Simulating Aluminum mobilization under different Chloride concentration

[rudolff16]

Dear PHREEQC users,
I am basic user of the PHREEQC, and have elementary experience about geochemical modeling. The case study located at a Tailing-site (salt mining site). Due to active vertical leaching processes of brine, high mineralized shallow aquifer is formed. That water supposed to mix with fresh uncontaminated groundwater along the general flow path.
The contact of high mineralized water (rich with chloride) with clayey minerals of the hosting rocks, Aluminium will be released in water as a result of the cation exchange processes, reducing the pH-Value.
So I'd like to simulate that process to predict at which Chloride concentration, Aluminum will be released into water. The idea to mix high mineralized groundwater with fresh uncontaminated groundwater at different mixing ratios, where chloride is considered as main controlling factor. So I started the PHREEQC script as follows:

SOLUTION 0 High mineralized groundwater
    temp      12.7
    pH        5.2
    pe        4
    redox     pe
    units     mmol/kgw
    density   1.007
    Na        1019
    K         176
    Ca        866
    Mg        1164
    Cl        5412 
    Alkalinity 115.9 as HCO3
    N(5)      33 as NO3
    S(6)      1751 as SO4
    Al        5.7
    Ni        0.35
    Pb        0.03
    Br        33
    Mn        7
    Zn        0.22
    Fe        0.096
    -water    1 # kg

EQUILIBRIUM_PHASES 0
    Ferryhydrite 0 0
    Gibbsite  0 0

EXCHANGE 0 Exchnage with Loham Sediments
    AlX3    0.00999
    CaX2    0.22176
    FeX2    0.003915
    KX      0.04392
    MgX2    0.039735
    MnX2    9e-005
    NaX     0.00567
    -pitzer_exchange_gammas true

SAVE Solution 0
END

TITLE Fresh Groundwater
SOLUTION 1
    temp      8.6
    pH        7.5
    pe        4
    redox     pe
    units     mg/l
    density   0.998
    Na        5.11
    K         3
    Ca        62.3
    Mg        12.9
    Cl        14
    Alkalinity 207 as HCO3
    N(5)      2.7 as NO3
    S(6)      29.1 as SO4
    Al        0.2
    Ni        0.0025
    Pb        0.001
    Mn        0.036
    Zn        0.22
    Fe        0.049
    -water    1 # kg

GAS_PHASE 1
    -fixed_pressure
    -pressure 1
    -volume 1
    -temperature 8.6
    CO2(g)    0.00079

EQUILIBRIUM_PHASES 5
    Ferryhydrite 0 0
    Gibbsite  0 0

END
MIX 1
    1    1
    2    9
SAVE SOLUTION 2
SELECTED_OUTPUT 1
    -file                 selected_output_1.sel
    -totals               Al  Cd  Zn  Cl  Na  K  Ni

END

MIX 2
    1    2
    2    8
SAVE SOLUTION 3
SELECTED_OUTPUT 2
    -file                 selected_output_1.sel
    -totals               Al  Cd  Zn  Cl  Na  K  Ni

END

MIX 3
    1    3
    2    7
SAVE SOLUTION 4
SELECTED_OUTPUT 3
    -file                 selected_output_1.sel
    -totals               Al  Cd  Zn  Cl  Na  K  Ni

END

MIX 4
    1    4
    2    6
SAVE SOLUTION 5
SELECTED_OUTPUT 4
    -file                 selected_output_1.sel
    -totals               Al  Cd  Zn  Cl  Na  K  Ni

END

###
the question how to simulate the process above where Aluminium is released gradually due to enrichment process of groundwater with Chloride. Supposed chloride concentrations from 200 mg/l to 10000 mg/l in 50 steps.

I am so grateful for your help,

[John Mahoney]

I noticed a couple of things.  You appear to want to equilibrate solution 1 with the gas-phase and Ferrihydrite and Gibbsite but you do not save it after you equilibrated it.  Did you mean to do that?   

The way that the EQUILIBRIUM_PHASES block is set you can only precipitate Ferrihdyrite or Gibbsite. You will only precipitate those phases if they are oversaturated, which is fine if that is your intent.     But realize that there is no process in this model that will increase Al concentrations later. 

Also I am unsure why you used the gas_phase option, and did not set a partial pressure of CO2(g) with equilibrium_phases.   The Gas_phase option as you set it up represent a liter of gas in contact with one liter of Solution 1.  If that is your intent fine but I suggest you read over the Gas_phases discussion, and think if that is really what you want to do.

your mixtures also do not react with Gibbsite or Ferrihydrite (again maybe that is your intent), or you intend to add more steps to the model later.  I suggest you go over the output file and track your results and see if they make sense with what you want to do.

Good Luck.
 

[dlparkhurst]

A few comments.

First, you defined an EXCHANGE composition, but that exchange composition is not in equilibrium with either SOLUTION 0 or any of the mixes. So, if you react the brine (solution 0) and exchanger, there will be a major redistribution of ions between the solution and the exchanger. I think that makes it difficult to determine the effect of the brine and the effect of the freshwater mixes.

I agree with John that GAS_PHASE is not commonly used. Use EQUILIBRIUM_PHASES with CO2(g) if you want to fix the partial pressure of carbon dioxide.

Here would be an outline of one possible calculation:

SOLUTION 0
...
EQUILIBRIUM_PHASES 0
...
SAVE solution 0
END
EXCHANGE 0
X 0.6
-eq 0
END
SOLUTION 1
...
END
MIX
0 0.9
1 0.1
USE exchange 0
USE equilibrium_phases 0
END

There are a lot of variations on how you handle the sequence of reactions. You could save the new exchange composition (say, SAVE exchange 1) and react it further, or you could equilibrate exchange 0 with more dilute mixtures. You may want to set up a TRANSPORT calculation, where the initial condition is a solution in equilbrium with the exchanger, and the fresh water moves through the column with some dispersion.

I suggest you simplify and remove N(5) (to avoid some redox issues) and the minor elements, so you can concentrate on the elements of interest.

[rudolff16]

Dear dlparkhurst, Dear John,
Thanks for you valuable comments, I will modifiy the Input file and check the results. I will Keep you updated.
 

[rudolff16]

Dear dlparkhurst,
I've modified the input script as follows:

SOLUTION 0 High mineralized groundwater
    temp      12.7
    pH        5.2
    pe        4
    redox     pe
    units     mmol/kgw
    density   1.007
    Na        1019
    K         176
    Ca        866
    Mg        1164
    Cl        5412 
    Alkalinity 115.9 as HCO3
    S(6)      1751 as SO4
    Al        5.7
    Ni        0.35
    Br        33
    Mn        7
    Zn        0.22
    -water    1 # kg

EQUILIBRIUM_PHASES 0
    Alunite   0 0
SAVE SOLUTION 0
END

SOLUTION 1 Fresh Groundwater
    temp      8.6
    pH        7.5
    pe        4
    redox     pe
    units     mg/l
    density   0.998
    Na        5.11
    K         3
    Ca        62.3
    Mg        12.9
    Cl        14
    Alkalinity 207 as HCO3
    S(6)      29.1 as SO4
    Al        0.2
    Zn        0.22
    -water    1 # kg
USE EQUILIBRIUM_PHASES 0
   
END

EXCHANGE 0 Exchnage with hosting rocks
    AlX3    0.00999
    CaX2    0.22176
    FeX2    0.003915
    KX      0.04392
    MgX2    0.039735
    MnX2    9e-005
    NaX     0.00567
    -pitzer_exchange_gammas true
END
MIX 1
    0    0.1
    1    0.9
USE EQUILIBRIUM_PHASES 0

USE EXCHANGE 0
SAVE SOLUTION 2
   
END

MIX 2
    0    0.2
    1    0.8
USE EQUILIBRIUM_PHASES 0

USE EXCHANGE 1
SAVE SOLUTION 3

MIX 3
    0    0.3
    1    0.7
USE EQUILIBRIUM_PHASES 0

USE EXCHANGE 1
SAVE SOLUTION 4

MIX 4
    4    0.4
    5    0.6

USE EQUILIBRIUM_PHASES 0

USE EXCHANGE 0
SAVE SOLUTION 5

SELECTED_OUTPUT 1
-file                 C:\...\Solution1.csv
    -totals               Al  Ca  Cd  Cl
                          Co  Cr  Cu  Fe  Hg  K  Mg
                          Mn  N  Na  Ni  Pb  S  Si
                          Zn


TRANSPORT
    -cells                 20
    -shifts                50
    -time_step             15768000 # seconds
    -lengths               20*0.5
    -dispersivities        20*0.05   
END



# Error massage:  Calculations terminating due to input errors.
I'm wondering if the input file correctly modified.

I greatly appreciate your help 

[dlparkhurst]

Look at the ERROR messages in the output file.

[rudolff16]

I will Keep trying

[dlparkhurst]

If you are going to have 20 cells in TRANSPORT, you need to define solutions for each cell. You can define them to be the same by defining SOLUTION 1-20, or you can define them individually. I would probably start defining all equal to the brine composition and SOLUTION 0 as the fresh water.

[rudolff16]

Dear dlparkhurst,
thanks for your valuable hints. I'll start a simple simulation then expand it with transport modeling. I've just modified the input script. It works fine, but how can I reinforce the dissolution of Aluminum?

####
PHASES
Fix_pH
    H+ = H+
    log_k     0
SOLUTION 0 Brine
    temp      12.5
    pH        6.1
    pe        6.74
    units     mg/l
    density   1.2680
    Na        57050
    K         25830
    Ca        94.90
    Mg        42233
    Cl        76333 
    Alkalinity 122 as HCO3
    S(6)      78706 as SO4
    Al        0.054
    Pb        0.035
    Cu        0.340
    Ni        0.062
    Br        847
    Mn        7
    Fe        0.340
    Zn        0.920
    B         0.940
    -water    1 # kg
   
SAVE SOLUTION 0
END

USE SOLUTION 0
EQUILIBRIUM_PHASES 0
    Fix_pH    -3 HCl       100
    Hematite  0 0
    Alunite   0 0
SAVE SOLUTION 1 # High mineralized Groundwater
END

EXCHANGE 0 Exchange with loam Sed.
    AlX3    0.00999
    CaX2    0.22176
    FeX2    0.003915
    KX      0.04392
    MgX2    0.039735
    MnX2    9e-05
    NaX     0.00567
    -equilibrate with solution 1
    -pitzer_exchange_gammas true
END
SOLUTION 2 Fresh Groundwater
    temp      15.9
    pH        6
    pe        5.59
    units     mg/l
    density   0.998
    Na        11.5
    K         4.16
    Ca        68.80
    Mg        11.40
    Cl        83
    Alkalinity 31 as HCO3
    S(6)      52.8 as SO4
    Fe        0.031
    Al        0.015
    Zn        0.078
    -water    1 # kg
EQUILIBRIUM_PHASES 1
    Alunite   0 10
    Hematite  0 0
    Ferryhydrite 0 0
   
SAVE SOLUTION 2   
END

EXCHANGE 1 Exchange with Sandstone
    AlX3    0
    CaX2    0.956633333
    FeX2    0.0055
    KX      0.442933333
    MgX2    0.421666667
    MnX2    0.000366667
    NaX     0.044
    -equilibrate with solution 2
    -pitzer_exchange_gammas true
END

MIX 1
    1    0.1
    2    0.9
USE equilibrium_phases 1
SAVE SOLUTION 2 
END

MIX 2
    1    0.15
    2    0.85
USE equilibrium_phases 1
SAVE SOLUTION 3
END

MIX 3
    1    0.2
    2    0.8
USE equilibrium_phases 1
SAVE SOLUTION 4
END

MIX 4
    1    0.25
    2    0.75
USE equilibrium_phases 1
SAVE SOLUTION 5
END

MIX 5
    1    0.3
    2    0.7
USE equilibrium_phases 1
SAVE SOLUTION 6
END

MIX 6
    1    0.35
    2    0.65
USE equilibrium_phases 1
SAVE SOLUTION 7
END

MIX 7
    1    0.4
    2    0.6
USE equilibrium_phases 1
SAVE SOLUTION 8
END

MIX 8
    1    0.45
    2    0.55
USE equilibrium_phases 1
SAVE SOLUTION 9
END

MIX 9
    1    0.5
    2    0.5
USE equilibrium_phases 1
SAVE SOLUTION 10
END

SELECTED_OUTPUT 1
    -file                 C:\Users\...Phreeqc\output.csv
    -ph                   true
    -totals               Al  Cd  Cl Fe  Hg  K  Mg
                          Na  Ni  Pb  S  Zn

END

[dlparkhurst]

First, you are not including any exchange reactions in your mixing simulations.

I suggest you use just a few cells, say 5. Put the brine, exchange, and equilibrium reactions in each cell, and run transport for 10 shifts. That should give you the rough outline of  aluminum reactions.