0 2 4 6 8 10 12 14
–.5
0
.5
1
pH
Eh
(vo
lts)
Activity As 0.0001 Activity S 0.001
As(OH)4-
AsO4---
As(OH)3
AsO2OH--
H2AsO4-
H3AsO4
HAsO4--
Orpiment
Realgar
25°CD
iagra
m A
s(O
H) 4- ,
T =
25 °
C ,
P =
1.0
13 b
ars
, a [m
ain
] =
10
–4 ,
a [H
2O] =
1, a [S
O4--] =
10
–3 (
specia
tes)
0.001
0.01
0.1
1
10
100
1000
6 7 8 9 10 11
Ni (m
g/L
)
pH
Dissolved Nickel at 0, 20 or 50 mg/L Cyanide At Two Different Ni(OH)2 Solubility Products
CN- = 50 mg/L
CN- = 20 mg/L
Ni(OH)2 log Ksp = - 15.2
No CN-
No CN-
Ni(OH)2
log Ksp = - 17.2
log Slope = -2
INTRODUCTION TO GEOCHEMICAL MODELING TOOLS: EQUILIBRIUM
AND TRANSPORT APPLICATIONS
PRESENTED BY MAHONEY GEOCHEMICAL CONSULTING LLC
This five day course will provide participants with a detailed understanding of geochemical modeling using
the publically available programs PHREEQC, PHAST, and the graphics package HYDRA/MEDUSA.
Major features of this course include numerous hands on exercises to allow participants to work through the
various capabilities in the programs. These exercises are drawn from the instructor’s experience and are
selected to provide some “outside the box” thinking in the application of geochemical models. The PHAST
program, which couples PHREEQC with a three dimensional groundwater flow model, allows for the
construction of solute transport models that include pertinent geochemical reactions in flowing reacting
systems, thus avoiding problems with the simpler distribution coefficient type models. By the end of the
course, participants will understand geochemical modeling, including its shortcomings, and be able to apply
geochemical models to numerous environmental issues.
MONDAY APRIL 16 TH
- INTRODUCTION
8:00 – 8:15 ARRIVAL
8:15 – 8:30 WELCOME - PARTICIPANT INTRODUCTIONS
8:30 – 10:00 INTRODUCTION TO GEOCHEMICAL MODELING
10:00 – 10:15 BREAK
10:15 – 11:15 GEOCHEMICAL PROCESSES
11:15- 12:00 INTRODUCTION TO PHREEQC
12:00 – 1:00 LUNCH
1:00 – 2:30 INTERACTIVE SESSION - BEAKER MODELS IN PHREEQC
2:30 – 3:15 FIXING PHASES AND PHASE RULE, REACTANT
3:15 – 3:30 BREAK
3:30 – 5:15 EXERCISES 1 AND 2
5:15 – 5:30 DISCUSSION, FEEDBACK, CLOSE
0
20
40
60
80
100
120
0.00 0.05 0.10 0.15 0.20 0.25
Ura
niu
m m
g/L
Time in Years
PHREEQC 1-D 10 CELL TRANSPORT MODEL OF KINETIC
BASED LEACHING OF URANINITE - WITH PYRITE
Cell 1
Cell 2
Cell 5
Cell 10
Pyrite SA/V = 5 (0.7)
Dispersivity = 1
-1
-0.5
0
0.5
1
1.5
3 5 7 9 11
Eh
(vo
lts
)
pH
Eh - pH Diagram for the System U - O - H - C at
25°C
UO22+
U4+
UOH3+
U(OH)4
U
r
a
n
y
l
M
o
n
o
c
a
r
b
o
n
a
t
e
U
r
a
n
y
l
D
i
c
a
r
b
o
n
a
t
e
Uranyl Tricarbonate
H2O(l)
H2O(l)
H2(g)
O2(g)
UO2(c)
UO2(c)
ΣU = 10-8 MPCO2 = 10-2 bar
after Langmuir, 1997
REACTION PATH MODELS OF ORGANIC MATTER ADDITION
OPEN AND CLOSED WRT CO2(g)
EQ3/EQ6NR (solid lines) and PHREECQ (dashed lines)
0.E+00
2.E-07
4.E-07
6.E-07
8.E-07
1.E-06
3 4 5 6 7 8 9 10 11
U(V
I) A
ds
orb
ed
(m
ol/
Kg
w)
pH
DLM Fit and Distribution of Uranyl Surface Complexes on Hydrous Ferric Oxide
TOT_USCsHfo_sOUO2+
Hfo_wOUO2+Hfo_wOUO2CO3-Hfo_wOUO2(CO3)2-3
Experimental data
Hfo_wOUO2(CO3)2-3
Hfo_wOUO2+
Hfo_sOUO2+
Hfo_wOUO2CO3-
Data from Payne 1999
Constants from
Mahoney et al. 2009
TUESDAY APRIL 17TH
- REDOX, DATABASES AND HYDRA/MEDUSA
8:15 – 9:30 REDOX CHEMISTRY
9:30 – 10:15 DATABASE ISSUES
10:15 – 10:30 BREAK
10:30 – 12:00 EXERCISES 3 - REDOX AND DATABASES
12:00 – 1:00 LUNCH
1:00 – 3:00 INTERACTIVE SESSION - HYDRA/MEDUSA
3:00 – 3:15 BREAK
3:15 – 4:30 EXERCISES 3 AND 4 - HYDRA/MEDUSA
4:30 – 5:15 COPRECIPITATION PRESENTATION
5:15 – 5:30 DISCUSSION, FEEDBACK, CLOSE
WEDNESDAY APRIL 18TH
- SORPTION AND KINETICS
8:15 – 10:15 SURFACE COMPLEXATION (SORPTION)
10:15 – 10:30 BREAK
10:30 – 12:00 EXERCISES 5 - SURFACE COMPLEXATION
12:00 – 1:00 LUNCH
1:00 – 2:45 KINETICS
2:45 – 3:00 BREAK
3:00 – 4:30 EXERCISES 6 – KINETICS
4:30 – 5:15 EPICS LECTURE – EXAMPLE AND APPLICATION OF SURFACE COMPLEXATION
MODELING
5:15 – 5:30 DISCUSSION, FEEDBACK, CLOSE
4
4.5
5
5.5
6
6.5
7
7.5
8
-6
-5
-4
-3
-2
-1
0 10 20 30 40 50 60 70 80 90 100
pH
Lo
g m
ole
s p
rod
uct
min
era
ls
Extent of Evaporation
Mineral Precipitation Sequence Evaporation of Reverse Osmosis Brine
Using EQ3NR/EQ6
Magnesite Gypsum Epsomite Mirabilite Halite pH
THURSDAY APRIL 19TH
- MATH, TRANSPORT AND WPHAST
8:15 – 9:30 MATH TALK
9:30 – 10:15 TRANSPORT KEYWORD
10:15 – 10:30 BREAK
10:30 - 12:00 EXERCISES 7 - TRANSPORT
12:00 – 1:00 LUNCH
1:00 – 3:15 INTERACTIVE PHAST
3:15 – 3:30 BREAK
3:30 – 5:15 URANIUM TALK
5:15 – 5:30 DISCUSSION, FEEDBACK, CLOSE
FRIDAY APRIL 20TH
– MINING, ERRORS AND MISCELLANEOUS TOPICS
8:15 – 9:30 MINING, ARD, PIT LAKES
9:30 – 10:15 ARSENIC TALK
10:15 – 10:30 BREAK
10:30 – 11:15 ERRORS IN MODELING
11:15 – 12:00 OPEN DISCUSSION
12:00 – 1:00 LUNCH
1:00 – 3:30 MINING EXERCISES, STUDENT TOPICS - FINAL DISCUSSIONS AND CLOSE
The course organizer and lead instructor is John J. Mahoney, Ph.D. He has over 25 years of experience in geochemical
consulting and in applying geochemical models to solving environmental problems. In addition to the programs used in
this course, Dr. Mahoney also has extensive experience using other geochemical modeling programs such as
MINTEQA2, GWB and EQ3NR/EQ6 and developed flowing and reacting models using differential equation solver
programs.
Dr. Mahoney was the course organizer and lead instructor for Introduction
to Geochemical Modeling Tools held at the Fifth International Conference
on Acid Rock Drainage (ICARD 2000). He also presented a course at the Department of Mining, Metallurgy and Materials Engineering at McGill
University (December 2002). He has also been part of a team of instructors
for the Short Course in Environmental Geochemistry and Geochemical
Modeling held at the University of Alberta (Edmonton) in May 2006, and
May 2008. He has prepared specialized courses for consulting firms and
mining companies. He has presented this course previously in November
2010, and June 2011 in Colorado, and in July 2011 in South Africa.