19 - Modeling Cd+2 Sorption
This example corresponds to the “Example 19-Modeling Cd+2 Sorption With Linear, Freundlich, and Langmuir Isotherms, and With a Deterministic Distribution of Sorption Sites for Organic Matter, Clay Minerals, and Iron Oxyhydroxides” from the Phreeqc manual. It can be retrieved from the Phreeqc Website.
Studies
This project contains 2 Studies.
PhreeqcStudy: “study_19 - Modeling Cd+2 Sorption”
Db used: “Phreeqc_dat” database
TITLE Example 19.--Linear, Freundlich and Langmuir isotherms for
Cd sorption on loamy sand. Calculates Example 7.1
from Appelo and Postma, 2005. Data from Christensen, 1984.
SURFACE_MASTER_SPECIES
Linear Linear
Freundlich Freundlich
Langmuir Langmuir
SURFACE_SPECIES
Linear = Linear
Linear + Cd+2 = LinearCd+2
-log_k -100.7 # log10(0.2) - 100
-mole_balance LinearCdCl2
Freundlich = Freundlich
Freundlich + 0.722 Cd+2 = FreundlichCd+2
-log_k -102.61 # log10(0.421) + (0.722 - 1) * log10(112.4e6) - 100
-no_check
-mole_balance FreundlichCdCl2
Langmuir = Langmuir
Langmuir + Cd+2 = LangmuirCd+2
-log_k 6.56 # log10(112.4 / 30.9e-6)
-mole_balance LangmuirCdCl2
SURFACE 1
Linear 1e100 1 1
Freundlich 1e100 1 1
Langmuir 8.45e-8 1 1 # 9.5 / 112.4e6
-no_edl
SOLUTION 1
pH 6
Ca 1
Cl 2
REACTION 1
CdCl2 1
0.7e-6 in 20
PRINT
-reset false
END
/n
PhreeqcStudy: “study_19 - Modeling Cd+2 Sorptionb”
Db used: “Phreeqc_dat” database
TITLE Example 19B.--Cd sorption on X, Hfo and OC in loamy soil
#
PRINT
-reset false
-user_print true
SURFACE_MASTER_SPECIES
# Monodentate 60%
H_a H_aH; H_b H_bH; H_c H_cH; H_d H_dH
H_e H_eH; H_f H_fH; H_g H_gH; H_h H_hH
# Bidentate 40%
H_ab H_abH2; H_ad H_adH2; H_af H_afH2; H_ah H_ahH2
H_bc H_bcH2; H_be H_beH2; H_bg H_bgH2; H_cd H_cdH2
H_cf H_cfH2; H_ch H_chH2; H_de H_deH2; H_dg H_dgH2
SURFACE_SPECIES
H_aH = H_aH; log_k 0; H_bH = H_bH; log_k 0; H_cH = H_cH; log_k 0; \
H_dH = H_dH; log_k 0;
H_eH = H_eH; log_k 0; H_fH = H_fH; log_k 0; H_gH = H_gH; log_k 0; \
H_hH = H_hH; log_k 0;
H_abH2 = H_abH2; log_k 0; H_adH2 = H_adH2; log_k 0; H_afH2 = H_afH2; log_k 0;
H_ahH2 = H_ahH2; log_k 0; H_bcH2 = H_bcH2; log_k 0; H_beH2 = H_beH2; log_k 0;
H_bgH2 = H_bgH2; log_k 0; H_cdH2 = H_cdH2; log_k 0; H_cfH2 = H_cfH2; log_k 0;
H_chH2 = H_chH2; log_k 0; H_deH2 = H_deH2; log_k 0; H_dgH2 = H_dgH2; log_k 0;
# Protons
H_aH = H_a- + H+; log_k -1.59
H_bH = H_b- + H+; log_k -2.70
H_cH = H_c- + H+; log_k -3.82
H_dH = H_d- + H+; log_k -4.93
H_eH = H_e- + H+; log_k -6.88
H_fH = H_f- + H+; log_k -8.72
H_gH = H_g- + H+; log_k -10.56
H_hH = H_h- + H+; log_k -12.40
H_abH2 = H_abH- + H+; log_k -1.59; H_abH- = H_ab-2 + H+; log_k -2.70
H_adH2 = H_adH- + H+; log_k -1.59; H_adH- = H_ad-2 + H+; log_k -4.93
H_afH2 = H_afH- + H+; log_k -1.59; H_afH- = H_af-2 + H+; log_k -8.72
H_ahH2 = H_ahH- + H+; log_k -1.59; H_ahH- = H_ah-2 + H+; log_k -12.40
H_bcH2 = H_bcH- + H+; log_k -2.70; H_bcH- = H_bc-2 + H+; log_k -3.82
H_beH2 = H_beH- + H+; log_k -2.70; H_beH- = H_be-2 + H+; log_k -6.88
H_bgH2 = H_bgH- + H+; log_k -2.70; H_bgH- = H_bg-2 + H+; log_k -10.56
H_cdH2 = H_cdH- + H+; log_k -3.82; H_cdH- = H_cd-2 + H+; log_k -4.93
H_cfH2 = H_cfH- + H+; log_k -3.82; H_cfH- = H_cf-2 + H+; log_k -8.72
H_chH2 = H_chH- + H+; log_k -3.82; H_chH- = H_ch-2 + H+; log_k -12.40
H_deH2 = H_deH- + H+; log_k -4.93; H_deH- = H_de-2 + H+; log_k -6.88
H_dgH2 = H_dgH- + H+; log_k -4.93; H_dgH- = H_dg-2 + H+; log_k -10.56
# Calcium
H_aH + Ca+2 = H_aCa+ + H+; log_k -3.20
H_bH + Ca+2 = H_bCa+ + H+; log_k -3.20
H_cH + Ca+2 = H_cCa+ + H+; log_k -3.20
H_dH + Ca+2 = H_dCa+ + H+; log_k -3.20
H_eH + Ca+2 = H_eCa+ + H+; log_k -6.99
H_fH + Ca+2 = H_fCa+ + H+; log_k -6.99
H_gH + Ca+2 = H_gCa+ + H+; log_k -6.99
H_hH + Ca+2 = H_hCa+ + H+; log_k -6.99
H_abH2 + Ca+2 = H_abCa + 2H+; log_k -6.40
H_adH2 + Ca+2 = H_adCa + 2H+; log_k -6.40
H_afH2 + Ca+2 = H_afCa + 2H+; log_k -7.45
H_ahH2 + Ca+2 = H_ahCa + 2H+; log_k -10.2
H_bcH2 + Ca+2 = H_bcCa + 2H+; log_k -6.40
H_beH2 + Ca+2 = H_beCa + 2H+; log_k -10.2
H_bgH2 + Ca+2 = H_bgCa + 2H+; log_k -10.2
H_cdH2 + Ca+2 = H_cdCa + 2H+; log_k -6.40
H_cfH2 + Ca+2 = H_cfCa + 2H+; log_k -10.2
H_chH2 + Ca+2 = H_chCa + 2H+; log_k -10.2
H_deH2 + Ca+2 = H_deCa + 2H+; log_k -10.2
H_dgH2 + Ca+2 = H_dgCa + 2H+; log_k -10.2
# Cadmium
H_aH + Cd+2 = H_aCd+ + H+; log_k -1.52
H_bH + Cd+2 = H_bCd+ + H+; log_k -1.52
H_cH + Cd+2 = H_cCd+ + H+; log_k -1.52
H_dH + Cd+2 = H_dCd+ + H+; log_k -1.52
H_eH + Cd+2 = H_eCd+ + H+; log_k -5.57
H_fH + Cd+2 = H_fCd+ + H+; log_k -5.57
H_gH + Cd+2 = H_gCd+ + H+; log_k -5.57
H_hH + Cd+2 = H_hCd+ + H+; log_k -5.57
H_abH2 + Cd+2 = H_abCd + 2H+; log_k -3.04
H_adH2 + Cd+2 = H_adCd + 2H+; log_k -3.04
H_afH2 + Cd+2 = H_afCd + 2H+; log_k -7.09
H_ahH2 + Cd+2 = H_ahCd + 2H+; log_k -7.09
H_bcH2 + Cd+2 = H_bcCd + 2H+; log_k -3.04
H_beH2 + Cd+2 = H_beCd + 2H+; log_k -7.09
H_bgH2 + Cd+2 = H_bgCd + 2H+; log_k -7.09
H_cdH2 + Cd+2 = H_cdCd + 2H+; log_k -3.04
H_cfH2 + Cd+2 = H_cfCd + 2H+; log_k -7.09
H_chH2 + Cd+2 = H_chCd + 2H+; log_k -7.09
H_deH2 + Cd+2 = H_deCd + 2H+; log_k -7.09
H_dgH2 + Cd+2 = H_dgCd + 2H+; log_k -7.09
END
SURFACE 1
# 1 g soil = 0.7% Organic Matter ~ 3.5 mg Organic Carbon.
# 7.1 meq charge per g OC
# For Psi vs I (= ionic strength) dependence, adapt specific surface area in PHRC:
# SS = 159300 - 220800/(I)^0.09 + 91260/(I)^0.18
# Example: SS = 46514 m2/g for I = 0.003 mol/l
#
# 3.5 mg OC, 0.025 meq total charge, distributed over the sites:
# charge on 4 nHA sites: -2.84 / 4 * 3.5e-3 / 1e3 (eq)
H_a 2.48e-06 46.5e3 3.50e-03
H_b 2.48e-06; H_c 2.48e-06; H_d 2.48e-06
# charge on 4 nHB sites: 0.5 * charge on nHA sites
H_e 1.24e-06; H_f 1.24e-06; H_g 1.24e-06; H_h 1.24e-06
# charge on 12 diprotic sites: -2.84 / 12 * 3.5e-3 / 1e3
H_ab 8.28e-07; H_ad 8.28e-07; H_af 8.28e-07; H_ah 8.28e-07
H_bc 8.28e-07; H_be 8.28e-07; H_bg 8.28e-07; H_cd 8.28e-07
H_cf 8.28e-07; H_ch 8.28e-07; H_de 8.28e-07; H_dg 8.28e-07
-donnan
# 1 g soil = 2.79 mg Fe = 0.05 mmol Fe = 4.45 mg FeOOH
# 10% has ferrihydrite reactivity
Hfo_w 1e-6 600 4.45e-4
Hfo_s 0.025e-6
-equilibrate 1
EXCHANGE 1
X 55.7e-6
-equilibrate 1
SOLUTION 1
pH 6.0
Ca 1
Cl 2
Cd 1e-6
REACTION 1
CdCl2 1
2e-6 in 20
END
/n
Plots
This project contains 2 Plots.
Plot 1: “plot_1”
Plot 2: “plot_2”
