Structural state of rare earth elements in eudialyte-group minerals

This work was carried out under the NERC-funded SOS RARE consortium [grant NE/M010856/1 to AMB, NJH and AF]. We thank Diamond Light Source and KIT Karlsruhe Light Source for beam time at I18 [grants SP14793 and SP15903 to AMB and AF] and SUL-X, respectively. PG was funded by the People Programme (Marie Curie Actions) in the EU Seventh Framework Programme (FP7/2007-2013), REA grant agreement no. 609405 (COFUNDPostdocDTU).Eudialyte-group minerals (EGM) attract global interest as potential resources for high-field-strength elements (e.g. Zr, Nb, Ta, and rare-earth elements), i.e. critical materials for modern technologies. They are particularly valued for their relative enrichment in the most critical lanthanides, i.e. Nd and heavy rare earth elements (Gd–Lu). However, rare earth element (REE) substitution mechanisms into the EGM structure are still poorly understood. Light and heavy REE may occupy different sites and there may be ordering and/or defect clustering in the structure. This study uses X-ray absorption spectroscopy to determine the structural state of REE in EGM from prospective eudialyte-bearing complexes. Yttrium K-edge and Nd L3-edge spectra were collected as proxies for heavy and light REE, respectively, and compared to natural and synthetic REE-bearing standards. Extended X-ray absorption fine structure data yield best fits for Y in six-fold coordination with Y–O distances of 2.24–2.32 Å, and a second coordination sphere comprising Fe, Na, Ca, Si and O at radial distances of 3.6–3.8 Å. These findings are consistent with dominant Y3+ substitution for Ca2+ on the octahedral M1 site in all the samples studied, and exclude preferential substitution of Y3+ onto the smaller octahedral Z site or the large low-symmetry N4 site. Using lattice strain theory, we constructed relative partitioning models to predict site preferences of lanthanides we have not measured directly. The models predict that all REE are favoured on the Ca-dominant M1 site and that preferential partitioning of heavy over light REE increases in EGM containing significant Mn in the M1-octahedral rings (oneillite subgroup). Thus, the flat REE profiles that make EGM such attractive exploration targets are not due to preferential partitioning of light and heavy REE onto different sites. Instead, local ordering of Mn- and Ca-occupied M1 sites may influence the capacity of EGM to accommodate heavy REE.Publisher PDFPeer reviewe

REE induced defects in minerals : a spectroscopic study

This thesis examines the luminescence and mineral physics of Rare Earth Element (REE) bearingminerals as a precursor to developing smart sorting tools for critical metals used in low-carbontechnologies. I characterise luminescence responses of complex zirconosilicates; eudialyte(Na₁₅Ca₆(Fe²⁺,Mn²⁺)₃Zr₃[Si₂₅O₇₃](O,OH,H₂O)₃(OH,Cl)₂), wöhlerite (NaCa₂(Zr,Nb)(Si₂O₇)(O,OH,F)₂) andcatapleiite (Na₂Zr(Si₃O₉) · 2H2₂O). Fluorite was included as it is commonly associated with REE ores anddisplays strong REE luminescence. Its behaviour provides key insights into REE substitution into ionicminerals.X-ray Excited Optical Luminescence (XEOL) and Thermoluminescence (TL) measurements were taken from 20 to 673 K. Fluorite responses result from a balance of intrinsic luminescence and REEsubstituents and evidence for REE and defect coupling. TL indicates the presence of electron traps andthe coupling of these traps to lanthanide emissions, and it shows that the defect and the lanthanideare clustered in physical space. The absence of changes in TL for different lanthanides shows thatenergy is passed efficiently between rare earths, indicating that the REE are clustered. The zirconosilicates all show increased intensity in XEOL response below 150 K. Cryogenic emissionsare interpreted as originating from the host mineral. There are 3 shared features: UV (~280 nm)paramagnetic oxygen or oxygen vacancy; blue (440 nm) Al-O⁻-Al /Ti centres; and REE. Wöhlerite and eudialyte show Fe³⁺ band (~708 nm) and wöhlerite displays broad emission attributed to Mn²⁺. Eudialyte shows two additional responses; UV (~320 nm) tentatively assigned to Na migration andUV/blue (~400 nm) potentially associated with charge balances associated with the coupledsubstitution of Al³⁺. Eudialyte shows little emission at room temperature, this is attributed to quenching from Fe²⁺. Emission from eudialyte above room temperature is attributed to alterationminerals such as catapleiite and potentially to inclusions of luminescent primary mineral phases.I demonstrate that smart sorting could be a valuable beneficiation tool for REE minerals

REE induced defects in minerals; a spectroscopic study (thesis data)

Data associated with thesis. The data files are embargoed until 24/06/202

Structural state of rare earth elements in eudialyte-group minerals

Eudialyte-group minerals (EGM) attract global interest as potential resources for high-field-strength elements (e.g. Zr, Nb, Ta, and rare-earth elements), i.e. critical materials for modern technologies. They are particularly valued for their relative enrichment in the most critical lanthanides, i.e. Nd and heavy rare earth elements (Gd–Lu). However, rare earth element (REE) substitution mechanisms into the EGM structure are still poorly understood. Light and heavy REE may occupy different sites and there may be ordering and/or defect clustering in the structure. This study uses X-ray absorption spectroscopy to determine the structural state of REE in EGM from prospective eudialyte-bearing complexes. Yttrium K-edge and Nd L3-edge spectra were collected as proxies for heavy and light REE, respectively, and compared to natural and synthetic REE-bearing standards. Extended X-ray absorption fine structure data yield best fits for Y in six-fold coordination with Y–O distances of 2.24–2.32 Å, and a second coordination sphere comprising Fe, Na, Ca, Si and O at radial distances of 3.6–3.8 Å. These findings are consistent with dominant Y3+ substitution for Ca2+ on the octahedral M1 site in all the samples studied, and exclude preferential substitution of Y3+ onto the smaller octahedral Z site or the large low-symmetry N4 site.Using lattice strain theory, we constructed relative partitioning models to predict site preferences of lanthanides we have not measured directly. The models predict that all REE are favoured on the Ca-dominant M1 site and that preferential partitioning of heavy over light REE increases in EGM containing significant Mn in the M1-octahedral rings (oneillite subgroup). Thus, the flat REE profiles that make EGM such attractive exploration targets are not due to preferential partitioning of light and heavy REE onto different sites. Instead, local ordering of Mn- and Ca-occupied M1 sites may influence the capacity of EGM to accommodate heavy REE.</p

Lanthanide and yttrium substitution in natural fluorite (dataset)

“The data files are embargoed until 28/04/202

Prevalence of opioid dependence in Scotland 2015-2020: a Multi-Parameter Estimation of Prevalence (MPEP) Study

Background and aims: Drug-related deaths in Scotland more than doubled between 2011 and 2020. To inform policymakers and understand drivers of this increase, we estimated the number of people with opioid dependence aged 15–64 from 2014/15 to 2019/20.Design: We fitted a Bayesian multi-parameter estimation of prevalence (MPEP) model, using adverse event rates to estimate prevalence of opioid dependence jointly from Opioid Agonist Therapy (OAT), opioid-related mortality and hospital admissions data. Estimates are stratified by age group, sex and year.Setting: Scotland, 2014/15 to 2019/20.Participants: People with opioid dependence and potential to benefit from OAT, whether ever treated or not. Using data from the Scottish Public Health Drug Linkage Programme, we identified a baseline cohort of individuals who had received OAT within the last 5 years, and all opioid-related deaths and hospital admissions (whether among or outside of this cohort).Measurements: Rates of each adverse event type and (unobserved) prevalence were jointly modelled.Findings: The estimated number and prevalence of people with opioid dependence in Scotland in 2019/20 was 47 100 (95% Credible Interval [CrI] 45 700 to 48 600) and 1.32% (95% CrI 1.28% to 1.37%). Of these, 61% received OAT during 2019/20. Prevalence in Greater Glasgow and Clyde was estimated as 1.77% (95% CrI 1.69% to 1.85%). There was weak evidence that overall prevalence fell slightly from 2014/15 (change −0.07%, 95% CrI -0.14% to 0.00%). The population of people with opioid dependence is ageing, with the estimated number of people aged 15–34 reducing by 5100 (95% CrI 3800 to 6400) and number aged 50–64 increasing by 2800 (95% CrI 2100 to 3500) between 2014/15 and 2019/20.Conclusions: The prevalence of opioid dependence in Scotland remained high but was relatively stable, with only weak evidence of a small reduction, between 2014/15 and 2019/20. Increased numbers of opioid-related deaths can be attributed to increased risk among people with opioid dependence, rather than increasing prevalence

Healthy, regenerative and just: Guiding the development of a national strategy on climate, health and well-being for Australia

This case report is a reflective narrative, documenting the methods used to develop a policy framework for a National Strategy on Climate, Health and Well-being for Australia. The report aims to guide advocates, communities of practice, and governments in developing a comprehensive policy response to climate change and its health impacts.</p