Looking for CO2 diffuser for lab experiment

RichW

New Member
Joined
4 Nov 2019
Messages
10
Location
UK
Hi, I am a scientist and stumbled upon your website whilst looking for a CO2 diffuser. It seems you guys know more about this than the guys in our chemistry department! So was hoping you may be able to help.

Anyway, I wont bore you with the details but I need a good way of getting CO2 into solution so it changes the pH of solution (as well as possible). I looked at ceramic diffusers and they look ideal! The problem is that most (if not all of them) have lots of metal parts, which I don't want in the reaction vessel.

So I eventually found this...

https://www.boconline.co.uk/en/proc...nation-for-aquaculture/solvox-b/solvox-b.html

But not sure it's ceramic and they guy said it needs to be supported.

Does anyone here know of a ceramic diffuser system that has limited metal parts? ideally it would be ~5.5" (14 cm) in diameter or bigger.

Thanks for any help!
 

zozo

Member
Joined
16 Apr 2015
Messages
7,410
Location
Netherlands
Search google for Glass CO² diffuser and you'll find all kinds of designs from Mini to Large. No metal parts only glass and ceramic disk. To buy one i would advise searching Aliexpress, there they offer them rather cheap and might be effective enough for what you want.

https://aliexpress.com/item/4000002...chweb0_0,searchweb201602_7,searchweb201603_52

Another option you might like to try first without spending to much money is the old school toothpick diffuser. :)

Any piece of round wood that fits snuggly into your hose diameter might do as well. Chopstick?

You could use plastic T hose connectors and put several in row to get a beter distribution over the intire volume. Only one diffuser with no flow distribution a lot will gass off at the surface again. For creating flow you would need a pump which means metal parts again. Best guess to avoid this diffuse over multiple points.
 
Last edited:

RichW

New Member
Joined
4 Nov 2019
Messages
10
Location
UK
Apologies for the delay. Awesome, thank you for the suggestions they are very much appreciated!

I had not realised there were glass CO2 / acrylic diffusers out there, this may certainly solve our problem. The toothpick, very imaginative! And the DIY option is something I am presently working on.

Thanks all!

If I ever decide to keep fish in the future I know exactly where to come!
 

zozo

Member
Joined
16 Apr 2015
Messages
7,410
Location
Netherlands
Last edited:

RichW

New Member
Joined
4 Nov 2019
Messages
10
Location
UK
Also, I have never used CO2 before. In my case it will be to lower the pH of the water by "several pH units" (this is what the paper I am reading says), so that I can dissolve calcium carbonate into the solution. In your guys' experience does a decrease in pH with CO2 occur rapidly? (my "tank" will be 20 L). I am going to order my CO2 from BOC (https://www.boconline.co.uk) and could do with some idea of the pH change, how much CO2 I will need and the pressure I should set on the regulator. Thanks again for any experience you can give.
 

X3NiTH

Member
Joined
13 Apr 2014
Messages
997
Hi, I am a scientist.......... I wont bore you with the details.............

Please do!

How much CaCO₃ do you need to saturate the water with and how much of a drop in pH do you hope to gain. Does the experiment need to run for a length of time or do you just need a saturated CaCO₃ solution stored to hand.

For stored CaCO₃ saturated solutions, pressurising the water using a soda stream system is the quickest way to achieve a rapid pH drop of the water for addition of CaCO₃. If the whole tank needs the pH drop to a consistent level to achieve saturation of CaCO₃ to a desired mg/L level then depending how much you need the pH drop to be and the amount of CaCO₃ you need to add will determine how much CO₂ you will be diffusing into the water, efficiency of the device providing the diffusion rate may be dependent on the pressure it is being delivered at, higher pressures could force a diffuser to produce larger sized bubble that may escape the tank quicker than it can diffuse into the water, multiple devices providing a very fine mist may be needed for efficacy.
 

RichW

New Member
Joined
4 Nov 2019
Messages
10
Location
UK
Please do!

Okay, I need to make some saturated calcium carbonate solution because we are studying scaling effects. So I need a solution so we can apply to a heated metal surface (~120 degrees C) to form scales on the surface.

How much CaCO₃ do you need to saturate the water with

According to Wiki the solubility of calcium bicarbonate is 16.6 g/100 mL (20 °C). For the spraying part alone I think I will need ~ 150 L of calcium carbonate solution, so a lot! Unless i have made a mistake I calculate around 25 kg :-O

and how much of a drop in pH do you hope to gain

The paper I read uses the CO2 method to lower pH and just says pH is lowered by "several pH units" so around pH4. If I can get lower pH then I assume this would be a good thing as it would increase the calcium carbonate solubility and give more precipitation (scale). After the CaCO3 is completely dissolved, the paper says to let the solution stand until it returns to pH7 (the excess CO2 is released), and you then have a saturated CaCO3 solution.

Does the experiment need to run for a length of time or do you just need a saturated CaCO₃ solution stored to hand.

I just need to make a calcium carbonate solution as saturated as possible so precipitation will be quicker / easier. Each solution would be made for spraying the same day on the heated metal surface.

For stored CaCO₃ saturated solutions, pressurising the water using a soda stream system is the quickest way to achieve a rapid pH drop of the water for addition of CaCO₃. If the whole tank needs the pH drop to a consistent level to achieve saturation of CaCO₃ to a desired mg/L level then depending how much you need the pH drop to be and the amount of CaCO₃ you need to add will determine how much CO₂ you will be diffusing into the water, efficiency of the device providing the diffusion rate may be dependent on the pressure it is being delivered at, higher pressures could force a diffuser to produce larger sized bubble that may escape the tank quicker than it can diffuse into the water, multiple devices providing a very fine mist may be needed for efficacy.

Interesting, I had not considered this option. Do you think this method would be more advantageous over CO2?

Yes i am looking at a couple of larger ceramic (glass) CO2 diffusers for small dissolving bubbles to prevent loss.
 

dw1305

Expert
Joined
7 Apr 2008
Messages
10,645
Location
nr Bath
Hi all,
I just need to make a calcium carbonate solution as saturated as possible so precipitation will be quicker / easier.
You need the original solution to be both cold and under pressure, that way you can super-saturate the solution with Ca++ and 2HCO3- ions.

If you think of opening a carbonated soft drink, when you release the pressure the dissolved CO2 will come out of solution. If your carbonated drink could contain more Ca++ and 2HCO3- ions (than would be possible at atmospheric pressure) then you would get a simultaneous precipitation of solid CaCO3. This is the same process you have naturally when you have tufa/travertine deposition.

Calcium carbonate (CaCO3) isn't soluble in water, but it is soluble in weak acids, and water is a weak acid because of the small proportion of atmospheric CO2 that goes into solution as H2CO3. According to <"Henry’s law">, the equilibrium ratio between the abundances in the gas phase and in the aqueous phase is constant for a dilute solution.

The solubility constant of CO2 is quite high, but you only get a small proportion of CO2 dissolved, because there is only about <"400ppm of CO2 in the atmosphere">.. The equilibrium point for the CO2 ~ CO3 ~ pH relationship is ~pH8 at 400 ppm of CO2, but add more CO2 to the water and the pH will fall.

You can potentially dissolve a lot more CO2 into the water, which in a carbonate buffered system, will mean a lot more Ca++ and HCO3- ions in solution. When the dissolved CO2 level falls CaCO3 will be deposited.

If you think back to opening the carbonated drink you get a lot of bubbles because the CO2 concentration gradient between the liquid and air is really steep, when they've reached equilibrium your drink is "flat" and a lot less acid.

The cold bit is just that gas solubility declines with increasing temperature, and carbonate solubility is dependent upon dissolved CO2 concentration, so carbonates are less soluble at higher temperatures. You can think of the gas bubbles that rise from a kettle element as the water heats, when you get to boiling the water is de-gassed.

cheers Darrel
 

X3NiTH

Member
Joined
13 Apr 2014
Messages
997
Before sinking money into buying glass diffusers it might be worth visiting the chemistry department bods again and ask to borrow a Büchner Flask (boroscilate glass type, ceramic sintered filter) if they have one, pretty much exactly the same as an aquarium glass diffuser as long as it's a pressure rated vessel. It's entirely up to you if you want to own up and tell them you are going to run it in reverse with pressurised CO₂. I would start at a low pressure say 10psi and work your way up carefully until you are comfortable with it operating how you want it (I would only pressurise under water for safety), hopefully you don't have to report back that you accidentally dropped it ;) .
 

zozo

Member
Joined
16 Apr 2015
Messages
7,410
Location
Netherlands
Büchner Flask

That's a good one, a Buncher Funnel can indeed be used as a big a$$ CO² diffuser if used in reverse with a plugin the bottleneck. And they are actually not that expensive at all and available in different volumes and with a range of ceramic disks in different microns.
https://www.banggood.com/nl/200mL-2...lter-Lab-Experiment-Glassware-p-1063369.html?

Knipsel.JPG


:thumbup: Learning everyday again @ UKAPS :clap: Thanks!
 

RichW

New Member
Joined
4 Nov 2019
Messages
10
Location
UK
It's entirely up to you if you want to own up and tell them you are going to run it in reverse with pressurised CO₂.

:lol:

Awesome thanks guys, you've given me some great ideas and some things to think about! Glad it has been interesting for you too! Will let you know how things go :happy:
 

RichW

New Member
Joined
4 Nov 2019
Messages
10
Location
UK
Hi guys back again, I am going to do the experiment in a large glass vessel that I found laying around in our lab. The vessel has a really thick glass bottom:

x0wJeJX.jpg


I need to heat the solution inside to 60 deg C. I tried to do this with a heating plate at 60 deg C but the glass is very thick and the solution did not change temperature. I am afraid to increase the temperature of the heating plate because I am not sure of the type of glass! (the heat might crack the glass and destroy my vessel :()

So I am thinking perhaps an immersion heating element, which brings me back here!! I need it to be glass / plastic because I can't have metal in the solution (electrochemistry experiment), so found this one:

https://docs.rs-online.com/000d/0900766b8158322e.pdf

But it only goes to 34 deg C. Do any of you use an immersion heater, that is not metal, that if you wanted could heat your tank to 60 deg C?

I'm also concerned about calcium carbonate precipitation on the heating element because the solution will be saturated :banghead:, but one step at a time I guess.

Thank you for any advice about this.
 

zozo

Member
Joined
16 Apr 2015
Messages
7,410
Location
Netherlands
On Aliexpress they sell Waterproof Silicone heating pads. They come in different sizes and specifications.
You might want a look at the 12-volt versions. But then you still need a external thermostat to regulate the temperature with a plastic covered thermistor.

www.aliexpress.com/item/4000396779975.html?spm=a2g0o.productlist.0.0.5e957c2dk0oxWZ&algo_pvid=93d6eb0b-0307-4a03-8dfb-f930d93a7597&algo_expid=93d6eb0b-0307-4a03-8dfb-f930d93a7597-22&btsid=0faf75f3-7190-47c4-abdd-5ceb213d0a58&ws_ab_test=searchweb0_0,searchweb201602_7,searchweb201603_52
 

RichW

New Member
Joined
4 Nov 2019
Messages
10
Location
UK
On Aliexpress they sell Waterproof Silicone heating pads. They come in different sizes and specifications.
You might want a look at the 12-volt versions. But then you still need a external thermostat to regulate the temperature with a plastic covered thermistor.

www.aliexpress.com/item/4000396779975.html?spm=a2g0o.productlist.0.0.5e957c2dk0oxWZ&algo_pvid=93d6eb0b-0307-4a03-8dfb-f930d93a7597&algo_expid=93d6eb0b-0307-4a03-8dfb-f930d93a7597-22&btsid=0faf75f3-7190-47c4-abdd-5ceb213d0a58&ws_ab_test=searchweb0_0,searchweb201602_7,searchweb201603_52

Wow, really interesting, I would never have thought of this! Thanks :cool:
 
Similar threads
Thread starter Title Forum Replies Date
MrClockOff Looking for Vallisneria Nana Where to buy ... 4
Jack B Looking for shrimpsafe Hornwort Where to buy ... 8

Similar threads

Top