Novel Purification Method for Isotopically Enriched Molybdenum and Determination of Its Mass Fractionation Effect†

doi:10.7503/cjcu20140631

Abstract

Abstract:

A novel purification method for isotopically enriched molybdenum was established according to the differences in sublimation temperature of MoO₃ comparing with other species. The oxidation time, sample volume and sublimation temperature in this procedure were optimized using Synthetic-Mo with nature Mo compositions. As measured by HR-ICP-MS, Mo could be effectively separated from other matrix elements, and the purities of ⁹⁵Mo and ⁹⁸Mo were 99.992% and 99.990%, respectively, after purification. Isotopic compositions of Synthetic-Mo and Purified-MoO₃ samples were determined by MC-ICP-MS, their $δ X / 95$ Mo(X=92, 94, 97, 98, 100)values were indistinguishable within analytical uncertainty(<0.3‰), revealing that isotopic fractionation of Mo was unlikely during purification. The proposed purification method is of great importance in developing high-accuracy measurement method for isotopic compositions of Mo.

Key words: Isotopically enriched molybdenum, Purification, Mass fractionation

CLC Number:

O658

TrendMD:

SONG Panshu, WANG Jun, REN Tongxiang, ZHOU Tao, LU Hai. Novel Purification Method for Isotopically Enriched Molybdenum and Determination of Its Mass Fractionation Effect^†[J]. Chem. J. Chinese Universities, 2015, 36(2): 248.

Figures/Tables 8

Fig.1 Vacuum sublimation device with quartz boat(a), sample collection tube(ϕ 14 mm×80 mm)(b) and quartz tube(ϕ 18 mm×550 mm)(c)

Table 1 Measurement conditions of Mo isotope ratios with MC-ICP-MS

RF power/W	1310
Ar cooling gas flow rate/(L·min^-1)	13.2
Intermediate gas flow rate/(L·min^-1)	1.05
Nebulization gas flow rate/(L·min^-1)	0.66
Collision gas flow rate/(mL·min^-1)	Ar 2.4
Sample cone	Ni sampler cone
Skimmer cone	Ni skimmer cone
Sample uptake rate/(mL·min^-1)	0.2
Mass resolution	450
Cup configuration	L3	L2	AX	H1	H2	H3	H4	H5	H6
	⁹⁰Zr	⁹²Mo	⁹⁴Mo	⁹⁵Mo	⁹⁶Mo	⁹⁷Mo	⁹⁸Mo	⁹⁹Ru+⁹⁹Tc	¹⁰⁰Mo

Table 2 Main impurities in 95Mo and 98Mo

Sample	Amount of impurities/(μg·g^-1)
Sample	Na	Si	K	Al	Fe	Ni	Cu	W
⁹⁵Mo	89.6	87.2	55.2	4.6	6.6	20.9	0.9	18.7
⁹⁸Mo	85.5	95.1	9.3	21.3	165.3	526.6	4.6	1.8

Table 3 Main impurities in Synthetic-Mo/Purified-MoO3 and recovery of various evaporation temperatures

Sample	t/℃	Amount of impurities/(μg·g^-1)								Recovery(%)^b
Sample	t/℃	Na		Si	K	Al	Fe	Ni	Cu	W
Synthetic-Mo	600	205.7	73.5	12.3	88.6	145.3	136.6	142.5	162.0
Purified-MoO₃	600	5.1	$a$	0.3			2.9	1.4	45.9	87.7±1.4
Purified-MoO₃	625	7.9		3.7		0.7	2.5	3.9	81.2	88.3±1.2
Purified-MoO₃	675	8.7	12.5	3.6			3.1	7.3	93.0	87.5±1.5
Purified-MoO₃	720			2.3			0.9	14.3	161.4	86.5±1.7

Table 3 Main impurities in Synthetic-Mo/Purified-MoO3 and recovery of various evaporation temperatures

Sample	t/℃	Amount of impurities/(μg·g^-1)								Recovery(%)^b
Sample	t/℃	Na		Si	K	Al	Fe	Ni	Cu	W
Synthetic-Mo	600	205.7	73.5	12.3	88.6	145.3	136.6	142.5	162.0
Purified-MoO₃	600	5.1	$a$	0.3			2.9	1.4	45.9	87.7±1.4
Purified-MoO₃	625	7.9		3.7		0.7	2.5	3.9	81.2	88.3±1.2
Purified-MoO₃	675	8.7	12.5	3.6			3.1	7.3	93.0	87.5±1.5
Purified-MoO₃	720			2.3			0.9	14.3	161.4	86.5±1.7

Fig.2 ESR analysis of Purified-MoO3(a) and Synthetic-MoO3(b) powders at room temperature

Fig.3 Logarithmic plots of 100Mo/95Mo against 98Mo/95Mo(A) and 100Mo/95Mo against 97Mo/95Mo(B)

Fig.4 δX/95Mo values for Purified-MoO3 relative to Synthetic-Mo solution

Table 4 Main impurities and recovery of purified 95Mo and 98Mo

Sample	Amount of impurities/(μg·g^-1)								Recovery(%)^b
Sample	Na		Si	K	Al	Fe	Ni	Cu	W
Purified ⁹⁵Mo	7.8	17.7	1.3	$a$	0.5	1.8	0.3	16.5	89.6±0.8
Purified ⁹⁸Mo	6.6		2.2	0.4		2.4	2.0	1.6	86.7±0.3

Table 4 Main impurities and recovery of purified 95Mo and 98Mo

Sample	Amount of impurities/(μg·g^-1)								Recovery(%)^b
Sample	Na		Si	K	Al	Fe	Ni	Cu	W
Purified ⁹⁵Mo	7.8	17.7	1.3	$a$	0.5	1.8	0.3	16.5	89.6±0.8
Purified ⁹⁸Mo	6.6		2.2	0.4		2.4	2.0	1.6	86.7±0.3

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