Anyone using a CO2 scrubber for their skimmer intake?

[Anonymous]

Have you been able to test your dissolved O2 before and after?

 

[Len]

Sorry, but nope. I should have gotten some test kits.

 

[Anonymous]

It is not obvious to me how would the scrubber affect the dissolved O2. Why do you want Len to test for it?

 

[Len]

Because I had the silly theory that oxygen levels may have increased.

 

[Anonymous]

Because I had the silly theory that oxygen levels may have increased.

I don't think the solubility of O2 in seawater is a function of the CO2 concentration. What is your rationale?

 

[Len]

I thought soda lime stripped carbon from CO2 and oxygen was a byproduct. So I thought more O2 was getting into the tank, and assuming the water wasn't fully oxygen saturated, I thought it would increase oxygen levels.

 

[Anonymous]

Because I had the silly theory that oxygen levels may have increased.

I don't think the solubility of O2 in seawater is a function of the CO2 concentration. What is your rationale?

That's what I was trying to sort out, thanks for wording it better. (Damn! outdone by a non-native :x )

 

[Anonymous]

At least you don't call me an invasive species. :lol:

When it come to chemistry, I guess you are the non-native. :wink:

 

[Anonymous]

At least you don't call me an invasive species. :lol:

When it come to chemistry, I guess you are the non-native. :wink:

Do you know that I still can't figure out how I passed my chem class with an A? I look at chemical reactions and draw a blank. I can barely remember what a molar value is!

But wait! It gets worse! Yesterday I subtracted 20,000 from 28,000 in my head and came up with a result of 18,000. :roll: It stayed that way for almost an hour.

 

[Anonymous]

I don't know what is a molar either, but my dentist does...

Wait, I think we both are having a good alzheimer today.

 

[Anonymous]

At least you don't call me an invasive species. :lol:

When it come to chemistry, I guess you are the non-native. :wink:

Do you know that I still can't figure out how I passed my chem class with an A? I look at chemical reactions and draw a blank. I can barely remember what a molar value is!

But wait! It gets worse! Yesterday I subtracted 20,000 from 28,000 in my head and came up with a result of 18,000. :roll: It stayed that way for almost an hour.

Must have been your checkbook. And it took an hour for them to notify ya.

 

[Len]

Well, my pH level is starting to trend back down. I don't think the media (soda lime?) keeps efficacy for very long :? I'll have to see about buying it in bulk, or just using carbon in it to purify the air and silence my skimmer's air intake at the same time.

 

[Anonymous]

I will have to review my calcium chemistry, but you may want to find out if the spent media can be reactivated with the oven's temperature. Can save you money if it does. Overall, IMO, it is a waste of money.

 

[Anonymous]

I will have to review my calcium chemistry, but you may want to find out if the spent media can be reactivated with the oven's temperature. Can save you money if it does. Overall, IMO, it is a waste of money.

It sounds like the reactivation would just be the same as converting CaCO3 to CaOH which I think is just heating it up. I doubt it's worth the time and effort involved though!

The overall reaction is:
CO2 + Ca(OH)2 → CaCO3 + H2O + heat (in the presence of water)
The reaction can be considered as a strong base catalysed, water facilitated reaction.
steps:
1) CO2 + H2O → CO2 (aq) (CO2 dissolves in water - slow and rate determining)

2) CO2 (aq) + NaOH → NaHCO3 (bicarbonate formation at high pH)

3) NaHCO3 + Ca(OH)2 → CaCO3 + H2O + NaOH (NaOH recycled to step 2) - hence a catalyst)
each mole of CO2 (44g) reacted produces one mole of water (18g)

 

[Anonymous]

Well, my pH level is starting to trend back down. I don't think the media (soda lime?) keeps efficacy for very long :?

A local guy who tried this reported the same thing. He said within about 10 days his pH returned to its pre-scrubber value.

 

[Anonymous]

Heating the media may just reactivate it...at least, that sounds reasonable to me.

I don't however think a CO2 scrubber will affect oxygen concentration. We had a tank here that was exhibiting low pH values and drastically high alkalinity (our tap water is poop). I was trying to convince my group that we should consider CO2 as the reason the pH was so depressed. They brought out an oxygen meter to prove that the CO2 wasn't high. What we found was that even though the CO2 was high (based on a calculated value) that the O2 was well within acceptable ranges as well.

I can't think of anything happening in the Ca or CO3 equilibria that would affect oxygen. Course, I've been wrong before....


Len, I'd like to get some more info from you on this scrubber after you've been using it a few months. Be sure to keep us informed.

 

[Anonymous]

Heating the media may just reactivate it...at least, that sounds reasonable to me.

I looked into this--something like an 850 degree C kiln is required...

 

[Anonymous]

Do you know what type of substrate it is? Is it a carbonate or hydroxide type material?

 

[Len]

I think it's just soda lime.