Processes > Dissolution and precipitation

Mineral dissolution and precipitation

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Mira:
Hello...
I'm trying to dissolve anorthite for calcite precipitation on various environmental condition.. But I'm not getting any of these. May be there is an error in my code. I'm attaching my code. And also I want to check dissolution of Augite separately but in my database there is no augite. where can I find it. Please help me with this also.

--- Code: ---RATES
    anorthite
-start
1 rem unit should be mol,kgw-1 and second-1
2 rem parm(1) is surface area in the unit of m2/kgw
3 rem calculation of surface area can be found in the note
4 rem M is current moles of minerals M0 is the initial moles of minerals
5 rem parm(2) is a scaling factor
10 rem acid solution parameters
11 a1=2.58E-01
12 E1=16601
13 n1=1.411
20 rem neutral solution parameters
21 a2=1.00E-06
22 E2=17821
30 rem base solution parameters
31 a3=1.00E-22
32 E3=18150
33 n2=-1.767
36 rem rate=0 if no minerals and undersaturated
40 SR_mineral=SR("anorthite")
41 if (M<0) then goto 200
42 if (M=0 and SR_mineral<1) then goto 200
43 if (M0<=0) then SA=PARM(1) else SA=PARM(1)*(M/M0)^0.67
50 if (SA<=0) then SA=1
60 R=8.31451
75 Rate1=a1*EXP(-E1/R/TK)*ACT("H+")^n1  #acid rate expression
80 Rate2=a2*EXP(-E2/R/TK)               #neutral rate expression
85 Rate3=a3*EXP(-E3/R/TK)*ACT("H+")^n2    #base rate expression
90 Rate=(Rate1+Rate2+Rate3)*(1-Sr_mineral)*SA*parm(2)
100 moles= rate*Time
110 rem do not dissolve more minerals than present
115 if (moles>M) then moles=M
200 save moles
-end
   
    Calcite
-start
 10 rem unit should be mol,kgw-1 and second-1
 20 rem parm(1) is surface area in the unit of m2/kgw
 30 rem calculation of surface area can be foundin the note
 40 rem M is current moles of minerals M0 is the initial moles of minerals
 50 rem parm(2) is a scaling factor
 60 rem acid soltion parameters
 70 a1=0
 80 E1=0
 90 n1=0
100 rem neutral solution parameters
110 a2=6.59E+04
120 E2=66000
130 rem co2 solution parameters
140 a3=1.04E+09
150 E3=67000
160 n2=1.6
170 rem rate = 0 if no minerals and undersaturated
180 SR_mineral=SR("calcite")
190 if (M<0) then goto 310
200 if (M=0 and SR_mineral<1) then goto 310
210 if (M0<=0) then SA=PARM(1) else SA=PARM(1)*(M/M0)^0.67
220 if (SA<=0) then SA=1
230 R=8.31451
240 Rate1= a1*EXP(-E1/R/TK)*ACT("H+")^n1
250 Rate2=a2*EXP(-E2/R/TK)
260 Rate3=a3*EXP(-E3/R/TK)*ACT("HCO3-")^n2
270 Rate=(Rate1+Rate2+Rate3)*(1-SR_mineral)*SA*parm(2)
280 moles= Rate*Time
290 rem do not dissolve more minerals than present
300 if (moles>M) then moles=M
310 save moles
-end

SOLUTION_SPECIES
#Al+3 + 4H2O = Al(OH)4- + 4H+
#log_k   -22.7
#H4SiO4 = H4SiO4
# -dw  1.10e-9
# -Vm  10.5  1.7  20  -2.7  0.1291 # supcrt + 2*H2O in a1
SiO2 + 2H2O = H4SiO4
        log_k   -2.71
        delta_h 3.91    kcal

PHASES
Anorthite
        CaAl2(SiO4)2 +8.0000 H+  =  + 1.0000 Ca++ + 2.0000 Al+++ + 2.0000 SiO2 + 4.0000 H2O
        log_k           26.5780
-delta_H -303.039 kJ/mol # Calculated enthalpy of reaction Anorthite
# Enthalpy of formation: -1007.55 kcal/mol
        -analytic 3.9717e-001 -1.8751e-002 1.4897e+004 -6.3078e+000 -2.3885e+005
#       -Range:  0-300
Calcite
        CaCO3 +1.0000 H+  =  + 1.0000 Ca++ + 1.0000 HCO3-
        log_k           1.8487
-delta_H -25.7149 kJ/mol # Calculated enthalpy of reaction Calcite
# Enthalpy of formation: -288.552 kcal/mol
        -analytic -1.4978e+002 -4.8370e-002 4.8974e+003 6.0458e+001 7.6464e+001
#       -Range:  0-300

END
SOLUTION 1
    temp      80
    pH         4
    pe         4
    redox     pe
    units     mol/kgw
    density   1
    -water    1 # kg

GAS_PHASE 1
    -fixed_pressure
    -pressure 100
    -volume 1e5
    -temperature 80
    CO2(g)     100

KINETICS 1
anorthite
    -formula  anorthite  1
    -m        1
    -m0       1
    -parms    1000 1
    -tol      1e-08
Calcite
    -formula  CaCO3  1
    -m        0
    -m0       0
    -parms    1 1
    -tol      1e-08
-steps       8640000 in 100 steps # seconds
-step_divide 1
-runge_kutta 3
-bad_step_max 500
-cvode true
-cvode_steps 100
-cvode_order 5

INCREMENTAL_REACTIONS True
USER_GRAPH 1
    -headings               TIME(Days) SI("anorthite") SI("calcite")
    -axis_titles            "Time (Days)" "SI" ""
    -chart_title            "Saturation Index"
    -initial_solutions      false
    -connect_simulations    true
    -plot_concentration_vs  x
  -start
10 GRAPH_X Total_TIME/86400
20 GRAPH_Y SI("anorthite")
30 GRAPH_Y SI("calcite")
  -end
    -active                 true

USER_GRAPH 2
    -headings               rxn KIN("anorthite") KIN("calcite")
    -axis_titles            "TIME (Days)" "milli moles" ""
    -chart_title            "Dissolution/precipitation"
    -initial_solutions      false
    -connect_simulations    true
    -plot_concentration_vs  t
  -start
10 GRAPH_X TOTAL_TIME/(86400)
20 GRAPH_Y KIN("anorthite")*1000 KIN("calcite")*1000
  -end
    -active                 true
SELECTED_OUTPUT 1
    -file                 C:\Users\hp\Desktop\25_April\Anorthite\An_1-25.sel
    -reset                false
    -time                 true
    -pH                   true
USER_PUNCH 1
    -headings KIN("anorthite") KIN("calcite") Ca_conc
    -start
 10 PUNCH KIN("anorthite")*1000
 20 PUNCH KIN("calcite")*1000
 30 PUNCH TOT("Ca")*1000
    -end
 END
--- End code ---

dlparkhurst:
All of the reaction solutions are in equilibrium with anorthite and undersaturated with calcite at pH 4.1. Calcite simply does not form under your conditions.

H4SiO4(aq) and SiO2(aq) represent the same dissolved silica species; don't define both. With your definition of anorthite, you need to use a database like llnl.dat or Kinec_v3.dat that has SiO2 as a silica aqueous species.

Kinec.v2.dat and Kinec_v3.dat have a RATES definition for Augite as a solid solution of other phases.

Mira:
Thank You for the help...
But how can I check the dissolution of anorthite and precipitation of calcite. What changes should be in the code to get it?

dlparkhurst:
Lower the PCO2.

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