inverse modelling for batch leaching test at various pH

[P.Merdy]

Dear all, Here is a script we created for leaching test on soil at 6 different pH obtained with addition of HCl/NaOH and specified by using REACTION. The solution composition is known in term of element cconcentration by ICP analysis. We specified minerals present in soil. How can we indicate to PHREEQC that the SOLUTION is in fact the result of the previous REACTION? INVERSE_MODELING seems to be adequate?  Indeed, as is, the script leads to addition of HCl/NaOH to the solution which is in fact the result of acid-base addition. Could you suggest a piece of script that would help us...

PHASES

water
H2O = H2O
log_K 0

Fe-Kaolinite
Al1.9Fe0.1Si2O5(OH)4 + 6H+ = 1.9Al+3 + 0.1Fe+3 + 2SiO2 + 5H2O
log_k 6.471

Fe-Illite
(K0.18)(Si3.61 Al0.39)O10 (Al0.62 Fe1.45)(OH)2  + 7.56 H+ = 1.45Fe+3 + 0.18K+ + 1.01 Al+3 + 3.61000 SiO2 + 4.78 H2O
log_k 9.0260

Stevensite
Ca0.21K0.05Mg2.3Fe0.19Al0.12Si4O10(OH)2 + 6H+ = 0.21Ca+2 + 0.05K+ + 2.3Mg+2 + 0.19Fe+3 + 0.12 Al+3 + 4SiO2 + 4H2O
log_k 16.55
END

EQUILIBRIUM_PHASES 1 #Equilibrium with the main minerals present
Quartz 0 0
Calcite 0 0
Dolomite 0 0
END

REACTION 1 #Adding HCl and NaOH
HCl 1
0.02089 moles

SOLUTION 1 #Final solutions pH and composition from ALS
-temp 25; pH 3.116; pe 4; units mg/L; Na 11.5; Al 67.5; Mg 59.0; Fe 41.55; P 153.5; Ca 116.0; K 4385.0; Ti 0.0; Mn 87.0
SAVE Solution 1
END

REACTION 2 #pH4.5
HCl 1
0.017405 moles

SOLUTION 2
-temp 25; pH 4.589; pe 4; units mg/L; Na 11.55; Al 43.55; Mg 30.5; Fe 51.5; P 170.5; Ca 79.0; K 3620.0; Ti 1.65; Mn 36.1
SAVE Solution 2
END

REACTION 3 #pH6
HCl 1
0.01645 moles
NaOH 1
0.00005 moles

SOLUTION 3
-temp 25; pH 5.997; pe 4; units mg/L; Na 11.15; Al 65.0; Mg 27.45; Fe 60.0; P 169.5; Ca 67.0; K 4130.0; Ti 2.55; Mn 18.7
SAVE Solution 3
END

REACTION 4 #pH7.5
HCl 1
0.016425 moles

SOLUTION 4
-temp 25; pH 7.59; pe 4; units mg/L; Na 11.75; Al 30.0; Mg 20.60; Fe 30.95; P 168.5; Ca 93.5; K 5100.0; Ti 1.16; Mn 6.15
SAVE Solution 4
END

REACTION 5 #pH9
HCl 1
0.0065 moles
NaOH 1
0.0045 moles

SOLUTION 5
-temp 25; pH 9.128; pe 4; units mg/L; Na 12.15; Al 46.0; Mg 13.60; Fe 47.8; P 134.0; Ca 55.0; K 5150.0; Ti 2.73; Mn 6.45
SAVE Solution 5
END

REACTION 6 #pH10.5
HCl 1
0.0007 moles

SOLUTION 6
-temp 25; pH 10.49; pe 4; units mg/L; Na 12.3; Al 69.0; Mg 12.75; Fe 59.0; P 186.0; Ca 48.4; K 5150.0; Ti 3.68; Mn 4.875
SAVE Solution 6
END

[dlparkhurst]

You can't do much with inverse modeling without the anions.

I'm not sure what your other questions are. You can run a sequence of reactions by using SAVE solution n in one calculation, and then USE solution n in the next calculation. Calculations are defined by END statements.

[P.Merdy]

Hello! Great! I will try this. Thank you for your help!