Deportment of radionuclides in copper concentrate from Olympic Dam

The Olympic copper-gold province of South Australia is home to the world’s largest uranium resource, representing at least 23% of the known global uranium budget. The primary commodity produced is copper, with secondary Au, Ag, and U (as U₃O₈) also recoverable in economic quantities. Processing the complex, fine-grained ore from Olympic Dam involves multiple, customisable stages of physical and chemical separation of target elements from non-target elements. During some stages of processing, deleterious components of the ore may behave adversely, affecting recovery efficiency or purity of product. Of particular interest to process engineers are daughter radionuclides (RNs) created from decay of ²³²th, ²³⁵U, and especially ²³⁸U. Specific activities of ²²⁶Ra, ²¹⁰Pb, and ²¹⁰Po are such that even concentrations of parts-per-trillion may be above acceptable levels for marketable copper concentrate. Most conventional analytical platforms emphasise either sensitivity (solution inductively coupled plasma mass spectrometry, thermal ionisation mass spectrometry) or high-resolution imaging (transmission electron microscopy, atom probe tomography). Ultra-trace-level RN concentrations combined with the extremely fine-grained nano-included mineral textures of Olympic Dam ore present an unusual challenge for researchers, in that few analytical techniques excel in both sensitivity and resolution. A comparison of available methods yielded excellent results from the CAMECA nanoscale secondary ion mass spectrometry (nanoSIMS) platform, capable of detecting (for the first time) extremely low RN signals in minerals with sub-micron resolution; consequently, nanoSIMS was chosen as the primary analytical method for this project. Subsequent to extensive method development and testing, over 3200 isotopic spatial distribution maps were collected on mineral samples from raw ore material, flotation concentrate, and acid-leached concentrate provided by BHP Olympic Dam. A qualitative RN budget has been created, prioritising minerals which contain significant RNs but also including unexpected minor host minerals and surficial adherence. Four manuscripts have resulted from these analyses, detailing RN host capabilities of various minerals including uraninite, brannerite, coffinite, thorianite, euxenite, apatite, fluorite, xenotime, monazite, baryte, anglesite, and Sr- and Ca-rich alunite-series phases. Mechanisms for surface-sequestration of RNs in high surface area minerals such as covellite and molybdenite have been identified, as well as electrokinetic effects responsible for substantial uptake of RNs on the surface of sulphide minerals. Additionally, diffusion experiments were performed on synthetic minerals to determine mobility of Sr, Ba, Pb, and Ra under varying conditions common to mineral processing. Two manuscripts have resulted from these investigations, emphasizing that baryte and anglesite are well-suited to remove substantial amounts of Ra and Pb from processing streams, especially during acid-leaching, through coupled dissolution-reprecipitation mechanisms. Laser ablation inductively coupled plasma mass spectrometry and nanoSIMS both provided excellent visual evidence for Ra uptake, well in agreement with published results from other research teams As a whole, the data set produced during this project has greatly increased our understanding of the deportment of radionuclides at Olympic Dam – and in uranium-bearing ore systems in general. Provided these data, process engineers are now better-suited to design and implement efficient RN removal procedures, thereby resulting in cleaner ore concentrates available to the global marketplace.Thesis (Ph.D.) -- University of Adelaide, School of Chemical Engineering and Advanced Materials, 201

Der Einfluss symbiotischer Bodenpilze auf den Stickstoffzyklus

To increase nutrient use efficiency and reduce nutrient losses are key aspects for sustainable agriculture. Arbuscular mycorrhizal fungi (AMF) are an import and widespread group of plant-symbiotic soil fungi. Here we investigate the role of those soil microorganisms, for effective nutrient recycling. We conducted greenhouse and lysimeter experiments to compare the cycling of important plant nutrients in systems with high and low abundance of AMF. AMF increased plant N nutrition, reduced leaching losses of mineral N, and prevented emissions of N2O, an important greenhouse gas. The results show the importance of AMF for an effective nutrient management. Farmers should implement strategies to promote AMF in the soil, as they are an indispensable compound of sustainable agriculture

Detection of Trace Elements/Isotopes in Olympic Dam Copper Concentrates by nanoSIMS

Many analytical techniques for trace element analysis are available to the geochemist and geometallurgist to understand and, ideally, quantify the distribution of trace and minor components in a mineral deposit. Bulk trace element data are useful, but do not provide information regarding specific host minerals—or lack thereof, in cases of surface adherence or fracture fill—for each element. The CAMECA nanoscale secondary ion mass spectrometer (nanoSIMS) 50 and 50L instruments feature ultra-low minimum detection limits (to parts-per-billion) and sub-micron spatial resolution, a combination not found in any other analytical platform. Using ore and copper concentrate samples from the Olympic Dam mining-processing operation, South Australia, we demonstrate the application of nanoSIMS to understand the mineralogical distribution of potential by-product and detrimental elements. Results show previously undetected mineral host assemblages and elemental associations, providing geochemists with insight into mineral formation and elemental remobilization—and metallurgists with critical information necessary for optimizing ore processing techniques. Gold and Te may be seen associated with brannerite, and Ag prefers chalcocite over bornite. Rare earth elements may be found in trace quantities in fluorapatite and fluorite, which may report to final concentrates as entrained liberated or gangue-sulfide composite particles. Selenium, As, and Te reside in sulfides, commonly in association with Pb, Bi, Ag, and Au. Radionuclide daughters of the 238U decay chain may be located using nanoSIMS, providing critical information on these trace components that is unavailable using other microanalytical techniques. These radionuclides are observed in many minerals but seem particularly enriched in uranium minerals, some phosphates and sulfates, and within high surface area minerals. The nanoSIMS has proven a valuable tool in determining the spatial distribution of trace elements and isotopes in fine-grained copper ore, providing researchers with crucial evidence needed to answer questions of ore formation, ore alteration, and ore processing

210Pb and 210Po in Geological and Related Anthropogenic Materials: Implications for Their Mineralogical Distribution in Base Metal Ores

The distributions of 210Pb and 210Po, short half-life products of 238U decay, in geological and related anthropogenic materials are reviewed, with emphasis on their geochemical behaviours and likely mineral hosts. Concentrations of natural 210Pb and 210Po in igneous and related hydrothermal environments are governed by release from crustal reservoirs. 210Po may undergo volatilisation, inducing disequilibrium in magmatic systems. In sedimentary environments (marine, lacustrine, deltaic and fluvial), as in soils, concentrations of 210Pb and 210Po are commonly derived from a combination of natural and anthropogenic sources. Enhanced concentrations of both radionuclides are reported in media from a variety of industrial operations, including uranium mill tailings, waste from phosphoric acid production, oil and gas exploitation and energy production from coals, as well as in residues from the mining and smelting of uranium-bearing copper ores. Although the mineral hosts of the two radionuclides in most solid media are readily defined as those containing parent 238U and 226Ra, their distributions in some hydrothermal U-bearing ores and the products of processing those ores are much less well constrained. Much of the present understanding of these radionuclides is based on indirect data rather than direct observation and potential hosts are likely to be diverse, with deportments depending on the local geochemical environment. Some predictions can nevertheless be made based on the geochemical properties of 210Pb and 210Po and those of the intermediate products of 238U decay, including isotopes of Ra and Rn. Alongside all U-bearing minerals, the potential hosts of 210Pb and 210Po may include Pb-bearing chalcogenides such as galena, as well as a range of sulphates, carbonates, and Fe-oxides. 210Pb and 210Po are also likely to occur as nanoparticles adsorbed onto the surface of other minerals, such as clays, Fe-(hydr)oxides and possibly also carbonates. In rocks, unsupported 210Pb- and/or 210Po-bearing nanoparticles may also be present within micro-fractures in minerals and at the interfaces of mineral grains. Despite forming under very limited and special conditions, the local-scale isotopic disequilibrium they infer is highly relevant for understanding their distributions in mineralized rocks and processing products

210pb and 210po in geological and related anthropogenic materials: Implications for their mineralogical distribution in base metal ores

The distributions of Pb-210 and Po-210, short half-life products of U-238 decay, in geological and related anthropogenic materials are reviewed, with emphasis on their geochemical behaviours and likely mineral hosts. Concentrations of natural Pb-210 and Po-210 in igneous and related hydrothermal environments are governed by release from crustal reservoirs. Po-210 may undergo volatilisation, inducing disequilibrium in magmatic systems. In sedimentary environments (marine, lacustrine, deltaic and fluvial), as in soils, concentrations of Pb-210 and Po-210 are commonly derived from a combination of natural and anthropogenic sources. Enhanced concentrations of both radionuclides are reported in media from a variety of industrial operations, including uranium mill tailings, waste from phosphoric acid production, oil and gas exploitation and energy production from coals, as well as in residues from the mining and smelting of uranium-bearing copper ores. Although the mineral hosts of the two radionuclides in most solid media are readily defined as those containing parent U-238 and Ra-226, their distributions in some hydrothermal U-bearing ores and the products of processing those ores are much less well constrained. Much of the present understanding of these radionuclides is based on indirect data rather than direct observation and potential hosts are likely to be diverse, with deportments depending on the local geochemical environment. Some predictions can nevertheless be made based on the geochemical properties of Pb-210 and Po-210 and those of the intermediate products of U-238 decay, including isotopes of Ra and Rn. Alongside all U-bearing minerals, the potential hosts of Pb-210 and Po-210 may include Pb-bearing chalcogenides such as galena, as well as a range of sulphates, carbonates, and Fe-oxides. Pb-210 and Po-210 are also likely to occur as nanoparticles adsorbed onto the surface of other minerals, such as clays, Fe-(hydr)oxides and possibly also carbonates. In rocks, unsupported Pb-210- and/or Po-210-bearing nanoparticles may also be present within micro-fractures in minerals and at the interfaces of mineral grains. Despite forming under very limited and special conditions, the local-scale isotopic disequilibrium they infer is highly relevant for understanding their distributions in mineralized rocks and processing products