ARSENIC REMOVAL FROM GROUNDWATER WITH IRON

152 Pages·2009·1.28 MB·English

The Pennsylvania State University

The Graduate School

Department of Civil and Environmental Engineering

ARSENIC REMOVAL FROM GROUNDWATER WITH IRON

TAILORED GRANULAR ACTIVATED CARBON PRECEDED BY

PRE-CORRODED STEEL

A Dissertation in
Environmental Engineering
By
Jiying Zou

© 2009 Jiying Zou

Submitted in Partial Fulfillment
Of the Requirements for
The Degree of

Doctor of Philosophy

May 2009
The dissertation of Jiying Zou was reviewed and approved* by the following

Fred S. Cannon
Professor of Environmental Engineering
Dissertation Advisor
Chair of Committee

Brian A. Dempsey
Kappe Professor of Environmental Engineering

Paul Painter
Professor of polymer Science
Department of Material Science and Engineering

John M. Regan
Associate Professor of Environmental Engineering

Peggy A. Johnson
Professor of Civil Engineering
Head of the Department of Civil and Environmental Engineering

*Signatures are on file in the Graduate School

ii
ABSTRACT

ARSENIC REMOVAL FROM GROUNDWATER BY IRON
TAILORED GAC PLUS PRECORRODED IRON
Ph.D. Candidate: Jiying Zou
Thesis Advisor: Fred S. Cannon, Professor
The Pennsylvania State University (University Park, PA)
Department of Civil and Environmental Engineering

Arsenic of over 50 ppb level in drinking water could cause a lifetime risk of dying from
cancer for the consumer. Although, conventional granular activated carbon (GAC) has a very
limited capacity for removing arsenic, it was found that tailoring GAC by preloading iron could
enhance its bed life, when the iron tailored GAC was coupled with precorroded iron, the GAC’s
bed life could greatly enhanced.
For carbon tailoring, incipient wetness method and organic-iron preloading method were
employed. 1-3% Fe loading was achieved with organic-iron preloading method and 3-6% Fe
loading was achieved via incipient wetness method. Compared with virgin GAC, the citric
acid-iron preloaded GAC could extend the GAC’s bedlife by over 20 times to 7000 bed volumes
of 50 ppb arsenic containing water processed before 10 ppb breakthrough. The incipient wetness
method could further extend the GAC’s bedlife by 2 times.
Precorroded iron material, coupled with Organic carboxyl-Fe preloaded granular
activated carbons (GAC), have been appraised as an innovative technique for removing arsenic
from groundwater. The effective precorroded iron materials have included Galvanized Steel
Fittings and Perforated Steel Sheets. Rapid Small Scale Column Tests (RSSCT’s) and mini
column tests had been conducted to evaluate the arsenic removal capacity of the procorroded iron
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coupled with tailored carbon. The arsenic was found to be removed by both the iron column and
the GAC column, with GAC column as the major absorber. The pH, idling and precorrosion
protocol affect the iron release and arsenic removal. The combination of a precorroded iron
column followed by a iron – tailored GAC column removed arsenic to below 10 ppb for as much
as 248,000 bed volumes (BVs) at pH 6. These tests employed Rutland, MA groundwater with
native As of 47 ~ 55 ppb. Idling the system for one time extended the bed life of by 2 time, but
caused a short period arsenic breakthrough after column restart.
Arsenic removal in the GAC column was proportional to the iron amount accumulated in
the GAC column. The iron amount accumulated in the GAC column was generally controlled by
the operating pH, but was also affected by the precorrosion conditions of the iron and the idling of
the system. The arsenic removal in the iron column was generally higher with lower pH.
Moreover, as the column just started up, the removal was also controlled by the iron pre-corrosion
condition. A longer precorrosion period has promoted arsenic removal in the iron column. The
arsenic removal was generally lower with aged PSSs as the column just started, this was attributed
to the release of iron (hydr)oxides particles from the iron column; but with longer aging period of
more than 10 days, arsenic removal by aged PSSs could be greatly increased.
The precorrosion protocol influenced the formation of surface corrosion layer of the iron,
which in turn, affected how the iron was released and accumulated in the GAC column, especially
when the column just restarted. The morphology and structure of surface corrosion products on
precorroded steel sheets were studied via scanning electron microscope (SEM), X-ray diffraction
(XRD) and X-ray photoelectron spectroscopy (XPS) method. The results showed that the
morphology of surface corrosion products was highly related to iron release and arsenic removal.
iv
Fresh precorroded steel sheets have a uniform surface, while aged precorroded steel sheets
exhibited a heterogeneous surface with some areas covered with thick, porous scales.
Lepidocrocite (γ-FeOOH), humboditine (FeC O (H O) ) and clinoferrosilite (Fe Mg Si O ) are
2 4 2 2 1.5 0.5 2 6
the mainly component on the fresh precorroded steel sheet, while goethite (α-FeOOH),
lepidocrocite and magnetite (Fe O )are the primary component of the aged precorroded steel sheet
3 4
surface. After they were employed in the column for arsenic removal, the primary phase on
precorroded steel sheet changed to goethite and magnetite, calcite was also detected. Arsenic
extracted from precorroded steel in iron columns contain only As(III) when the column was
operated at pH < 7 and had been idled. XAFS study of the GAC in pH 7.5 column indicated the
presence of reduced iron phases such as FeO and green rust, some As(V) has also been reduced to
As(III). Idling the columns for 7 days is promoted a reduction reaction in both the iron and the
GAC columns.

v
TABLE OF CONTENTS

LIST OF TABLES...........................................................................................................................ix
LIST OF FIGURES..........................................................................................................................x
Acknowledgements........................................................................................................................xii

CHAPTER 1.....................................................................................................................................1

CHAPTER 2.....................................................................................................................................5
2.1 ARSENIC............................................................................................................................5
2.1.1 Background..............................................................................................................5
2.1.2 Toxicology................................................................................................................6
2.1.3 Regulatory................................................................................................................7
2.1.4 Chemistry of Arsenic................................................................................................8
2.1.4.1 Immobilization of arsenic..............................................................................8
2.1.4.2 Arsenic speciation.......................................................................................10
2.1.5 Treatment Technologies.........................................................................................11
2.1.5.1 Modified conventional treatment methods – precipitation/coprecipitation
methods...................................................................................................................11
2.1.5.1.1 Precipitation by Alum.......................................................................12
2.1.5.1.2 Precipitation by Iron.........................................................................12
2.1.5.1.3 Lime softening.................................................................................13
2.1.5.2 Adsorption and Ion exchange reactions...............................................14
2.1.5.2.1 Adsorption by activated carbon........................................................14
2.1.5.2.2 Adsorption by Activated Alumina....................................................16
2.1.5.2.3 Adsorption by iron hydroxide/iron oxides........................................17
2.1.5.2.4 Adsorption by zero valent iron (ZVI)...............................................21
2.1.5.2.5 Adsorption by other low cost adsorbents..........................................24
2.1.5.2.6 Adsorption by Iron Based Sorbents..................................................24
2.2 ACTIVATED CARBON...................................................................................................26
2.2.1 The Physical Characteristics and Surface Chemistry of Activated Carbon............26
2.2.2 Fe loading onto Activated Carbon for Arsenic Removal........................................28
2.2.2.1 Impregnation...............................................................................................28
2.2.2.2 Precipitation.............................................................................................29
2.2.2.3 With Chelating Agent...............................................................................29
2.3 IRON CORROSION.........................................................................................................30
2.3.1 Corrosion process...................................................................................................30
2.3.1.1 Anaerobic iron corrosion.............................................................................30
2.3.1.2 Iron corrosion with the presence of oxygen or other oxidizer.....................32
2.3.1.3 Reduction of surface corrosion product on Fe0........................................33
2.3.2 Corrosion product characterization........................................................................34
2.3.2.1 Corrosion scales on iron pipes in water distribution systems......................34
vi
2.3.2.2 Corrosion layers on the surface of iron used in contaminant removal........36
2.3.3 Surface corrosion products and contaminant removal...........................................39
2.3.3.1 Iron corrosion and contaminant reduction in PRBs....................................40
2.3.3.2 Iron corrosion and contaminant adsorption in PBRs...................................41
2.4 THE MECHANISMS OF ARSENIC REMOVAL BY IRON BASED SORBENTS.......42
2.4.1 Adsorption of Arsenic by iron oxide/hydroxide—As removal mechanisms..........42
2.4.2 Arsenic removal by ZVI.........................................................................................43
2.4.2.1 Iron corrosion and arsenic removal on ZVI – the process...........................43
2.4.2.2 Rate controlling arsenic removal by ZVI....................................................44
2.4.3 Redox reaction in ZVI system................................................................................45
2.4.4 Arsenic release.......................................................................................................46
2.5 REFERENCES.......................................................................................................48

CHAPTER 3...................................................................................................................................56
3.1 INTRODUCTION............................................................................................................56
3.2 MATERIALS AND METHODS....................................................................................59
3.2.1 Materials.................................................................................................................59
3.2.2 Organic carboxylic-Fe preloaded carbon...............................................................60
3.2.3 Preparation of Fe-GAC through incipient wetness impregnation (IWI)................60
3.2.4 Adsorption Isotherm...............................................................................................61
3.2.5 Column tests...........................................................................................................61
3.2.6 Chemical Analysis..................................................................................................61
3.3 RESULTS AND DISSCUSIONS...................................................................................62
3.3.1 Organic acid-Fe loading onto GAC........................................................................62
3.3.2 Iron loading via incipient wetness method..........................................................63
3.3.3 Batch test of the citric acid-iron preloaded activated carbon..............................64
3.3.4 Isotherm results...................................................................................................65
3.3.5 Rapid Small Scale Column Tests........................................................................67
3.4 CONCLUSIONS............................................................................................................68
3.5 REFERENCES...............................................................................................................68

CHAPTER 4...................................................................................................................................75
ABSTRACT............................................................................................................................75
4.1 INTRODUCTION.........................................................................................................76
4.1.1 Background............................................................................................................76
4.1.2 Arsenic Removal Technology................................................................................76
4.1.3 pH Effect on Arsenic Removal by ZVI and Iron (hydr)oxides..............................77
4.1.4 Iron Corrosion and Iron Release............................................................................77
4.2 MATERIALS AND METHODS....................................................................................79
4.2.1 Materials..............................................................................................................79
4.2.2 Citrate-Fe preloaded carbon................................................................................80
4.2.3 Iron Pre-corrosion...............................................................................................80
4.2.4 Column tests........................................................................................................80
4.2. 5 Chemical Analysis..............................................................................................82
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4.3 RESULTS AND DISCUSSION.....................................................................................84
4.3.1 Arsenic removal with and without precorroded iron..............................................84
4.3.2 pH effect on Arsenic removal.................................................................................87
4.3.3 Idle Effect on Arsenic Removal.............................................................................92
4.3.4 Precorrosion iron amount effect.............................................................................96
4.3.5 Iron release and arsenic removal in iron column – A summary..........................96
4.4 CONCLUSIONS............................................................................................................98
4.5 REFERENCES.............................................................................................................100

CHAPTER 5.................................................................................................................................110
ABSTRACT..........................................................................................................................110
5.1 INTRODUCTION.......................................................................................................111
5.1.1 Surface corrosion layer and its effect on contaminant removal........................111
5.1.2 Arsenic – iron redox reaction and As removal by ZVI.....................................112
5.1.3 As release..........................................................................................................114
5.2 MATERIALS and METHODS....................................................................................115
5.2.1 Precorroded steel sheets....................................................................................115
5.2.2 Scanning Electron Microscopy and energy-dispersive X-ray spectroscopy
(SEM-EDS) tests...........................................................................................................116
5.2.3 X-ray Diffraction (XRD) Measurements.............................................................117
5.2.4 X-ray Diffraction (XRD) Measurements of the powders collected from PSS
surface...........................................................................................................................117
5.2.5 X-ray Photoelectron Spectroscopy (XPS) analysis...........................................117
5.2.6 Digestion of precorroded steel sheets for arsenic speciation.............................118
5.3 RESULTS and DISCUSSION....................................................................................118
5.3.1 SEM result............................................................................................................118
5.3.2 XPS results........................................................................................................120
5.3.3 XRD result........................................................................................................123
5.3.4 Arsenic extraction from precorroded steel sheets in iron column.....................125
5.3.5 XAFS result.......................................................................................................125
5.4 Conclusions..................................................................................................................126
5.5 REFERENCES.............................................................................................................127

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LIST OF TABLES
Table 1.1 pKa Values of Arsenate and Arsenite.............................................................10
Table 3.1 Water quality characteristics of Cool Sandy Beach Groundwater (Rutland,
MA).................................................................................................................................62
Table 3.2 Fe loading result a..............................................................................................63
Table 3.3 Iron loading result b..........................................................................................64
Table 3.4 Iron loading via incipient wetness method.........................................................64
Table 3.5. Arsenic adsorption capacity with respect to water pH and carbon properties
.........................................................................................................................................66
Table 4.1: Configuration of Rapid Small Scale Column Tests (RSSCTs) and mini
columns...........................................................................................................................82
Table 4.2. Water quality characteristics of Cool Sandy Beach Groundwater (Rutland,
MA).................................................................................................................................83
Table 4.3. Column operating parameters and 10 ppb breakthrougha..............................85
Table 4.4. Arsenic distribution in GS #1 (iron - tailored GAC coupled with corrosion of
galvanized steel fittings) after 250,000 BV..................................................................87
Table 4.5. Correlation of 10 ppb As breakthrough..........................................................92
Table 4.6. Fe release amount and arsenic removal in iron column................................97
Table 5.1 The pretreatment precorroded steel sheets and columnoperating conditions
.......................................................................................................................................116
Table 5.2 Quatitative analysis of precorroded steel sheets – atomic percentage of each
element.........................................................................................................................122

ix
LIST OF FIGURES
Figure 1.1 Molecular configurations of arsenite and arsenate..........................................55
Figure 1.2 (A) arsenate and (B) arsenite speciation as a function of pH..........................55
Figure 3.1. Adsorption Isotherm of Citrate-Fe preloaded GAC and Virgin GAC.
(A)Freudlich Isotherm (B) Langmuir Isotherm.........................................................70
Figure 3.2 Kinetics tests of CA-Fe (1.2) and CA-Fe-Mg (2.18)......................................71
Figure 3.3 Pore volume analysis of virgin Ultracarb and various iron loaded
Ultracarb........................................................................................................................72
Figure 3.4 Kinetics tests of Fe loaded carbon made via incipient wetness method......73
Figure 3.6 RSSCT’s of amorphous iron oxide preloaded GAC.....................................74
Figure 4.1 RSSCT of iron tailored GAC with (solid triangle, GS #1) and without
(hollow square, #1) corroded iron, both columns operated at pH 6±0.3. Rutland
groundwater as influent (As 47~55 ppb, Fe < 3 ppb). Dashed line indicated where
the column (solid triangle) was stopped and ceased for 6 days...............................103
Figure 4.3 pH effect on (A) Total Fe release. (B) Filterable Fe release. (C) Fe
accumulated in GAC column.....................................................................................105
Figure 4.4 Arsenic removal with no idle (open diamond, PS #3), one idle (solid
reactangle, PS #1) and 3 idle (solid triangle, PS #2). (A) As effluent from GAC
column. (B) As removal in Fe column. (C) Filterable arsenic from Fe column. Solid
line indicate where PS #2 was stopped for 7 days, dashed line indicate where PS #1
was stopped for 7 days. All columns were operated at pH 6±0.3............................106
Figure 4.6 The effect of precorroded iron amount on arsenic removal. (A) Arsenic
breakthrough curve. (B) Arsenic removal by Fe column. Both columns were
operated at pH 7.5. Dashed line indicated where Run #6 was idled for 7 days, solid
line indicated where PS #5 was idled for 7 days.......................................................108
Figure 4.7 The effect of precorroded iron amount on (A) Total Fe release, (B) Filtrable
Fe release, (C) Fe accumulation in GAC column. Both columns operated at pH 7.5.
.......................................................................................................................................109
Figure 5.1 SEM of precorroded steel sheets (A) Fresh precorroded steel sheets – clean
surface (B) Aged precorroded steel sheets – rough and rusty (C) Steel surface in PS
# 6 (pH 7.5, idle once) – amorphous and uniform. (D) Steel surface in PS # 7(pH
7.5, idle once) – amorphous and uniform. (E) Steel surface in PS # 4 (pH 6-6.5, idle
once) – rough with lots of precipitates. (F) Steel surface in PS #2 (pH 6, idle 3 times)
– rough with lots of precipitates. (G) Steel surface in PS #2 (pH 6, idle 3 times) –
porous (H) Steel surface in PS #4 (pH 6-6.5, idle once) – porous............................131
Figure 5.2 Various crystals on surfaces of PSSs # 2 and PSSs #4. (A) to (E) Iron oxides,
(F) Calcium oxides and iron oxides............................................................................132
Figure 5.3 Elements identification on precorroded steel sheets by XPS survey. Top
spectrum– iron particles ultrasounded from PSS #2 (pH 6, idle three times); 2nd
spectrum–iron particles detached from PSS #1 (pH 6, idle once); 3rd spectrum –
fresh precorroded steel sheets; 4th spectrum – PSS #3 (pH 6, no idle); 5th spectrum
– PSS #4 (pH 6 ~ 6.5, idle once)..................................................................................133
x