Mineral dissolution sequence

Processes > Dissolution and precipitation

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Jay Chou:
Hello, Doctor

I am doing research on the sequence of mineral precipitation after evaporation of water with different concentrations

The following are the concentrations of three different water bodies. During the evaporation simulation, I found that with the concentration of Ca2+and SO42 - getting lower and lower, gypsum can be separated more and more; With the increasing concentration of Na2+, mirabilite cannot be separated! What is the reason?

Na+     573.51     687.55     831.77
K+     82.02    98.22    118.71
Mg2+   11.04    7.93      3.98
Ca2+   23.50    17.28    9.42
Cl-     483.21    592.75    731.28
SO42-   94.36    86.69    76.99
HCO3-   744.84    858.46    1002.16
Li     24.78    30.45    37.62
B     336.78    418.89    522.75

The following is one of my water evaporation simulation methods
PHASES
LiCl
LiCl:H2O = Cl- + H2O + Li+
log_k 4.978
Li2CO3
Li2CO3 = CO3-2 + 2Li+
log_k -4.271
LiKSO4
LiKSO4 = K+ + Li+ + SO4-2
log_k -1.3828
Li2SO4:H2O
Li2SO4:H2O = 2Li+ + SO4-2+H2O
log_k 0.6036
SOLUTION 1 SMZB-LQS-sm114
temp 5
pH 8.711
pe 4
redox pe
units mg/l
density 1
Alkalinity 858.46
B 418.89
Ca 17.28
Cl 592.75
K 98.22
Li 30.45
Mg 7.93
Na 687.55
S(6) 86.69
-water 1 # kg
EQUILIBRIUM_PHASES 1
Anhydrite 0 0 precipitate_only
Bischofite 0 0 precipitate_only
Bloedite 0 0 precipitate_only
Borax 0 0 precipitate_only
CO2(g) -3.4 100
Calcite 0 0 precipitate_only
Dolomite 0 0 precipitate_only
Epsomite 0 0 precipitate_only
Gaylussite 0 0 precipitate_only
Glaserite 0 0 precipitate_only
Glauberite 0 0 precipitate_only
Gypsum 0 0 precipitate_only
Halite 0 0 precipitate_only
Huntite 0 0 precipitate_only
K2B4O7:4H2O 0 0 precipitate_only
KB5O8:4H2O 0 0 precipitate_only
Kainite 0 0 precipitate_only
Li2CO3 0 0 precipitate_only
Li2SO4:H2O 0 0 precipitate_only
LiKSO4 0 0 precipitate_only
Magnesite 0 0 precipitate_only
Mirabilite 0 0 precipitate_only
NaB5O8:5H2O 0 0 precipitate_only
NaBO2:4H2O 0 0 precipitate_only
Pirssonite 0 0 precipitate_only
Polyhalite 0 0 precipitate_only
Sylvite 0 0 precipitate_only
Syngenite 0 0 precipitate_only
Thenardite 0 0 precipitate_only
Trona 0 0 precipitate_only
LiCl 0 0 precipitate_only
REACTION 1
H2O(g) -1
55.51 moles in 300 steps

Jay Chou:
Is there any researcher who can help solve the problem?
I don't know if there is something wrong with my code
Thank you！！！

dlparkhurst:
First, that is a lot of boron. Are you sure that is mg/L B, not ug/L?

PHREEQC can have numerical issues at high concentrations and high ionic strength. It is likely that very high concentrations exceed the range over which the Pitzer parameters were fit.

I have found that it is more reliable to use a KINETIC reaction that removes H2O compared to using REACTION. The kinetic reaction I defined removes about 5 percent of the water per second. The time frame is not meaningful, but the kinetics provides a way to produce exponentially less water. Ultimately the calculations fail, but I think it is well past the point of reliable Pitzer calculations with PHREEQC.

The attached script considers the sequence of minerals that form as water is removed. Minerals that precipitate are not allowed to dissolve once they form (precipitate only). The script also plots the SI of mirabilite and the terms that produce log10(IAP). The SI of mirabilite approaches saturation, but does not quite precipitate mirabilite before the saturation index decreases. Although the log10 activity of Na+ increases, the contributions of log10 activity of water and sulfate cause the SI to decrease.

--- Code: ---PHASES
H2O
H2O = H2O
log_k 0
LiCl
LiCl:H2O = Cl- + H2O + Li+
log_k 4.978
Li2CO3
Li2CO3 = CO3-2 + 2Li+
log_k -4.271
LiKSO4
LiKSO4 = K+ + Li+ + SO4-2
log_k -1.3828
Li2SO4:H2O
Li2SO4:H2O = 2Li+ + SO4-2+H2O
log_k 0.6036
END
RATES
H2O
10 k = 0.05
20 rate = k*TOT("Water")/(1e-3*GFW("H2O"))
30 SAVE -rate*TIME

SOLUTION 1 SMZB-LQS-sm114
temp 5
pH 8.711
pe 4
redox pe
units mg/l
density 1
Alkalinity 858.46
B 418.89
Ca 17.28
Cl 592.75 #charge
K 98.22
Li 30.45
Mg 7.93
Na 687.55
S(6) 86.69
-water 1 # kg
EQUILIBRIUM_PHASES 1
Anhydrite 0 0 precipitate_only
Bischofite 0 0 precipitate_only
Bloedite 0 0 precipitate_only
Borax 0 0 precipitate_only
CO2(g) -3.4 100
Calcite 0 0 precipitate_only
Dolomite 0 0 precipitate_only
Epsomite 0 0 precipitate_only
Gaylussite 0 0 precipitate_only
Glaserite 0 0 precipitate_only
Glauberite 0 0 precipitate_only
Gypsum 0 0 precipitate_only
Halite 0 0 precipitate_only
Huntite 0 0 precipitate_only
K2B4O7:4H2O 0 0 precipitate_only
KB5O8:4H2O 0 0 precipitate_only
Kainite 0 0 precipitate_only
Li2CO3 0 0 precipitate_only
Li2SO4:H2O 0 0 precipitate_only
LiKSO4 0 0 precipitate_only
Magnesite 0 0 precipitate_only
Mirabilite 0 0 precipitate_only
NaB5O8:5H2O 0 0 precipitate_only
NaBO2:4H2O 0 0 precipitate_only
Pirssonite 0 0 precipitate_only
Polyhalite 0 0 precipitate_only
Sylvite 0 0 precipitate_only
Syngenite 0 0 precipitate_only
Thenardite 0 0 precipitate_only
Trona 0 0 precipitate_only
LiCl 0 0 precipitate_only
INCREMENTAL_REACTIONS true
KINETICS
-cvode
H2O
-M 0
-step 196 in 196
USER_GRAPH 1
-headings time Water Calcite Dolomite Borax KB5O8:4H2O \
Glauberite Gypsum Halite Li2SO4:H2O LiCl LiKSO4 NaB5O8:5H2O Sylvite
-axis_titles "Time" "Water, kg" "Log10 Moles"
-axis_scale x_axis 0 200 auto auto
-axis_scale y_axis auto auto auto auto log
-axis_scale sy_axis -5 -1 auto auto
-initial_solutions false
-connect_simulations true
-plot_concentration_vs x
-start
10 GRAPH_X TOTAL_TIME
20 GRAPH_Y TOT("Water")
30 GRAPH_SY LOG10(EQUI("Calcite")), LOG10(EQUI("Dolomite"))
40 GRAPH_SY LOG10(EQUI("Borax")), LOG10(EQUI("KB5O8:4H2O"))
50 GRAPH_SY LOG10(EQUI("Glauberite")), LOG10(EQUI("Gypsum"))
60 GRAPH_SY LOG10(EQUI("Halite")), LOG10(EQUI("Li2SO4:H2O")), LOG10(EQUI("LiCl"))
70 GRAPH_SY LOG10(EQUI("LiKSO4")), LOG10(EQUI("NaB5O8:5H2O")), LOG10(EQUI("Sylvite"))
-end
-active true
USER_GRAPH 2
-headings time Water SI(Mirabilite) 2*LA(Na+) LA(SO4-2) 10*LA(H2O)
-axis_titles "Time" "Water, kg" "SI and Log10 activity"
-axis_scale x_axis 0 200 auto auto
-axis_scale y_axis auto auto auto auto log
#-axis_scale sy_axis -5 -1 auto auto
-initial_solutions false
-connect_simulations true
-plot_concentration_vs x
-start
10 GRAPH_X TOTAL_TIME
20 GRAPH_Y TOT("Water")
30 GRAPH_SY SI("Mirabilite"), 2*LA("Na+"), LA("SO4-2"), 10*LA("H2O")
END

--- End code ---

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