more or less depending on their filtration system and quality of the carbon product they use. Most carbon products last about six weeks in a marine “fish” aquarium. Reef aquaria produce more organics than a regular aquarium and may require more frequent replacement. Activated carbon cannot be reactivated by boiling in water or heating in an oven, the temperature is too low to destroy the sorbed pollutants and restore sorptive capacity.
http://www.hallman.org/filter/gac.html
 

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