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Metal corrosion studies with the fluorosulphonic acid–antimony pentafluoride superacid system
Journal of Alloys and Compounds 365 (2004) 134–137
Metal corrosion studies with the fluorosulphonic acid–antimony pentafluoride superacid system P. Gary Eller a , Richard J. Kissane b , Kent D. Abney c , Larry R. Avens a , Scott A. Kinkead d , Robert J. Hanrahan e,∗ a
Nuclear Materials Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87544, USA Environmental, Safety, and Health Division, Los Alamos National Laboratory, Los Alamos, NM 87544, USA c Chemical Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87544, USA d Dynamic Experimentation Division, Los Alamos National Laboratory, Los Alamos, NM 87544, USA Materials Science and Technology Division, MST-6, Los Alamos National Laboratory, Los Alamos, NM 87545, USA b
e
Received 9 September 2002; received in revised form 26 May 2003; accepted 26 May 2003
Abstract Because of their rapid dissolution of many actinide metals and refractory oxides, superacids such as HSO3 F/SbF5 have potential applications in actinide processing. However, material compatibility must first be addressed because of the highly corrosive nature of superacids. This paper describes the qualitative rates of attack of fluorosulphonic acid–antimony pentafluoride superacid on a variety of metal substrates relevant to nuclear processing. Published by Elsevier B.V. Keywords: Actinide alloys; Nuclear reactor materials; Corrosion
1. Introduction Superacids are substances with acidities greater than that of anhydrous perchloric acid [1]. The strongest superacids are derived by combining a powerful nonaqueous protonic acid such as HF or HSO3 F with a strong Lewis acid such as SbF5 or AsF5 . Such combinations can increase the proton acidity by six or more orders of magnitude and often lead to unusual chemical activity. For instance, superacids have been used to stabilize highly electrophilic cations such as S2+ 4 and tertiary carbocations in solution. Recently it has been shown that actinide metals and oxides, including some processing residues which normally are highly intractable, readily dissolve in AsF5 - and SbF5 -based superacids to give solutions as concentrated as 0.5 M in actinide ion [2–7]. In addition to having relevance for actinide recovery and analytical applications, this property also suggests the potential utility of superacids for actinide decontamination purposes.
In this paper we describe metal corrosion experiments related to such purposes with 25% SbF5 /HSO3 F, one of the very strongest superacids. The fluorosulphonic acid-based system is particularly attractive in an applied sense since its compatibility with glass, commercial availability, and low vapor pressure make handling very convenient relative to HF-based superacids.
2. Experimental 2.1. Materials Fluorosulphonic acid was used as received from Aldrich. Twenty-five mol.% SbF5 /HSO3 F (‘Magic Acid’) was used as received from Aldrich or produced by mixing SbF5 (Aldrich or Ozark-Mahoning/ATO) and HSO3 F in the desired proportions in a drybox. 2.2. Metal coupon experiments
∗
Corresponding author. Fax: +1-505-667-5268. E-mail address: [email protected] (R.J. Hanrahan).
0925-8388/$ – see front matter. Published by Elsevier B.V. doi:10.1016/S0925-8388(03)00646-7
Generally, metal coupons for superacid treatment with ∼1 cm2 total geometrical surface area were cut from locally
P.G. Eller et al. / Journal of Alloys and Compounds 365 (2004) 134–137
available high purity metal sheet. For some metals (e.g. Ca, Mg), foil or sheet forms were not available and therefore other metallic forms were used, as indicated in Table 1. No polishing or any other control of surface finish was employed, so the results obtained must be regarded as only qualitative. The individual preweighed metal coupons were placed in PyrexTM glass tubes containing a small TeflonTM -coated stirring bar, ∼3 ml of 25% SbF5 /HSO3 F were added, the tube was sealed, and the mixture was agitated gently for 1 h. The coupons were then removed from the superacid solution, washed with water, air dried, and reweighed. Afterwards, the coupons were returned to the superacid solutions and heated at 94 ◦ C for an additional hour by immersion of the tube in a boiling water bath. The coupons were then again removed, washed, dried, and weighed. Runs at ∼155 ◦ C (the boiling point of 25% SbF5 /HSO3 F) were carried out similarly, using an oil bath as a heat source. 2.3. Dissolution of plutonium oxide (PuO2 ) In a glovebox designed and equipped for handling transuranics, 200 mg (1.355 mmol) of low-fired PuO2 and 9.23 g (4.4 ml) of 25 mol.% Magic Acid were added to a tared 1/2 in. O.D. PyrexTM glass tube fitted with a glass seal (Fischer-Porter Solv-sealTM ). The tube was heated in an oven to ∼125 ◦ C for 2 h. At the solid–liquid interface, the solid turned from dark brown to pink, similar in appearance to PuF4 . In a few minutes, the solution began to turn brown. After about 8 h of heating, all of the solid had dissolved, yielding a deep brown solution with a UV–Vis-NIR absorption spectrum indicative of Pu(IV).
3. Results and discussion Tables 1 and 2 summarize the qualitative metal corrosion experiments using 25% SbF5 /HSO3 F at 25, 94, and 155 ◦ C. In considering the results, it should be kept in mind that for those cases where substantial reaction occurred, an appreciable fraction of the superacid was consumed and consequently, a large depression of acidity occurred. In addition, in some cases the final product was a rather viscous suspension. These effects no doubt limited the rate and extent of attack on the more reactive metal substrates, therefore the weight losses given in Table 1 for the more reactive metals would undoubtedly be higher for higher initial superacid/metal ratios than might be inferred from Table 1. Not surprisingly, most of the platinum-group metals are essentially inert to 25% SbF5 /HSO3 F under the conditions of our experiments. The exception is iridium, which is attacked slowly at elevated temperature. The lanthanide (Pr, Gd, and Lu) metals are attacked aggressively at room temperature.
135
In contrast, the actinide metals tested (Th, U, Np, Pu) are relatively inert except when exposed as high surface-area turnings. As observed with the powerful superacid HF/SbF35 , thorium metal is essentially unaffected at room temperature by 25% SbF5 /HSO3 F. Aluminum, molybdenum, Zircalloy II, and Hastelloy C-22, are essentially unaffected by Magic Acid even at elevated temperatures. However, most other common metals of construction are attacked at moderate to rapid rates. Other metals in Table 1 are attacked at highly variable rates that do not correlate in an obvious way with the usual chemical reactivity of the metals. For example, lead, silver, and copper are attacked aggressively while beryllium and titanium are unaffected at room temperature. Molybdenum is relatively inert, even in refluxing superacid, which may explain the resistance of Hastelloy C-22 (21% Cr, 13% Mo, 66% Ni) and the much greater corrosion rate of 304 stainless steel versus 316 stainless steel. The stainless compositions are quite similar except for the presence of 2–3% Mo in the 316 variety. Formation of insoluble surface complexes undoubtedly plays a role in limiting the extent of superacid attack on the metal surfaces. This was visually evident—especially in the case of Hastelloy C-22—as a clear lacquer-like film on the metal coupon when removed from the superacid. This film deliquesced on exposure to moist air for a few days. Common glass (quartz and PyrexTM ) and fluoropolymers (TeflonTM , FEP, PFA, and Kel-F) are not attacked at a significant rate even at elevated temperatures, which allowed these materials to be used as vessels and apparatus in this series of experiments For some active metals (e.g. Mg, Np, and Pu), initial gas evolution was observed which diminished quickly. In only one case was massive gas evolution observed. This result suggests that SbF5 is the net oxidant—rather than protons or H2 F+ —and that strong hydrogen evolution does not generally occur. Of course, this does not exclude the possibility that the metal surface is attacked by protons and the generated hydrogen is immediately oxidized by SbF5 . With highly active metals (e.g. alkaline earth and lanthanide metals), intensely colored blue or purple solutions were sometimes observed when rapid corrosion occurred. In the exposure of calcium at room temperature, rapid reaction and gas evolution was observed. The color of the solution in this case (indigo blue) was determined to be due to the formation of S2+ 8 —via reduction of HSO3 F—was verified by the close match of the UV–Vis spectrum of the blue solution with that reported [8]. The gas evolved by the reaction of Ca with Magic Acid was most likely a mixture of hydrogen and HF judging by the effect on the drybox atmosphere. The extent of reaction in this case was clearly limited by the quantity of acid available to react with the metal. Neither the blue solution nor the vigorous reaction was observed, even at 155 ◦ C, when calcium possessing an intact surface oxide layer was exposed to the superacid.
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P.G. Eller et al. / Journal of Alloys and Compounds 365 (2004) 134–137
Table 1 Summary of corrosion tests of pure elements Metal
% Weight loss 25 ◦ C, 1 h
% Weight loss 94 ◦ C, 1 h
Final appearance
Platinum group metals Pt Au Ir Ag Rh Pd Ru (sintered lump)
<0.1 <0.1 <0.1 19.9 <0.1 <0.1 <0.1
<0.1 <0.1 1.4 44.2 <0.1 <0.1 <0.1
Light tan solution; shiny metal Slight tarnishing of metal; light brown solution Tarnished metal; light brown solution Purple solution; dull gray metal Medium brown solution; shiny metal Peach colored solution; shiny metal with black sheen No reaction observed
Lanthanide metals Pr (ingot) Gd (ingot) Lu (ingot)
17.0 26.1 8.98
20.8 30.9 41.8
Dark gray suspension; gray–black metal Blue–gray suspension; gray metal Dark blue–green solution; flat black metal
Actinide metals Th (ingot) U (rod) U (turning) Np (turning) Pu/Ga alloy (turning)
0.38 <0.1 17.5 16.8 14.3
27.9 2.68 100 >95 >95
Dark purple solution; dull gray metal Deep purple solution; dull gray metal Blue–gray suspension Lavender-green solution Blue–green solution
Construction metals SS304 SS316 Cu Ni Al Hastelloy C-22 Mild steel Brass Zircalloy II
24.0 1.0 100 5.8 <0.1 <0.1 1.85 14.7 <0.1
100 31.2 100 98.0 0.15 0.23 5.33 21.9 <0.1
Blue–black solution; minor dark residue Dark green solution; dull metal Dark purple solution Dark green solution; dull metal Light brown solution; dull gray metal Light brown solution; shiny metal Purple solution; flat gray metal Viscous gray suspension; dull brown metal Light brown solution; shiny metal
Other metals Pb Mo Ti Be Cr (shot) Ta Nb Ca (chunks) Mg W Ga
11.6 <0.1 <0.1 <0.1 1.72 <0.1 0.3 21.4 2.70 <0.1 0.2
68.5 <0.1 59 4.7 43.5 6.40 2.1 100 17.6 <0.1 ∼60
Chalky blue–gray solution; dull pitted metal Light tan solution; shiny metal Blue–green solution; highly pitted metal Light brown solution; dull gray metal Black solution; dull gray metal Light brown solution; medium brown metal Turbid medium yellow solution; dull gray metal Deep purple solution Purple–black solution; flat-gray metal Colorless solution; shiny metal a
a
Gray suspension. After centrifuging and washing, a mixture of a black–brown powder (minor) and shiny metal (major) was recovered. The final % weight change is not very accurate.
Results of a limited number of plutonium coupon decontamination experiments show that 25% HSO3 F/SbF5 is an effective agent for removing plutonium contamination from type 316 stainless steel. In initial experiments at room temperature, 98% or greater plutonium removal in single treatments was observed. The obvious mechanism of removal is a combination of direct plutonium compound dissolution and attack on the metal substrate. Superacid decontamination should also be effective with other substrate metals examined in this study, including those that are not attacked aggressively by the superacid.
4. Summary The susceptibility to attack of a variety of metals pertinent to nuclear materials processing by the strong superacid 25% SbF5 /HSO3 F has been studied. When combined with evolving information on dissolution rates of refractory actinide oxides and other substrates, the information from the present study provides an initial database for considering possible radionuclide decontamination, analytical chemistry, and recovery processes using this superacid system.
P.G. Eller et al. / Journal of Alloys and Compounds 365 (2004) 134–137
137
Table 2 Corrosion results in refluxing 25% Magic Acid Metal
% Weight loss 155 ◦ C, 1 h
Final appearance
Pt Ir Au Al W Mo Hastelloy C-22 Ru Pd Rh Zircalloy II Be
0.3 1.5 <0.1 <0.1 5.5 7.8 0.7 <0.1 10.4 <0.1 0.7 45.5
Light brown solution; shiny metal Light brown solution; shiny metal Light brown solution; shiny metal Turbid white solution; shiny metal Turbid light gold solution; dull gray pitted metal Turbid deep gold solution; dull gray metal with blue coating Very turbid white solution; shiny metal with clear coating Amber solution, shiny metal Purple solution; dull charcoal gray metal Light brown solution, shiny metal Light brown solution; shiny metal Purple solution; flat black metal
References [1] G.A. Olah, G.K.S. Prakash, J. Sommer, in: Superacids, John Wiley, New York, 1985; T.A. O’Donnell, Chem. Rev. 6 (1987) 1; R.J. Gillespie, J. Liang, J. Am. Chem. Soc. 110 (1988) 6053. [2] L.R. Avens, P.G. Eller, L.B. Asprey, K.D. Abney, S.A. Kinkead, J. Radioanal. Nucl. Chem. 123 (1988) 707. [3] K.D. Abney, P.G. Eller, L.R. Avens, P.G. Eller, in preparation. [4] M. Baluka, N. Edelstein, T.A. O’Donnell, Inorg. Chem. 20 (1981) 3279. [5] J.H. Holloway, D. Laycock, J. Chem. Soc. Dalton 20 (1983) 2303;
R. Bougon, J. Fawcett, J.H. Holloway, D.R. Russell, in: J. Chem. Soc. Dalton, Vol. 20, 1979, p. 1881; J.H. Holloway, D. Laycock, R. Bougon, in: J. Chem. Soc. Dalton, 1982, p. 1635; J. Fawcett, J.H. Holloway, D. Laycock, D.R. Russell, in: J. Chem. Soc. Dalton, 1982, p. 1355; R. Bougon, J. Fawcett, J.H. Holloway, D.R. Russell, CR Acad. Sci. Paris 287C (1978) 423. [6] M. Tarnero, CEA-R-3205 Report, 1967. [7] T.A. O’Donnell, unpublished results. [8] R.J. Gillespie, J. Passmore, Homopolyatomic cations of the elements, Adv. Inorg. Chem. Radiochem. 17 (1975) 49.
Metal corrosion studies with the fluorosulphonic acid–antimony pentafluoride superacid system P. Gary Eller a , Richard J. Kissane b , Kent D. Abney c , Larry R. Avens a , Scott A. Kinkead d , Robert J. Hanrahan e,∗ a
Nuclear Materials Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87544, USA Environmental, Safety, and Health Division, Los Alamos National Laboratory, Los Alamos, NM 87544, USA c Chemical Science and Technology Division, Los Alamos National Laboratory, Los Alamos, NM 87544, USA d Dynamic Experimentation Division, Los Alamos National Laboratory, Los Alamos, NM 87544, USA Materials Science and Technology Division, MST-6, Los Alamos National Laboratory, Los Alamos, NM 87545, USA b
e
Received 9 September 2002; received in revised form 26 May 2003; accepted 26 May 2003
Abstract Because of their rapid dissolution of many actinide metals and refractory oxides, superacids such as HSO3 F/SbF5 have potential applications in actinide processing. However, material compatibility must first be addressed because of the highly corrosive nature of superacids. This paper describes the qualitative rates of attack of fluorosulphonic acid–antimony pentafluoride superacid on a variety of metal substrates relevant to nuclear processing. Published by Elsevier B.V. Keywords: Actinide alloys; Nuclear reactor materials; Corrosion
1. Introduction Superacids are substances with acidities greater than that of anhydrous perchloric acid [1]. The strongest superacids are derived by combining a powerful nonaqueous protonic acid such as HF or HSO3 F with a strong Lewis acid such as SbF5 or AsF5 . Such combinations can increase the proton acidity by six or more orders of magnitude and often lead to unusual chemical activity. For instance, superacids have been used to stabilize highly electrophilic cations such as S2+ 4 and tertiary carbocations in solution. Recently it has been shown that actinide metals and oxides, including some processing residues which normally are highly intractable, readily dissolve in AsF5 - and SbF5 -based superacids to give solutions as concentrated as 0.5 M in actinide ion [2–7]. In addition to having relevance for actinide recovery and analytical applications, this property also suggests the potential utility of superacids for actinide decontamination purposes.
In this paper we describe metal corrosion experiments related to such purposes with 25% SbF5 /HSO3 F, one of the very strongest superacids. The fluorosulphonic acid-based system is particularly attractive in an applied sense since its compatibility with glass, commercial availability, and low vapor pressure make handling very convenient relative to HF-based superacids.
2. Experimental 2.1. Materials Fluorosulphonic acid was used as received from Aldrich. Twenty-five mol.% SbF5 /HSO3 F (‘Magic Acid’) was used as received from Aldrich or produced by mixing SbF5 (Aldrich or Ozark-Mahoning/ATO) and HSO3 F in the desired proportions in a drybox. 2.2. Metal coupon experiments
∗
Corresponding author. Fax: +1-505-667-5268. E-mail address: [email protected] (R.J. Hanrahan).
0925-8388/$ – see front matter. Published by Elsevier B.V. doi:10.1016/S0925-8388(03)00646-7
Generally, metal coupons for superacid treatment with ∼1 cm2 total geometrical surface area were cut from locally
P.G. Eller et al. / Journal of Alloys and Compounds 365 (2004) 134–137
available high purity metal sheet. For some metals (e.g. Ca, Mg), foil or sheet forms were not available and therefore other metallic forms were used, as indicated in Table 1. No polishing or any other control of surface finish was employed, so the results obtained must be regarded as only qualitative. The individual preweighed metal coupons were placed in PyrexTM glass tubes containing a small TeflonTM -coated stirring bar, ∼3 ml of 25% SbF5 /HSO3 F were added, the tube was sealed, and the mixture was agitated gently for 1 h. The coupons were then removed from the superacid solution, washed with water, air dried, and reweighed. Afterwards, the coupons were returned to the superacid solutions and heated at 94 ◦ C for an additional hour by immersion of the tube in a boiling water bath. The coupons were then again removed, washed, dried, and weighed. Runs at ∼155 ◦ C (the boiling point of 25% SbF5 /HSO3 F) were carried out similarly, using an oil bath as a heat source. 2.3. Dissolution of plutonium oxide (PuO2 ) In a glovebox designed and equipped for handling transuranics, 200 mg (1.355 mmol) of low-fired PuO2 and 9.23 g (4.4 ml) of 25 mol.% Magic Acid were added to a tared 1/2 in. O.D. PyrexTM glass tube fitted with a glass seal (Fischer-Porter Solv-sealTM ). The tube was heated in an oven to ∼125 ◦ C for 2 h. At the solid–liquid interface, the solid turned from dark brown to pink, similar in appearance to PuF4 . In a few minutes, the solution began to turn brown. After about 8 h of heating, all of the solid had dissolved, yielding a deep brown solution with a UV–Vis-NIR absorption spectrum indicative of Pu(IV).
3. Results and discussion Tables 1 and 2 summarize the qualitative metal corrosion experiments using 25% SbF5 /HSO3 F at 25, 94, and 155 ◦ C. In considering the results, it should be kept in mind that for those cases where substantial reaction occurred, an appreciable fraction of the superacid was consumed and consequently, a large depression of acidity occurred. In addition, in some cases the final product was a rather viscous suspension. These effects no doubt limited the rate and extent of attack on the more reactive metal substrates, therefore the weight losses given in Table 1 for the more reactive metals would undoubtedly be higher for higher initial superacid/metal ratios than might be inferred from Table 1. Not surprisingly, most of the platinum-group metals are essentially inert to 25% SbF5 /HSO3 F under the conditions of our experiments. The exception is iridium, which is attacked slowly at elevated temperature. The lanthanide (Pr, Gd, and Lu) metals are attacked aggressively at room temperature.
135
In contrast, the actinide metals tested (Th, U, Np, Pu) are relatively inert except when exposed as high surface-area turnings. As observed with the powerful superacid HF/SbF35 , thorium metal is essentially unaffected at room temperature by 25% SbF5 /HSO3 F. Aluminum, molybdenum, Zircalloy II, and Hastelloy C-22, are essentially unaffected by Magic Acid even at elevated temperatures. However, most other common metals of construction are attacked at moderate to rapid rates. Other metals in Table 1 are attacked at highly variable rates that do not correlate in an obvious way with the usual chemical reactivity of the metals. For example, lead, silver, and copper are attacked aggressively while beryllium and titanium are unaffected at room temperature. Molybdenum is relatively inert, even in refluxing superacid, which may explain the resistance of Hastelloy C-22 (21% Cr, 13% Mo, 66% Ni) and the much greater corrosion rate of 304 stainless steel versus 316 stainless steel. The stainless compositions are quite similar except for the presence of 2–3% Mo in the 316 variety. Formation of insoluble surface complexes undoubtedly plays a role in limiting the extent of superacid attack on the metal surfaces. This was visually evident—especially in the case of Hastelloy C-22—as a clear lacquer-like film on the metal coupon when removed from the superacid. This film deliquesced on exposure to moist air for a few days. Common glass (quartz and PyrexTM ) and fluoropolymers (TeflonTM , FEP, PFA, and Kel-F) are not attacked at a significant rate even at elevated temperatures, which allowed these materials to be used as vessels and apparatus in this series of experiments For some active metals (e.g. Mg, Np, and Pu), initial gas evolution was observed which diminished quickly. In only one case was massive gas evolution observed. This result suggests that SbF5 is the net oxidant—rather than protons or H2 F+ —and that strong hydrogen evolution does not generally occur. Of course, this does not exclude the possibility that the metal surface is attacked by protons and the generated hydrogen is immediately oxidized by SbF5 . With highly active metals (e.g. alkaline earth and lanthanide metals), intensely colored blue or purple solutions were sometimes observed when rapid corrosion occurred. In the exposure of calcium at room temperature, rapid reaction and gas evolution was observed. The color of the solution in this case (indigo blue) was determined to be due to the formation of S2+ 8 —via reduction of HSO3 F—was verified by the close match of the UV–Vis spectrum of the blue solution with that reported [8]. The gas evolved by the reaction of Ca with Magic Acid was most likely a mixture of hydrogen and HF judging by the effect on the drybox atmosphere. The extent of reaction in this case was clearly limited by the quantity of acid available to react with the metal. Neither the blue solution nor the vigorous reaction was observed, even at 155 ◦ C, when calcium possessing an intact surface oxide layer was exposed to the superacid.
136
P.G. Eller et al. / Journal of Alloys and Compounds 365 (2004) 134–137
Table 1 Summary of corrosion tests of pure elements Metal
% Weight loss 25 ◦ C, 1 h
% Weight loss 94 ◦ C, 1 h
Final appearance
Platinum group metals Pt Au Ir Ag Rh Pd Ru (sintered lump)
<0.1 <0.1 <0.1 19.9 <0.1 <0.1 <0.1
<0.1 <0.1 1.4 44.2 <0.1 <0.1 <0.1
Light tan solution; shiny metal Slight tarnishing of metal; light brown solution Tarnished metal; light brown solution Purple solution; dull gray metal Medium brown solution; shiny metal Peach colored solution; shiny metal with black sheen No reaction observed
Lanthanide metals Pr (ingot) Gd (ingot) Lu (ingot)
17.0 26.1 8.98
20.8 30.9 41.8
Dark gray suspension; gray–black metal Blue–gray suspension; gray metal Dark blue–green solution; flat black metal
Actinide metals Th (ingot) U (rod) U (turning) Np (turning) Pu/Ga alloy (turning)
0.38 <0.1 17.5 16.8 14.3
27.9 2.68 100 >95 >95
Dark purple solution; dull gray metal Deep purple solution; dull gray metal Blue–gray suspension Lavender-green solution Blue–green solution
Construction metals SS304 SS316 Cu Ni Al Hastelloy C-22 Mild steel Brass Zircalloy II
24.0 1.0 100 5.8 <0.1 <0.1 1.85 14.7 <0.1
100 31.2 100 98.0 0.15 0.23 5.33 21.9 <0.1
Blue–black solution; minor dark residue Dark green solution; dull metal Dark purple solution Dark green solution; dull metal Light brown solution; dull gray metal Light brown solution; shiny metal Purple solution; flat gray metal Viscous gray suspension; dull brown metal Light brown solution; shiny metal
Other metals Pb Mo Ti Be Cr (shot) Ta Nb Ca (chunks) Mg W Ga
11.6 <0.1 <0.1 <0.1 1.72 <0.1 0.3 21.4 2.70 <0.1 0.2
68.5 <0.1 59 4.7 43.5 6.40 2.1 100 17.6 <0.1 ∼60
Chalky blue–gray solution; dull pitted metal Light tan solution; shiny metal Blue–green solution; highly pitted metal Light brown solution; dull gray metal Black solution; dull gray metal Light brown solution; medium brown metal Turbid medium yellow solution; dull gray metal Deep purple solution Purple–black solution; flat-gray metal Colorless solution; shiny metal a
a
Gray suspension. After centrifuging and washing, a mixture of a black–brown powder (minor) and shiny metal (major) was recovered. The final % weight change is not very accurate.
Results of a limited number of plutonium coupon decontamination experiments show that 25% HSO3 F/SbF5 is an effective agent for removing plutonium contamination from type 316 stainless steel. In initial experiments at room temperature, 98% or greater plutonium removal in single treatments was observed. The obvious mechanism of removal is a combination of direct plutonium compound dissolution and attack on the metal substrate. Superacid decontamination should also be effective with other substrate metals examined in this study, including those that are not attacked aggressively by the superacid.
4. Summary The susceptibility to attack of a variety of metals pertinent to nuclear materials processing by the strong superacid 25% SbF5 /HSO3 F has been studied. When combined with evolving information on dissolution rates of refractory actinide oxides and other substrates, the information from the present study provides an initial database for considering possible radionuclide decontamination, analytical chemistry, and recovery processes using this superacid system.
P.G. Eller et al. / Journal of Alloys and Compounds 365 (2004) 134–137
137
Table 2 Corrosion results in refluxing 25% Magic Acid Metal
% Weight loss 155 ◦ C, 1 h
Final appearance
Pt Ir Au Al W Mo Hastelloy C-22 Ru Pd Rh Zircalloy II Be
0.3 1.5 <0.1 <0.1 5.5 7.8 0.7 <0.1 10.4 <0.1 0.7 45.5
Light brown solution; shiny metal Light brown solution; shiny metal Light brown solution; shiny metal Turbid white solution; shiny metal Turbid light gold solution; dull gray pitted metal Turbid deep gold solution; dull gray metal with blue coating Very turbid white solution; shiny metal with clear coating Amber solution, shiny metal Purple solution; dull charcoal gray metal Light brown solution, shiny metal Light brown solution; shiny metal Purple solution; flat black metal
References [1] G.A. Olah, G.K.S. Prakash, J. Sommer, in: Superacids, John Wiley, New York, 1985; T.A. O’Donnell, Chem. Rev. 6 (1987) 1; R.J. Gillespie, J. Liang, J. Am. Chem. Soc. 110 (1988) 6053. [2] L.R. Avens, P.G. Eller, L.B. Asprey, K.D. Abney, S.A. Kinkead, J. Radioanal. Nucl. Chem. 123 (1988) 707. [3] K.D. Abney, P.G. Eller, L.R. Avens, P.G. Eller, in preparation. [4] M. Baluka, N. Edelstein, T.A. O’Donnell, Inorg. Chem. 20 (1981) 3279. [5] J.H. Holloway, D. Laycock, J. Chem. Soc. Dalton 20 (1983) 2303;
R. Bougon, J. Fawcett, J.H. Holloway, D.R. Russell, in: J. Chem. Soc. Dalton, Vol. 20, 1979, p. 1881; J.H. Holloway, D. Laycock, R. Bougon, in: J. Chem. Soc. Dalton, 1982, p. 1635; J. Fawcett, J.H. Holloway, D. Laycock, D.R. Russell, in: J. Chem. Soc. Dalton, 1982, p. 1355; R. Bougon, J. Fawcett, J.H. Holloway, D.R. Russell, CR Acad. Sci. Paris 287C (1978) 423. [6] M. Tarnero, CEA-R-3205 Report, 1967. [7] T.A. O’Donnell, unpublished results. [8] R.J. Gillespie, J. Passmore, Homopolyatomic cations of the elements, Adv. Inorg. Chem. Radiochem. 17 (1975) 49.