Why add water to DIY CO2 scrubber?

[rhdoug]

I installed a DIY CO2 scrubber in January of 2017, and have had pretty good results raising my low ph. I spent a good amount of time researching this yesterday and it's only mentioned in passing or not at all in most of the posts/instructions that I have come across. I have yet to find anything to explain why, so...Why do it and how important is it?

I have very little room to add water due to the intake holes being so close to the bottom, and since there is so little water it evaporates quickly. I can easily make a new one with more room between the intake holes and the bottom in order to hold more water if need be, but I'd like to understand the "why" before I do it.

 

[Reeferdood]

I assume you are using lime your media?
if so, I read somewhere that it lasts longer with more moisture in the air.
If @Randy Holmes-Farley is still lurking about perhaps he can enlighten you with a better explanation.

 

[GoPitt88]

Good question.....I'd like to know as well.

 

[Randy Holmes-Farley Verified Community Expert]

It is a solid media. The CO2 can only react with the surface, and much is inaccessible. Moisture deposits on the surface and dissolves it a bit, allowing access to deeper regions of available media.

 

[GoVols]

It is a solid media. The CO2 can only react with the surface, and much is inaccessible. Moisture deposits on the surface and dissolves it a bit, allowing access to deeper regions of available media.

Thank You

 

[Raptor72]

Can any reactor be used for this purpose? I have an Aquamaxx Biomaxx Reactor that I’m planning to use for this purpose in the very near future.

 

[rhdoug]

Thank you RH-F, now it makes sense.

 

[Larry L]

I have very little room to add water due to the intake holes being so close to the bottom, and since there is so little water it evaporates quickly.

Trying to keep some water in the bottom of the scrubber can be a pain - humidifying the air before it gets into the scrubber is easier, you'll find a number of threads about it. You can either run tubing into the scrubber from another container that's partially filled with water (so the humid air gets sucked in, not the water), or you can run tubing into the scrubber from the top of your skimmer collection cup, like here: https://www.reef2reef.com/threads/the-best-way-to-implement-a-co2-scrubber.330806/#post-4113530

Pulling in humid air from the skimmer also has the advantage that the air in the skimmer has already been scrubbed of CO2, so the scrubber has to do less work. My media started lasting much longer when I hooked things up this way.

 

[rhdoug]

Thank you Larry L, that is interesting and gave me an idea... My scrubber is made from a square plastic jar that once held BRS GFO media. It has holes drilled along the bottom sides and air enters there and gets pulled through the media.

I could put the scrubber in a small bucket or other container with some water in it; the scubber would sit on a raised platform in the bucket so it shouldn't get flooded. I may give that a try.

OR -- I could make a new one with the air intake holes placed a couple of inches higher so it can hold more water. The biggest issue with that is I will need to make a way to keep the suspended media out of the water. Maybe some small diameter dowels pushed thru the sides of the jar would do the trick. I would then place a sponge or filter pad on top of the dowels to keep the media from falling thru.

 

[BiggestE222]

Best way to get moisture in this icecap co2 scrubber?

 

[BiggestE222]

Unfortunately can’t add today as BRS sent a MH ballast instead of my milwaukee PH controller

 

[BiggestE222]

Looks like I can run the air intake line into a partially filled water jug which would keep the water slight moist as opposed to adding water to bottom of reactor. Would that be best option?

 

[Randy Holmes-Farley Verified Community Expert]

Looks like I can run the air intake line into a partially filled water jug which would keep the water slight moist as opposed to adding water to bottom of reactor. Would that be best option?

That may help, but may also slow the air input.

 

[srobertb]

Looks like I can run the air intake line into a partially filled water jug which would keep the water slight moist as opposed to adding water to bottom of reactor. Would that be best option?

I believe this is a common method. Not like a water pipe, just a small sealed container of water that the air passes through before hitting the CO2 media. I bet you could use a canister filter 1/2 filled with water and no filter cartridge. I don’t think this would slow flow down too much so long as the input and output are not bottlenecks.

 

[sneekapeek]

Wanted to revisit the humidity/moisture aspect. Couldn’t you just crush the media to a smaller form? Wouldn’t that solve the issue of contact?

 

[Randy Holmes-Farley Verified Community Expert]

Wanted to revisit the humidity/moisture aspect. Couldn’t you just crush the media to a smaller form? Wouldn’t that solve the issue of contact?

There are two reasons I think that is not useful.

The first is that air does not easily travel through fine powders. Imagine trying to breather through fine beach sand.

Second, the moisture on the particle surface speeds up the reactions to form calcium carbonate. A little moisture goes a long way for allowing ions to move around on a solid surface to find each other and precipitate.

 

[sneekapeek]

There are two reasons I think that is not useful.

The first is that air does not easily travel through fine powders. Imagine trying to breather through fine beach sand.

Second, the moisture on the particle surface speeds up the reactions to form calcium carbonate. A little moisture goes a long way for allowing ions to move around on a solid surface to find each other and precipitate.

I was thinking more of the size of a grain of rice or rox carbon. With enough flow I think it would work to increase contact. The media is too bulky as it is. And I think it could be reduced in size to better suit our needs. Unfortunately, we are fighting the suffocation of any reactor. I bought in an oversized air pump to hopefully help remedy. I just think a normal amount of moisture would be sufficient.

 

[Randy Holmes-Farley Verified Community Expert]

I was thinking more of the size of a grain of rice or rox carbon. With enough flow I think it would work to increase contact. The media is too bulky as it is. And I think it could be reduced in size to better suit our needs. Unfortunately, we are fighting the suffocation of any reactor. I bought in an oversized air pump to hopefully help remedy. I just think a normal amount of moisture would be sufficient.

Well, scientists have studied the moisture effect on sodalime for CO2 removal since at least the 1940's, so I doubt you'll discover it can be eliminated by using smaller particles, , but let us know how it works.

Soda lime production

Soda lime production. Soda Lime absorbs carbon dioxide from exhaled air flowing through it.

www.ebme.co.uk

This is the standard chemical explanation, and shows one reason moisture is needed:

• Carbon dioxide and the water contained in the soda lime react to form carbonic acid: CO2 + H2O = H2CO3
• In the second intermediate step, the carbonic acid reacts exothermically with sodium hydroxide to form sodium carbonate and water: H2CO3 + 2 NaOH = Na2CO3 + 2 H2O + heat
• Finally, the sodium carbonate reacts with the slaked lime to form calcium carbonate and sodium hydroxide: Na2CO3 + Ca(OH)2 = CaCO3 + 2 NaOH

 

[sneekapeek]

Well, scientists have studied the moisture effect on sodalime for CO2 removal since at least the 1940's, so I doubt you'll discover it can be eliminated by using smaller particles, , but let us know how it works.

Soda lime production

Soda lime production. Soda Lime absorbs carbon dioxide from exhaled air flowing through it.

www.ebme.co.uk

This is the standard chemical explanation, and shows one reason moisture is needed:

• Carbon dioxide and the water contained in the soda lime react to form carbonic acid: CO2 + H2O = H2CO3
• In the second intermediate step, the carbonic acid reacts exothermically with sodium hydroxide to form sodium carbonate and water: H2CO3 + 2 NaOH = Na2CO3 + 2 H2O + heat
• Finally, the sodium carbonate reacts with the slaked lime to form calcium carbonate and sodium hydroxide: Na2CO3 + Ca(OH)2 = CaCO3 + 2 NaOH

I’m by no means saying to run an air dryer before the scrubber media. I just find that a recirculating scrubber to have a normal amount of moisture. To add more moisture is my breaking point and I’d like to stay away from. We’ll see how she goes!

 

[Randy Holmes-Farley Verified Community Expert]

I’m by no means saying to run an air dryer before the scrubber media. I just find that a recirculating scrubber to have a normal amount of moisture. To add more moisture is my breaking point and I’d like to stay away from. We’ll see how she goes!

OK, I didn't recall seeing it was a recirculating scrubber. I'm not a big fan of those due to the loss of O2 exchange, but recirculating will reduce or eliminate the moisture concern and I agree that extra moisture may not be needed..