Calcite precipitation with Co2 degassing

[SsamRroberts]

Hi,
Apologies for what is probably quite a basic question however I have struggled to affect a solution despite reading this forum and the manual thoroughly.
I'm aware of:
 https://phreeqcusers.org/index.php/topic,224.msg666/topicseen.html#msg666
But this has not helped - my output file is blank bar the titles?

Calcite and Co2 are supersaturated in every sample, therefore I know Co2 will degass and calcite will precipitate. however quantifying these values is the issue. How can I calculate moles of co2 degassing and moles calcite precipitation precipitated?

Any help would be much appreciated c:

Code: [Select]

SOLUTION 1

SOLUTION_SPREAD
-units ppm
Number Description Ca K Mg Na Cl N(5) S(6) pH temp Alkalinity
1 AB2 104.20 1.561773165 5.42 11.85 22.34 22.06 15.22 8.38 11 325.8802046
2 AB3 105.19 1.246475175 5.51 12.08 22.70 22.28 15.29 8.44 11.3 324.5972117
3 AB4 105.42 1.445180946 5.55 13.08 23.75 22.27 16.19 8.37 11.4 322.0312258
4 AB5 106.01 1.276251785 5.50 12.13 23.76 41.73 15.44 8.38 11.8 332.9366657
5 AB6 105.90 1.260741671 5.46 12.12 23.04 23.15 15.36 8.34 11.3 331.0121763
6 AB7 105.18 1.218566822 5.44 11.93 22.90 22.82 15.63 8.24 11 336.7856445
7 AB8 116.95 1.262823912 5.51 12.05 22.72 22.73 9.74 8.23 10.5 331.0121763
8 AB9 107.30 1.231293319 5.54 12.08 22.80 23.09 15.49 8.21 10.2 343.2006092
9 AB10 106.83 1.2018748 5.51 11.93 22.87 22.96 15.71 8.19 9.9 347.049588
10 AB11 107.42 1.230412097 5.53 12.03 22.88 22.83 15.77 8.1 9.6 339.9931269
11 AB12 108.03 1.246601512 5.59 12.16 22.88 24.37 15.68 8.14 9.2 340.6346233
12 AB13 108.26 1.254807927 5.55 12.25 21.68 22.01 14.76 8.35 8.7 332.2951693
13 AB14 108.91 1.284693565 5.66 12.49 21.91 21.67 14.80 8.34 8.6 332.9366657
14 AB15 108.80 1.218368042 5.63 12.23 21.52 21.24 14.63 8.3 8.7 332.9366657
15 AB16 107.95 1.207376102 5.54 12.05 23.63 20.59 14.64 8.25 8.8 337.427141
16 AB17 107.64 1.210973831 5.60 11.97 21.62 20.32 14.69 8.49 9.4 331.0121763
17 AB18 107.84 1.208670229 5.57 12.07 21.89 20.95 14.65 8.29 10.4 335.5026516
18 AB19 106.83 1.172064231 5.55 12.01 22.03 20.39 14.05 8.37 10.7 325.8802046
19 AB20 106.33 1.176115495 5.55 12.01 21.94 19.75 14.76 8.39 11.1 328.4461905
20 AB21 104.89 1.171435823 5.48 11.93 21.90 19.40 14.81 8.39 11.6 328.4461905
21 AB22 104.91 1.298516789 5.56 12.28 22.49 20.35 15.24 8.37 12.1 334.2196587
22 AB23 104.72 1.184164966 5.52 12.01 22.18 18.80 15.16 8.38 12.1 329.087687
23 CB2 109.57 1.26 5.63 12.77 21.24 21.84 14.17 8.26 11.3 333.5781622
24 CB3 108.16 1.33 5.62 12.41 20.70 22.35 14.37 8.2 10.9 332.2951693
25 CB4 107.89 1.23 5.63 12.20 20.71 24.83 14.50 8.15 10.6 334.8611551
26 CB5 108.86 1.23 5.64 12.18 21.32 23.55 15.21 8.12 10 341.2761198
27 CB6 109.71 1.23 5.69 12.28 21.69 23.36 15.47 8.09 9.9 341.2761198
28 CB7 109.19 1.20 5.66 12.32 22.22 22.60 15.25 8.03 9.4 340.6346233
29 CB8 108.94 1.20 5.60 12.12 21.39 21.39 14.41 8.02 9 345.7665951
30 CB9 109.08 1.23 5.66 12.28 21.68 21.65 14.67 7.97 8.8 333.5781622
31 CB10 108.66 1.18 5.63 12.13 22.13 23.05 15.25 7.92 8.7 336.7856445
32 CB11 100.98 1.17 5.04 11.96 20.91 21.27 13.52 7.9 8.6 344.4836021
33 CB12 109.66 1.30 5.76 12.78 21.65 20.89 13.36 7.94 8.4 341.2761198
34 CB13 108.73 1.19 5.65 12.08 21.28 20.94 13.66 8.13 8.1 337.427141
35 CB14 108.90 1.20 5.59 12.17 20.99 20.63 13.76 8.18 8.2 337.427141
36 CB15 109.32 1.18 5.61 12.20 21.44 20.74 18.39 8.01 8.5 338.0686375
37 CB16 109.05 1.20 5.73 12.33 22.16 21.96 14.61 8.08 8.8 336.1441481
38 CB17 109.09 1.20 5.63 12.29 22.87 23.50 14.83 8.21 10.1 325.8802046
39 CB18 108.27 1.16 5.60 12.07 22.92 27.01 14.45 8.13 10.7 339.3516304
40 CB19 108.44 1.25 5.65 12.43 24.25 86.82 14.83 8.15 11.1 336.7856445
41 CB20 109.10 1.22 5.65 12.39 22.98 21.81 14.63 8.2 12 330.3706799
42 CB21 109.12 1.21 5.67 12.38 24.01 22.14 15.21 8.15 13.1 336.1441481
43 CB22 108.76 1.25 5.65 12.31 23.93 22.25 15.26 8.13 11.3 343.8421057
44 CB23 109.03 1.22 5.67 12.32 24.25 22.23 15.18 8.1 10.6 336.1441481
45 BS2 108.14 1.22 5.61 12.18 24.05 24.98 15.08 7.56 9.5 334.2196587
46 BS3 109.14 1.22 5.64 12.31 24.50 22.91 15.48 7.66 9.5 338.7101339
47 BS4 109.23 1.23 5.66 12.38 24.91 23.09 15.60 7.74 9.5 347.049588
48 BS5 109.41 1.24 5.67 12.48 24.55 23.19 15.28 7.69 9.3 338.7101339
49 BS6 108.51 1.21 5.63 12.29 24.26 23.02 15.38 7.8 9.3 347.049588
50 BS7 108.29 1.21 5.63 12.32 24.60 23.32 15.34 7.55 9.1 343.2006092
51 BS8 107.77 1.32 5.68 13.05 26.30 59.68 15.71 7.94 8.6 333.5781622
52 BS9 108.42 1.25 5.65 12.51 24.64 23.33 15.59 7.63 9.4 336.7856445
53 BS10 106.96 1.18 5.60 12.11 23.79 23.54 15.44 7.83 10 336.7856445
54 BS11 107.34 1.20 5.60 12.16 23.91 22.87 15.57 7.6 9.7 332.9366657
55 BS12 107.64 1.20 5.63 12.20 23.97 23.62 15.56 7.64 10.6 334.8611551
56 BS13 107.50 1.23 5.62 12.26 24.07 22.90 15.67 7.55 9.7 341.2761198
57 AB1 107.45 1.21 5.43 11.84 22.08 22.24 15.24 8.11 12 331.6536728
58 OH1 107.47 1.05 6.43 14.25 30.48 351.10 16.06 8.23 11.2 339.3516304
59 BS1 108.86 1.21 5.61 12.16 24.13 23.04 15.18 7.32 9.5 334.8611551
60 W1 108.08 1.23 5.60 12.13 24.42 22.45 15.92 7.46 9.6 333.5781622
61 W2 107.57 1.24 5.56 12.14 24.25 22.01 15.61 7.89 10.4 335.5026516
62 W3 108.12 1.48 5.61 12.44 24.24 21.84 15.80 8.07 11.2 332.9366657
63 CB1 107.90 1.28 5.55 12.29 20.44 21.49 13.60 8.23 11.3 332.9366657
64 RB1 84.37 1.06 12.88 7.75 24.12 21.71 15.74 8.31 11.4 327.1631976
65 BM1 109.98 1.33 5.70 12.67 24.08 22.84 15.80 8.32 11 327.1631976
66 BR1 106.49 1.44 5.57 12.27 15.95 20.99 14.89 8.49 12.4 307.9183036

EQUILIBRIUM_PHASES 1
co2(g) -1.5 0.0
calcite 0.0 0.0
END

USE solution 1 ; USE equilibrium_phase 1; END;
USE solution 2 ; USE equilibrium_phase 1; END;
USE solution 3 ; USE equilibrium_phase 1; END;
USE solution 4 ; USE equilibrium_phase 1; END;
USE solution 5 ; USE equilibrium_phase 1; END;
USE solution 6 ; USE equilibrium_phase 1; END;
USE solution 7 ; USE equilibrium_phase 1; END;
USE solution 8 ; USE equilibrium_phase 1; END;
USE solution 9 ; USE equilibrium_phase 1; END;
USE solution 10 ; USE equilibrium_phase 1; END;
USE solution 11 ; USE equilibrium_phase 1; END;
USE solution 12 ; USE equilibrium_phase 1; END;
USE solution 13 ; USE equilibrium_phase 1; END;
USE solution 14 ; USE equilibrium_phase 1; END;
USE solution 15 ; USE equilibrium_phase 1; END;
USE solution 16 ; USE equilibrium_phase 1; END;
USE solution 17 ; USE equilibrium_phase 1; END;
USE solution 18 ; USE equilibrium_phase 1; END;
USE solution 19 ; USE equilibrium_phase 1; END;
USE solution 20 ; USE equilibrium_phase 1; END;
USE solution 21 ; USE equilibrium_phase 1; END;
USE solution 22 ; USE equilibrium_phase 1; END;
USE solution 23 ; USE equilibrium_phase 1; END;
USE solution 24 ; USE equilibrium_phase 1; END;
USE solution 25 ; USE equilibrium_phase 1; END;
USE solution 26 ; USE equilibrium_phase 1; END;
USE solution 27 ; USE equilibrium_phase 1; END;
USE solution 28 ; USE equilibrium_phase 1; END;
USE solution 29 ; USE equilibrium_phase 1; END;
USE solution 30 ; USE equilibrium_phase 1; END;
USE solution 31 ; USE equilibrium_phase 1; END;
USE solution 32 ; USE equilibrium_phase 1; END;
USE solution 33 ; USE equilibrium_phase 1; END;
USE solution 34 ; USE equilibrium_phase 1; END;
USE solution 35 ; USE equilibrium_phase 1; END;
USE solution 36 ; USE equilibrium_phase 1; END;
USE solution 37 ; USE equilibrium_phase 1; END;
USE solution 38 ; USE equilibrium_phase 1; END;
USE solution 39 ; USE equilibrium_phase 1; END;
USE solution 40 ; USE equilibrium_phase 1; END;
USE solution 41 ; USE equilibrium_phase 1; END;
USE solution 42 ; USE equilibrium_phase 1; END;
USE solution 43 ; USE equilibrium_phase 1; END;
USE solution 44 ; USE equilibrium_phase 1; END;
USE solution 45 ; USE equilibrium_phase 1; END;
USE solution 46 ; USE equilibrium_phase 1; END;
USE solution 47 ; USE equilibrium_phase 1; END;
USE solution 48 ; USE equilibrium_phase 1; END;
USE solution 49 ; USE equilibrium_phase 1; END;
USE solution 50 ; USE equilibrium_phase 1; END;
USE solution 51 ; USE equilibrium_phase 1; END;
USE solution 52 ; USE equilibrium_phase 1; END;
USE solution 53 ; USE equilibrium_phase 1; END;
USE solution 54 ; USE equilibrium_phase 1; END;
USE solution 55 ; USE equilibrium_phase 1; END;
USE solution 56 ; USE equilibrium_phase 1; END;
USE solution 57 ; USE equilibrium_phase 1; END;
USE solution 58 ; USE equilibrium_phase 1; END;
USE solution 59 ; USE equilibrium_phase 1; END;
USE solution 60 ; USE equilibrium_phase 1; END;
USE solution 61 ; USE equilibrium_phase 1; END;
USE solution 62 ; USE equilibrium_phase 1; END;
USE solution 63 ; USE equilibrium_phase 1; END;
USE solution 64 ; USE equilibrium_phase 1; END;
USE solution 65 ; USE equilibrium_phase 1; END;
USE solution 66 ; USE equilibrium_phase 1; END;

SELECTED_OUTPUT
-file lathkill_results_2020.xls
-charge_balance true
-activities Ca+2 HCO3- H+ CO2 H2O
-molalities Ca+2 HCO3- H+ CO2 H2O
-saturation_indices Calcite CO2(g)
-totals C(4)
-equilibrium_phases   Calcite
-gases CO2(g)
-solid_solutions Calcite
-ionic_strength true
-user_punch


USER_PUNCH
-headings sample
10 PUNCH DESCRIPTION
END



[dlparkhurst]

Move the SELECTED_OUTPUT definition before the series of USE definitions. All of the calculations have been completed before SELECTED_OUTPUT is defined.

[SsamRroberts]

Thank you very much for your prompt response!

Calcite and d_calcite in the excel file generated from:

Code: [Select]

-equilibrium_phases Calcite
under SELECTED_OUTPUT state values averaging 0.07 grams, which seems reasonable for precipitated calcite, thanks!

However listing either C(4) or CO2(g) in the same format as Calcite is above results in an output of 0.
How do you tell PHREEQC to output Co2 degassed?

[dlparkhurst]

-gases refers to gas components defined in GAS_PHASE.

CO2(g) is defined in EQUILIBRIUM_PHASES, so you need

-equilibrium_phases   Calcite CO2(g)

[SsamRroberts]

I've rectified the line of code as suggested however the CO2(g) and d_CO2(g) columns are still all 0. Any further suggestions?

[dlparkhurst]

Have you looked at the output file? Look carefully at the "Phase assemblage" output for the reactions.

[SsamRroberts]

PHREEQC gives an average co2 degassing is -1.61E-03 moles, Thanks!

[dlparkhurst]

I guess we looked at different results. I saw that zero moles were available to react, and zero moles reacted.

All of the calculated P(CO2) values were on the order of 10^-1.9, whereas the target saturation index (log10 P(CO2)) was -1.5. Thus, ingassing (not degassing) was necessary to reach a partial pressure of 10^-1.5. With no moles of CO2 available, no mass transfer occurred.

You must have increased the amount of CO2 available to react, something like EQUILIBRIUM_PHASES; CO2(g) -1.5 10. The negative number (-1.6e-3) indicates that the amount of CO2 available to react decreased during the reaction. In other words, CO2 moved from EQUILIBRIUM_PHASES into the solution so that the amount of CO2 in EQUILIBRIUM_PHASES decreased (for example, from 10 moles to 10 - 1.6e-3 = 9.998 moles).

If the target log10 partial pressure were less than -1.9, then, in fact, CO2 would degas, the mass transfer of CO2(g) would be positive (transfer from solution to EQUILIBRIUM_PHASES), and the precipitation of calcite would be greater.

[SsamRroberts]

In an ideal solution I'd input the PHREEQC calculated moles CO2(g) as those available to react.

This being an open system I have used -1.5 as the saturation point, correct me if i'm wrong here?

In PHREEQC degassing causes d_Co2(g) to become more positive, whilst ingassing causes d_Co2(g) to fall. Therefore we see ingassing in our system?

[dlparkhurst]

You must add CO2 into your solutions to produce equilibrium with calcite and a  P(CO2) of 10^-1.5. I don't know your system, but 10^-1.5 is a fairly high soil P(CO2) corresponding to a temperate, productive soil zone. If you used atmospheric P(CO2), 10^-3.4, you would find that CO2 is removed from the solution.

[SsamRroberts]

Thats cleared allot up, your continued dedication to the forum is admirable. Thanks.