Modeling the change of Aluminium in mine water

[rudolff16]

Dear PHREEQC members,

any hints about the simulation of the change of Aluminium concentration in mine water at different pH Value and possible complexes.
the main hosting rocks are the Carnallit (KCl.MgCl2.6H2O), where Aluminum minerals dissolved at low pH and precipitated at pH> 8.

thanks for any idea or help 

[dlparkhurst]

Carnallite will be very soluble with concentrations exceeding several molal. pitzer.dat would be the appropriate database, but pitzer.dat does not contain aluminum species. To model aluminum you will need to use one of the other databases.

However, the general chemistry of aluminum will be similar regardless of th ionic strength. It will be quite soluble at low pH, insoluble at intermediate pH, and soluble again at high pH. Here is a simulation from pH 2 to 9, but limiting the total amount of gibbsite in the system to 2 moles. Actual solubility of gibbsite at pH 2 is probably greater than 10 molal.

Code: [Select]

PHASES
Fix_H+
    H+ = H+
    log_k     0
END
SOLUTION
END
USER_GRAPH
10 GRAPH_X -LA("H+")
20 GRAPH_Y LOG10(TOT("Al"))
USE solution 1
EQUILIBRIUM_PHASES
Fix_H+     -2 HCl  100
Gibbsite  0  2
SAVE solution 1
END
USE solution 1
EQUILIBRIUM_PHASES
Fix_H+    -2.5 NaOH 100
Gibbsite  0  2
END
USE solution 1
EQUILIBRIUM_PHASES
Fix_H+    -3 NaOH 100
Gibbsite  0  2
END
USE solution 1
EQUILIBRIUM_PHASES
Fix_H+    -4 NaOH 100
Gibbsite  0  2
END
USE solution 1
EQUILIBRIUM_PHASES
Fix_H+    -5 NaOH 100
Gibbsite  0  2
END
USE solution 1
EQUILIBRIUM_PHASES
Fix_H+    -6 NaOH 100
Gibbsite  0  2
END
USE solution 1
EQUILIBRIUM_PHASES
Fix_H+    -7 NaOH 100
Gibbsite  0  2
END
USE solution 1
EQUILIBRIUM_PHASES
Fix_H+    -8 NaOH 100
Gibbsite  0  2
END
USE solution 1
EQUILIBRIUM_PHASES
Fix_H+    -9 NaOH 100
Gibbsite  0  2
END


[rudolff16]

Dear Parkhurst,

thanks for your quick response and provided script. Unfortunately, I couldn't converge the script with the available databases. Another question, can we include the cation exchange processes, mixing with fresh water?  the aquifer lithology exhibits clay formation along the groundwater flow path.

Regards,

[dlparkhurst]

The script should run with the database phreeqc.dat and I would think any PHREEQC or PhreeqcI version 3. If it fails with phreeqc.dat and version 3, I would like to see the output.

PHREEQC has a selection of chemistry including MIX (solutions), EQUILIBRIUM_PHASES, EXCHANGE, SURFACE, SOLID_SOLUTIONS, and KINETICS.