Elements of Environmental Engineering: Thermodynamics and Kinetics, Third Edition

486 Pages·2009·3.37 MB·English

by  Kalliat T. Valsaraj

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CRC Press
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Contents

Preface...............................................................................
xi
Author ...............................................................................
xv

1
Introduction ...................................................................
1
1.1
Energy, Population, and Pollution.......................................
1
1.2
Environmental Standards and Criteria ..................................
2
1.3
The Discipline of Environmental Engineering..........................
2
1.4
Chemical Thermodynamics and Kinetics in Environmental
Engineering...............................................................
4
1.4.1
Applications of Thermodynamics and Kinetics ................
4
1.4.1.1
Equilibrium Partitioning...............................
4
1.4.1.2
Fate and Transport Modeling..........................
5
1.4.1.3
Design of Separation Processes .......................
8
1.5
Units and Dimensions....................................................
11
1.6
Structure of the Book ....................................................
12
References......................................................................
12

2
Basic Chemical Thermodynamics ..........................................
13
2.1
Equilibrium...............................................................
13
2.2
Fundamental Laws of Thermodynamics ................................
14
2.2.1
Zeroth Law of Thermodynamics................................
15
2.2.2
First Law of Thermodynamics ..................................
16
2.2.3
Second Law of Thermodynamics ...............................
17
2.2.4
Third Law of Thermodynamics .................................
18
2.2.5
Enthalpy and Heat Capacity ....................................
22
2.2.6
Thermodynamic Standard States: Enthalpies of Reaction,
Formation, and Combustion ....................................
23
2.2.7
Combination of First and Second Laws ........................
25
2.3
Chemical Equilibrium and Gibbs Free Energy .........................
26
2.3.1
Free Energy Variation with Temperature and Pressure ........
26
2.4
Concept of Maximum Work .............................................
28
2.5
Gibbs Free Energy and Chemical Potential.............................
29
2.5.1
Gibbs–Duhem Relationship for a Single Phase ................
30
2.5.2
Standard States for Chemical Potential.........................
31
2.6
Thermodynamics of Surfaces and Colloidal Systems ..................
32
2.6.1
Surface Tension..................................................
32
2.6.2
Curved Interfaces and the Young–Laplace Equation ..........
33
2.6.3
Surface Thickness and Gibbs Dividing Surface................
35

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2.6.4
Surface Thermodynamics and Gibbs Equation ................
36
2.6.5
Gibbs Adsorption Equation .....................................
37
Problems .......................................................................
37
References......................................................................
41

3
Multicomponent Equilibrium Thermodynamics..........................
43
3.1
Ideal and Nonideal Fluids ...............................................
43
3.1.1
Concentration Units in Environmental Engineering ...........
44
3.1.2
Dilute Solution Definition.......................................
45
3.2
Fugacity ..................................................................
45
3.2.1
Fugacity of Gases................................................
46
3.2.2
Fugacity of Condensed Phases (Liquids and Solids) ..........
46
3.2.3
Activities of Solutes and Activity Coefficients .................
47
3.2.4
Ionic Strength and Activity Coefficients .......................
49
3.2.5
Fugacity and Environmental Models ...........................
51
3.3
Ideal Solutions and Dilute Solutions ....................................
55
3.3.1
Vapor–Liquid Equilibrium: Henry’s and Raoult’s Laws ......
55
3.3.1.1
Henry’s Law............................................
55
3.3.1.2
Raoult’s Law ...........................................
56
3.3.2
Vapor Pressure of Organic Compounds, Clausius–Clapeyron
Equation..........................................................
58
3.3.3
Vapor Pressure over Curved Surfaces ..........................
63
3.3.4
Liquid–Liquid Equilibrium .....................................
66
3.3.4.1
Octanol–Water Partition Constant ....................
66
3.3.4.2
Linear Free Energy Relationships.....................
69
3.4
Nonideal Solutions .......................................................
69
3.4.1
Activity Coefficient for Nonideal Systems .....................
69
3.4.1.1
Excess Functions and Activity Coefficients ..........
70
3.4.2
Activity Coefficient and Solubility .............................
70
3.4.3
Correlations with Hydrophobicity ..............................
72
3.4.3.1
Special Structural Features of Water ..................
73
3.4.3.2
Hydrophobic Hydration of Nonpolar Solutes ........
75
3.4.3.3
Hydrophobic Interactions between Solutes...........
78
3.4.3.4
Hydrophilic Interactions for Solutes in Water ........
79
3.4.3.5
Molecular Theories of Solubility:
An Overview ...........................................
80
3.4.4
Structure–Activity Relationships and Activity
Coefficients in Water ............................................
82
3.4.5
Theoretical and Semi-Empirical Approaches to Aqueous
Solubility Prediction.............................................
83
3.4.5.1
First-Generation Group Contribution Methods.......
83
3.4.5.2
Excess Gibbs Free Energy Models....................
86
3.4.5.3
Second-Generation Group Contribution
Methods: The UNIFAC Method ......................
86
3.4.6
Solubility of Inorganic Compounds in Water ..................
88
3.5 Adsorption on Surfaces and Interfaces ..................................
88

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3.5.1
Gibbs Equation for Nonionic and Ionic Systems ..............
89
3.5.2
Equilibrium Adsorption Isotherms at Interfaces ...............
90
3.5.3
Adsorption at Charged Surfaces ................................ 101
Problems ....................................................................... 103
References...................................................................... 116

4
Applications of Equilibrium Thermodynamics............................ 119
4.1 Air–Water Phase Equilibrium............................................ 119
4.1.1
Estimation of Henry’s Constant from Group
Contributions .................................................... 123
4.1.2
Experimental Determination of Henry’s Law Constants ...... 125
4.1.3
Effects of Environmental Variables on Kaw .................... 126
4.2 Air–Water Equilibrium in Atmospheric Chemistry..................... 136
4.2.1
Wet Deposition of Vapor Species............................... 137
4.2.2
Wet Deposition of Aerosol-Bound Fraction.................... 138
4.2.3
Dry Deposition of Aerosol-Bound Pollutants .................. 143
4.2.4
Dry Deposition Flux of Gases from the Atmosphere .......... 144
4.2.5
Thermodynamics of Aqueous Droplets
in the Atmosphere ............................................... 147
4.2.6
Air/Water Equilibrium in Waste Treatment Systems .......... 150
4.3
Soil–Water and Sediment–Water Equilibrium .......................... 152
4.3.1
Partitioning into Soils and Sediments from Water ............. 153
4.3.2
Adsorption of Metal Ions on Soils and Sediments ............. 155
4.3.3
Adsorption of Organic Molecules on Soils
and Sediments ................................................... 159
4.4
Biota/Water Partition Constant (Bioconcentration Factor) ............ 164
4.5 Air-to-Aerosol Partition Constant ....................................... 167
4.6 Air-to-Vegetation Partition Constant .................................... 171
4.7 Adsorption on Activated Carbon for Wastewater Treatment ........... 172
Problems ....................................................................... 175
References...................................................................... 183

5
Concepts from Chemical Reaction Kinetics ............................... 189
5.1
Progress toward Equilibrium in a Chemical Reaction.................. 190
5.2
Reaction Rate, Order, and Rate Constant ............................... 193
5.3
Kinetic Rate Laws........................................................ 194
5.3.1
Isolation Method................................................. 195
5.3.2
Initial Rate Method .............................................. 195
5.3.3
Integrated Rate Laws ............................................ 195
5.3.3.1
Reversible Reactions................................... 198
5.3.3.2
Series Reactions and Steady-State Approximation... 201
5.3.4
Parallel Reactions ............................................... 207
5.4 Activation Energy ........................................................ 208
5.4.1
Activated Complex Theory...................................... 210
5.4.2
Effect of Solvent on Reaction Rates ............................ 213
5.4.3
Linear Free Energy Relationships .............................. 215

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5.5
Reaction Mechanisms.................................................... 216
5.5.1
Chain Reactions ................................................. 216
5.6
Reactions in Solutions ................................................... 219
5.6.1
Effects of Ionic Strength on Rate Constants ................... 219
5.7
Environmental Catalysis ................................................. 221
5.7.1
Mechanisms and Rate Expressions for Catalyzed
Reactions......................................................... 222
5.7.2
Homogeneous Catalysis......................................... 224
5.7.3
Heterogeneous Catalysis ........................................ 228
5.7.4
General Mechanisms of Surface Catalysis ..................... 228
5.7.5
Autocatalysis in Environmental Reactions ..................... 234
5.8
Redox Reactions in Environmental Systems ........................... 237
5.8.1
Rates of Redox Reactions ....................................... 240
5.9
Environmental Photochemical Reactions ............................... 244
5.10 Enzyme Catalysis ........................................................ 247
5.10.1 Michaelis–Menten Kinetics and Monod Kinetics.............. 247
Problems ....................................................................... 254
References...................................................................... 264

6
Applications of Chemical Kinetics in Environmental Systems .......... 267
6.1
Types of Reactors ........................................................ 267
6.1.1
Ideal Reactors.................................................... 267
6.1.1.1
Batch Reactor .......................................... 269
6.1.1.2
Continuous-Flow Stirred Tank Reactor ............... 269
6.1.1.3
Plug-Flow Reactor (PFR) or Tubular Reactor ........ 270
6.1.1.4
Design Equations for CSTR and PFR ................ 271
6.1.1.5
Relationship between Steady State
and Equilibrium for a CSTR .......................... 276
6.1.2
Nonideal Reactors ............................................... 277
6.1.2.1
Dispersion Model ...................................... 277
6.1.2.2
Tanks-in-Series Model................................. 278
6.1.3
Dispersion and Reaction ........................................ 280
6.1.4
Reaction in a Heterogeneous Medium.......................... 281
6.1.4.1
Kinetics and Transport at
Fluid–Fluid Interfaces ................................. 284
6.1.5
Diffusion and Reaction in a Porous Medium................... 286
6.2
The Water Environment.................................................. 290
6.2.1
Fate and Transport............................................... 290
6.2.1.1
Chemicals in Lakes and Oceans....................... 290
6.2.1.2
Chemicals in Surface Waters .......................... 293
6.2.1.3
Biochemical Oxygen Demand in
Natural Streams ........................................ 295
6.2.2
Water Pollution Control ......................................... 299
6.2.2.1 Air Stripping in Aeration Basins ...................... 299
6.2.2.2
Oxidation Reactor ..................................... 303

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6.2.2.3
Photochemical Reactions and Wastewater
Treatment............................................... 309
6.2.2.4
Photochemical Reactions in Natural Waters.......... 311
6.3
The Air Environment..................................................... 313
6.3.1
F&T Models ..................................................... 313
6.3.1.1
Box Models ............................................ 313
6.3.1.2
Dispersion Models ..................................... 319
6.3.2
Air Pollution Control ............................................ 324
6.3.2.1 Adsorption.............................................. 324
6.3.2.2
Thermal Destruction ................................... 327
6.3.3
Atmospheric Processes .......................................... 330
6.3.3.1
Reactions in Aqueous Droplets ....................... 330
6.3.3.2
Global Warming and Greenhouse Effect ............. 337
6.3.3.3
Ozone in the Stratosphere and Troposphere .......... 347
6.4
Soil and Sediment Environments........................................ 357
6.4.1
F&T Modeling................................................... 357
6.4.1.1
Transport in Groundwater ............................. 358
6.4.1.2
Sediment–Water Exchange of Chemicals ............ 364
6.4.1.3
Soil–Air Exchange of Chemicals ..................... 366
6.4.2
Soil and Groundwater Treatment ............................... 369
6.4.2.1
P&T for NAPL Removal from Groundwater ......... 370
6.4.2.2
In Situ Soil Vapor Stripping in the Vadose Zone ..... 373
6.4.2.3
Incineration for ex Situ Treatment of Soils
and Solid Waste ........................................ 375
6.5 Applications of Chemical Kinetics in Environmental
Bioengineering ........................................................... 376
6.5.1
Enzyme Reactors ................................................ 380
6.5.1.1
Batch Reactor .......................................... 381
6.5.1.2
Plug-Flow Enzyme Reactor ........................... 382
6.5.1.3
Continuous Stirred Tank Enzyme Reactor............ 383
6.5.1.4
Immobilized Enzyme or Cell Reactor ................ 387
6.5.1.5
In Situ Subsoil Bioremediation........................ 391
6.5.2
Kinetics of Bioaccumulation of Chemicals in the Aquatic
Food Chain....................................................... 393
6.6 Applications in Green Engineering...................................... 398
6.6.1
Environmental Impact Analysis................................. 399
6.6.2
Life Cycle Assessment .......................................... 405
Problems ....................................................................... 406
References...................................................................... 420

Appendix 1
Properties of Selected Chemicals of Environmental
Significance .................................................... 425

Appendix 2
Standard Free Energy, Enthalpy, and Entropy of
Formation for Compounds of Environmental
Significance.................................................... 431

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Appendix 3
Selected Fragment (bj) and Structural Factors (Bk) for
Octanol–Water Partition Constant Estimation................ 433

Appendix 4
Concentration Units for Compartments in
Environmental Engineering ................................... 435

Appendix 5
Dissociation Constants for Environmentally Significant
Acids and Bases ............................................... 437

Appendix 6
Bond Contributions to Log Kaw for the Meylan and
Howard Model................................................. 439

Appendix 7
Regression Analysis (the Linear Least-Squares
Methodology).................................................. 441

Appendix 8
Error Function and Complementary Error Function
Definitions ..................................................... 445

Appendix 9
Cancer Slope Factor and Inhalation Unit Risk for
Selected Carcinogens ......................................... 447

Appendix 10 U.S. National Ambient Air Quality Standards ............... 449

Index ........................................................................... 451

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Preface

Energy and environmental concerns are the most important issues for the current
generation.Theseproblemsarerelatedtotheincreaseddemandforavailableresources
but human beings have become adept at meeting these challenges. Unfortunately, our
attempts to resolve our problems also contribute to the degradation of the environment.
The consequences of environmental pollution can be disastrous, with many examples
that demonstrate the severity of the problem. The present-day debate about global
warming, climate change, water quality, air quality, and solid waste disposal are
examples.
Our prescription for alleviating environmental problems requires that we train stu-
dents in the science and engineering of environmental issues. A well-trained cadre of
professionals is required to make sure that sound science is involved in the formula-
tion of public policy. To this end, the present-day environmental professional needs
broad interdisciplinary training across the disciplines of physics, chemistry, biology,
and engineering.
Environmental engineering is interdisciplinary. It is a challenge to develop courses
that will provide students with a thorough, broad-based curriculum that includes
every aspect of the environmental engineering profession. Traditionally, environmen-
tal engineering has been a subdiscipline of civil engineering with primary emphasis
on municipal wastewater treatment, sewage treatment, and landfill management prac-
tices. During the second half of the twentieth century more emphasis was placed on
end-of-pipe treatment in manufacturing operations to control release of water, air,
and solid wastes. With the realization that environmental problems are not confined
to end-of-pipe treatment, the attention turned toward pollutant fate and transport in
the general environment, waste minimization, pollution prevention, and green engi-
neering. Thus stand-alone programs in environmental engineering began to appear in
many universities.
Environmental engineers perform a variety of functions, the most critical of which
are process design for waste treatment or pollution prevention, fate and transport
modeling, green engineering, and risk assessment. Physical chemistry is an essential
element of environmental engineering. In particular, chemical thermodynamics and
chemical kinetics, the two main pillars of physical chemistry, are crucial to environ-
mental engineering. Unfortunately, these topics are not covered in the environmental
engineeringcurriculainmostuniversities.Chemicalengineerstakeseparatecoursesin
thermodynamics and kinetics. They also take several prerequisites in chemistry, such
as physical chemistry, organic chemistry, inorganic chemistry, and analytical chem-
istry. Most environmental engineering programs do not require such a broad spectrum
of chemistry courses, but rely on an introductory chemistry course for environmen-
tal engineers. However, such a course lacks the proper depth in the two important
aspects of physical chemistry. I believe that an additional course should be taught that

xi

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Preface

introduces these subjects and lays the foundation for more advanced courses in envi-
ronmental process design, environmental transport modeling, green engineering, and
risk assessment. To accomplish this objective I wrote the first edition of this textbook
in 1995. It is based on a course entitled “Chemical Thermodynamics and Kinetics
for Environmental Processes” that I have been offering to environmental engineering
majors and as a single semester required course for the Accreditation Board for Engi-
neering and Technology (ABET)–accredited BS degree program in environmental
engineering. It is also taught in the chemical engineering department at Louisiana
State University (LSU). Students taking this course also take a fundamental ther-
modynamics course in the mechanical engineering department at LSU, which deals
primarily with the laws of thermodynamics, concepts of heat engines, and mechan-
ical applications of thermodynamics. They also take an introductory environmental
engineering course preceding this.
This is an undergraduate textbook, but portions of it are also suitable for an
introductory graduate-level course. A basic understanding of physics, chemistry, and
mathematics (especially differential calculus) is assumed. In writing this third edition,
I have considered the comments of several instructors who have used the past editions
of the book. In response to their requests, I have eliminated redundant material and
refocused the chapters. Sections such as green engineering, biological processes, life
cycle analysis, etc., have been added. I have provided a larger number of examples
and problems in this edition. The examples are chosen to represent important appli-
cations, but, since the choice is subjective, I do admit that some may be more relevant
than others. The problems are of varying levels of difficulty and they are ranked 1,
2, and 3, with 1 indicating the “least difficult” and 3 indicating the “most difficult”
or “advanced.” These are represented by subscripts beside the problem number. In a
typical single semester course, I follow the general outline as follows:

Lecture Number
Sections Covered

2 lectures
1.1–1.6
3 lectures
2.1–2.5, 2.6.1
9 lectures
3.2.1, 3.2.2, 3.2.5, 3.3.1, 3.3.2, 3.3.4.1, 3.4.1, 3.4.2, 3.5.1, 3.5.2
9 lectures
4.1.1–4.1.3, 4.2.1–4.2.4, 4.2.6, 4.3.1, 4.3.3, 4.4–4.6
6 lectures
5.2, 5.3.3, 5.4.1, 5.5.1, 5.7.1, 5.9, 5.10.1
14 lectures
6.1.1, 6.2.1.1–6.2.1.3, 6.2.2.2, 6.3.1.1, 6.3.3.2, 6.3.3.3, 6.4.1.2,
6.5.1.1–6.5.1.3, 6.6.2

In writing this book, I have received help and encouragement from a number of
people. Special thanks to Louis Thibodeaux, a friend and colleague of mine at LSU,
with whom I have collaborated for over two decades in environmental engineering
research. I extend special thanks to David J. Wilson for being a great role model as
an educator and researcher, especially for his infectious enthusiasm for teaching. My
present and past graduate students, in particular, Nick Ashley and R. Ravikrishna,
have contributed in many ways by working out problems and pointing out errors in
the previous editions.

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xiii

This work would not have been possible without the unconditional love and support
from my family (my wife, Nisha, and my two children, Viveca and Vinay).
This book is dedicated to my beloved father, who was always there for me when I
needed him, but did not live to see his son’s achievements, and my dear mother, who
is a source of inspiration to me in my life.

Kalliat T. Valsaraj

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