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Frost, Ray L. and Cejka, Jiri (2009) Near- and mid-infrared spectroscopy of the uranyl selenite mineral haynesite (UO2)3(SeO3)2(OH)2.5H2O. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 71:pp. 1959-1963.

© Copyright 2009 Elsevier

1 Near- and mid-infrared spectroscopy of the uranyl selenite mineral haynesite . 2 (UO2)3(SeO3)2(OH)2 5H2O 3

4 Ray L. Frost 1 • and Jiří Čejka 1,2

5

6 1 Inorganic Materials Research Program, School of Physical and Chemical Sciences, 7 Queensland University of Technology, GPO Box 2434, Brisbane Queensland 4001, 8 Australia. 9 10 2 National Museum, Václavské náměstí 68, CZ-115 79 Praha 1, Czech Republic. 11 12 Abstract 13 14 Near- and mid-infrared spectra of uranyl selenite mineral haynesite, . 15 (UO2)3(SeO3)2(OH)2 5H2O, were studied and assigned. Observed bands were assigned 16 to the stretching vibrations of uranyl and selenite units, stretching, bending and

17 libration modes of water molecules and hydroxyl ions, and δ U-OH bending

18 vibrations. U-O bond lengths in uranyl and hydrogen bond lengths O-H…O were 19 inferred from the spectra. 20 21 Keywords: Haynesite, Uranyl Selenite, Mineral, NIR Spectrum, infrared Spectrum, U- 22 O Bond Lengths, O-H…O Bond Lengths 23 24 1. Introduction 25 26 Uranyl selenite minerals are expected to occur where Se-bearing sulphides minerals 27 are undergoing oxidation and dissolution [1]. Known uranyl selenite minerals may be 28 divided in three groups: (a) demesmaekerite (U:Se = 1:3); (b) derriksite (U:Se = 1:2); 29 (c) guilleminite, marthozite, piretite, haynesite, larisaite (U:Se = 3:2) [2, 3]. 30 Unfortunately, crystal structure of haynesite is not known. However this mineral is 31 obviously related to other uranyl selenite minerals such as larisaite, guilleminite and 32 piretite. These three minerals are orthorhombic or pseudo-orthorhombic and their

• Author to whom correspondence should be addressed ([email protected]) 33 structures are based on the same uranyl-selenite layer (with U:Se=3:2). Interlayer 34 cations for these three minerals are Na, Ba and Ca respectively. Known are also some 35 synthetic uranyl selenites [4-10]. Crystallochemical systematics of selenites was 36 established by Serezhkina et al. [11] 37 Verma [12] reviewed synthesis, thermoanalytical, IR, Raman and X-ray studies on 38 metal selenites. According to Koskenlinna [13], the electronic configuration (Ar) 39 3d104s2 of the selenium(IV) ion promotes the formation of three bonding electron 40 pairs with oxygen, thus facilitating the shape and structure of the selenium(IV) 41 oxoanion. A trigonal selenite ligand with a pyramidal shape is formed with three 42 oxygens. There is, in addition, a lone pair, which protrudes in the opposite direction 43 from the bonding pairs, perpendicularly to the base formed by the oxygen. 44 Koskenlinna [13] states, that the ideal angle between bonds would be 109o28’, but as 45 the space requirement of the lone-pair differs from those of the bonding pairs, the 46 shape of the tetrahedron formed by the lone pair of selenium(IV) and its bonding 47 electron pairs with three oxygens is distorted. 48 . 49 Haynesite, (UO2)3(SeO3)2(OH)2 5 H2O, is a rare uranyl selenite minerals 50 formed in an oxidized uranium deposit in mudstones and sand stones at Repete mine, 51 San Juan Co, Utah, USA [14]. Haynesite is orthorhombic, a 8.025(5), b 17.43(1), c 52 6.935(3) Å, space group Pncm or Pnc2, Z = 2 [14]. Crystal structure of haynesite is 53 not known. Deliens and Piret [14] assume ideal formula of haynesite to be . 54 (UO2)3(OH)2(SeO3)2 5H2O, however, the formula of haynesite may be according to . 55 these authors (H3O)2(UO2)3(OH)4(SeO3)2 H2O. This formula is supported by 56 Chukanov et al. From the uranyl anion sheet topology point of view, haynesite may 57 be structurally related to guilleminite, marthozite, piretite and larisaite. This uranyl

58 anion sheet [(UO2)3(SeO3)2(O, OH)2] is related to the [(UO2)3(PO4)2(O, OH)2] sheets 59 in phosphuranylite type minerals [15-19] Infrared spectrum of haynesite was 60 presented by Čejka [20]. Frost et al. published a Raman spectroscopic study of 61 haynesite [21]. 62 63 The aim of this paper is the NIR spectroscopic study of the uranyl selenite 64 mineral haynesite complemented by Mid-IR spectroscopic investigations. The paper 65 is a part of systematic vibrational spectroscopy research of secondary minerals, 66 formed in oxide zone, inclusive uranyl minerals [22-36].

2 67 68 2. Experimental 69 70 2.1 Mineral 71 72 The haynesite mineral was supplied by The Mineralogical Research Company 73 and was obtained from the Repete Mine, Utah, USA. The composition [14] and 74 formula of the mineral has been published (Anthony et al. page 281) [37]. 75

76 2.2 Mid-IR spectroscopy

77 Infrared spectra were obtained using a Nicolet Nexus 870 FTIR spectrometer

78 with a smart endurance single bounce diamond ATR cell. Spectra over the 4000−525

79 cm-1 range were obtained by the co-addition of 128 scans with a resolution of 4 cm-1 80 and a mirror velocity of 0.6329 cm/s. Spectra were co-added to improve the signal to 81 noise ratio.

82

83 2.3 Near-infrared (NIR) spectroscopy

84 85 NIR spectra were collected on a Nicolet Nexus FT-IR spectrometer with a 86 Nicolet Near-IR Fibreport accessory (Madison, Wisconsin). A white light source was 87 used, with a quartz beam splitter and TEC NIR InGaAs detector. Spectra were 88 obtained from 13 000 to 4000 cm-1 (0.77-2.50 µm) by the co-addition of 64 scans at a 89 spectral resolution of 8 cm-1. A mirror velocity of 1.266 m sec-1 was used. The 90 spectra were transformed using the Kubelka-Munk algorithm to provide spectra for 91 comparison with published absorption spectra. Spectral manipulations, such as 92 baseline correction, smoothing and normalisation, were performed using the software 93 package GRAMS (Galactic Industries Corporation, NH, USA). 94 95 Band component analysis was undertaken using the Jandel ‘Peakfit’ (Erkrath, 96 Germany) software package which enabled the type of fitting function to be selected 97 and allows specific parameters to be fixed or varied accordingly. Band fitting was

3 98 done using a Lorentz-Gauss cross-product function with the minimum number of 99 component bands used for the fitting process. The Lorentz-Gauss ratio was 100 maintained at values greater than 0.7 and fitting was undertaken until reproducible 101 results were obtained with squared correlations ( r2) greater than 0.995. Band fitting 102 of the spectra is quite reliable providing there is some band separation or changes in 103 the spectral profile. 104 105 3 Results and Discussion 106 107 3.1 Near-infrared (NIR) spectroscopy 108 109 The near-infrared spectra may be conveniently divided into sections according 110 to the attribution of bands in this spectral region. Accordingly spectra are divided into 111 (a) the spectral region between 5500 and 8000 cm-1; this region is corresponds to the 112 first fundamental overtone of the mid-infrared OH stretching vibration (b) the spectral 113 region between 4000 and 5500 cm-1; this region is corresponds to the water OH 114 overtones, carbonate combination bands; (c) the spectral region between 8000 and 115 12000 cm-1; this region is corresponds to the second fundamental overtone of the OH 116 stretching vibrations and also includes electronic bands resulting from transition metal 117 ions in the structure [38-46]. 118 119 NIR spectroscopy has proven most useful for the study of minerals [47-52]. 120 The NIR spectrum of haynesite in the 8000 to 10000 cm-1 region is shown in Figure 1. 121 Mierjerink showed that the position of the higher energy states can be obtained from 122 the UV-Vis absorption spectrum [53]. This band is associated with electronic 123 transitions and is the region of the second fundamental overtone of the OH stretching 124 vibrations. These OH stretching vibrations will be composed of two components 125 resulting from the overtones of the OH units and the water vibrations. However the 126 intensity of the electronic band will significantly override the latter. Three component 127 bands are observed at 8740, 8815 and 9445 cm-1. The broad band at 8740 cm-1 is 2+ 128 assigned to the UO2 ion. This band contributes to the colour of uranyl containing 129 minerals [54].The information in this spectral region reveals the oxidation states of 130 uranium and can fundamentally be used to fingerprint minerals containing uranium 131 [55, 56]. The absorption properties of U4+ and U6+ are well known [54]. The principal

4 4+ -1 2+ 132 absorption bands of U are in the 22,000 to 8000 cm region. The UO2 unit -1 133 absorbs below 22,000 cm . Most uranium minerals absorb in the UV-Visible region 134 as well as the NIR. In NIR spectra bands have been reported for selected uranium 135 minerals at around 14,000 cm-1 and broad bands for meta-autunite and uranophane at 2+ 136 this position were assigned to the UO2 units [54]. No further detail of the absorption 137 bands such as the electronic transitions were made. The band at 8740 cm-1 with the -1 2+ 138 shoulder at 9445 cm is assigned to the UO2 ion. 139 140 The NIR spectrum in the 6000 to 8000 cm-1 region is reported in Figure 2. The 141 NIR spectra in the 4000 to 6000 cm-1 region is shown in Figure 3. Four NIR bands are 142 observed at 6495, 6815, 7035 and 7360 cm-1. These bands result from the first 143 fundamental overtone of the OH stretching vibrations. These bands were observed at 144 3234, 3415, 3563 and 3625 cm-1 (Figure 4). The last band is assigned to the 145 stretching vibrations of the OH units in the haynesite structure. The other bands are 146 assigned to the stretching vibrations of water. It must be considered that all 147 combination of bands is allowed. Thus the possibility of bands as shown in Figure 2

148 can arise from the following combinations (a) 2ν1 (IR) (b) 2ν1 (Raman) (c) 2ν3 (IR)

149 and (d) 2ν3 (Raman) . The combination of Raman and infrared bands is also allowed.

150 Thus bands may also arise form (ν1(IR) + ν1 (Raman)) and other combinations. Thus 151 although the spectral profile as shown in Figure 2 shows four component bands it is 152 probable that all the combinations delineated above are contained in this spectral 153 profile. 154 155 The spectra in the 4000 to 6000 cm-1 region is where combination bands

156 involving the selenate and/or water units. The selenate unit in haynesite shows a ν1 -1 -1 157 band at 851 cm and a ν3 band at 777 and 797 cm (Figure 5). Thus the combination

158 of ν1 and ν3 results in a band at around say 1650 and the first overtone 2(ν1+ν3) of this 159 combination would be expected to be ~3200 cm-1. Thus it would be only the second 160 overtone of the combination band at arouind 6000 cm-1. Such a band would be of low 161 intensity. The bands at 4525 and 5580 cm-1 may be ascribed to combination bands 162 resulting from the selenate ion. The intense NIR band at 5140 cm-1 is assigned to 163 water combination bands. 164

5 165 3.2 Mid-infrared spectroscopy 166 2+ 167 Four normal vibrations of the linear (UO2) ion (point symmetry D∞h) exhibit

168 three fundamentals: the Raman active symmetric stretching vibration ν1 (900-700 -1 -1 169 cm ); the IR active doubly degenerate bending vibration ν2 (δ) (350-180 cm ); and -1 170 the IR active antisymmetric stretching vibration ν3 (100-850 cm ). D∞h symmetry 171 lowering may cause IR and Raman activation of all vibrations and splitting of the 2+ 2- 172 doubly degenerate ν2 (UO2) . The pyramidal group (SeO3) with point symmetry

173 C3v exhibits six normal vibrations with four fundamentals: the symmetric stretching -1 -1 174 vibration ν1 (~807 cm ); the bending vibration ν2 (~432 cm ); the antisymmetric -1 -1 175 stretching vibration ν3 (~737 cm ); and the bending vibration ν4 (~374 cm ). All 176 vibrations are active both in Raman and infrared spectra. 177

178 Molecular water (point symmetry C2v) is characterized by three fundamentals: -1 179 the ν1 and ν3 OH stretching vibrations (3600 - 2900 cm ) and the bending vibration -1 -1 180 ν2 (δ) H2O (1700 - 1590 cm ). In the range of approximately 1100 – 300 cm 181 libration modes of water molecules may occur. The wavenumbers of molecular water 182 vibrations strongly depend on hydrogen bonds formed. If (OH)- ions (point symmetry

183 C∞v) are present, they will usually be indicated by sharp bands between 3700 and 184 3450 cm-1, but sometimes lower, if any appreciable amount of hydrogen bonding is 185 involved. The restricted rotational and librational motion of this ion occurs with a 186 wavenumber usually within the 600 – 300 cm-1 range. A M-O-H bending vibration -1 + 187 may occur ower wide range usually below 1500 cm . Hydroxonium, H3O (point

188 symmetry C3v), has 6 normal vibrations which exhibit four fundamentals: the -1 189 symmetric stretching vibration ν1 (~3160 cm ); the bending vibration ν2 (1140 - 1050 -1 -1 190 cm ); the doubly degenerate antisymmetric stretching vibration ν3 (~3320 cm ); and -1 191 the doubly degenerate bending vibration ν4 (~1750 cm ). All vibrations are Raman 192 and infrared active. Tentative assignment of hydroxonium ions seems, however, to be 193 very difficult [20]. 194 195 The full spectrum of haynesite is shown in Fig. 4. Infrared bands at 3625,

196 3563, 3415 and 3234 cm-1 (Fig. 5) are assigned to the ν OH stretching vibrations,

197 which are connected with vibrations of water molecules and hydroxyl ions. According

6 198 to Libowitzky [57], these bands are related to hydrogen bonds, the O-H…O hydrogen

199 bond lengths of which are > 3.2 (probably free hydroxyl group), 3.06, 2.81 and 2.72

200 Å. The presence of water molecules (Fig. 7) is characterized by a band at 1632 cm-1,

201 which is attributed to the δ H2O bending vibration. Bands observed at 1160, 1113 and

202 1017 cm-1 may be connected with δ U-OH bending vibrations, overtones and + 203 combination bands. Another possibility is that these bands are related to H3O ions. 204 However it would be expected that the first fundamental overtone in the near-infrared 205 spectra could be expected (as would be observed in Figure 2). However no such band 206 is observed. Chukanov et al. published a paper on a new uranyl selenite mineral 207 larisaite [58], in which they assumed the presence of hydroxonium ions in the 208 structure of larisaite. In this paper, the authors also assumed the presence of 209 hydroxonium ions in the crystal structure of haynesite, based on the IR specrum of 210 haynesite, as publihsed by Cejka [20]. Chukanov et al. do not agree with our 211 interpretation of the IR spectrum of haynesite. A band at 717 cm-1 (Fig. 6) may be 212 assigned to the libration mode of water molecule. Presence of hydroxonium ions in 213 the crystal structure of haynesite cannot be unambiguously inferred from the spectrum 214 observed. 215 2+ -1 216 The ν3 (UO2) antisymmetric stretching vibration was observed at 902 cm 217 (Fig.6). This is close to 898 cm-1 (piretite) [59], 901 cm-1 (larisaite) [3], 912 cm-1 218 (guilleminite) [Frost et al. submitted], and 909 cm-1 (synthetic

219 Sr[(UO2)3(SeO3)2O2].4H2O) [4]. U-O bond length 1.783 Å in uranyl was calculated 2+ -2/3 220 with Bartlett-Cooney empirical relation [60] RU-O = 91.41[ν3(UO2) ] + 0.804 Å. 221 This value is in agreement with the U-O bond lengths in guilleminite (average 1.795 222 Å) [61], marthozite (average 1.795 Å) [62], larisaite (average 1.813 Å) [3],

223 Sr[(UO2)3(SeO3)2O2].4H2O (average 1.821 Å) [4] and ~1.8 inferred by Burns for a 224 set of well defined crystal structures of natural and synthetic uranyl compounds [15, -1 2+ 225 16, 63, 64]. A band at 851 cm was assigned to the ν1 (UO2) symmetric stretching 2+ -2/3 226 vibration. Bartlett-Cooney empirical relation RU-O = 106.5[ν1(UO2) ] + 0.575 Å 227 [60] was used for calculation of the U-O bond length in uranyl. Obtained value (1.761 228 Å) is also close to the data from X-ray single crystal structure analyses of natural and 2- 229 synthetic uranyl compounds [63, 64]. The ν1 (SeO3) symmetric stretching

7 2- 230 vibration and the ν3 (SeO3) antisymmetric stretching vibrations are characterized by 231 bands observed at 797 cm-1 and 777 and 756 cm-1, respectively (Fig.6). 232 233 Infrared spectrum of the studied sample of haynesite is comparable with 234 infrared spectra of some uranyl selenites which should have the same phosphuranylite 235 anion sheet topology as larisaite [58], guilleminite [Frost et al., submitted], marthozite 236 [Frost et al., submitted], piretite [65], other haynesite mineral samples [20], and

237 synthetic Sr[(UO2)3(SeO3)2O2].4H2O [6]. 238 239 240 4. Conclusions 241 242 Uranyl selenite mineral haynesite was studied with NIR- and IR- 243 spectroscopy. Obtained spectra were tentatively interpreted. Bands assigned to the 244 stretching vibrations of uranyl, selenite units and OH groupings, bending vibration 245 and libration mode of molecular water were inferred from the spectra. U-O bond 246 lengths in uranyl and O-H…O hydrogen bond lengths were also inferred from the 247 spectra on the basis of empirical relations by Bartlett and Cooney [60] and Libowitzky 248 [57], respectively. Infrared spectrum of haynesite sample studied is comparable with 249 the spectra of other natural and synthetic uranyl selenites having the similar 250 phosphuranylite anion sheet topology. 251 252 Acknowledgments 253 254 The financial and infra-structure support of the Queensland University of Technology, 255 Inorganic Materials Research Program is gratefully acknowledged. The Australian 256 Research Council (ARC) is thanked for funding the instrumentation. Mr Dermot 257 Henry of Museum Victoria is thanked for the loan of the minerals.

8 258 References 259 [1] R. Finch, T. Murakami, Reviews in Mineralogy 38 (1999) 91-179. 260 [2] J.W. Anthony, R.A. Bideaux, K.W. Bladh, M.C. Nichols, Handbook of 261 Mineralogy, Mineral Data Publishing,, Tucson, Arizona 2003. 262 [3] N.V. Chukanov, D.Y. Pushcharovsky, M. Pasero, S. Merlino, A.V. Barinova, 263 S. Möckel, I.V. Pekov, A.E. Zadov, V.T. Dubinchuk, Eur. J. Min. 16 (2004) 264 367-374. 265 [4] P.M. Almond, T.E. Albrecht-Schmitt, Am. Min. 89 (2004) 976-980. 266 [5] P.M. Almond, T.E. Albrecht-Schmitt, Inorg. Chem. 42 (2003) 5693-5698. 267 [6] P.M. Almond, T.E. Albrecht-Schmitt, Am. Min. 89 (2004) 976-980. 268 [7] P.M. Almond, T.E. Albrecht-Schmitt., Inorg. Chem. 41 (2002) 1177-1183. 269 [8] M. Koskenlinna, Helsinki University of Technology, Espoo, Helsinki 1996. 270 [9] B.L. Khandelwal, V.P. Verma, J. Inorg. Nucl. Chem. 38 (1976) 763-769. 271 [10] R.E. Sykora, T.Y. Shvareva, T.E. Albrecht-Schmitt, Actinide compounds with 272 heavy oxoanions containing a stereochemically active lone-pair of electrons, 273 Elsevier Amsterdam 2007. 274 [11] L.B. Serezhkina, R.K. Rastsvetaeva, V.N. Serezhkin, Koord. Khim. 16 (1990) 275 1327-1339. 276 [12] V.P. Verma, Thermochimica Acta 327 (1999) 63-102. 277 [13] M. Koskenlinna, Helsinky University of Technology, Helsinky, 1996. 278 [14] M. Deliens, P. Piret, Can. Min. 29 (1991) 561-564. 279 [15] P.C. Burns, Can. Mineral. 38 (1999) 23-90. 280 [16] P.C. Burns, Can. Min. 43 (2005) 1839-1894. 281 [17] M.A. Cooper, F.C. Hawthorne, Can. Mineral. 33 (1995) 1103-1109. 282 [18] M.A. Cooper, F.C. Hawthorne, Can. Min. 39 (2001) 797-807. 283 [19] F.C. Hawthorne, M. Schindler, Z. Kristallogr. 223 (2008) 41-68. 284 [20] J. Cejka, J. Sejkora, M. Deliens, Neues Jahrbuch fuer Mineralogie, 285 Monatshefte (1999) 241-252. 286 [21] R.L. Frost, M.L. Weier, B.J. Reddy, J. Cejka, J. Raman Spectrosc. 37 (2006) 287 816-821. 288 [22] R.L. Frost, J. Cejka, G. Ayoko, J. Raman Spectrosc. 39 (2008) 495-502. 289 [23] R.L. Frost, J. Cejka, G.A. Ayoko, M.J. Dickfos, J. Raman Spectrosc. 39 290 (2008) 374-379. 291 [24] R.L. Frost, M.J. Dickfos, J. Cejka, J. Raman Spectrosc. 39 (2008) 582-586. 292 [25] R.L. Frost, M.C. Hales, D.L. Wain, J. Raman Spectrosc. 39 (2008) 108-114. 293 [26] R.L. Frost, E.C. Keeffe, J. Raman Spectrosc. in press (2008). 294 [27] R.L. Frost, J.M. Bouzaid, J. Raman Spectrosc. 38 (2007) 873-879. 295 [28] R.L. Frost, J.M. Bouzaid, W.N. Martens, B.J. Reddy, J. Raman Spectrosc. 38 296 (2007) 135-141. 297 [29] R.L. Frost, J. Cejka, J. Raman Spectrosc. 38 (2007) 1488-1493. 298 [30] R.L. Frost, J. Cejka, G.A. Ayoko, M.L. Weier, J. Raman Spectrosc. 38 (2007) 299 1311-1319. 300 [31] R.L. Frost, J. Cejka, M.L. Weier, J. Raman Spectrosc. 38 (2007) 460-466. 301 [32] R.L. Frost, J. Cejka, M.L. Weier, W.N. Martens, G.A. Ayoko, J. Raman 302 Spectrosc. 38 (2007) 398-409. 303 [33] R.L. Frost, M.J. Dickfos, J. Raman Spectrosc. 38 (2007) 1516-1522. 304 [34] R.L. Frost, S.J. Palmer, J.M. Bouzaid, B.J. Reddy, J. Raman Spectrosc. 38 305 (2007) 68-77. 306 [35] R.L. Frost, C. Pinto, J. Raman Spectrosc. 38 (2007) 841-845.

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10 353 List of Figures 354 355 Figure 1 NIR spectra of haynesite in the 8000-10,000 cm-1 region 356 357 Figure 2 NIR spectra of haynesite in the 6000-8,000 cm-1 region 358 359 Figure 3 NIR spectra of haynesite in the 4000-6,000 cm-1 region 360 361 Figure 4 Infrared spectrum of haynesite 362 363 Figure 5 IR spectra of haynesite in the 3000-3800 cm-1 region 364 365 Figure 6 IR spectra of haynesite in the 600-1200 cm-1 region 366 367 Figure 7 IR spectra of haynesite in the 1500-1700 cm-1 region

11 368 369 370 Figure 1 371

12 372 373 374 Figure 2 375

13 376 377 378 Figure 3 379

14 380 381 382 Figure 4 Infrared spectrum of haynesite

15 383 384 385 Figure 5 386

16 387 388 389 390 Figure 6 391

17 392 393 394 Figure 7 395 396

18