CATALYTIC
EFFECTS
OF
THE
Y-FeOOH
(LEPIDOCROCITE)
SURFACE
ON
THE
OXYGENATION
REMOVAL
KINETICS
OF
Fe(II)
AND
Mn(II)
by
Windsor
Sung
W.
M.
Keck
Laboratory
of
Environmental
Engineering
Science
Division
of
Engineering
and
Applied
Science
CALIFORNIA
INSTITUTE
OF
TECHNOLOGY
Pasadena,
California
91125
Report
No.
AC-12-80
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December
1980
CATALYTIC
EFFECTS
OF
THE
y-FeOOH
(LEPIDOCROCITE)
SURFACE
ON
THE
OXYGENATION
REMOVAL
KINETICS
OF
Fe(II)
AND
Mn(II)
by
Windsor
Sung
Thesis
Advisor:
James
J.
Morgan
Professor
of
Environmental
Engineering
Science
Supported
by
Grants
from
E.
I.
Du
Pont
De
Nemours
&
Company
Union
Oil
Company
Keck
Laboratories
of
Environmental
Engineering
Science
Division
of
Engineering
and
Applied
Science
California
Institute
of
Technology
Pasadena,
California
91125
Report
No.
AC-12-80
December
1980
;1
ACKNOWLEDGMENTS
I
wish
to
thank
my
advisor,
James
J.
Morgan,
for
his
patience.
His
timely
criticisms
were
very
helpful.
Thanks
are
due
to
the
following
professors
who
have
served
on
my
committees:
F.
C.
Anson,
N.
H.
Brooks,
R.
C.
Flagan,
W.
L.
Johnson,
W.
J.
North
and
G.
R.
Rossman.
R.
B.
Burns
at
MIT
has
been
a
most
stimulating
professor
during
my
undergraduate
days
and
continues
to
be
of
much
support.
Technical
help
has
been
invaluable
from
the
following:
P.
E.
Duwez,
S.
Kotake
and
S.
Samson
for
X-ray
diffraction.
R.
Potter
and
G.
R.
Rossman
for
instructions
on
the
infrared
spectroscopy
work.
J.
B.
Earnest
kindly
did
the
BET
surface
area
measurements
for
me
in
his
spare
time
at
JPL.
Heartfelt
thanks
are
due
to
Elaine
Granger
for
typing
my
manuscript
efficiently.
Discussions
with
J.
R.
Hunt
and
J.
R.
Young
have
helped
clear
my
thinking.
I thank
their
patience
for
those
uninvited
walk-in
discussions.
Mr.
and
Mrs.
K.
Y.
Ho
and
Mr.
and
Mrs.
Z.
K.
Sung
provided
much
needed
moral
support.
Cal
tech
has
been
an
enjoyable
institution
to
pursue
academic
work.
Classical
guitar
lessons
with
D.
Denning
provided
cultural
breaks.
Financial
support
from
the
Dupont
and
Union
Oil
companies
is
gratefully
acknowledged.
iii
ABSTRACT
Previous
investigations
of
Fe(II)
oxygenation
had
resulted
in
a
wide
range
in
the
reported
rate
constant(s).
While
Fe(II)
oxygenation
rates
are
fast
in
simple
laboratory
systems
(seconds
to
minutes
when
pH
>
7),
actual
rates
observed
in
natural
waters
can
be
orders
of
magnitude
lower.
Conversely,
while
Mn(II)
oxygenation
rates
are
slow
in
laboratory
systems
(days
when
pH
<
9),
much
faster
rates
are
observed
in
natural
waters
or
implicated
in
model
studies.
The
influences
of
ionic
strength,
temperature
and
anions
on
the
Fe(II)
homogeneous
oxygenation
rates
were
examined
in
this
study.
Other
rate
constants
from
the
literature
were
successfully
incorporated
into
this
framework.
Complexation
by
major
anions
(e.g.,
SO~-
and
Cl-)
and
ionic
strength
effects
were
sufficient
to
account
for
the
retardation
of
Fe(II)
oxygenation
in
seawater.
Autocatalysis
of
Fe(II)
oxygenation
was
observed
for
pH
>
7.
A general
integrated
autocatalytic
rate
expression
suitable
for
Fe(II)
or
Mn(II)
oxygenation
was
used
to
interpret
laboratory-
obtained
kinetic
data.
Oxidation
of
FeCII)
in
various
laboratory
systems
with
characteristics
like
those
of
natural
water
was
shown
to
form
the
allotrope
y-FeOOH.
The
y-FeOOH
surface
was
shown
to
be
an
excellent
catalyst
for
Fe(II)
and
Mn(II)
oxygenation.
The
y-FeOOH
surface
obtained
by
oxidizing
milli-molar
levels
of
Fe(II)
in
0.7
M
NaCl
was
studied
in
the
following
ways:
surface
charge
characteristics
by
acid/base
titration;
adsorption
of
Mn(II)
and
surface
oxidation
of
Mn(II).
A
rate
law
was
formulated
to
account
for
the
effects
of
pH
and
the
amount
of
surface
on
the
surface
oxidation
rate
of
iv
Mn(II).
The
presence
of
mill
i-molar
levels
of
y-FeOOH
was
shown
to
reduce
significantly
the
half-life
of
Mn(II)
in
0.7
M
NaCl
from
hundreds
of
hours
to
hours.
The
y-FeOOH
surface
was
shown
to
be
as
effective
as
colloidal
Mn0
2
in
catalysing
Mn(II)
oxygenation.
Chapter
1
2
3
v
TABLE
OF
CONTENTS
NOTATIONS
INTRODUCTION
1.1
Interest
in
Iron
and
Manganese
1.2
Brief
Overview
of
Iron
and
Manganese
Chemistry
1.3
The
Objective
of
this
Study
1.3.1
General
Considerations
1.3.2
Experimental
Design
EXPERIMENTAL
TECHNIQUES
2.1
General
Information
2.2
Reaction
Vessel
2.3
Analytical
Methods
2.3.1
Iron
Analysis
2.3.2
Manganese
Analysis
2.4
X-ray
Diffraction
2.5
Infrared
Spectroscopy
2.6
Synthetic
Scheme
of
y-FeOOH
for
Surface
Experiments
2.6.1
Procedure
A
2.6.2
Procedure
B
KINETICS
AND
PRODUCT
OF
Fe(II)
OXYGENATION
IN
AQUEOUS
SYSTEMS
3.1
Homogeneous
Oxygenation
3.1.1
Ionic
Strength
Effects
3.1.2
Temperature
Effects
3.1.3
Anion
Effects
3.2
Heterogeneous
Oxygenation
3.3
Product
Identification
3.4
Implications
for
Natural
Systems
x
1
1
4
5
5
5
6
6
6
8
8
9
10
12
12
13
14
15
15
16
20
20
23
31
39