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Frost, Ray, Couperthwaite, Sara,& Xi, Yunfei (2011) The molecular structure of the multianion mineral hidalgoite PbAl3(AsO4)(SO4)(OH)6 - Implications for removal from soils. Journal of Molecular Structure, 1005(1-3), pp. 214-219.

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The molecular structure of the multianion mineral hidalgoite PbAl3(AsO4)(SO4)(OH)6 Implications for arsenic removal of soils :

Catalogue from Homo Faber 2007

The objective of this research is to determine the molecular structure of the mineral hidalgoite

PbAl3(AsO4)(SO4)(OH)6 using vibrational spectroscopy. The mineral is found in old mine sites. Observed 2− 3− Abstractbands are assigned to the stretching and bending vibrations of (SO4) and (AsO4) units, stretching and Bbending vibrations of hydrogen bonded (OH)− ions and Al3+–(O,OH) units. The approximate range of O–

H O hydrogen bond lengths is inferred from the Raman and infrared spectra. Values of 2.6989 Å,

2.7682⋯ Å, 2.8659 Å were obtained. The formation of hidalgoite may offer a mechanism for the removal of arsenic from the environment.

1 The molecular structure of the multianion mineral hidalgoite PbAl3(AsO4)(SO4)(OH)6

2 - Implications for arsenic removal from soils

3

4 Ray L. Frost, • Sara J. Palmer and Yunfei Xi

5 6 Chemistry Discipline, Faculty of Science and Technology, Queensland University of 7 Technology, GPO Box 2434, Brisbane Queensland 4001, Australia. 8

9 Abstract

10 The objective of this research is to determine the molecular structure of the mineral hidalgoite

11 PbAl3(AsO4)(SO4)(OH)6 using vibrational spectroscopy. The mineral is found in old mine 2- 12 sites. Observed bands are assigned to the stretching and bending vibrations of (SO4) and 3- - 3+ 13 (AsO4) units, stretching and bending vibrations of hydrogen bonded (OH) ions and Al - 14 (O,OH) units. The approximate range of O-H...O hydrogen bond lengths is inferred from the 15 Raman and infrared spectra. Values of 2.6989 Å, 2.7682 Å, 2.8659 Å were obtained. The 16 formation of hidalgoite may offer a mechanism for the removal of arsenic from the 17 environment.

18

19 Keywords: Raman spectroscopy, hidalgoite, arsenate contamination, arsenic in cattle dips, 20 soil remediation

21

22

23

• Author to whom correspondence should be addressed ([email protected]) 1

24 Introduction

25 Hidalgoite PbAl3(AsO4)(SO4)(OH)6 [1] is a multi anion mineral with arsenate and sulphate in 26 the structure. It is a fairly rare mineral found in the oxide zone of polymetallic deposits [1-3]. 27 The mineral is related to the mineral group. It is the arsenate analogue of the 28 phosphate hinsdalite and the analogue of beudantite. The mineral has a hexagonal 29 with Point Group: 3m and cell data Space Group: R3m, a = 7.04(2, c = 30 16.99(2, Z = 3. The mineral is named after the Hidalgo district of Mexico (San Pascal Mine, 31 Zimapan mining district, Hidalgo, Mexico). The mineral hidalgoite is isostructural with

32 corkite PbFe3(PO4,SO4)2(OH)6.

33

34 Hidalgoite can be described as an environmental mineral in that its formation, for example in 35 soils, enables the entrapment and immobilisation of arsenic [4, 5]. Hidalgoite is formed in old 36 mine sites and slag piles [6-8]. This mineral is important for the formation of compounds 37 containing arsenic [6, 8, 9]. In Australia, arsenic compounds such as arsenic trichloride and 38 arsenic pentachloride are used as tick control chemicals in cattle dips. This results in the 39 contamination of soils around dip sites with arsenic compounds [10]. If the soils contain clays 40 then hidalgoite may form. There is a need to be able to identify consequential mineral 41 formation in soils. There are many cattle dips in and around Brisbane (see for example 42 http://www.chermsidedistrict.org.au/chermsidedistrict/01_cms/details.asp?ID=207). Many 43 cattle dip sites have been converted to parklands and also house sites. Often the soil is toxic 44 and is a health risk to families living near such sites. To remove arsenic from soils, the 45 arsenic must be oxidised to arsenate followed by reaction with appropriate cations in the 46 soils. The arsenate then reacts with Fe3+ of Al3+ to form arsenate containing minerals such as 47 hidalgoite. It is important to be able to remove and immobilise arsenic. This research forms 48 part of a systematic study of arsenic forming compounds in soils.

49

50 Complex equilibria exist with the formation of the mineral, which may redissolve in heavy 51 rainfall events [6]. Such mineral formation can be made to control the concentrations of 52 and arsenic in mine tailings [11]. Arsenate is accumulated in the formation of secondary 53 minerals in the beudantite-jarosite mineral groups [9]. The formation of secondary arsenate 54 containing minerals is extremely important in the accumulation and immobilization of arsenic

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55 and heavy metals [12]. Of course, other minerals such as segnitite, jarosite, bukovskýite may 56 also function as metal collectors. Such mineral formation will depend upon the conditions of 57 formation and the associated equilibria.

58

59 According to the original analyses of Smith et al. [1] there is minor substitution of for 60 lead, for aluminium and for arsenic. The analysis shows a departure from the

61 1: 1 ratio between AsO4 (or PO4) and SO4 ordinarily shown by members of the beudantite 62 group. However, a comparable departure may be observed in some of the published analyses

63 of beudantite and corkite, where SO4 predominant over AsO4 and PO4 respectively and in

64 svanbergite, where PO4 predominates over SO4. Hidalgoite also shows a slight excess of 65 water, according to Smith et al. [1]. If the Al is replaced by Fe3+, then the mineral beaudantite

66 is formed. If the sulphate is either completely or partially replaced by HAsO4 then the

67 mineral philipsbornite is formed. If AsO4 is replaced by PO4 then the mineral hinsdalite is 68 obtained. Another mineral that could form solid solutions is plumbogummite. All of these 69 minerals belong to the beaudantite mineral group, a subset of the supergroup [13]. 70 Jambor et al. described by the use of ternary phase diagrams the relationship between these 71 minerals [14]. The Raman spectroscopy of many of these mineral groups and their solid 72 solutions has not been reported. It is noted some infrared studies of hidalgoite and related 73 minerals have been undertaken [15].

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75 The reason for this research is that minerals such as hidalgoite are found in soils and in old 76 mine sites. Further, the formation of hidalgoite can be used as the basis for arsenic 77 accumulation. Therefore, this research focuses on the molecular structure of hidalgoite. 78 Raman spectroscopy has proven very useful for the study of minerals, [16-22] especially for 79 the study of diagenetically related minerals as often occurs with minerals containing arsenate 80 and phosphate groups, including tsumebite and arsenotsumebite. This paper is a part of 81 systematic studies of vibrational spectra of minerals of secondary origin in the oxide 82 supergene zone [23-27]. In this work we attribute bands at various wavenumbers to 83 vibrational modes of hidalgoite using Raman spectroscopy complimented with infrared 84 spectroscopy and relate the spectra to the structure of the mineral.

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86 Experimental

87 Minerals

88 The mineral hidalgoite was supplied by The Mineralogical research Company. The mineral 89 originated from The Gold Hill Mine, Tooele County, Utah, USA [2]. The mineral is also 90 known from the Adelaide Mine, Dundas, South Australia and at Broken Hill, New South 91 Wales. Details of the mineral have been published (page 245) [28]. A Raman spectrum of 92 hidalgoite in the 100 to 1200 cm-1 region is reported in the RRUFF data base 93 (http://rruff.info/Hidalgoite) . The sample number is R060683 and originated from the same 94 source The Gold Hill Mine, Tooele County, Utah, USA. The down loaded spectra are shown 95 in the supplementary information.

96 Raman spectroscopy

97 Crystals of hidalgoite were placed on a polished metal surface on the stage of an Olympus 98 BHSM microscope, which is equipped with 10x, 20x, and 50x objectives. The microscope is 99 part of a Renishaw 1000 Raman microscope system, which also includes a monochromator, a 100 filter system and a CCD detector (1024 pixels). The Raman spectra were excited by a 101 Spectra-Physics model 127 He-Ne laser producing highly polarised light at 633 nm and 102 collected at a nominal resolution of 2 cm-1 and a precision of ± 1 cm-1 in the range between 103 100 and 4000 cm-1. Repeated acquisition on the crystals using the highest magnification (50x) 104 was accumulated to improve the signal to noise ratio in the spectra. The spectrometer 105 calibrated using the 520.5 cm-1 line of a silicon wafer.

106 Infrared spectroscopy

107 Infrared spectra were obtained using a Nicolet Nexus 870 FTIR spectrometer with a smart 108 endurance single bounce diamond ATR cell. Spectra over the 4000−525 cm-1 range were 109 obtained by the co-addition of 128 scans with a resolution of 4 cm-1 and a mirror velocity of 110 0.6329 cm/s. Spectra were co-added to improve the signal to noise ratio.

111 Band component analysis was undertaken using the Jandel ‘Peakfit’ (Erkrath, 112 Germany) software package which enabled the type of fitting function to be selected and 113 allowed specific parameters to be fixed or varied accordingly. Band fitting was done using a 114 Lorentz-Gauss cross-product function with the minimum number of component bands used 115 for the fitting process. The Lorentz-Gauss ratio was maintained at values greater than 0.7 and

4

116 fitting was undertaken until reproducible results were obtained with squared correlations ( r2) 117 greater than 0.995. Band fitting of the spectra is quite reliable providing there is some band 118 separation or changes in the spectral profile.

119 Results and discussion 120 Background

121 The of jarosites and and related minerals have been studied for some 122 considerable time [29]. The structures are characterised by binding between the hydroxyl 123 units and the oxygens of the sulphate group [29]. In the case of hidalgoite, hydrogen bonding 124 with the arsenate anion will also occur. The sulphate tetrahedra are affected by the octahedral 125 cation and influenced by the monovalent cation [30]. Extensive studies of the 126 crystallography and thermodynamics of alunites and jarosites have been undertaken [31]. 127 Very few studies of the compounds with mixed anions in the structure have been forth 128 coming. Some vibrational spectroscopic studies have been reported [32]. No spectroscopic 129 studies of hidalgoite have been forthcoming.

2- 3- 130 The Td symmetry is characteristic for both free units (SO4) and (AsO4) ions. In dilute 2- -1 131 aqueous solutions, (SO4) ions exhibit the symmetric stretching vibration (A1, ν1), 983 cm – -1 132 Raman active, the doubly degenerate bending vibration (E, ν2), 450 cm – Raman active, the -1 133 triply degenerate antisymmetric stretching vibration (F2, ν3), 1105 cm – Raman and infrared -1 134 active, and the triply degenerate bending vibration (F2, ν4), 611 cm – Raman and infrared 135 active. Any symmetry lowering may activate some or all vibrations in both Raman and IR 136 and cause the splitting of degenerate vibrations [33-35] . Fundamental vibrational modes for 3- -1 137 (AsO4) are the symmetric stretching vibration (A1, ν1), 837 cm – Raman active, the doubly -1 138 degenerate bending vibration (E, ν2), 349 cm – Raman active, the triply degenerate -1 139 antisymmetric stretching vibration (F2, ν3) – 878 cm – Raman and infrared active, and the -1 140 triply degenerate bending vibration (F2, ν4), 463 cm – Raman and infrared active. Similarly, 141 as in the case of sulfate ions, any symmetry lowering may cause Raman and infrared 142 activation of some or all vibrations and the splitting of degenerate vibrations [34, 36].

143 Raman spectroscopy

144 The Raman spectrum of hidalgoite in the 700 to 1200 cm-1 region and the infrared spectrum 145 in the 500 to 1300 cm-1 region are reported in Figures 1a and 1b. This spectral region is 146 where the sulphate and arsenate stretching vibrations are to be found. The Raman spectrum of

5

147 hidalgoite extracted from the RRUFF data base is displayed in the supplementary information 148 (Figures S1-3). The spectrum is very similar to that reported in this work (Figure S1). The 149 Raman spectrum displays the symmetric stretching modes and the infrared spectrum tends to 150 show the antisymmetric stretching bands. Two Raman bands are observed at 853 and 879 -1 3- 151 cm . These bands are assigned to the ν3 (AsO4) antisymmetric stretching mode and ν1 3- -1 152 (AsO4) symmetric stretching mode respectively. An intense Raman band at 1014 cm with -1 2- 153 a broad shoulder at 998 cm is assigned to the ν1 (SO4) symmetric stretching mode. The -1 2- 154 broad band at 1093 cm is attributed to the ν3 (SO4) antisymmetric stretching mode.

155

156 The infrared spectrum in this spectral region shows a broad band which may be resolved into -1 -1 157 component bands at 902, 855 and 800 cm . The band at 800 cm is assigned to the ν3 3- -1 2- 158 (AsO4) antisymmetric stretching mode. The band at 1013 cm is assigned to the ν1 (SO4) 159 symmetric stretching mode. The infrared bands at 1043, 1074, 1115, 1182 and 1207 cm-1 are 2- 160 assigned to the ν3 (SO4) antisymmetric stretching mode. The observation of multiple 161 sulphate bands in this spectral region supports the concept of a reduction in symmetry of the 162 sulphate anion. However, this concept is not supported by the Raman spectrum where a 163 single band at 1093 cm-1 is observed. The band is broad and is probably composed of a 164 number of component bands.

165

166 Interestingly, a large number of peaks are observed in the infrared spectrum between 500 and 167 700 cm-1 region. Infrared bands are observed at 583, 590, 615, 627 and 653 cm-1. These 2- 168 bands are assigned to the ν4 (SO4) bending modes. The observation of multiple bands also 169 supports the concept of the reduction in symmetry of the sulphate anion. Multiple bands are 170 also observed in the Raman spectrum of hidalgoite at 595, 631 and 649 cm-1. An intense 171 Raman band is observed at 528 cm-1 with a shoulder band at 513 cm-1. These bands are of 172 lower intensity in the RUFF hidalgoite spectrum and are observed at 513 and 527 cm-1 173 (Figure S2). The Raman bands at 433 and 480 cm-1 are ascribed to the triply degenerate 3- -1 174 (AsO4) bending vibration (F2, ν4). The bands were observed at 435 and 479 cm in the 175 RRUFF hidalgoite spectrum. The Raman spectrum of hidalgoite in the 75 to 375 cm-1 region 176 is shown in Figure 3. The strong Raman band at 334 cm-1 with a shoulder at 351 cm-1 is 3- -1 177 assigned to the (AsO4) ν2 bending vibration. These bands were found at 308 and 328 cm

6

178 in the RRUFF hidalgoite Raman spectrum. Other Raman bands are observed at 107, 142, 179 157, 210, 234 and 265 cm-1.

180

181 The Raman spectrum of hidalgoite in the 3000 to 3600 cm-1 region and the infrared spectrum 182 in the 2600 to 3700 cm-1 region are displayed in Figures 4a and 4b. Raman bands are 183 observed at 3185, 3351 and 3477 cm-1. The first two bands appear to be water stretching 184 vibrations and the sharper band at 3477 cm-1 may be assigned to the OH stretching vibration. 185 Smith et al. [1] proposed that there may be water in the hidalgoite structure and perhaps 186 Raman spectroscopy confirms its presence. The infrared spectrum shows bands at 3072, 187 3231, 3376 and 3455 cm-1. The Raman spectrum of hidalgoite in the 1600 to 1850 cm-1 188 region and the infrared spectrum in the 1300 to 1850 cm-1 region are reported in Figures 5a 189 and 5b. A broad band is observed in the Raman spectrum at 1730 cm-1. The infrared 190 spectrum shows more complexity with bands observed at 1366, 1413, 1448, 1491, 1601 and 191 1646 cm-1. This latter band may be assigned to the water bending vibrational mode. The 192 position of this band indicates that the water molecules are involved in strong hydrogen 193 bonds. The band at 1601 cm-1 is attributed to weakly hydrogen bonded water molecules. The 194 first four bands are due to OH deformation modes of the OH units. The observation of 195 multiple bands suggests that the OH units are not equivalent. Clarkson et al. [2] provided an 196 analysis of the Gold Hill mine hidalgoite and reported the mineral analysed with 13.8% 197 water. Both the Raman and infrared spectra support the presence of water in the hidalgoite 198 structure. Based upon these facts the formula of hidalgoite may be modified from

199 PbAl3(AsO4)(SO4)(OH)6 to PbAl3(AsO4)(SO4)(OH)6·xH2O or even

200 PbAl3(AsO4)(SO4)(OH)5·xH2O. In either case molecular water is involved in the hidalgoite

201 structure.

202

203 Studies have shown a strong correlation between OH stretching frequencies and both 204 O…O bond distances and H…O hydrogen bond distances [37-40]. Libowitzky showed that a 205 regression function can be employed relating the hydroxyl stretching frequencies with 206 regression coefficients better than 0.96 using infrared spectroscopy [41]. The function is

−d (O−O) 0.1321 -1 207 described as: ν1 = (3592 − 304) ×109 cm . Thus, OH---O hydrogen bond distances 208 may be calculated using this Libowitzky empirical function.

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209

210 The values for the OH stretching vibrations labelled in Figure 4, provide hydrogen 211 bond distances using the Raman wavenumber positions, of 2.6989 Å (3185 cm-1), 2.7682 Å 212 (3351cm-1), 2.8659 Å (3477 cm-1) and using the infrared wavenumber positions of 2.6666 Å 213 (3072 cm-1), 2.7826 Å (3376 cm-1), 2.8428 Å (3455 cm-1). The values for the mineral 214 beudantite are hydrogen bond distances of 2.800 Å (3403 cm-1), 2.634 Å (3198 cm-1), 2.681 215 Å (3128 cm-1), and 2.634 Å (3022 cm-1). The large hydrogen bond distances observed for 216 hidalgoite are also observed in other mixed anion minerals such as beaudantite, where the 217 distances range between 3.052(5) and 2.683(6) Å. Such hydrogen bond distances are typical 218 of secondary minerals. A range of hydrogen bond distances are observed from reasonably 219 strong to weak hydrogen bonding. This range of hydrogen bonding contributes to the stability 220 of the mineral.

221

222 Mechanism of arsenic migration and entrapment

223 A number of methods have been tried to remove arsenic from the environment [42-44]. It is 224 known that ferric chloride and FeO(OH) are useful for the entrapment of arsenic [45-48]. 225 Minerals such as goethite and haematite are often found as components in soils.

2+ 3+ 3- 2- 226 If the solution contains the appropriate ions including Pb , Al , AsO4 , SO4 then a 227 chemical reaction may occur to form an intermediate colloidal mineral in the form of a gel. 228 Upon removal of water and upon crystallization, the mineral hidalgoite

229 PbAl3(AsO4)(SO4)(OH)6 may form. The following reaction is envisaged.

2+ 3+ 3- 2- 230 Pb + 3Al + 2AsO4 + 2SO4 + 6 OH- → PbAl3(AsO4,SO4)2(OH)6

231 This formation offers a mechanism for the capture and entrapment of the arsenate 232 anion. Of course, other minerals other than hidalgoite can form depending on pH, 233 temperature, solubility and other conditions. Red mud has nearly all of the ions required to 234 form hidalgoite and the concentration of the hydroxyl ions may facilitate its formation [49].

235

236 Arsenic contamination in soils is a real problem. Remediation of soils is even a more difficult 237 problem. Arsenic accumulation in soils ahs resulted from the use of arsenic compounds in

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238 cattle dips and in the use of arsenic compounds for wood preservation. The question arises as 239 to whether the arsenic is labile and whether it will translocate into subterranean water 240 systems. It is important to find technology which will lock up the arsenic/arsenate 241 compounds. The formation of minerals such as hidalgoite offers a mechanism for soil 242 remediation from arsenic contamination.

243

244 Conclusions 245

246 This research has used vibrational spectroscopy to determine the molecular structure of the 247 mineral hidalgoite. A mineral sample from the Gold Hill mine has been analysed by a 248 combination of Raman and infrared spectroscopy. Raman bands were assigned to the 2- 3- - 249 stretching and bending vibrations of (SO4) , (AsO4) and hydrogen bonded (OH) ions, to the 250 stretching and bending vibrations and libration modes of hydrogen bonded OH units, to Al- 251 (O,OH) stretching vibrations and to lattice vibrations. The Raman and infrared spectra were 252 identical except in the OH vibrational regions. These differences were attributed to 253 differences in the hydrogen bonding of OH units. Raman and infrared spectroscopy proves 254 the presence of water in the hidalgoite structure. This brings into question the formula of 255 hidalgoite.

256

257 Acknowledgments

258 The financial and infra-structure support of the Queensland University of Technology, 259 Chemistry discipline is gratefully acknowledged. The Australian Research Council (ARC) is 260 thanked for funding the instrumentation.

261

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262 REFERENCES

263 [1] R.L. Smith, F.S. Simons, A.C. Vlisidis, American Mineralogist 38 (1953) 1218. 264 [2] J.F. Clarkson, W.L. Roberts, A.L. Lingard, Mineralogical Record 2 (1971) 212. 265 [3] C. Guillemin, Bulletin de la Societe Francaise de Mineralogie et de Cristallographie 266 78 (1955) 27. 267 [4] K.Y. Chiang, K.C. Lin, S.C. Lin, T.-K. Chang, M.K. Wang, Journal of Hazardous 268 Materials 181 (2010) 1066. 269 [5] A. Courtin-Nomade, C. Neel, H. Bril, M. Davranche, Bulletin de la Societe 270 Geologique de France 173 (2002) 479. 271 [6] D.L. Harris, B.G. Lottermoser, J. Duchesne, Australian Journal of Earth Sciences 50 272 (2003) 797. 273 [7] C. Rewitzer, R. Hochleitner, Rivista Mineralogica Italiana (1989) 83. 274 [8] F.M. Romero, R.M. Prol-Ledesma, C. Canet, L.N. Alvares, R. Perez-Vazquez, 275 Applied Geochemistry 25 (2010) 716. 276 [9] R. Giere, N.V. Sidenko, E.V. Lazareva, Applied Geochemistry 18 (2003) 1347. 277 [10] J.O. Okonkwo, Bull Environ Contam Toxicol 79 (2007) 380. 278 [11] C. Roussel, C. Neel, H. Bril, Science of the Total Environment 263 (2000) 209. 279 [12] J.M. Nieto, M.A. Capitan, R. Saez, G.R. Almodovar, Transactions of the Institutions 280 of Mining and Metallurgy, Section B: Applied Earth Science 112 (2003) B293. 281 [13] K.M. Scott, American Mineralogist 72 (1987) 178. 282 [14] J.L. Jambor, D.R. Owens, J.D. Grice, M.N. Feinglos, Canadian Mineralogist 34 283 (1996) 1305. 284 [15] S.V. Gevorkyan, A.A. Petrunina, A.S. Povarennykh, Konstitutsiya i Svoistva 285 Mineralov 10 (1976) 51. 286 [16] R.L. Frost, S. Bahfenne, J. Raman Spectrosc. 41 (2010) 207. 287 [17] R.L. Frost, S. Bahfenne, J. Raman Spectrosc. 41 (2010) 325. 288 [18] R.L. Frost, S. Bahfenne, J. Cejka, J. Sejkora, S.J. Palmer, R. Skoda, J. Raman 289 Spectrosc. 41 (2010) 690. 290 [19] R.L. Frost, S. Bahfenne, J. Cejka, J. Sejkora, J. Plasil, S.J. Palmer, J. Raman 291 Spectrosc. 41 (2010) 814. 292 [20] R.L. Frost, K.H. Bakon, S.J. Palmer, J. Raman Spectrosc. 41 (2010) 78. 293 [21] R.L. Frost, J. Cejka, J. Sejkora, J. Plasil, S. Bahfenne, S.J. Palmer, J. Raman 294 Spectrosc. 41 (2010) 571. 295 [22] R.L. Frost, J. Cejka, J. Sejkora, J. Plasil, S. Bahfenne, S.J. Palmer, J. Raman 296 Spectrosc. 41 (2010) 566. 297 [23] R.L. Frost, S.J. Palmer, J. Mol. Struct. 988 (2011) 47. 298 [24] R.L. Frost, S.J. Palmer, H.J. Spratt, W.N. Martens, J. Mol. Struct. 988 (2011) 52. 299 [25] R.L. Frost, S.J. Palmer, Y. Xi, J. Mol. Struct. 1001 (2011) 43. 300 [26] R.L. Frost, Y. Xi, S.J. Palmer, J. Mol. Struct. 1001 (2011) 56. 301 [27] S.J. Palmer, R.L. Frost, J. Mol. Struct. 994 (2011) 283. 302 [28] J.W. Anthony, R.A. Bideaux, K.W. Bladh, M.C. Nichols, Handbook of Mineralogy 303 Vol.IV. Arsenates, phosphates, vanadates - Mineral Data Publishing, Tucson, Arizona. 304 Mineral data Publishing, Tucson, Arizona, 2000. 305 [29] S.B. Hendricks, American Mineralogist 22 (1937) 773. 306 [30] T. Kato, Y. Miura, Mineralogical Journal 8 (1977) 419. 307 [31] R.E. Stoffregen, C.N. Alpers, J.L. Jambor, Reviews in Mineralogy & Geochemistry 308 40 (2000) 453. 309 [32] S.C.B. Myneni, Reviews in Mineralogy & Geochemistry 40 (2000) 113. 310 [33] H.A. Szymanski, L. Marabella, J. Hoke, J. Harter, Appl. Spectrosc. 22 (1968) 297.

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311 [34] S.C.B. Myneni, Rev. Mineral 40 (2000) 113. 312 [35] M.D. Lane, American Mineralogist 92 (2007) 1. 313 [36] P. Keller, Neues Jb. Mineral. Mh. 11 (1971H) 491. 314 [37] J. Emsley, Chemical Society Reviews 9 (1980) 91. 315 [38] H. Lutz, Structure and Bonding (Berlin, Germany) 82 (1995) 85. 316 [39] W. Mikenda, Journal of Molecular Structure 147 (1986) 1. 317 [40] A. Novak, Structure and Bonding (Berlin) 18 (1974) 177. 318 [41] E. Libowitsky, Monatschefte fÜr chemie 130 (1999) 1047. 319 [42] D. Burghardt, E. Simon, K. Knoeller, A. Kassahun, Journal of Contaminant 320 Hydrology 94 (2007) 305. 321 [43] J. Miller, H. Akhter, F.K. Cartledge, M. McLearn, Journal of Environmental 322 Engineering (Reston, Virginia) 126 (2000) 1004. 323 [44] C. Singhakant, T. Koottatep, J. Satayavivad, J. Environ. Sci. Health, Part A 324 Toxic/Hazard. Subst. Environ. Eng. 44 (2009) 163. 325 [45] W. Davidson, J.C. Schaumloffel, Abstracts of Papers, 233rd ACS National Meeting, 326 Chicago, IL, United States, March 25-29, 2007 (2007) CHED. 327 [46] J.L. Mathieu, A.J. Gadgil, S.E.A. Addy, K. Kowolik, J. Environ. Sci. Health, Part A 328 Toxic/Hazard. Subst. Environ. Eng. 45 (2010) 1446. 329 [47] C. Su, R.W. Puls, Environ. Sci. Technol. 38 (2004) 5224. 330 [48] C.T. Yavuz, J.T. Mayo, C. Suchecki, J. Wang, A.Z. Ellsworth, H. D'Couto, E. 331 Quevedo, A. Prakash, L. Gonzalez, C. Nguyen, C. Kelty, V.L. Colvin, Environmental 332 Geochemistry and Health 32 (2010) 327. 333 [49] D. McConchie, M. Clark, H. Genc-Fuhrman, Iron Control Technol., Proc. Int. Symp. 334 Iron Control Hydrometall., 3rd (2006) 927. 335 336

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343 List of Figures

344 Figure 1a Raman spectrum of hidalgoite in the 700 to 1200 cm-1 region.

345 Figure 1b Infrared spectrum of hidalgoite in the 500 to 1300 cm-1 region.

346 Figure 2 Raman spectrum of hidalgoite in the 400 to 700 cm-1 region.

347 Figure 3 Raman spectrum of hidalgoite in the 75 to 375 cm-1 region.

348 Figure 4a Raman spectrum of hidalgoite in the 3000 to 3600 cm-1 region.

349 Figure 4b Infrared spectrum of hidalgoite in the 2600 to 3700 cm-1 region.

350 Figure 5a Raman spectrum of hidalgoite in the 1600 to 1850 cm-1 region.

351 Figure 5b Infrared spectrum of hidalgoite in the 1300 to 1900 cm-1 region.

352

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Figure 1a Figure 1b

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367 Figure 2

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370 Figure 3

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Figure 4a Figure 4b

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Figure 5a Figure 5b

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