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There was a recent discussion of calcite kinetics:http://phreeqcusers.org/index.php/topic,1131.msg3392.html#msg3392

Calcite -start1 REM PARM(1) = specific surface area of calcite, cm^2/mol calcite2 REM PARM(2) = exponent for M/M010 si_cc = SI("Calcite")20 IF (M <= 0 and si_cc < 0) THEN GOTO 20030 k1 = 10^(0.198 - 444.0 / TK )40 k2 = 10^(2.84 - 2177.0 /TK )50 IF TC <= 25 THEN k3 = 10^(-5.86 - 317.0 / TK)60 IF TC > 25 THEN k3 = 10^(-1.1 - 1737.0 / TK )80 IF M0 > 0 THEN area = PARM(1)*M0*(M/M0)^PARM(2) ELSE area = PARM(1)*M110 rate = area * (k1 * ACT("H+") + k2 * ACT("CO2") + k3 * ACT("H2O"))120 rate = rate * (1 - 10^(2/3*si_cc))130 moles = rate * 0.001 * TIME # convert from mmol to mol200 SAVE moles -endENDSOLUTION 1 Pure Water temp 25 pH 7 pe 4ENDKINETICS 1Calcite -tol 1e-8 -m0 10 -m 10 -parms 1.67e5 0.6 # cm^2/mol calcite, exp factor -time 1 dayUSE solution 1EQUILIBRIUM_PHASES 1 CO2(g) -3.58 10

RATESCalcite -start1 REM PARM(1) = specific surface area of calcite, cm^2/mol calcite2 REM PARM(2) = exponent for M/M010 si_cc = SI("Calcite")20 IF (M <= 0 and si_cc < 0) THEN GOTO 20030 k1 = 10^(0.198 - 444.0 / TK )40 k2 = 10^(2.84 - 2177.0 /TK )50 IF TC <= 25 THEN k3 = 10^(-5.86 - 317.0 / TK)60 IF TC > 25 THEN k3 = 10^(-1.1 - 1737.0 / TK )80 IF M0 > 0 THEN area = PARM(1)*M0*(M/M0)^PARM(2) ELSE area = PARM(1)*M110 rate = area * (k1 * ACT("H+") + k2 * ACT("CO2") + k3 * ACT("H2O"))120 rate = rate * (1 - 10^(2/3*si_cc))130 moles = rate * 0.001 * TIME # convert from mmol to mol200 SAVE moles -endENDSOLUTION 1 Pure Water temp 25 pH 7 pe 4ENDKINETICS 1Calcite -tol 1e-8 -m0 10 -m 10 -parms 1.67e5 0.6 # cm^2/mol calcite, exp factor -time 10 s -cvodeUSE solution 1EQUILIBRIUM_PHASES 1 CO2(g) -3.58 10