Adsorption of some actinide elements on MnO2

The Science o/the Total Environment, 70 (1988) 253-263 Elsevier Science Publishers B.V., Amsterdam - - Printed in The Netherlands

253

A D S O R P T I O N OF SOME A C T I N I D E E L E M E N T S ON blnO2

M.T. CRESPO, M.L. ACENA and E. GARCIA-TORANO

CIEMAT-JEN, Avda. Complutense 22, 28040-MADRID (SPAIN)

ABSTRACT

Managanese water

dioxide

solutions.

has

been

used

to

scavenge

radionuclides

from

In this work the behaviour of Mn02 with uranium and

plutonium has been

studied by batch equilibration experiments,

column

experiments and cartridge experiments.

I.

INTRODUCTION

Manganese dioxide has important adsorbing properties and hence it can be used to scavenge radionuclides from water solutions. structural

forms

of

properties

depend

manganese both

on

dioxide

the

method

are

known

of

and

its

preparation

Different adsorption and

drying

temperature.

In 1913 the adsorption of radium on manganese dioxide was studied (Ebler and Bender,

1913) and more recently Moore and Cook (1975) have

used

impregnated with manganese

acrylic

fibre

dioxide

for the radium

removal from drinking water and for the radium determination in Amazon river

(Moore

and Edmunds,

rapid

procedure

0048-9697/88/$03.50

1984).

Wong et al (1978) have described a

for plutonium separation in large volumes of seawater

© Elsevier Science Publishers B.V.

254 by manganese dioxide coprecipitation.

Mann et al (1984) have also used

the method proposed by Wong, adapted for in situ collection of samples. Apparently,

using

this

method

the

efficiency

of plutonium collection

does not show a constant value and varies greatly.

In

order

to

obtain

further

information

about

the

behaviour

of

manganese dioxide with actinide elements we have proceeded to study the efficiency solutions

of by

plutonium

batch

and

uranium

equilibration

adsorption

experiments,

from

column

freshwater

experiments

and

cartridge experiments.

2.

EXPERIMENTAL

2.1

Preparation of Managanese Dioxide

The KMnO~

manganese

solution

on

pieces

was

cotton analysis

after

dioxide cotton

was

fibre

obtained

adsorption

by

prepared at

50°C.

weight

experiments,

dry-ashed at 500°C for 8 hours.

by

direct The

when

amount

dry.

the

reduction

of

0.1M

of MnO 2 in the

When

impregnated

required

for

cotton

was

The ashed sample with the appropriate

yield tracers was dissolved in HCl-hydroxylamine hydrochloride solution and

the

Ashing

filtered

solution

was

then processed

of samples containing plutonium above

soluble plutonium oxides.

by

analytical

methods.

500°C can produce poorly

The addition of plutonium tracers before the

dry-ashing can avoid an apparent lack of plutonium in sample.

Because

of that we have tried dissolving the impregnated cotton directly in a solution

of

solution we sample.

HCI found

and

hydroxylamine

a recovery

of

hydrochloride.

In

the

filtered

10% more plutonium than in the ashed

255 2.2

Analytical

The

HCl-hydroxylamine

dryness. if

The samples

necessary

the

hydroxylamine was

passed

Dowex of

Method

eluted

out

100-200

with with

I00 ml

40-50

ml

by

the

method

A typical

shown

i.

2.3

silicon

spectrometric

implanted

amplifier.

channel

2.4

analyser

Adsorption

Batch one

The

HCI

and

alpha

then

from

with

x

15 cm,

at a flow the

and

solution

rate

column

(or uranium)

evaporated.

by was

Electro-

steel discs was carried

(1984)

spectrum

Pu(IV)

sample

9M HC1

plutonium

on stainless

Hallstadius

to

(i cm i.d.

removed

to

with

obtained

some

additional

with these

sources

is

Instrumentation

Alpha

2020

1.2M

with

evaporated

9M HC1 solution

The

column

was

9M HCI.

or uranium

modifications. in Figure

of

of

nitrite.

resin

manganese

of

of plutonium

sodium

were

adjusted

pre-conditioned

The

about

was

exchange

mesh)

solutions

as 40-50 ml of

valence and

an anion

3 ml.min -I.

deposition

prepared

hydrochloride

1 x 8,

washing

were

plutonium

through

about

hydrochloride

hour

be studied

detector,

an

Data

acquired

were

connected

ORTEC

were 124 in

made

with

a 250 mm 2 ENERTEC

preamplifier a

SERIES

"on line" with a PDP

40

and

a CANBERRA

CANBERRA

multi-

11/34 computer.

Experiments

equilibration

at

measurements

constant

experiments

temperature

were

a solution

at a given pH and a piece

carried

out

containing

of cotton

by

shaking

the

impregnated

element

for to

with a known

256

233 U

400

300'

232 U

E)') ¢.

_

2oo o

o 100

0

50

0

FIGURE

i:

amount filtered

150 number

200

Alpha spectrum of 232U and 233U after analytical separation

from manganese.

manganese

dioxide.

of

and

corresponding

Columns impregnated

the

passed

7 ml.min -I.

After

impregnated

equilibrium

the

analysed

after

cotton

solution

was

adding

the

tracers.

having cotton

column experiments. were

100 Channel

through

1.3 (0.2

cm g

i.d.

MnO 2

Solutions

+

and 1.5

a g

length cotton

of fibre)

8

cm were

of

MnO 2

used

in

of 50 ml volume of uranium and plutonium

them at room

temperature,

Then several column volumes

at a flow rate of about

of water at the same pH as the

initial solution were also passed through the column.

257 In cartridge at

basic

experiments,

pH (8-9)

prepared

were

cartridges,

fibre.

The

five or ten litres of plutonium solution

pumped each

cartridges

through

one

were

two cylindrical

filled

with

connected

in

MnO 2

and

identically

impregnated

series

and

the

cotton

water

was

pumped through at flow rates between 6 and 24 litres per hour.

3.

RESULTS AND DISCUSSION

Prior

to the

manganese

dioxide

information reported

study

by

in

i.

the adsorption

flow

batch

in Table

of

systems

we

proceeded

equilibration We checked

of uranium to

and plutonium

obtain

experiments.

The

that an increase

preliminary results

changes

percentages by varying

influence

experiments

was

equilibrated

of

and

there were

to slightly

of

natural

studied.

with

uranium

uranium

on

Six solutions ranging

acid

no appreciable (8.7-4.0).

The

MnO 2

per litre.

the

logarithms

batch

of 200 ml,

0.2 g of MnO 2 at 27°C.

against

by

equilibration

each one containing

from 0.8 ~g to 8 mg at pH 8.7 were

of the uranium concentration

adsorbent

nanomoles

(75-92%)

the pH from basic

of natural

logarithms

high

The

of a pH lower than 4 has not yet been studied.

Adsorption

amounts

were

are

in the equilibration

time of more than an hour did not change the adsorbed percentages. adsorbed

on

of

In Figure

expressed the

2 are plotted

in nanomoles

solution

the

per gram

concentration

The results were adjusted by least squares

in

to the

Freundlich equation:

X = (0.76 ± 0.08) C (I'01 ± 0.02)

No saturation

of the 0.2 g of MnO 2 was obtained,

concentration

of uranium.

even with the highest

258 TABLE 1

A D S O R P T I O N OF ACTINIDES ON MnO 2 - BATCH EQUILIBRATION EXPERIMENTS

NUCLIDE

239pu

AMOUNT

VOLUME

(~g)

(ml)

MnO 2 (g)

7 x 10 -3

I00

0.17

pH

8.7

Temperature

Distribution

(°C)

Coef flclent*

20

Adsorbed Percentage (%)

0.2 x 104

80.0 ± 3**

238pu

3 × 10 -6

900

0.45

8.5

20

1.0 x 104

83.5 i 8

238pu

3 x 10 -6

900

0.45

4.5

21

0.8 x 104

80.0 ± 5

233U

7 × 10 -3

I00

0.17

8.7

20

1.1 x 104

95.0 ± 4

Natural U

0.86

200

0.20

8.8

27

0.3

x 10 4

76.0 ± 3

Natural U

1.69

200

0.20

8.7

27

0.5 x 104

83.0 ± 4

232U

9 x 10 -6

200

0.20

4.0

22

0.5 x lO 4

82.0 ± 3

230TU

7 x 10 -3

lO0

0.17

8.7

20

0.7 × 104

92.0 ± 5

*

Distribution coefficient given as percentage of nuclide adsorbed per g of MnO2/percentage of nuclide remaining in solution per ml of solution.

** Data given as X ± 1~.

TABLE 2

COLUMN A D S O R P T I O N OF URANIUM AND PLUTONIUM ON MnO 2 - TEMPERATURE N 22oc; COLUMN VOLUME ~ ii ml (1.5 g of COTTON FIBRE + 0.2 g OF MnO2);

NUCLIDE

RATE N 7 ml/min.

AMOUNT

SOLUTION

WASHING

(~g)

VOLUME

VOLUME

(ml)

(ml)

ADSORBED pH

PERCENTAGE (%)

232U

9 x 10 -6

50

250

9.0

73 ± 3*

2320

9 x 10 -6

50

250

3.7

86 ± 3

238pu

8 x 10 -6

50

250

8.9

67 ± 3

238pu

8 x 10 -6

50

250

9,0

61 ± 4

238pu

8 ~ 10 - 6

50

250

3,5

75 ± 5

238pu + 232U

(1 x I0-5) + (i x I0 -5)

50

250

9,0

(89 ± 3) + (73 ± 2)

238pu + 2330

(5 x 10 -6) + (i × 10 -2)

50

250

9.0

(72 ± 4) + (86 ± 4)

* Data given as X ± I~.

259

~m4 O

E ~

3

X O

-~ ~2

0

I 1

I 2

I 3 Log

Figure

2:

Adsorption

nanomoles

of

also

behaviour

studied

given

pH.

adsorption initial

the

adsorbed

with

yield

liquid on

The was

dioxide

retention

column elements

column results

from

volumes are

to be N

that

MnO 2 was

in the

first

the

was

shown

of

and

these

made

at

by by

for plutonium

but

percentage of

in

logarithms

of

plutonium

was

elements

at a

checking

the same 2.

50 ml

expressed

washing

Table

the

in

Plot of the

per litre.

column

of water

60%

the

uranium

the

found

liquid.

with

of solutions

showed

250 ml of washing

against

in nanomoles

fractions

the

concentration

on columns

these

several

solution.

adsorption of

of

of

on 0.2 g of MnO 2.

adsorbent

concentration

by passage

elution

of

I 6

(nmol/l)

uranium

of manganese

Analysis

possible

gram

I 5

uranium

the

per

the solution

The

C

of natural

logarithms

I 4

eluate

the

after

pH as the The

lowest

the analysis

of and

element not

not

in the

260 In MnO 2

our

experiments,

impregnated

Hashimoto

et

membrane precise

al

cotton (1985)

filters

the at

pH

is

4 while

the uranium

impregnated

chemical

uranium

with

efficiently in

showed

the no

method

adsorption

manganese

formula of both manganese

adsorbed

oxides.

dioxides

on

the

developed

by

tendency

on

However,

has not

the

yet

been

determined.

We

have

collection

also

from

experiments.

proceeded

larger

to

volumes

study of

the

efficiency

solutions

than

in

in

plutonium

the

previous

Two identically prepared cartridges, each one filled with

MnO 2 impregnated cotton, were connected in series and 5 or 10 litres of plutonium solutions were pumped through.

The cartridges were analysed

and we compared the real efficiency (known because the water solutions were

prepared with known amounts of radionuclide) with that determined

by using the following equation (Schell et al,

1972):

Activity of second cartridge Efficiency

=

i

Activity of first cartridge

This

equation

is very

useful

trations have to be measured. the

above

second

equation,

cartridges

the

is

of

the

significantly

first

and

sampling where

unknown

concen-

The results are shown in Table 3.

calculated

efficiency in the cartridges. efficiency

in field

efficiency higher

between

than

the

the

Using

first

measured

and

(real)

This is a consequence of the different second

cartridges.

From

experiments

8

and 9 of Table 3 and comparing with experiment I0, regarding the concentration,

it

can

be

observed

that

the

differences

in

the

261

TABLE 3

ADSORPTION

EXPERIMENT

OF PLUTONIUM

ON MnO 2 IMPREGNATED

CARTRIDGE

SOLUTION

DIAMETER

VOLUME

COTTON

CARTRIDGES

INITIAL

FLOW

ACTIVITY

RATE

CONNECTED

IN SERIES

MnO 2 CARTRIDGE

(g)

REAL EFFICIENCY

E = I -

2nd Ist

1

2

3

(mm)

(%)

(dpm 2 3 8 p u )

(%/h)

21

10

1000

12

21

25

10

10

4

25

I0

5

29

5

6

29

5

1000

100

1130

1000

I000

12

Ist

1.0

0.20

2nd

[.0

0.05

ist

1.0

0.20

2nd

1.0

0.04

1st

1.5

0.27

2nd

1.5

O. t I

6

1st

1.7

0.28

17

1st

1.5

0.27

2nd

1.5

0.16

6

22

Ist

1.5

0.28

2nd

1.5

0.17

7

29

5

I000

24

Ist

1.5

0.27

8

29

5

IOOO

23

ist

1.5

0.27

29

5

solution

23

Ist

1.5

0.16

23

Ist

1.5

0.27

from exp.8

10

29

5

700

0.80

0.84

0.77

0.57

0.58

262 efficiency second the

comes

cartridge

contrary,

value

from

of

the

fact

is affected

preliminary

about

80%

that

solution

by its passing

results

in

the

the

through

with uranium

collection

passing

through

the

the first one.

On

solutions

efficiency

showed

through

a high

only

one

cartridge.

4.

CONCLUSIONS

The

MnO 2 impregnated

adsorption

adsorption

tendency on varying

small

amount

According

by

has

been

proven

that there are not appreciable

of

MnO 2

amount of uranium without

element

fibre

valid

for

the

of uranium and plutonium from water samples.

It is noteworthy

A

cotton

to

passing

liquid

can

in

principle

adsorb

a

significant

saturation.

results

on the manganese at

in the

the pH from basic to acid (9-4).

experimental

is adsorbed

differences

the

same

it

seems

dioxide

conditions

that

once

the

radio-

it is not easily desorbed (pH,

temperature)

as

the

initial solution.

From

cartridge

influence

of

plutonium

or

plutonium explain

in the

efficiencies. has

only

the

information.

experiments

manganese on the

a

dioxide

with on

competition

adsorption

differences Similar trivalent

plutonium changes

of

processes found

experiments oxidation

some have

between carried state,

in

solutions, the

dissolved to be the out could

valence

with

possible state

manganese

studied

real

a

and

with

in order

to

calculated

americium,

provide

of

very

which useful

263

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direct water.

L.,

T.,

yon

Radium-Bariumsalzen

A

method

Instr. and Meth.,

K.

an

Kolloidalem

Z. Anorg. Allgem. Chem., 84, 77-91.

1984.

Nucl.

Hashimoto,

Uber die "fraktionierte Adsorption" und

Desadsorption"

Mangamsuperoxydht drat.

Hallstadius,

1913.

Satoh

and

M.

for

the

electrodeposition

of

223, 266-267.

Aoyagi,

1985.

Simple

collection

and

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1984.

In situ chemisorption

Instr. and Meth.

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Moore,

W.S.

and L.M.

Cook,

1975.

Radium removal from drinking water.

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W.S.

and

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J.M.

Edmond,

1984.

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Barium

1972.

Natural 210pb and 210po in

In Proceeding of IAEA Symposium on the Interaction

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with

Constituents

of

the Marine

Environ-

ment, July 10-14, 1972, Seattle, Washington.

Wong,

K.M.,

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G.S.

Brown and V.E. Noshkin,

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in

large

volumes

manganese dioxide coprecipitation.

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A rapid procedure for and

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by