Hydro-Lime Scrubber - Hybrid Sodium Hydroxide bubbler/Soda lime CO2 scrubber

[Tacticool-Reefer]

Tank - 150-gallon euro with ~20-gallon sump
Lights - Radion XR15 Pro x4, 9-hour for radion
Algae scrubber - the reverse of light schedule with a 60-minute overlap on each side
Dose 25.6 ML of BRS soda-ash via Neptune DOS every 3hrs +/-35%
Hybrid Sodium Hydroxide bubbler/CO2 (BRS Soda-lime media) (knicked name Hydro-Lime Scrubber) plumbed into skimmer - skimmer on 24/7

At night PH drops to 8.17, during the day PH has reached ~8.29
Tank located in basement approx. 3 feet from back door/bulkhead that is open often throughout the day in the spring and cracked about 1/2 in winter.
The basement is VERY airtight, 4 mil plastic moisture barrier fixed to concrete walls, 2x4 walls ALL with R-21 insulation, another 4 mil plastic moisture barrier, drywall, and that includes an R-30 insulation+drywall ceiling. No windows open as they are sealed and I have plans on replacing them this yr.

Alk- 8.86 to 9.2
Ca- 456
Mg- 1450

Inhabitants - fish load- 8 x Chromis, 3x Bimaculatus Anthias, 1 Naso. 1 Blue hippo
A mixed bag of sticks all growing very well.

Tank overall is doing well.

...Let me start by saying that I'm no scientist, I'm simply posting my observations and my engineering skills with implementing a hybrid approach to a Sodalime scrubber using @Randy Holmes-Farley information about Sodium Hydroxide and its ability to be more effective at scrubbing CO2.

The Hydro-lime scrubber that I created is a simple bucket filled with RO/DI water and about 40ml cup of Sodium Hydroxide, two air Stones along with an air pump introduce air into the solution - the unit has an airtight lid however it still allows for some air to be pulled in due to the holes drilled for the airlines. From there, an air hose to the CO2 reactor Inlet and then another airline from the CO2 reactors Outlet to my skimmer air Inlet. This is a good time to note that the Sodium Hydroxide bubbler/scrubber by itself was not able to remove/scrub enough CO2 to get my pH above ~8, but that is still a very excitable range.

The main reason I decided to try this was that I was exhausting the Soda Lime media in a little over 2-1/2 days, I figured if I can get the incoming air to be less saturated with atmospheric CO2 prior to hitting the soda-lime it would last that much longer, or so I hoped. As of right now, I'm getting into the ~3-day mark and the soda-lime media shows no signs of being exhausted (yet). The added bonus of courses is the fact that my pH now reaches well above 8.20 (when the lights are on) and closer to that magic 8.3 some folks seem to obsess about.

The layout of the Hydro-Lime Scrubber.

...of course, only time will tell the longevity of this new (new to me) hybrid approach to scrubbing CO2 but I'm hopeful this will work out for me.

 

[P-Dub]

Tank - 150-gallon euro with ~20-gallon sump
Lights - Radion XR15 Pro x4, 9-hour for radion
Algae scrubber - the reverse of light schedule with a 60-minute overlap on each side
Dose 25.6 ML of BRS soda-ash via Neptune DOS every 3hrs +/-35%
Hybrid Sodium Hydroxide bubbler/CO2 (BRS Soda-lime media) (knicked name Hydro-Lime Scrubber) plumbed into skimmer - skimmer on 24/7

At night PH drops to 8.17, during the day PH has reached ~8.29
Tank located in basement approx. 3 feet from back door/bulkhead that is open often throughout the day in the spring and cracked about 1/2 in winter.
The basement is VERY airtight, 4 mil plastic moisture barrier fixed to concrete walls, 2x4 walls ALL with R-21 insulation, another 4 mil plastic moisture barrier, drywall, and that includes an R-30 insulation+drywall ceiling. No windows open as they are sealed and I have plans on replacing them this yr.

Alk- 8.86 to 9.2
Ca- 456
Mg- 1450

Inhabitants - fish load- 8 x Chromis, 3x Bimaculatus Anthias, 1 Naso. 1 Blue hippo
A mixed bag of sticks all growing very well.

Tank overall is doing well.

...Let me start by saying that I'm no scientist, I'm simply posting my observations and my engineering skills with implementing a hybrid approach to a Sodalime scrubber using @Randy Holmes-Farley information about Sodium Hydroxide and its ability to be more effective at scrubbing CO2.

The Hydro-lime scrubber that I created is a simple bucket filled with RO/DI water and about 40ml cup of Sodium Hydroxide, two air Stones along with an air pump introduce air into the solution - the unit has an airtight lid however it still allows for some air to be pulled in due to the holes drilled for the airlines. From there, an air hose to the CO2 reactor Inlet and then another airline from the CO2 reactors Outlet to my skimmer air Inlet. This is a good time to note that the Sodium Hydroxide bubbler/scrubber by itself was not able to remove/scrub enough CO2 to get my pH above ~8, but that is still a very excitable range.

The main reason I decided to try this was that I was exhausting the Soda Lime media in a little over 2-1/2 days, I figured if I can get the incoming air to be less saturated with atmospheric CO2 prior to hitting the soda-lime it would last that much longer, or so I hoped. As of right now, I'm getting into the ~3-day mark and the soda-lime media shows no signs of being exhausted (yet). The added bonus of courses is the fact that my pH now reaches well above 8.20 (when the lights are on) and closer to that magic 8.3 some folks seem to obsess about.

The layout of the Hydro-Lime Scrubber.

...of course, only time will tell the longevity of this new (new to me) hybrid approach to scrubbing CO2 but I'm hopeful this will work out for me.

Excellent! Keep us posted on how long the sodium hydroxide solution keeps working before your co2 scrubber media begins to exhaust. Additionally, you told us you use 40 ml of SH but not how much water you use to make that solution. Care to share?

 

[Tacticool-Reefer]

Excellent! Keep us posted on how long the sodium hydroxide solution keeps working before your co2 scrubber media begins to exhaust. Additionally, you told us you use 40 ml of SH but not how much water you use to make that solution. Care to share?

Thx!
I thought I posted that, my mistake!
I used 2.5 quarts of RO/DI water.

Current progress:

 

[Tacticool-Reefer]

One thing I just noticed was the accumulation of precipitate of SC inside the hose leading to the SL scrubber, it was easy enough to rinse always with warm tap water. I recall Randy noted this would happen: "Sodium carbonate will precipitate from it as more and more CO2 gets trapped."

 

[Tacticool-Reefer]

Update: IMHO things are looking good for this hybrid approach! The receptacle that I’m currently using is a bit on the small side so I’ve had to top-off the amount of H2O (no additional sodium hydroxide added yet) roughly 2 times during this time frame.

 

[Randy Holmes-Farley]

Thanks for the update!

 

[Tacticool-Reefer]

Thanks for the update!

Thx, and thx for the idea !

 

[josephxsxn]

This is very interesting and has me wondering if I could make up some method to have a sodium hydroxide bucket on my external skimmer airline. Can't wait to learn how long the sodium hydroxide lasts.

 

[elysics]

Veeeery interesting. Does it foam at all to an extent where the foam could end up in the tubing somehow?

 

[Tacticool-Reefer]

Veeeery interesting. Does it foam at all to an extent where the foam could end up in the tubing somehow?

Nope, it doesn’t.

From my direct observations, the bubbles break at the surface of the water without much foaming.

 

[Tacticool-Reefer]

It’s now been approximately a little over two weeks since I started this hybrid approach and I am pretty sure I will continue it. The only thing I’ve had to do in that timeframe is to top off the container with RO/DI and clean the air tube of sodium carbonate precipitate.

The middle spike in the graph below was a recalibration on the pH probe.

 

[Tacticool-Reefer]

Update:

So I’m 18 days in to this little experiment of mine and I’ve had my first signs of the media being exhausted within the CO2 scrubber. I recall in a previous post that I noted that the BRS media tends not to change color, however I was clearly mistaken as you can see from the pictures below. I can only guess at this but I feel that the moisture must’ve had something to do with it. Also, at the same time you can clearly see that some CO2 is still making its way into the reactor body. That would lead me to believe that the sodium hydroxide solution isn’t stripping (it’s not an airtight container so I know it’s pulling atmospheric CO2) all of it.

However, for me in my system I will continue to use this as it has extended the active use of the soda lime well pass what I was observing when I first started scrubbing with it.

You can also see some sodium carbonate precipitate just under the refill lid, So that's clear evidence that it’s pulling in the air from the sodium hydroxide container.

I’m thinking I will probably upgrade the soda lime container to the 4.2 pound version in order to get this to last more roughly a month without me having to touch it.

 

[Tacticool-Reefer]

Good morning, @Randy Holmes-Farley, At what point, if at all, does the Hydroxide solution become saturated, and if so, will it release (I don't think it will) CO2 during the bubbling process?

 

[BranchingHammer]

Good morning, @Randy Holmes-Farley, At what point, if at all, does the Hydroxide solution become saturated, and if so, will it release (I don't think it will) CO2 during the bubbling process?

I think you would need to test pH to determine if the solution was saturated. You know how much CO2-absorbing-ability that the solution has, but you will not know how much CO2 is/has been bubbled into the solution. Once it is saturated, however, it will not release CO2. The CO2 is locked up in sodium carbonate (maybe some bi carbonate) in solution. The solution will not absorb any more CO2 though.

 

[Randy Holmes-Farley]

Good morning, @Randy Holmes-Farley, At what point, if at all, does the Hydroxide solution become saturated, and if so, will it release (I don't think it will) CO2 during the bubbling process?

It will never release the CO2 it is holding. It will slowly reduce its effectiveness as the pH drops.

FWIW, "saturation" is a confusing word in this context. The solution will quickly become saturated in sodium carbonate, and it will begin to precipitate, but the device will still work perfectly well until most of the hydroxide is consumed.

 

[Tacticool-Reefer]

I think you would need to test pH to determine if the solution was saturated. You know how much CO2-absorbing-ability that the solution has, but you will not know how much CO2 is/has been bubbled into the solution. Once it is saturated, however, it will not release CO2. The CO2 is locked up in sodium carbonate (maybe some bi carbonate) in solution. The solution will not absorb any more CO2 though.

Thank you for your reply!

I noticed today a negative (slight dip) impact on my pH values as they started to dip (8.05) even after replacing the soda-lime scrubber media.

The amount of solution that I used lasted well over ~20+ days.

It will never release the CO2 it is holding. It will slowly reduce its effectiveness as the pH drops.

FWIW, "saturation" is a confusing word in this context. The solution will quickly become saturated in sodium carbonate, and it will begin to precipitate, but the device will still work perfectly well until most of the hydroxide is consumed.

Thx!

 

[neyes_ice]

nice experiment!!! It would be interesting to know what are the co2 levels in your basement. I live in a 1 bedroom apartment I have a basic CO2 monitor I got from Amazon with the windows closed I get between 1200-1800 ppm CO2. opening windows would be nice but its not always possible. My PH is super low. my highest is 7.77. lowest is 7.6