Timothy D. Murphy

Klebelsbergite, Sb4O4SO4(OH)2: Stability relationships, formation in Nature, and refinement of its structure

Abstract The extent to which secondary Sb minerals control Sb dispersion in the supergene environment is yet to be fully understood. Stability studies of klebelsbergite have been undertaken to better under- stand its role in controlling Sb mobility and relationships with other secondary Sb minerals. Solubility in aqueous 0.1084 M HNO3 was determined at 298.15 K and the data obtained used to derive ∆Gfθ(klebelsbergite, s, 298.15 K) = -2056.4 ± 5.0 kJ/mol. Solubility data have been used to deduce the conditions under which the mineral can form as a thermodynamically stable phase. The single-crystal X-ray structure of synthetic klebelsbergite has been determined 293 K and is essentially the same as that reported earlier for atoms with Z ≥ 8. Crystal data: orthorhombic, space group Pca21, a = 5.7563(4), b = 11.2538(7), c = 14.8627(9) Å, V = 962.81(11) Å3, Z = 4. Refinement converged to R1 = 0.0154 for 2206 unique reflections with I > 2σ(I). The present study has located the hydroxyl H atoms on both O5 and O9. The H-bond arrangements are somewhat different to those proposed earlier with the quasi-linear O9-H···O3 interaction having <(DHA) = 171(6)°. The O5 hydroxyl H atom lies in a different position to that proposed earlier and is involved in a bifurcated H-bond arrangement with O2 and with itself in a symmetry-related position, with <(DHA) = 133(5) and 125(5)°, respectively.

Stabilities of byströmite, MgSb2O6, ordoñezite, ZnSb2O6 and rosiaite, PbSb2O6, and their possible roles in limiting antimony mobility in the supergene zone

Abstract In order to clarify the roles that secondary minerals may have in determining the extent of dispersion of Sb in the supergene environment, syntheses and stability studies of the Sb(V) oxides byströmite, MgSb2O6, ordoñezite, ZnSb2O6 and rosiaite, PbSb2O6, have been undertaken. Solubilities in aqueous HNO3 were determined at 298.2 K and the data obtained used to calculate values of DGfθ at the same temperature. The derived DGfθ (s, 298.2 K) values for MgSb2O6 (-1554.1 ±3.6 kJ mol-1), ZnSb2O6 (-1257.0 ±2.6 kJ mol-1) and PbSb2O6 (-1154.2 ±2.6 kJ mol-1) have been used in subsequent calculations to determine their relative stabilities and relationships with other secondary Sb minerals.

The stability of onoratoite, Sb8O11Cl2, in the supergene environment

Abstract Synthesis and solubility studies of onoratoite have been undertaken to determine the role of this rare secondary phase in the immobilization of Sb and the conditions responsible for its formation in the supergene zone. Solubility studies were undertaken at 298.15 K. A value of ΔGθf (Sb8O11Cl2, s, 298.15 K) = -2576 ± 12 kJ mol-1 was derived. Calculations involving sénarmontite, Sb2O3, klebelsbergite, Sb4O4SO4(OH)2 and schafarzikite, FeSb2O4, show that onoratoite is a thermodynamically stable phase only at negligible activities of SO42-(aq) and low activities of Fe2+(aq), at low pH and very high activities of Cl-(aq). This explains why onoratoite is such a rare secondary phase and why it cannot exert any significant influence on the dispersion of Sb in the supergene environment.

Syntheses and Structure Investigations of 3d Transition Metal Complexes with a Flexible N4O2-Donor Hexadentate Schiff-Base Ligand*

The syntheses and structure investigations of four new 3d transition metal complexes (1–4) with a flexible N4O2-donor hexadentate Schiff-base ligand are described; three complexes (1, 2, and 4) of FeIII, CoIII, and CuII metal ions have been investigated by UV-vis, FT-IR, high-resolution mass spectrometry (HR-MS), and scanning electron microscopy–electron dispersive spectroscopy, as well as single crystal X-ray diffraction. The X-ray structure of NiII complex 3 is also reported. The molecular structures of the complexes (1–3) demonstrate distorted octahedral coordination geometry, each exhibiting 1 : 1 (M : L) ratios and the CuII complex 4 shows a trinuclear structure with a CuII : L ratio of 3 : 2 in the solid state, which has been proven by X-ray diffraction. On the other hand, a mononuclear species of the CuII complex is formed in solution, which has been identified by electrospray ionization HR-MS.

Solubility of the nadorite group minerals: implications for mobility of Sb and Bi in oxidised settings

Environmental context The dispersion of antimony in the environment has been misunderstood over the last few decades. Investigating the solubility of naturally forming mineral phases such as nadorite resulted in determination of its limited role in Sb dispersion, providing evidence that nadorite can only limit antimony dispersion in mildly oxidising conditions. Nadorite can only play a significant role in Sb immobilisation in a particular redox window, which forms only a minor part of the framework of Sb dispersion. Abstract As part of a study of the control that secondary minerals exert on the dispersion of antimony and bismuth in the supergene environment, syntheses and stability studies of nadorite (PbSbO2Cl) and perite (PbBiO2Cl) have been undertaken. Solubilities in aqueous HNO3 were determined at 298.2K and the data obtained used to calculate values of ΔGfθ(298.2K). The ΔGfθ(s, 298.2K) values for PbSbO2Cl (–622.0±2.8kJmol–1) and PbBiO2Cl (–590.0±1.3kJmol–1) have been used in subsequent calculations to determine relative stabilities and relationships with other common secondary Sb and Bi minerals. While the role of nadorite in immobilising Sb is dependent upon the prevailing redox potential such that SbIII is stable, perite may be a significant phase in limiting the dispersion of Bi in certain supergene settings.

Characterisation of recycled aggregate concrete through x-ray mapping

Every year, urban development generates large volumes of solid waste due to the construction and demolition. Most of the waste from construction becomes landfilled; however, as the population grows continuously, land demand soon becomes a shortage. Therefore landfill is no longer a suitable option to deal with construction waste. Over the last decades, many researches have been carried out on the usage of recycled coarse aggregate. These researchers are primarily focused on the possibility of using recycled concrete aggregate (RCA) as a replacement for natural aggregate [1, 2]. RCA is produced by the crushing of original concrete, it is usually either fully or partially used in the recycled aggregate concrete (RAC) [3]. The use of recycled aggregate in concrete opens a whole new range of possibilities in the reuse of the waste materials.

Comparative Study between Microstructure of a Novel Durable Concrete and Normal Concrete Subjected to Harsh Environments

Degradation of concrete members exposed to aggressive sulphuric acid environments is a key durability issue that affects the life cycle performance and maintenance costs of vital civil infrastructures [1]. Groundwater, chemical waste, sulphur bearing compounds in backfill, acid rain in industrial zones and biogenic acid in sewage systems are the main sources of sulphuric acid affecting concrete structures. In this research, microstructures of a novel acid resistant concrete (ARC) and a type of conventional concrete (CC), as the reference, have been studied in the laboratory subjected to accelerated testing. For this purpose, ARC and CC, were immersed in 7% (by volume) sulphuric acid solution. Mechanical properties of both concretes as well as their microstructures were examined after 28 days of curing and then after two, four and eight weeks of exposure to acid. Scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Xray diffraction (XRD) and X-ray mapping (XRM) were employed to analyse the microstructure of concretes before and after exposure to acidic environment. The results of this analysis revealed interesting facts about the mechanism of sulphur penetration in both concrete samples. In addition, they showed differences in the crack locations and propagation patterns and in interfacial transition zones (ITZ) of concretes, particularly after acid exposure. These changes of microstructures, as was proved in experimental tests, could significantly contribute to changing the ductility of the concretes in modulus of rupture (MOR) test. DOI 10.21012/FC9.294 Shamila Salek et al. 1

X-ray Mapping Investigations of the Monazites from the Mt Weld Deposit - Compositional Variance as an Indicator of Provenance

The Mt Weld lanthanide deposit in central Western Australia is considered to be one of the largest high grade deposits known in the world, first reported as a carbonate and phosphate rich ultramafic silicate intrusion that contained a resource of the Lanthanide series [1]. It has been dated between 1.6 – 2.0 billion years, where the formation of a carbonate layer in the cooling melt created a preferred environment for elevated lanthanide deposition [2]. Mineralogical surveys of the area have outlined various primary lanthanide minerals however limited work has been undertaken on the supergene expression of the secondary lanthanide mineralogy, primarily due to the similar physical and electronic nature of the lanthanides.

Mineral Analyses & Implications on the Dispersion of Bismuth in the Supergene Environment of Eastern Australia.

In the Australian context, bismuth minerals are important constituents, associated with Mo, W and Sn, of highly acidic and very rich, low tonnage, deposits of the eastern ranges of Australia. Bi has been used extensively as a pathfinder element in geochemical exploration for a variety of such deposits and others and therefore it is important to understand its behaviour[1-3]. The behaviour of Bi has been described in the terms of its solution speciation as a function of pH which is well-established [4-7]and provides a first order, but simplistic, assessment of its mobility in pore solution in the regolith. Recent reviews have highlighted a lack of understanding in regards to bismuth in oxidising environments. Bismuth is estimated to have an average crustal abundance of 48 ppb [8], but is highly fractionated across different rock types and sediments with reported concentrations from 30 ppb to greater than 20 ppm an average Bi concentration in soils of 0.2 ppm but this is difficult to reconcile with the data mentioned above. A review of bismuth values [9] concluded similar concerns and further highlighted that a background ground water concentration could not be honestly concluded especially in uncontaminated environments. This is due to no independent focused study on Bi concentrations in the environment and that other factors such as sampling, testing methods and protocols were not consistent. To draw any conclusion on bismuth values, a proper understanding of the dispersion of Bi in oxidising environments must be made. This requires understanding of its low temperature aqueous chemistry and knowledge of the secondary Bi minerals that serve to buffer the element between the solid and solution states. This study used numerous natural and synthetic bismuth mineral samples and whole rock specimens. Full spectrum quantitative X-ray Mapping (XRM) was performed on a JEOL JXA 840 SEM with a Moran Scientific energy dispersive spectroscopy (EDS) Microanalysis system operated at 20kV. A JEOL 8600 EM Probe with a combined EDS and three JEOL wavelength dispersive spectrometers (WDS’s) were also used to perform trace and quantitative analysis. The analysis was undertaken at 15 kV and 20 nA. Drill core samples from the Mineral Hill mine site in regional NSW have been studied to determine the primary bismuth phases at this site which have been associated with a localised Au resource and then related to the known secondary expressions (Figure 1). Experiments have been carried out on a series of synthetic secondary bismuth minerals (Figure 2) to determine the chemical behaviour of these minerals by High Temperature X-ray Diffraction (HTXRD) and Thermogravimetric Analysis coupled with a Differential Scanning Calorimeter (TGA-DSC). These experiments have provided data which can be combined with low temperature solubility studies to give an in-depth understanding into the geochemical roles of secondary bismuth minerals in the supergene environment. For the first time a series of thermodynamic data sets for major and important bismuth mineral phases have been derived. As such a series of useful geochemical models have been