Granulated active carbon and iodine number, should we care?

Prah

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Hey Guys,
It's a pleasure to e-meet you all, I'm Francesco, I'm a fellow reefer from Italy and this is my very first post.

I have a question regarding GAC and iodine number, by digging a bit further into the various type of GAC, aside from the raw material they're made from, I understood that GAC can have different iodine levels, where it seems the standard rule is "the more, the better".
I'm quite interested in this, as I often scout through the reef2reef forum, but to my knowledge I couldn't find anything on this, and even by looking at some big brands, such as KZ and AF, they don't exactly write on their product pages the Iodine level of their GAC.

Does Iodine levels in GAC really make a difference?
 
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Garf

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Hey Guys,
It's a pleasure to e-meet you all, I'm Francesco, I'm a fellow reefer from Italy and this is my very first post.

I have a question regarding GAC and iodine number, by digging a bit further into the various type of GAC, aside from the raw material they're made from, I understood that GAC can have different iodine levels, where it seems the standard rule is "the more, the better".
I'm quite interested in this, as I often scout through the reef2reef forum, but to my knowledge I couldn't find anything on this, and even by looking at some big brands, such as KZ and AF, they don't exactly write on their product pages the Iodine level of their GAC.

Does Iodine levels in GAC really make a difference?
Welcome, never heard of it but watching :)
 

taricha

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If I read this right, I think "Iodine number" is a measure of how well GAC adsorbs, as quantified by iodine removal. Not an indicator that there is iodine in GAC.

"Determining the iodine number is one of the methods to determine the adsorption capacity of activated carbons. It is a measure of the micropore (0–20 Å) content of the activated carbon by adsorption of iodine from solution. The typical range is 500–1200 mg/g, which is equivalent to surface area of carbon between 900 and 1100 m2/g "
source
 
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Randy Holmes-Farley

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Right, the iodine number is not any sort of measure of iodine in the GAC or the ability to bind iodine in a reef tank.

it is a measure of surface area available to small molecules such as I2.
 
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Prah

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Alright guys great! Thank you so much for clarifying that! Unfortunately all my sources came from Chinese translated from English, that's where the "Iodine levels" originated from. Now I also understand why generally speaking the "more the better", because the higher this number, the higher the surface area available for binding.

Thank you so much!!
 

Randy Holmes-Farley

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Alright guys great! Thank you so much for clarifying that! Unfortunately all my sources came from Chinese translated from English, that's where the "Iodine levels" originated from. Now I also understand why generally speaking the "more the better", because the higher this number, the higher the surface area available for binding.

Thank you so much!!

yes, I would just caution that a higher value doesn’t mean more binding of organics from seawater because iodine number is evaluating for very small pores. A number such as the molasses value or methylene blue value might be more useful for evaluating binding of organics.
 
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