How to save a mixture Aqueous Solution+Solids ?

[jerome]

Dear users,

In PHREEQC we can use "SAVE Solution x" in order to save an aqueous solution. Is it possible to save a mixture Solution+Solids after using EQUILIBRIUM_PHASE ?
 
Indeed, I am working with a supersaturated solution with calcite and I would like to simulate a lime or other reagent addition (using REACTION).

I fixed the pH of the solution using a pH_fix PHASE and EQUILIBRIUM_PHASES in order to calculate the inital amount of calcite at the measured pH 7.48
The amount of calcite calculated thanks to PHREEQC at this pH is 9.711e-03 mol/kgw

I would like to start my first step of the lime dosing REACTION with this initial amount of solid and with this initial measured pH in a user graph.
Using "SAVE solution" only the aqueous components are saved. I tryed unsuccessfully "solid_solution" keyword and added manually  the inital Calite amount in a second EQUILIBRIUM_PHASES 2  in order to start the REACTION with the right initial amount of solid.
Is there a simplest method to save the initial solids amount automatically using a specific "SAVE keyword" or another combination?

SOLUTION 1
       temp         25
      density    1.007
       units        ppm
       C(4)         1874 
       Ca           416
       Mg           173
       Na           2500 charge
       Cl           2272
       S(6)         3228
   
PHASES      
   pH_fix      
      H+=H+   
      log_K   0

EQUILIBRIUM_PHASES 1
   pH_fix            -7.48  NaOH   10
   Calcite          0 0
       Nesquehonite      0 0
   Artinite         0 0
   Mg5(CO3)4(OH)2:4H2O(s)   0 0
   Brucite         0 0
   Gypsum          0 0

SAVE solution 1

END

USE solution 1

EQUILIBRIUM_PHASES 2
   Calcite          0 9.711e-03   
       Nesquehonite      0 0
   Artinite         0 0
   Mg5(CO3)4(OH)2:4H2O(s)   0 0
   Brucite         0 0
   Gypsum          0 0
   Portlandite         0 0

REACTION 1

Ca(OH)2 1
0.04 mol in 100 steps

USER_GRAPH
...

Many thanks by advance for your ideas,

Best regards,

Jerome

[dlparkhurst]

Check out the documentation for the SAVE keyword. Also, RUN_CELLS saves all reactants.

[jerome]

Thank you Mr Parkhurst,
I did not succeed with SAVE keyword, I will try with RUN_CELLS option, thank's again for your support.
Regards,
Jerome

[dlparkhurst]

SOLUTION 1
END
EQUILIBRIUM_PHASES 1
Calcite 0 0.1
END
USE solution 1
USE equilibrium_phases 1
SAVE solution 1
SAVE equilibrium_phases 1
END
USE solution 1
USE equilibrium_phases 1
REACTION
CO2 1
1 mmol
SAVE solution 1
SAVE equilibrium_phases 1
END

[xc1120]

Hi Sir,

Thank you so much form your feedback here. Really appreciate it!

Just add a related question here. I am wondering could we save the solution + solids from last KINETICS for the next same rule KINETICS?

For examples, firstly I let 700mg calcite naturally dissolve with the 1L water under open air to reach equilibrium. 700mg calcite is more than 1L water can dissolve.  Secondly, I wanna bubble cylinder co2 to the equilibrated solution and thus the left calcite  will be further dissolved until new equilibrium. 

My way is to use the following keyword to for first step:

RATES # for calcite precipitation law
SOLUTION # for ph 7 deionized water
KINETICS # for calcite precipitation detail settings
Calcite
   -formula  Calcite  1 # stoichiometric coefficient number 1mol reaction consumes 1mol calcite
   -m        0.007 #current moles 700mg=0.7g=0.007mol
   -m0       0.007 #initial moles
   -parms    380000 0.6 #cm2/mol(1st) parms defined in  RATES block
   -tol      1e-08
-steps   1800 in 30 steps # seconds in one day
-step_divide 1
-runge_kutta 3
-bad_step_max 500


could I save the solution and solids left in this step as the initial setting for the next calcite dissolution KINETICS? If yes do I need to modify the m, mo in the second KINETICS by myself? Hope I am clear!

Thank you!

[dlparkhurst]

It sounds like you want to SAVE equilibrium_phases 1 along with SAVE solution 1, and then USE solution 1 and USE equilibrium_phases 1.

You can save reactants involved in a reaction calculation with SAVE statements.

Code: [Select]

SAVE solution n
SAVE equilibrium_phases n
SAVE exchange n
SAVE surface n
SAVE solid_solution n
SAVE gas_phase n

Moles of KINETICS reactants are continuously updated (the values at the end of the reaction steps are retained), and there is no SAVE option.

You can look at RUN_CELLS, which is essentially a set of USE and SAVE statements for each user number. RUN_CELLS; -cells n, will use all reactants numbered n in a reaction calculation and save all of the reactants back to user number n (overwriting the previous definitions).