Australian Resources Research Centre

Spent neodymium–iron–boron (NdFeB) magnets represent a valuable secondary source of rare earth elements (REEs). This study presents an innovative process for recovering Neodymium (Nd) from spent NdFeB magnets using inorganic Al(NO 3 ) 3 ·9H 2 O solution composed of aluminium nitrate nonahydrate (Al(NO 3 ) 3 ·9H 2 O) and water referred to as a “green Brønsted solvent.” Hammett acidity measurements confirm that concentrated solutions of Al(NO 3 ) 3 ·9H 2 O and H 2 O exhibit strong Brønsted acidity, enabling the selective leaching of Nd from NdFeB magnet sample roasted at 660 °C. A high separation factor of 4150 for Nd over iron (Fe) was achieved. This Al(NO 3 ) 3 ·9H 2 O solution offers significant advantages, including non-volatility, safety, high solubility, and excellent selectivity for REEs. Under optimal conditions (80 °C, solid-to-liquid ratio of 1:20, and leaching time of 150 min), 96.9% of Nd was leached, while Fe leaching was limited to just 0.9%. The dissolved Nd 3+ was subsequently recovered from the leachate by precipitation with oxalic acid, followed by oxidative roasting, yielding Nd 2 O 3 with a purity greater than 95%. This high selectivity and product purity demonstrate the feasibility of this process for producing high-quality Nd 2 O 3 suitable for reuse in NdFeB magnet manufacturing. Moreover, the approach minimizes impurity incorporation and downstream processing requirements, offering an environmentally friendly strategy for REEs recovery from secondary resources. • Green Brønsted solvent enables selective Nd leaching from spent NdFeB magnets. • Roasting of NdFeB at 660 °C significantly enhances the selective recovery of Nd. • High Nd/Fe separation factor of 4150 achieved with Al(NO 3 ) 3 ·9H 2 O and H 2 O solution. • Optimised leaching yielded 96.9% Nd recovery with only 0.9% Fe co-leached. • Nd 3+ recovered as >95% pure Nd 2 O 3 via oxalic acid precipitation and roasting.

Marginal-marine successions deposited in restricted basins under arid conditions are characterised by complex interplay between variable hydrodynamic conditions, localised carbonate-evaporitic production and continental surface processes. In such scenario, climatically driven shifts of depositional belts may result in stratigraphic compartmentalisation through vertical facies and environments dislocation. As importantly, accommodation variations across marine margins can lead to preferential deposition of coeval systems which may ultimately translate into stratigraphic sealing through lateral facies transition. By deciphering the relative influence of allogenic controls upon marine margins stratigraphic architectures in arid and restricted settings and by documenting their sedimentary products, this work provides a generalised sequence stratigraphic model for arid epicratonic basin fills.Stratigraphic arrangement of mixed paralic deposits is investigated across two margin-perpendicular transects of the Middle to Upper Jurassic San Rafael Group in Utah. Transgressive sequences of the Carmel and the Curtis formations deposited during flooding events of the Sundance Sea are intercalated between the aeolian- to fluvially-dominated low stand deposits of the Entrada Sandstone and the Summerville Formation. Facies changes and sequence stratigraphic surfaces are documented through detailed sedimentary logging and architectural panel interpretations at locations representative of 1) sediment-supply and accommodation controlled continental basin flanks; 2) autogenically overprinted paralic basin margin settings; 3) climatically controlled basin centre. Gamma-ray log data were collected in parts of the basin characterised by differing tectonics settings.Successions deposited during transgressions are dominantly associated with complex tidal embayments reworking contemporaneous continental sediment deposited further inland and may present contrasting architectural and lithological characteristics linked to variability in basin physiographic settings and climatic conditions. Transgression sequences are generally recorded as composite surfaces in continental basin flank settings although thin fluvial deposits may locally be preserved in the case of favourable accommodation and sediment supply conditions. Sedimentary successions deposited during relative sea-/base-level low stands are characterised by the advance of aeolian systems during aridity maximums and translate basinward to coastal unconfined large-scale alluvial accretion successions. Maximum regression surfaces are associated with terminations of aeolian dune fields. High-frequency climatic fluctuations are preferentially recorded in continental basin flank settings during regressive trends as aeolian dune field growth stages bounded by deflationary supersurfaces. Larger-scale T-R sequential frameworks and their associated spatio-temporal facies evolution are more likely to be controlled by overarching changes in rates of accommodation creation due to foreland basin tectonics. By incorporating spatial facies variations within stacking trends at a basin scale, the proposed model highlights the architectural complexity and facies diversity of depositional sequences within arid epicratonic basins and may constrain reservoir characteristics and associated stratigraphic heterogeneities.

Per- and polyfluoroalkyl substances (PFAS) contamination is widespread in our environment and partitioning at interfaces is a major factor that influences their fate and transport within a soil pore space. To develop better PFAS management and remediation strategies, we need to gain a deeper understanding of PFAS soil-porewater partitioning processes in situ. In this study, we investigated the partitioning of PFAS in a spiked agricultural soil and an Aqueous Film-Forming Foam (AFFF) impacted "aged" soil under various soil moisture conditions and when the soil pores were filled with a non-aqueous phase liquid (NAPL). Sulfur (S) K-edge X-ray absorption near edge structure (XANES) spectroscopy was used to probe S speciation in situ, and spectra were analysed applying a Gaussian Curve Fitting (GCF) approach. Six major S species were identified in both soils and PFAS partitioning behaviour was interpreted based on changes in sulfonate fractions, representing sulfonic acid-based PFAS. In the spiked soil, sulfonate fractions increased the most when soil pores had a water saturation ratio (SW) of 0.25, whereas in the "aged" soil the most significant increase occurred for completely saturated soil pores. These differences were attributed to differing micellar formation behaviours in freshly spiked versus AFFF impacted "aged" soils. A linear correlation was also observed between the ratio of total reduced S and sulfonate fractions against the degree of saturation of "aged" soil. Furthermore, in spiked soil it was observed that a lower percentage NAPL content at SW=0.25 led to higher partitioning of sulfonic acid-based PFAS.

Direct air capture (DAC) is crucial for mitigating climate change by directly removing CO2 from the atmosphere. However, the large-scale deployment of DAC is hindered by the lack of durable...

Summary Induced polarization (IP) effects in airborne electromagnetic (AEM) surveys have commonly been investigated in helicopter-borne systems, leaving both a bibliographic and application gap for fixed-wing configurations. This gap partly reflects the large relative number of helicopter compared to fixed wing AEM systems, but also the geometric complexity of fixed wing platforms. In these platforms, nine geometric parameters come into play: the pitch, roll, and yaw of both transmitter and receiver, plus the three-axis offsets between the coils. Shifts in these factors can distort the measured data in ways that aren’t uniquely attributable, making it hard to pinpoint whether negative recordings truly arise from IP or from geometry-related effects. The non-fixed geometry also complicates removal of the primary field, often requiring iterative processing steps that may suppress or alter spectral content linked to IP. With advances in airborne IP understanding from helicopter-borne systems, revisiting fixed-wing platforms is both timely and necessary. Part A of this two-part study addresses this issue using the TEMPEST™ fixed-wing system connecting numerical modelling with field evidence. A suite of synthetic two-layer models with variable resistivity and chargeability parameters was developed to evaluate the system’s sensitivity to polarizable structures. The experiments demonstrate that IP effects, including negative secondary field responses, can be reliably detected in fixed-wing AEM data, both in X and Z magnetic field components. The capacity of these systems to detect IP phenomena is, however, strongly dependent on the electrical conductance of the environment. For instance, both fixed-wing and helicopter-borne systems, elevated near-surface conductance enhances the amplitude of purely electromagnetic induction currents, which in turn can dominate the recorded response and obscure the comparatively weaker polarization currents. More in general, IP detectability depends on the strength of the EM response generated by induction currents flowing elsewhere, which can dominate the small reverse current flow from a polarizable target. This highlights the critical role of near-surface conductivity in controlling the expression of IP responses and underscores the need to carefully account for these factors when interpreting survey data. The synthetic results are then connected with field-scale observations from a subset of the AusAEM dataset, over 470 000 line-km of TEMPESTTM data, where negative responses align with areas of low shallow conductance, confirming the simulation results. These finding open the way to the Part B of this study, where TEMPESTTM data are inverted taking into account IP and compared with helicopter-borne results and geological information.