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We present new data about the chemical and structural characteristics of bauxite residue (BR) from Greek Al industry, using a combination of microscopic, analytical, and spectroscopic techniques. SEM-EDS indicated a homogeneous dominant “Al-Fe-Ca-Ti-Si-Na-Cr matrix”, appearing at the microscale. The bulk chemical analyses showed considerable levels of Th (111 μg g−1), along with minor U (15 μg g−1), which are responsible for radioactivity (355 and 133 Bq kg−1 for 232Th and 238U, respectively) with a total dose rate of 295 nGy h−1. Leaching experiments, in conjunction with SF-ICP-MS, using Mediterranean seawater from Greece, indicated significant release of V, depending on S/L ratio, and negligible release of Th at least after 12 months leaching. STEM-EDS/EELS & HR-STEM-HAADF study of the leached BR at the nanoscale revealed that the significant immobility of Th4+ is due to its incorporation into an insoluble perovskite-type phase with major composition of Ca0.8Na0.2TiO3 and crystallites observed in nanoscale. The Th LIII-edge EXAFS spectra demonstrated that Th4+ ions, which are hosted in this novel nano-perovskite of BR, occupy Ca2+ sites, rather than Ti4+ sites. That is most likely the reason of no Th release in Mediterranean seawater.

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Antimony, an emergent global contaminant, that is hydrothermally discharged along with other epithermal metals (-loids) (Au, As, Hg, Ag, Tl, Ag)

The νg 9/2 , d 5/2 , s 1/2 orbitals are assumed to be responsible for the swift onset of collectivity observed in the region below 68 Ni. Especially the single-particle energies and strengths of these orbitals are of importance. We studied such properties in the nearby 67 Ni nucleus, by performing a (d, p)-experiment in inverse kinematics employing a post-accelerated radioactive ion beam (RIB) at the REX-ISOLDE facility. The experiment was performed at an energy of 2.95 MeV/u using a combination of the T-REX particle detectors, the Miniball γ -detection array and a newly-developed delayed-correlation technique as to investigate μs-isomers. Angular distributions of the ground state and multiple excited states in 67 Ni were obtained and compared with DWBA cross-section calculations, leading to the identification of positive-parity states with substantial νg 9/2 (1007 keV) and νd 5/2 (2207 keV and 3277 keV) singleparticle strengths up to an excitation energy of 5.8 MeV. 50% of the νd 5/2 single-particle strength relative to the νg 9/2 -orbital is concentrated in and shared between the first two observed 5/2 + levels.A comparison with extended Shell Model calculations and equivalent ( 3 He, d) studies in the region around 90 40 Zr 50 highlights similarities for the strength of the negative-parity pf and positive-parity g 9/2 state, but differences are observed for the d 5/2 single-particle strength.

We consider two competing sets of nuclear magic numbers, namely the harmonic oscillator (HO) set (2, 8, 20, 40, 70, 112, 168, 240,...) and the set corresponding to the proxy-SU(3) scheme, possessing shells 0-2, 2-4, 6-12, 14-26, 28-48, 50-80, 82-124, 126-182, 184-256... The two sets provide 0 + bands with different deformation and bandhead energies. We show that for proton (neutron) numbers starting from the regions where the quadrupole-quadrupole (Q · Q) interaction, as derived by the HO, becomes weaker than the one obtained in the proxy-SU(3) scheme, to the regions of HO shell closure, the shape coexistence phenomenon may emerge. Our analysis suggests that the possibility for appearance of shape coexistence has to be investigated in the following regions of proton (neutron) numbers : 8, 18-20, 34-40, 60-70, 96-112, 146-168, 210-240,...