。磷酸根离子在三价

铁的水解过程相当复杂 溶液中含有磷酸。

附件

1

：外 文原文

E

Hydrolysis Mechanism of Fe(

Ⅲ

)Solution Containing Phosphate

Abstract:

The hydrolysis process of Fe(

Ⅲ

)solution is rather complicated

when

small

amounts

of

phosphate

ions

are

present.

Two

mechanisms

can

be

used

to

describe

the

process,

i.e.,

those

before

nucleation

and

after

nucleation.

The former was studied by the Ferron complex ion timed spectrophotometric

method

and

the

aqueous

species

of

Fe(

Ⅲ

)

were

classified

into

three

categories,

which

represent

respectively

different

polymers

during

hydrolysis.

The

latter

was

investigated

by

the

phosphomolybdate

blue

method,

high resolution TEM and XPS spectrum. It was concluded that the rate of

nucleation

and

the

rate

of

phase

transformation

were

decreased

because

some

phosphate

ions

were

possibly

included

in

the

polymer

when

the

primary

particles of

α

Fe

2

O

3

hydrolyzed and aggregated.

Key words:

phosphate; ellipsoidal

α

Fe2O3particles; hydrolysis mechanism

Ellipsoidal hematite

particles

are ideal materials

to produce high grade

magnetic recording medium due to their smooth, hole free surface with no

magnetic

pole

in

the

interior.

At

present,

their

preparation

methods

include

the forced hydrolysis method of ferric salt solutions

[1

～

3]

and hydrothermal

synthesis

[4]

.

Both

methods

need

little

phosphate

ions

as

a

growth

regulating

gh

the

preparation

of

el lipsoidal

α

_Fe

2

O

3

particles

with

forced

hydrolysis has been reported

[5,6]

,no literature attempting to illustrate the

hydrolysis

process

of

Fe(

Ⅲ

)solutions

containing

phosphate

has

been

found.

In

order

to

understand

the

hydrolysis

process,

the

change

of

Fe(

Ⅲ

)polymers

during the hydrolysis in the presence or absence of phosphate was studied

with

the

Ferron

complex

ion

timed

spectrophotometric

method

[7]

and

the

reason

for

the

restraint

of

Fe(

Ⅲ

)solutions

hydrolysis

in

the

presence

of

phosphate

was also expounded in this paper.

1

Materials and Methods

1.1

Materials

The analytically pure reagents and doubly distilled water were needed in

the experiment.

The concentrations of Fe(

Ⅲ

)solution and that containing phosphate were

measured

before

their

uses.

The

preparation

of

0.2%(in

mass)Ferron

solution

was the same as that.

The concentrated HNO

3

solution was trebly diluted with doubly distilled

water.

The preparation of NaF SnCl

2

solution as follows: 24 g NaF were dissolved

in 100 mlhot water; after cooling, 2 g SnCl

2

were added; then the mixture

was filtered. The solution was only used on the day.

1.2

Measurement of Morphology Distribution of Fe(

Ⅲ

)in the Hydrolysis

Process

The solution with Fe(

Ⅲ

)only and the solution containing phosphate were

respectively

hydrolyzed

under

boiling

reflux.300

mL

reactant

was

added

into

a

500

mL

three

neck

flask,

which

was

heated

by

electromagnetic

stirrer,

and

a 700 mm global reflux condenser was installed. The samples were taken at

once

when

the

solutions

tarted

boiling.

Then

they

were

taken

once

in

several

minutes

till

the

initial

precipitates

came

into

being.

The

sample

absorptivity was measured by Ferron complex ion timed spectrophotometric

method

on

spectrophotometer

at

a

wavelength

of

600

nm. The

contents

of

Fe(a),

Fe(b)and Fe(c)could be calculated. Fe(a)includes free Fe(

Ⅲ

)ions and all

monomeric hydroxyl polymer; Fe(b), transitional low polymeric species and

Fe(c), polymer of several hundreds Fe(

Ⅲ

)ions.

1

.3

Measurement of Phosphate Concentration in the Hydrolysis Process

The experimental installation mentioned above was also used. As soon as

the initial precipitates appeared, the first sample was immediately taken

till

α

Fe

2

O

3

ellipsoidal

particles

were

completely

formed,

i.e.,

the

phosphate

concentration

did

not

change

speed

universal

centrifuges were used to remove the precipitates. The precipitates were

washed

for

several

times

and

the

washing

solution

was

added

into

the

mother

solution. Then, the mother solution was diluted to a definite volume. The

absorptivity of

this solution

was

measured by phosphomolybdate blue

method

on the spectrophotometer at a wavelength of 660 nm with same measurable

procedures

。

1.4

Experiment for the Latter Mechanism

In

order

to

elucidate

the

mechanism

after

nucleation,

high

resolution

TEM

was performed with an H 600 instrument. XPS spectrum of ellipsoidal

α

Fe

2

O

3

particles

was

also

performed

with

ESCA

LabMK

2

X

ray

photoelectron

spectroscopy using MgK

α

radiation.

2

Results and Discussion

2.1

Hydrolysis Process of Fe(NO

3

)

3

and Fe(NO

3

)

3

< br>NaH

2

PO

4

System

When

the

hydrolysis

of

0.097

1

mol/L

Fe(NO

3

)

3

solution

took

place

at

100

℃

,

reacting solution

was sampled

before the emergency

of initial precipitates

at 0, 3, 8, 15 min and 20 h and Fe(

Ⅲ

)concentration was measured regularly

as soon as every sample was mixed with Ferron solution. The changes of

Fe(

Ⅲ

)concentra tion with time are given for different samples.

2.2

Phosphate Adsorption and Desorption in the Growth of Ellipsoidal

α

_Fe

2

O

3

Particles

The

curve

of

phosphate

adsorption

and

desorption

are

given when

0.2

mol/L

-3

Fe(NO

3

)

3

and 2.4

×

10

mol/L, 1.8

×

10

mol/L NaH

2

PO

4

were mixed with boiling

reflux, respectively, for the hydrolysis.

3

Conclusions

(1) The changes of Fe(a), Fe(b) and Fe(c)during the hydrolysis of Fe(NO

3

)

3

solutions containing phosphate ions was measured by the Ferron complex ion

timed spectrophotometric method. It was shown that phosphate ions might

prevent

the

hydrolysis

of

Fe(NO

3

)

3

solutions.

Because

some

phosphate

ions

were

possibly

included

in

the

polymers

by

Fe(

Ⅲ

)aggregation,

the

Fe(

Ⅲ

)

solutions

could not be transformed into nuclei until phosphate ions were replaced by

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