How does carbon work?

[josephv]

I have always thought of it as a super fine filter used for polishing the water.
I am now learning that it is much more than a filter. But im still trying to get my head around it. My misunderstanding of carbon stems from years of using it in fresh water tanks. I would place gac in media bags and place it in a high flow area in the sump and then throw it away after a few days thinking that would absorb everything it could in that amount of time. Also thinking that it would leach out everything it captured and become a nitrate source if i did not remove it. Please in laymens terms explain how it works?How do you know when it is spent? Does carbon nutralize or eliminate organic material as it is captured?
Thanks for your help in advance as i realy want to understand carbon.

[Randy Holmes-Farley]

GAC works by providing hydrophobic spaces for organic matter to bind. It also provides some other sorts of binding, but hydrophobic binding dominates. So proteins and many other hydrophobic (like oils) and partly hydrophobic organic materials (like soaps and proteins, etc) will bind to it. Since many metals (like copper and iron) are bound to organics, these too can be bound as the organics they are attached to bind to the GAC.

It is certainly possible that one organic can displace another on a GAC surface, so things that are absorbed can come off if something with a higher affinity for GAC comes along and displaces it.

Over time (a few weeks or so), bacteria can also colonize the GAC surface, using it as a convenient place to grow. They do not use the GAC, except as a support. But they really do seem to like it. If you dose organic carbon (like vinegar or vodka) yopu may find that the GAC supports a lot of bacterial growth that can even be washed off if you want.

[josephv]

I have been digging deeper in the advanced reef forum and
reef chemistry forum. The more i learn the more i dont know. I better stick to cooking.
I think you may have some misunderstandings about how GAC works near the end of that thread. GAC does not work like very fine filtration. It works by absorption of individual organic molecules onto surfaces that are mostly flat in relation to the sizes of individual molecules. You cannot look at pictures of pores to know anything about the available surface area or quality of the carbon or how fast it would become fully occupied by organic matter.

ROX is among the best choices around, IMO, and I would recommend it over other brands. It is acid washed, it is largely dust free (possibly important in relation to issues such as HLLE in fish) and has a very high internal surface area. :)


I have always thought of it as a super fine filter used for polishing the water.
I am now learning that it is much more than a filter. But im still trying to get my head around it. My misunderstanding of carbon stems from years of using it in fresh water tanks. I would place gac in media bags and place it in a high flow area in the sump and then throw it away after a few days thinking that would absorb everything it could in that amount of time. Also thinking that it would leach out everything it captured and become a nitrate source if i did not remove it. Please in laymens terms explain how it works?How do you know when it is spent? Does carbon nutralize or eliminate organic material as it is captured?
Thanks for your help in advance as i realy want to understand carbon.



UOTE=Randy Holmes-Farley;18749658]GAC works by providing hydrophobic spaces for organic matter to bind. It also provides some other sorts of binding, but hydrophobic binding dominates. So proteins and many other hydrophobic (like oils) and partly hydrophobic organic materials (like soaps and proteins, etc) will bind to it. Since many metals (like copper and iron) are bound to organics, these too can be bound as the organics they are attached to bind to the GAC.

It is certainly possible that one organic can displace another on a GAC surface, so things that are absorbed can come off if something with a higher affinity for GAC comes along and displaces it.

Over time (a few weeks or so), bacteria can also colonize the GAC surface, using it as a convenient place to grow. They do not use the GAC, except as a support. But they really do seem to like it. If you dose organic carbon (like vinegar or vodka) yopu may find that the GAC supports a lot of bacterial growth that can even be washed off if you want.[/QUOTE]

[Randy Holmes-Farley]

:lol:

That's why were here. :)