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.