Use of CO2 to neutralize pH

[allancn]

Hello, I'm just new to PHREEQC.

I'm planning to use CO2 to neutralize an alkaline solution like : pH 11.5 containing 60 mg Ca/L. In my case I will pump 0.46 mL/min of an air containing 800ppm of CO2 during 6 hours. (to simulate and print the results each 30 minutes)

*The recipient is open on the top

I would like to know if anyone know how i cand do that?
Thank you =)

[dlparkhurst]

The rate that CO2 dissolves into your solution is not known, so it is not possible to simulate the process a priori.

I suggest you do a couple of calculations initially. First calculate the pH of the solution at equilibrium with your gas phase. Use EQUILIBRIUM_PHASES and CO2(g) with a log10 partial pressure of log10(800e-6).

Next, look at how much CO2 dissolved and add it to your original solution incrementally with REACTION. That will give you an idea of the evolution of your solution without actually dealing with time.

Finally, if you want to go through the process, you can set up RATES and KINETICS to add CO2 to your solution kinetically. I am not sure, but I think this post may be relevant https://phreeqcusers.org/index.php/topic,2260.msg8413.html#msg8413.