Atmospheric CO2 ingress into concentrate NaOH Solution

[magan.govender]

Hi all,
i would like to model atm CO2 ingress into concentrated NaOH (47%) solution over time, any guidance would be most appreciated.

Thanks
Magan

[dlparkhurst]

For starters, you can simply add CO2 to the solution with REACTION. Even the Pitzer model (pitzer.dat) may not be reliable at the high concentrations you are using, but the script below gives the basic trajectory of the reaction, without explicit consideration of time..

You can look at this thread for a kinetic approach. https://phreeqcusers.org/index.php/topic,2584.msg9711.html#msg9711
The concept is there, but you would need to determine realistic rate parameters, and again, the high concentrations would create large uncertainties in the details of the results.

Code: [Select]

SOLUTION 1
-water 0.53 #530 g H2O
REACTION
NaOH 1
11.75  # 470 g NaOH / GFW(NaOH)
SAVE solution 1
END
USE solution 1
REACTION
CO2 1
10 in 20 steps
USER_GRAPH 1
    -headings               CO2 pH
    -axis_titles            "CO2 dissolved, mol" "pH" ""
    -initial_solutions      false
    -connect_simulations    true
    -plot_concentration_vs  x
  -start
10 GRAPH_X RXN
20 GRAPH_Y -LA("H+")
  -end
    -active                 true
END


[magan.govender]

Thanks David. Regards Magan