Lag in pH response from CO2 injection

JoshP12

Member
Joined
8 Dec 2019
Messages
281
Location
Canada
Hi all,

I have been thinking again :oops:. Does anyone know how long the pH response is from CO2 injection.

In other words, the moment we begin injecting CO2, the CO2 + H2O side of the carbonate equilibrium gets loaded. Le Chetalier's principle kicks in and starts pushing the reaction towards the "right".

Ok so, all this time I have assumed it to be instant :banghead: -in other words, if we read a .1 drop, then in fact the CO2 concentration is in fact relative to the drop.

But now I am not sure. In particular, is it possible that we hit the needed CO2 concentration a "while ago" say an hour before we thought we actually hit it and the chemistry is just catching up?

I do notice the pH start to drop after I inject CO2, but how reflective is that of the actual concentration?

/shoulder shrug

I know this must be able to be calculated with some gen. chem - I just can't wrap my head around it as of right now.

Josh
 

kilnakorr

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Joined
16 Mar 2020
Messages
192
Location
Denmark
I don't think there's a delay. If you cut the CO2 the PH will go up pretty quickly. If there was a delay it would be steady for an hour.
 

Zeus.

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Joined
1 Oct 2016
Messages
3,047
Location
Yorkshire,UK
I would of thought is was quite quick or quick enough for it to of no/little concern to us in our tanks. When the CO2 comes in in my tank the pH drops very fast at first and slows down as the target pH gets closer and thats with duel injection where one solenoid switches off for rest of CO2 period at target pH, pH then remains steady. I do have both CO2 injection going off for about five mins once target pH is reach as there will be some lag with using CO2 reactors
 

hypnogogia

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Joined
6 Apr 2017
Messages
266
Location
Oxfordshire
I would think that the reaction is instantaneous. As you add co2 to water the reaction to form carbonic acid begins, and your pH drops.
 
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