UPTAKE OF VARIOUS RADIONUCLIDES BY HYDROTHERMALLY PREPARED MOLYBDENUM PHOSPHATES

• Published in: Separation science and technology Vol. 36; no. 5-6; pp. 885 - 897
• Main Authors: Möller, T., Harjula, R.
• Format: Journal Article
• Language: English
• Published: Taylor & Francis Group 30-06-2001
• ISSN: 0149-6395; 1520-5754
• DOI: 10.1081/SS-100103626

A series of molybdenum phosphates with three different structures were synthesized hydrothermally. The types include a one-dimensional polymer, (PPh
4
)
2
[(H
3
O)
2
NaMo
6
P
4
O
24
(OH)
7
]·5H
2
O; a microporous material with a framework structure, (TMA)
2
(NH
4
)
2
[Fe
2
Mo
12
O
30
(H
2
PO
4
)
6
(HPO
4
)
2
]·nH
2
O; and three compounds with layered structures, [N(C
3
H
7
)
4
(NH
4
)][(MoO)
4
O
4
(PO
4
)
2
], KMo(H
2
O)O
2
PO
4
, and NH
4
Mo(H
2
O)O
2
PO
4
. These compounds were tested for their ability to remove the radionuclides commonly found in nuclear waste solutions (
85
Sr,
134
Cs,
57
Co,
65
Zn,
59
Fe,
54
Mn,
51
Cr,
110
Ag,
236
Pu, and
241
Am). Experiments were carried out to determine the distribution coefficients (K
D
s) of the radionuclides in several "model" solutions (0.1 M HNO
3
, 0.1 M NaNO
3
, 0.1 M NaNO
3
/0.1 M NaOH). A well-known ammonium 12-molybdophosphate (AMP), prepared by cold synthesis, was tested in parallel for reference in acidic media. Of the tested materials, ferric molybdenum phosphate took up several radionuclides rather well in neutral and alkaline conditions and was selective for
241
Am in 0.1 M HNO
3
(K
D
= 2140mL/g). The hydrothermally prepared NH
4
MoPO was very selective for
134
Cs, having a K
D
of 23,400 mL/g in 0.1 MHNO
3
, about half of that of AMP (44,000 mL/g). Sodium molybdenum phosphate took up both
236
Pu and
241
Am in 0.1 M HNO
3
well, the K
D
s being 3350 and 8600 mL/g, respectively. Otherwise, the materials took up few of the tested radionuclides selectively as the K
D
s were usually below 1000 mL/g.