Characterization of uranium antimonite ion exchanger

Colloids and Surfaces A: Physicochem. Eng. Aspects 295 (2007) 1–6

Review

Characterization of uranium antimonite ion exchanger M.V. Sivaiah a , K.A. Venkatesan b , R.M. Krishna a , P. Sasidhar c,∗ , G.S. Murthy a b

a Nuclear Chemistry Section, Andhra University, Visakhapatnam-530003, India Fuel Chemistry Division, Indira Gandhi Centre for Atomic Research, Kalpakam-603102, India c Safety Research Institute, Atomic Energy Regulatory Board, Kalpakkam-603102, India

Received 7 April 2006; received in revised form 3 August 2006; accepted 11 August 2006 Available online 22 August 2006

Abstract Uranium antimonate (USb) has been prepared and characterized by various analytical techniques such as TG-DTA, EDXRF, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and FT-IR spectroscopy. The precipitation reaction of potassium pyroantimonate (KSb(OH)6 ) with uranyl nitrate results in the formation of amorphous USb with U/Sb mole ratio of 0.35, which crystallises at temperature above 900 ◦ C, leading to the formation of USb3 O10 . The amorphous form and heat treated uranium antimonate exhibits ion exchange with some fission products like 137 Cs+ , 90 Sr2+ and 154 Eu3+ due to the presence of surface hydroxyl groups and the distribution coefficient (Kd , mL/g) decreases with heat treatment. Thermal analysis of USb indicated the loss of surface hydroxyl groups due to the condensation reaction is responsible for the decrease in Kd values after heat treatment. Based on the analytical and sorption data on uranium antimonate a molecular formula of HUO2 Sb3 O4 (OH)10 ·4.7 H2 O has been arrived. © 2006 Elsevier B.V. All rights reserved. Keywords: Uranium antimonate; Ion exchange; Fission products; Photoelectron spectroscopy

Contents 1. 2.

3.

4.

∗

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Experimental. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1. Materials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2. Determination of distribution coefficient (Kd ) values . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.3. TG-DTA, EDXRF, XRD and FT-IR analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.4. X-ray photoelectron spectroscopy analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Results and discussion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1. Ion exchange studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2. Thermogravimetric analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3. EDXRF studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.4. X-ray diffraction studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.5. XPS studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.6. FT-IR pattern of USb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.7. Proposed formula for USb . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusions. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Corresponding author. Fax: +91 4114 280235. E-mail address: [email protected] (P. Sasidhar).

0927-7757/$ – see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.colsurfa.2006.08.033

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1. Introduction Removal of long-lived hazardous fission products like 137 Cs, from high level liquid wastes arising from reprocessing plants is desirable for the reduction of occupational exposure, radiation degradation to chemicals and structural materials, and to facilitate the easy and economic disposal of the effluent. Inorganic ion exchangers, because of their specificity and stability to high radiation doses, seem to be the obvious choice to achieve this end. Antimonates of multivalent metal ions, form a series important group of inorganic ion exchangers [1]. These metal antimonates show excellent ion exchange property [2] when compared to phosphates, molybdates, tungstates of different metal ions. The studies on zirconium [3], cerium [4], tin [5], titanium [6], silicon [7], and iron [8] antimonates were reported earlier. Recently we have reported [9,10] the superior ion exchange behaviour of uranium antimonate (USb) for the isolation of some fission products from acidic waste streams. In this paper the characterisation of uranium antimonate by various analytical techniques such as TG-DTA, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), EDXRF, FTIR spectroscopy is reported. The plausible molecular formula of prepared compound was arrived. 90 Sr

in air at the rate of 10 ◦ C/min from 25 ◦ C to 1200 ◦ C. EDXRF pattern of the sample was obtained using Philips MinPol X-ray fluorescence, with excitation voltage of 20 keV and at current of 120 ␮A. Aluminium filter was used in all the measurements. X-ray diffraction pattern of samples was obtained using Philips 1011 X-ray diffractometer (operating with 40 kV and 45 mA) ˚ radiation. FT-IR measurements were with Cu K␣ (1.5406 A) carried out using compressed KBr pellets containing 5 wt.% of the sample. IR spectra were recorded in 4000–400 cm−1 region using a Bomem FT-IR spectrometer model—103 with a resolution of 4 cm−1 . 2.4. X-ray photoelectron spectroscopy analysis The XPS pattern of USb samples was carried out using VG model—ESCALAB MK 200X spectrometer equipped with an aluminium K␣ source (1486.6 eV) and calibrated with Au 4f7/2 line at 84.0 eV from a specimen of Au film on Silica substrate. A few milligrams of the powder sample was spread uniformly over indium foil and pressed. The foil was attached to a stainless steel stub for mounting to the X–Y–Z translator of the XPS system. The carbon C 1s peak was taken as reference (285.1 eV) for calculating the binding energies (BE) (Eb ). The data acquisition and processing were carried out using Eclipse software.

2. Experimental 2.1. Materials Potassium pyroantimonate (KSb(OH)6 ) and uranyl nitrate were obtained from E.Merck. All the other chemicals and reagents used were of analytical AR grade. 134 Cs (t1/2 = 2.06 years), 85 Sr (t1/2 = 64.8 days) and 152+154 Eu (t1/2 = 13.5 years) radioisotopes were obtained from Board of Radiation and Isotope Technology, Mumbai, India. The compound USb was prepared as reported earlier [9,10]. The USb samples heated at different temperatures (50 ◦ C, 300 ◦ C, 600 ◦ C, 900 ◦ C, 1000 ◦ C and 1100 ◦ C) for 2.0 h are represented here after as USb-50, USb-300, etc. The as prepared compound is designated as USb. 2.2. Determination of distribution coefficient (Kd ) values 0.05 g of USb was equilibrated, for 24 h, with 10 mL solution containing the desired concentration of nitric acid (0.1 M or 0.01 M) spiked with a particular tracer. The solid material and the liquid supernatant were separated and the batch distribution coefficients (Kd ) were determined by Eq. (1)   Ai − Af V (1) Kd (mL/g) = Af m where Ai and Af are the initial and final activity of the supernatant, respectively, V the volume of the test solution (in mL), m is the weight of the sorbent (in g) taken for equilibration. 2.3. TG-DTA, EDXRF, XRD and FT-IR analysis Thermogravimetric analysis was carried out by using Mettler TGA/SDTA 851e . Nearly 20 mg of the sample was heated

3. Results and discussion 3.1. Ion exchange studies The distribution coefficient values of Cs+ , Sr2+ and Eu3+ on USb and after subjecting to different temperatures are given in Table 1. The order of affinity was found to be Cs+ < Sr2+ < Eu3+ . This affinity sequence was also observed when the sorption data was fitted in Longmuir model [10], which may be attributed to the stronger electrostatic interaction of the multivalent cations as compared to the lower valent cations [11]. The Kd values increases with heat treatment up to 150 ◦ C followed by gradual decrease in Kd values. It is also observed that there is negligible uptake for Cs+ , Sr2+ on USb-900 (Table 1), while Eu3+ shows considerable sorption. This general decrease of metal ion sorption on USb with increase in temperature was investigated in detail by characterizing the USb after subjecting to different temperatures. Table 1 Kd values of Cs+ , Sr2+ and Eu3+ on USb after thermal treatment at different temperatures for 2.0 h Sample

USb-50 USb-150 USb-300 USb-600 USb-900

Distribution coefficient Kd (mL/g), Cs+

Sr2+

Eu3+

1046 1799 954 242 5

2464 3684 1828 201 28

26615 36026 42742 13125 394

[HNO3 ] = 0.1 M for Eu3+ and 0.01 M for Cs+ and Sr2+ , [Mn+ ] = tracer, V/m = 200 mL/g, Temp = 300 K, equilibration time = 24 h.

M.V. Sivaiah et al. / Colloids and Surfaces A: Physicochem. Eng. Aspects 295 (2007) 1–6

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Table 2 EDXRF analysis of U and Sb in USb samples (pre heating at different temperatures) Sample

% of Ua

% Sba

Mole ratios of U/Sb

USb-50 USb-300 USb-600 USb-900 USb-1000 USb-1100

36.8 37.0 36.6 37.4 35.8 61.8

63.1 62.9 63.3 62.5 63.9 38.0

0.315 0.316 0.311 0.322 0.301 0.876

a EDXRF patterns above refer to U and Sb only. Percentages are given by excluding H and O molecules.

3.4. X-ray diffraction studies

Fig. 1. TG, DTG and DTA curves of USb.

3.2. Thermogravimetric analysis The thermal analysis (TG, DTG and differential thermal analysis, DTA) of USb is represented in Fig. 1. It can be seen from TG curve that significant loss in weight is continued up to 700 ◦ C followed by minimal weight loss in the temperature range of 700–1000 ◦ C. The total weight loss occurred from 25 ◦ C to 1000 ◦ C was found to be 21.5%. The DTG curve shows maximum rate of weight loss at 100 ◦ C, which is supported by an endothermic peak in the DTA curve. This was assigned to the loss of water molecules [12]. In differential thermal analysis curve, there is a broad exothermic peak in the temperature range 300–700 ◦ C which may be assigned to the decomposition of residual surface hydroxyl groups. Duval [13] also observed a weight loss of two-thirds of water at about 225 ◦ C and the rest one-third losses gradually and slowly till the temperature reaches 600 ◦ C in sodium antimonate. A similar trend in the weight loss of titanium antimonate was also reported by Abe et al. [3]. Weight loss of 0.5% is observed in the temperature range 700–1000 ◦ C followed by steep weight loss after 1010 ◦ C. This steep fall may be attributed to decomposition of USb probably due to evaporation of antimony oxides [14]. The endothermic peak observed in the temperature range 1050–1150 ◦ C could be attributed to the phase transition [15] in addition to weight loss.

Powder X-ray diffraction patterns of USb samples, which were heated at different temperatures for 2.0 h, are shown in Fig. 2. The XRD pattern of USb-50 reveals that it is poorly crystalline. A gradual increase in crystallinity with temperature was observed up to 900 ◦ C. It is also observed that the XRD pattern beyond 900 ◦ C, i.e. at 1000 ◦ C and 1100 ◦ C are different. The XRD pattern of USb-1000, corresponds to that of USb3 O10 [16,17]. The 2θ values obtained for the diffraction patterns of USb after thermal treatment at 1000 ◦ C are in good agreement with the values reported by Grasselli and Callahan [16] and Ayakan and Sleight [17] as shown in Table 3. The diffraction pattern and 2θ values of USb-1100 are in good agreement with reported [16] pattern of Sb3 U3 O14 . Thus, from the above findings it is proposed that the compound USb3 O10 , which is stable at 1000 ◦ C converts to Sb3 U3 O14 in the temperature, range 1000–1100 ◦ C. This corroborates with the observation made by Graselli et al. [15] that when USb3 O10 was subjected to thermal treatment at 1090 ◦ C results in the formation of Sb3 U3 O14 phase. In the present study, the XRD pattern of USb heated at 1100 ◦ C is in agreement with that of Sb3 U3 O14 . These obser-

3.3. EDXRF studies The mole ratio of uranium to antimony in USb was found to be about 0.32 from the EDXRF measurement of USb. The data obtained from the EDXRF analysis and the calculated U/Sb mole ratio through elemental analysis (Table 2) show that U/Sb mole ratio (∼0.32) remains almost constant for the heat treated samples up to 1000 ◦ C and thereafter increases to 0.88 for USb1100. This is due to the loss of antimony at higher temperature, which was also seen in the TG curve.

Fig. 2. XRD pattern of USb after thermal treatment for 2.0 h.

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Table 3 Comparison of X-ray diffraction pattern of USb-1000 Present study

Reported by Grasselli and Callahan [16]

Reported by Aykan and Sleight [17]

2θ

I/I0

2θ

I/I0

2θ

I/I0

23.81 28.22 34.93 36.84 47.68 50.06 55.72 58.20 63.52 71.30

44 100 8 63 13 43 23 14 14 8

23.082 28.036

65 100

36.649 47.305 49.669 55.403 57.993 63.298 70.844

60 12 30 30 14 20 18

23.265 28.035 28.216 36.679 47.513 49.552 55.510 58.031 63.488 71.025

85 100 75 70 35 30 45 30 20 20 Fig. 4. XPS of the U 4f7/2 for USb-50 and USb-1000.

vations show that the compound USb (as prepared) is poor crystalline at lower temperatures and crystallises above 900 ◦ C leading to the formation of USb3 O10 at 1000 ◦ C which again transforms to Sb3 U3 O14 at 1100 ◦ C. 3.5. XPS studies The XPS studies provide information about the presence of multivalent states of the metal ions in solid. The XPS spectra of Sb 3d3/2 and U 4f7/2 obtained for USb-50, USb-1000 are given in Figs. 3 and 4. The binding energies and full width at half maximum (FWHM) values of U 4f7/2 and Sb 3d3/2 for these compounds are given in Table 4 and compared with earlier work [18,19]. The BE values of Sb 3d3/2 for both USb-50 and USb1000 are in agreement with the reported [18] values confirming to antimony exists in the +5 oxidation state in both the samples. The BE value of U 4f7/2 in USb-50 was found to be 381.9 eV (with FWHM of 2.4 eV), which is in agreement with the reported value [18] of BE for U(VI) oxidation state. The BE value of U 4f7/2 in USb-1000 showed considerable difference when compared with USb-50 as shown in Fig. 4 and Table 4. The chemical shift in the U 4f7/2 peak position is directly related to the oxidation state of uranium. Higher valent ura-

nium generally exists as UO2 + or UO2 2+ ions instead of simple U5+ and U6+ ions [20]. Because of this oxygen bonding the chemical shift is only marginal and thus the difference in BE values of UO2 + and UO2 2+ are minimum. The decrease in BE of U 4f7/2 from 381.9 eV for USb-50 to 381.1 eV for USb-1000 shows that there is considerable contribution of lower oxidation states of uranium in USb-1000. In addition, FWHM of a peak is related to the lifetime of the excited state, which has a direct bearing on the chemical environment or bonding [21]. In a crystal lattice, the neighbouring ions influence the width of the photo peak by such interaction. Broadening of FWHM from 2.4 eV to 2.7 eV (Fig. 4 and Table 4) in case of USb-1000 as compared to USb-50 shows that uranium exists in different chemical environment or bonding. Deconvolution of U 4f7/2 peak of USb-1000 by standard deconvolution procedures was carried out and the calculated BE values are given in Table 3. The BE values of U 4f7/2 (Table 4) obtained after deconvolution indicate that the environment of uranium in USb-1000 resembles that of +6 and +5 oxidation states. This can be possible only when uranium in USb-1000 (i.e. USb3 O10 ) exists in pentavalent state and situated in a chemical environment similar to hexavalent state possibly surrounded by oxygen atom.

Table 4 BE and FWHM values of Sb 3d3/2 and U 4f7/2 photoelectron peaks of USb-50 and USb-1000 Sample

Fig. 3. XPS of the Sb 3d3/2 for USb-50 and USb-1000.

Sb 3d3/2

U 4f7/2

BE (eV)

FWHM (eV)

BE (eV)

FWHM (eV)

Present study

USb-50

540.1

2.0

381.9

2.4

Present study

USb-1000

540.0

2.0

381.1 381.7a 380.4a

2.7 2.4a 2.1a

Ref. [18] Ref. [18] Ref. [18] Ref. [19]

Sb2 O5 ␤-UO3 USb3 O10 USb3 O10

540.4 – 540.4 539.9

1.7 – 1.7

– 381.5 381.3 380.7

– 2.4 2.05

a

Data pertain to deconvoluted peaks.

M.V. Sivaiah et al. / Colloids and Surfaces A: Physicochem. Eng. Aspects 295 (2007) 1–6

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exchanging sites [28]. HUO2 Sb3 O4 (OH)10 · 4.7H2 O → HUO2 Sb3 O4 (OH)10 + 4.7H2 O

(2)

The weight loss observed in the temperature range 125–700 ◦ C is mainly due to the loss of water molecules formed due to the condensation of structural hydroxyl groups HUO2 Sb3 O4 (OH)10 → HUO2 Sb3 O9 + 5.0H2 O

Fig. 5. FT-IR pattern of USb after thermal treatment at different temperatures.

3.6. FT-IR pattern of USb Infrared absorption spectra of USb samples (subjected to different temperatures) are shown in Fig. 5. A characteristic band near 930 cm−1 was assigned to the U O stretching mode of the linear uranyl structure [22]. Other bands near 740 and 430 cm−1 were assigned to the Sb O stretching and O Sb O bending modes [23,24]. The band at 1402 cm−1 is due to the SbOH deformation vibration [25]. IR spectra of USb-50, USb-300 and USb-600 shows a broad peak in the region of 3650–3000 cm−1 and a medium peak at 1640 cm−1 , which may be assigned to the ν(OH) and δ(HOH) modes. The absence of these peaks (ν(OH), δ(HOH) and SbOH deformation vibrations) after thermal treatment at higher temperatures (above 600 ◦ C) is due to the loss of hydroxyl groups or water molecules. This could be the reason for the decrease in Kd values of fission products (Table 1) with increase of temperature during heat treatment. A peak at 621 cm−1 was clearly seen in the case of USb-1000 and is attributed to the Sb O Sb vibration [24]. 3.7. Proposed formula for USb The XRD patterns of USb-1000 are in good agreement with the diffraction pattern of USb3 O10 . The formula weight of USb3 O10 corresponds to 761. The thermal studies on USb shows that there is 21.5% weight loss up to the temperature of 1000 ◦ C, hence the formula weight of the synthesized USb could be given as 971. It is known that the antimony in moderately acidic solutions polymerizes [26–29] and forms (Sb3 O4 (OH)10 )3− . The investigations based on the instrument techniques EDXRF, XRD, XPS, FT-IR observations points out to the formula for the USb as HUO2 Sb3 O4 (OH)10 · 4.7H2 O The initial weight loss in the temperature range 25–125 ◦ C corresponds to the 4.7 mol of loosely bound water molecules. The increase in Kd values up to 150 ◦ C is due to improvement in the crystallinity of the sorbent facilitating the accessibility of

(3)

Baetsle and Huys [29] suggested that four oxygen atoms are common to three antimony atoms in trimeric structure of (Sb3 O4 (OH)10 )3− in, which the hydroxyl groups are attached to Sb in tetrahedral structure. The weight loss in this temperature range, 125–700 ◦ C is mainly due to condensation of hydroxyl groups and is taking place over a wide range of temperature, which may be attributed to the different bond strength of hydroxyl groups. A remarkable decrease in ion exchange property of USb after heating up to 600 ◦ C suggests that these hydroxyl groups are lost. The compound USb-900 (Table 1) shows considerable uptake of Eu3+ . Further it was observed, the absence of Sb OH stretching or any ν(OH) mode of vibrations in the IR spectra of USb900. Hence, it may be assumed that the H+ in HUO2 Sb3 O9 is also an exchangeable ion. The XRD pattern of USb-1000 shows the pattern relevant to USb3 O10 , in which oxidation states of both U and Sb are in +5. The distribution of the oxidation state of uranium between +6 and +5 is confirmed by XPS study as mention earlier. Deconvolution of U 4f7/2 indicated that the environment of uranium in USb-1000 is also similar to hexavalent uranium, which can arise from UO2 Sb3 O8 (≡USb3 O10 ). The IR spectra of USb-1000 shows Sb O Sb characteristic vibration peak at 621 cm−1 . Thus, the thermochemical change at 1000 ◦ C (USb-1000) may be represented as 1 1 HUO2 Sb3 O9 → USb3 O10 (UO2 Sb3 O8 ) + H2 O + O2 2 4

(4)

Thus, both the surface hydroxyl groups and hydrogen ion associated with USb are responsible for the ion exchange behaviour. 4. Conclusions Uranium antimonite—a new inorganic ion exchanger was characterised for the application of removing Cs+ , Sr2+ and Eu3+ . Uranium antimonate as prepared, with U/Sb mole ratio of 0.3, exhibits ion exchange property with these fission products and the distribution values decreased with increase in the temperature of heat treatment. The affinity sequence of metal ions decreased in the order Eu3+  Sr2+ > Cs+ . Uranium antimonate (as prepared) is poorly crystalline at lower temperatures and crystallises above 900 ◦ C leading to the formation of USb3 O10 at 1000 ◦ C. Antimony in USb-50 and USb-1000 is existing in pentavalent oxidation state. Uranium in USb-50 exists as UO2 2+ . However, uranium in USb3 O10 exists in pentavalent oxidation state and situated in an environment chemically similar to hexavalent oxidation state, possibly surrounded by oxygen atoms. The molecular formula of HUO2 Sb3 O4 (OH)10 ·4.7H2 O can be

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proposed based on the TG-DTA, EDXRF, XRD, XPS, FT-IR analysis of USb. Both the hydrogen ion and hydroxyl groups in USb were responsible for ion exchange behaviour. Acknowledgements The author (M.V. Sivaiah) is grateful to Atomic Energy Regulatory Board (AERB), Government of India for providing fellowship and thankful to Dr. P.R. Vasudeva Rao, Director, Chemical Group, IGCAR for providing the facilities. The author also express his thanks to Dr. M.V.R. Prasad, Dr. G. Pannerselvam and Dr. S. Bera, Dr. S. Sai Baba for providing EDXRF, XRD, XPS, TG-DTA faculties. References [1] V. Vesely, V. Pekarek, Talanta 19 (1972) 219. [2] M. Qureshi, V. Kumar, J. Chem. Soc. (A) (1970) 1488. [3] M. Abe, Proceedings of Technical committee meeting on inorganic ion exchangers and adsorbents for chemical processing in the nuclear fuel cycle, IAEA TECDOC-337, 1985, p. 282; (b) M. Abe, R. Chitrakar, M. Tsuji, K. Fukumoto, Solvent Extr. Ion Exch. 3 (1985) 149. [4] M.I. Eldessouky, Arab-J. Nucl. Sci. Appl. 27 (1994) 89. [5] R. Koviula, R. Harjula, J. Lehto, Sep. Sci. Technol. 38 (2003) 3795. [6] T. Moller, R. Harjula, P. Kelokaski, K. Vaaramaa, P. Karhu, J. Lehto, J. Mater. Chem. 13 (2003) 535. [7] T. Moller, A. Clearfield, R. Harjula, Microporous Mesoporous Mater. 54 (2002) 187. [8] J.P. Rawat, D.K. Singh, Anal. Chim. Acta 87 (1976) 157. [9] M.V. Sivaiah, K.A. Venkatesan, R.M. Krishna, P. Sasidhar, G.S. Murthy, Colloids Surf. A 236 (2004) 147.

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