Nanomagnetite Enhances Sand Filtration For Removal of Arsenic From Drinking Water

122 Pages·2010·3.18 MB·English

RICE UNIVERSITY
Nanomagnetite Enhances Sand Filtration For
Removal of Arsenic From Drinking Water
by
Jesse Walter Farrell
A THESIS SUBMITTED
IN PARTIAL FULFILLMENT OF THE
REQUIREMENTS FOR THE DEGREE
Master of Science
APPROVED, THESIS COMMITTEE:
/S^c
Mason Tomsonn,, PPrrooffeessssoorr,, Chair
Civil and Environmental Engineering
Qilin Li, Assistant Professor
Civil and Environmental Engineering
Pedro Alvarez, George R. Brown Professor,
Civil and Environmental Engineering
Vicki Colvin, Pitzer-Schlumberger Professor
of Chemistry, Chemical & Biomolecular
Engineering
HOUSTON, TEXAS
DECEMBER 2009
UMI Number: 1486012
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ABSTRACT
Nanomagnetite Enhances Sand Filtration
For Removal of Arsenic and Other Heavy Metals
From Drinking Water
By
Jesse Walter Farrell
Arsenic in drinking water affects millions globally causing skin disease and
cancers of the liver, stomach, and bladder. Large-scale treatment removes arsenic
effectively; however, community- and home-scale treatments are typically less effective,
more costly, or labor intensive. Nanomagnetite would enable effective, economical
arsenic removal in low maintenance, household sand filters. Adsorption isotherms were
used to display the As(V) capacity of nanomagnetite in a variety of natural waters and pH
conditions. Column design and operating conditions were assessed for optimal removal.
Breakthrough was most affected by nanomagnetite percentage, residence time, inlet
concentration, and nanomagnetite aggregate size. NH4OH regenerated the
nanomagnetite, allowing for repeated use. No detectable nanomagnetite escaped the
column; however, permanent magnets were shown to capture >98% of nanomagnetite
aggregates from a fluid stream. A case study proposes the use of nanomagnetite to treat
arsenic contaminated groundwater in Guanajuato, Mexico to below the Mexican EPA
drinking water standard for $0.23/m3.
ACKNOWLEDGEMENTS
This thesis was accomplished through immeasurable support from a dear
community of professors, colleagues, friends, and family.
I first want to thank God for always being present and my source of hope and
strength for this work and all that is to come. Thank you Dr. Mason Tomson, my
advisor, for facilitating the exceptional education experience over the past two years.
You have taught me the value of a scholar's mind, and your mentorship will always carry
with me. Dr. Qilin Li, thank you for your rigorous and stimulating courses; I thoroughly
enjoyed them. For all the late night help you heroically provided in the lab in
Guanajuato, I am indebted to you. Thank you, Dr. Pedro Alvarez, for your guidance
down the PhD pathway and your keen interest in my research. Dr. Vicki Colvin, I give
my full gratitude for your efforts in establishing the Guanajuato partnership and opening
this opportunity to be involved in such interesting work. Thank you all for your support.
Many thanks to each of my group members, Sarah Work, Ping Zhang, Hamad A1
Saiari, Chunfang Fan, Haiping Lu, Jie Yu, Lunliang Zhang, Nan Zhang, Lilin Wang, and
Dr. Gongmin Fu; you are all such a joy to work alongside and share graduate life with.
For group members-past, I want to thank Dong-Shen for encouraging me when I was first
getting my feet wet in the lab, Sujin Yean, and Weichun Yang. I am so happy for where
life is taking you. Thank you Amy Kan, for your always wise counsel and the patience as
I learn. Shu Wang, thank you for all you do and for the company in the office. Alice
Tsao, I want to reiterate again how much help you have been and what a pleasure it is to
work with you. To Araceli, Dora, and James, thank you for serving us faithfully behind
the scenes.
iv
I thank all my classmates and now fellow researchers in the CEVE department.
Thank you Sandra Baylor, Bob Dawson, and Andrea Torres for keeping the department
up and running. I thank all the undergraduates from Rice Engineers Without Borders on
the El Salvador and Honduras teams and Board, and my mentors Brian Davis and Luis
Marcias-Navaro for the adventure and the experience abroad. Thank you Ross Gordon,
for orienting me in your course to water technologies and sustainability considerations for
the developing world. I thank John Nadolski, Brad Saltzman, and the other folks at
Living Water International for sharing their inspiring work and taking interest in my own.
Thank you, Heather Shipley, for the quality of the groundwork you laid and for
being available to answer questions and share thoughts. JT Mayo, your senior knowledge
has been invaluable. Thank you, John Fortner, for being a visionary and providing
oversight in my work for the Guanajuato project. Jan Hewitt, thank you for the personal
and classroom attention to help equip and inspire me through your thesis-writing course.
Thank you Kim Lehecka; as a co-laborer in the library you kept me on-track. I owe a
huge debt of gratitude to my small group at Ecclesia for their prayer and support that
went far beyond words.
I cannot help but thank the entire Guanajuato crew for their vision and
tremendous support in bridging this research forward for field application. Thank you
Jorge Duran, Rafael Zarate-Araiza, Rafael Alzati, Alfredo Cesena, and Omar Flores; and
thank you Carlos Garcia for facilitating all the visits.
Mom and Dad, thank you for your loving support you so often communicate to
me through words, hugs, meals, and prayer. I am richly blessed to be your son.
V
The research was supported by the National Science Foundation through the
Center for Biological and Environmental Nanotechnology [EEC-0118007] and U.S. EPA
ORD/NCER/STAR nanotechnology program [#83171801].
TABE OF CONTENTS
1. Introduction 1
Organization of Thesis 3
2. Background and Literature Review 4
Arsenic chemistry, occurrence, uses 4
Arsenic Health Effects & Regulatory Limits 7
Methods of Arsenic Removal 8
Performance Review of Adsorbents 10
Small Scale Treatment 12
Conventional Slow Sand and Rapid Sand filtration 14
Magnetic force 16
CSTR versus Packed Column reactors 16
Packed Column Design 17
Adsorption and Surface Complexation 18
Interferences 19
Adsorption Kinetics Modeling 22
Filtration Theory: Equilibrium and Kinetics 23
Regeneration of iron-oxide based systems 26
Disposal & Leaching tests 27
3. Materials and Methods 30
Sample Waters 30
Sand and Adsorbent materials 31
Solution Preparation 34
vii
Batch adsorption experiments 35
Column Materials and Preparation 36
Method of controlled water flow 38
Washing 38
Chemical Analysis 38
Magnetic separation of magnetite in flowing pipe 40
4. Results and Discussion 42
4.1 Characterization of As(V) Adsorption 42
Effects of Source Water on Adsorption Behavior 42
Effect of pH 43
Effect of Aggregation 45
Effect of Solid Wetting Method 47
Effect of Fe(III) and Zn(II) Addition 48
Comparison of Adsorbents 49
4.2 Magnetic Capture of Nanomagnetite Aggregates from Suspension 52
Effect of Flow Rate on Magnetic Capture 52
Effect of Steel Wool 53
Effect of Various Magnetic Configurations 54
4.3 Observed Dynamics of Fixed Bed Column Experiments 57
Column Blank: Adsorption to Sand Alone 57
Effects of Residence Time and Weight Percent of Nanomagnetite 58
Effect of Intermittent Flow 61
Effect of Dispersion of Nanomagnetite 64
Effect of Inlet As(V) Concentration 65
Breakthrough of Multiple Elements 66
viii
Regeneration with NH4OH 67
5. Case Study 70
Abstract 70
Arsenic Problem 71
Background on Guanajuato 71
Collaboration Established 74
Water Quality Assessment 75
Materials and Methods 77
Sample Acquisition and Storage 77
Chemical Analysis 78
Metals Resuspension and Extraction from Sediments 79
Batch Adsorption Isotherms 80
Column Methods 80
Results and Discussion 81
Water Quality Assessments 81
Metal concentration in sediment samples 82
Adsorption Isotherms 84
Column Trials 85
Adsorbent Cost of Treatment 87
Conclusion 89
6. Conclusion 91
Future work 92
7.0 References 95
Appendices 102
Appendix A 103
Appendix B