Arsenic Coagulation with Iron, Aluminum, Titanium, and Zirconium

118 Pages·2009·0.9 MB·English

Arsenic Water Technology Partnership

Arsenic Coagulation with Iron, Aluminum, Titanium,
and Zirconium Salts

Arsenic Coagulation with Iron, Aluminum, Titanium,
and Zirconium Salts

Prepared by:
Divagar Lakshmanan, Dennis A. Clifford, and Gautam Samanta
Department of Civil and Environmental Engineering
University of Houston
Houston, TX 77204-4791

Jointly Sponsored by:
Awwa Research Foundation
6666 West Quincy Avenue, Denver CO 80235-3098

and

U.S. Department of Energy
Washington, D.C. 20585-1290

Published by:

WERC, a Consortium for Awwa Research Foundation
Environmental Education and
Technology Development at
New Mexico State University
DISCLAIMER

This study was jointly funded by the Awwa Research Foundation (AwwaRF) and the U.S.
Department of Energy (DOE) under Grant No. DE-FG02-03ER63619 through the Arsenic Water
Technology Partnership. The comments and views detailed herein may not necessarily reflect
the views of the Awwa Research Foundation, its officers, directors, affiliates or agents, or the
views of the U.S. Federal Government and the Arsenic Water Technology Partnership. The
mention of trade names for commercial products does not represent or imply the approval or
endorsement of AwwaRF or DOE. This report is presented solely for informational purposes.

Copyright 2008
By Awwa Research Foundation
and Arsenic Water Technology Partnership

All Rights Reserved

Printed in the U.S.A.
CONTENTS

LIST OF TABLES ......................................................................................................................... ix

LIST OF FIGURES ....................................................................................................................... xi

FOREWORD .............................................................................................................................. xvii

ACKNOWLEDGMENTS ........................................................................................................... xix

EXECUTIVE SUMMARY ......................................................................................................... xxi

CHAPTER 1 INTRODUCTION .................................................................................................... 1
Arsenic Occurrence, Health Effects and Regulations .......................................................1
Iron Coagulation-Filtration and Adsorption Processes .....................................................1
Background of the Study ..................................................................................................2
Significance of In-situ Formed Hydroxides in Arsenic Removal ........................... 2
Alum as Coagulant for Arsenic Removal ............................................................... 2
Zirconium Oxide/Hydroxide Adsorbent Media for Arsenic Removal ................... 3
Basis of the Project ................................................................................................. 3
Objectives .........................................................................................................................4
Anticipated Practical Benefits of the Project ....................................................................4

CHAPTER 2 MATERIALS AND METHODS ............................................................................. 7
Reagents and Stocks .........................................................................................................7
Preparation of NSFI-53 Challenge Water .........................................................................7
Preparation of Coagulant Stock ........................................................................................7
Coagulation-Filtration Procedure ......................................................................................8
Preservation and Speciation ..............................................................................................9
Instrumentation ...............................................................................................................10
Total Arsenic and Arsenic and Arsenic(III) Analysis Using FI- HG-AAS ....................10
Freundlich Isotherm ........................................................................................................11

CHAPTER 3 As(III) VS. As(V) REMOVAL .............................................................................. 13
Introduction .....................................................................................................................13
Arsenic Removal Study Procedure .................................................................................14
Arsenic Removal Using Ferric (III) Chloride ....................................................... 14
Arsenic Removal Using Alum .............................................................................. 15
Arsenic Removal Using Zirconium (IV) Chloride ............................................... 16
Arsenic Removal Using Titanium (IV) Chloride.................................................. 17
Arsenic Removal Using Titanium (III) Chloride .................................................. 18
Arsenic Removal Using Titanium (IV) Oxychloride ............................................ 19
Arsenic Removal Using Zirconium (IV) Oxychloride ......................................... 19
Arsenic Adsorption Isotherms ........................................................................................20
Comparison of Adsorption Capacities ............................................................................24
v
Arsenic Adsorption Comparison on a Mass Basis ................................................ 24
Arsenic Adsorption Comparison on a Molar Basis .............................................. 25
Oxidation Study of Arsenic(III) in the Presence of Titanium(III) chloride ....................28
TiCl Oxidation Study Results .............................................................................. 28
3
Proposed Mechanism for the Oxidation of Arsenic(III) in Presence of
Titanium(III) ................................................................................................... 29
Summary and Conclusions .............................................................................................30

CHAPTER 4 EFFECT OF COMPETING IONS ON ARSENIC (III)/(V) ADSORPTION........ 31
Introduction .....................................................................................................................31
Effect of Silica in NSFI Challenge Water Containing Phosphate ..................................32
Effect of Silica in NSFI Water with Phosphate Using Ferric (III) Chloride as
Coagulant ........................................................................................................ 32
Effect of Silica in NSFI Water with Phosphate Using Alum as Coagulant .......... 34
Effect of Silica in NSFI Water with Phosphate Using Zirconium (IV)
Chloride as Coagulant ..................................................................................... 34
Effect of Silica in NSFI Water with Phosphate Using Titanium (IV)
Chloride as Coagulant ..................................................................................... 36
Effect of Silica in NSFI Water with Phosphate Using Titanium (III)
Chloride as Coagulant ..................................................................................... 37
Effect of Phosphate in NSFI Challenge Water Containing Silica ..................................38
Effect of Phosphate in NSFI Water with Silica Using Ferric (III) Chloride as
Coagulant ........................................................................................................ 39
Effect of Phosphate in NSFI Water with Silica Using Alum as Coagulant .......... 40
Effect of Phosphate in NSFI Water with Silica Using Zirconium (IV)
Chloride as Coagulant ..................................................................................... 41
Effect of Phosphate in NSFI Water with Silica Using Titanium (IV)
Chloride as Coagulant ..................................................................................... 42
Effect of Phosphate in NSFI Water with Silica Using Titanium (III)
Chloride as Coagulant ..................................................................................... 43
Effect of Vanadate in NSFI Challenge Water Containing Silica and Phosphate ...........45
Effect of Vanadate in NSFI Water with Silica and Phosphate Using Ferric
(III) Chloride as Coagulant ............................................................................. 45
Effect of Vanadate in NSFI Water with Silica and Phosphate Using Alum as
Coagulant ........................................................................................................ 46
Effect of Vanadate in NSFI Water with Silica and Phosphate Using
Zirconium (IV) Chloride as Coagulant ........................................................... 47
Effect of Vanadate in NSFI Water with Silica and Phosphate Using
Titanium (IV) Chloride as Coagulant ............................................................. 48
Effect of Vanadate in NSFI Water with Silica and Phosphate Using
Titanium (III) Chloride as Coagulant ............................................................. 49
Individual Effects of Silica, Phosphate and Vanadate with Ferric (III) Chloride as
Coagulant in NSFI Challenge Water Without Competing Ions................................50
Effect of Silica in the Absence of Phosphate and Vanadate ................................. 51
Effect of Phosphate in the Absence of Silica and Vanadate ................................. 52
Effect of Vanadate in the Absence of Silica and Phosphate ................................. 53
vi
Summarizing the Effects of Competing Ions on the Arsenic Adsorption Capacity
in NSFI Challenge Water ..........................................................................................55
Individual Effects of Competing Ions on the Arsenic Adsorption Capacity of
Ferric (III) Hydroxide ...............................................................................................61
Conclusions .....................................................................................................................63

CHAPTER 5 TOXICITY CHARACTERISTIC STUDIES ......................................................... 65
Introduction .....................................................................................................................65
Preliminary Toxicity Characteristic Evaluation ..............................................................65
Experimental Study Procedure ............................................................................. 66
Toxicity Characteristic Study Results .............................................................................67
Experimental Evaluation of the Adsorption of High Concentrations of Arsenic
onto Metal Hydroxides .............................................................................................67
Conclusions .....................................................................................................................68

CHAPTER 6 ARSENIC REMOVAL WITH FeCl COAGULATION: COMPARISON OF
3
EXPERIMENTAL RESULTS WITH MINEQL+ 4.50 CHEMICAL EQUILIBRIUM
MODELING PROGRAM PREDICTIONS ........................................................................... 69
Introduction .....................................................................................................................69
Mineql+ Program Modeling Procedure ..........................................................................69
As(III) and As(V) Adsorption Isotherms Based on Mineql+ Modeling .........................72
Comparison of Model-predicted vs Experimentally Observed Arsenic Adsorption
onto Fe(OH) (s) ........................................................................................................76
3
Conclusions .....................................................................................................................79

CHAPTER 7 SUMMARY AND CONCLUSIONS ..................................................................... 81
SUMMARY ....................................................................................................................81
Conclusions .....................................................................................................................81
Recommendations ...........................................................................................................85

REFERENCES ............................................................................................................................. 87

ABBREVIATIONS ...................................................................................................................... 91

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viii
TABLES

Table 2.1 Composition of NSFI 53 challenge water........................................................................8

Table 2.2 Composition of reagents in preparation of coagulant stock for coagulation study ........ 8

Table 2.3 Experimental conditions for the determination of As(III) and As(Tot) by FI-HG-
AAS.......................................................................................................................... 10

Table 3.1 Equilibrium constants for some important arsenic containing acids ............................ 13

Table 3.2 Comparison of chemical costs for treating one million gallons of NSFI-53 water
to reduce As(V)/As(III) from 50 to < 10 μg/L ......................................................... 27

Table 4.1 Composition of species of some important acids present in pH 6.5-8.5 ...................... 32

Table 5.1 Percent dry solids in the liquid wastes after 3-hr settling ............................................. 67

Table 5.2 Arsenic concentrations in the TCLP- or WET-defined extract (liquid waste after
filtration) .................................................................................................................. 68

Table 5.3 Comparison of expected and measured arsenic adsorption capacities of metal
hydroxides for all coagulants ................................................................................... 68

Table 6.1 Composition of NSFI-53 challenge water .................................................................... 70

Table 6.2 Mineql+ titration parameters ........................................................................................ 70

Table 6.3 As(V) adsorption capacity of Fe(OH) based on Mineql+ program ............................. 71
3

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