Phase relations at 900 °C, crystal chemistry, electrical and thermal transport measurements, and heat capacity data are reported for the clathrate systems: Ba ₈ {Pd,Pt} _x Si _{46- x} . For both systems a ternary clathrate phase was identified with a small homogeneity region extending at 900 °C for 2.5≤ x _Pd ≤4.1 and 2.8≤ x _Pt ≤4.9, respectively. Structural investigations of these clathrate phases at 300, 200 and 100 K define cubic primitive symmetry with the space group type P m 3 n consistent with clathrate type I. Studies of electronic and thermal transport groups both series of compounds close-by a semiconducting state. An sizeable charge carrier concentration in these systems, however, prevents sufficiently large thermopower values. In comparison to isostructural type I clathrates based on Ge, thermal conductivity – dominated by the lattice contribution – is larger due to the smaller mass of Si.

The continuous deposition of hazardous metalliferous wastes derived from industrial steelmaking processes will lead to space shortages while valuable raw metals are being depleted. Currently, these landfilled waste products pose a rich resource for microbial thermoacidophilic bioleaching processes. Six thermoacidophilic archaea (Sulfolobus metallicus, Sulfolobus acidocaldarius, Metallosphaera hakonensis, Metallosphaera sedula, Acidianus brierleyi, andAcidianus manzaensis) were cultivated on metal waste product derived from a steelmaking process to assess microbial proliferation and bioleaching potential. While all six strains were capable of growth and bioleaching of different elements,A. manzaensisoutperformed other strains and its bioleaching potential was further studied in detail. The ability ofA. manzaensiscells to break down and solubilize the mineral matrix of the metal waste product was observedviascanning and transmission electron microscopy. Refinement of bioleaching operation parameters shows that changes in pH influence the solubilization of certain elements, which might be considered for element-specific solubilization processes. Slight temperature shifts did not influence the release of metals from the metal waste product, but an increase in dust load in the bioreactors leads to increased element solubilization. The formation of gypsum crystals in course ofA. manzaensiscultivation on dust was observed and clarified using single-crystal X-ray diffraction analysis. The results obtained from this study highlight the importance of thermoacidophilic archaea for future small-scale as well as large-scale bioleaching operations and metal recycling processes in regard to circular economies and waste management. A thorough understanding of the bioleaching performance of thermoacidophilic archaea facilitates further environmental biotechnological advancements.

Cu- and Mn-bearing tourmalines from Brazil and Mozambique were characterised chemically (EMPA and LA-ICP-MS) and by X-ray single-crystal structure refinement. All these samples are rich in Al, Li and F (fluor-elbaite) and contain significant amounts of CuO (up to ~1.8 wt%) and MnO (up to ~3.5 wt%). Structurally investigated samples show a pronounced positive correlation between the <Y-O> distances and the (Li + Mn²⁺ + Cu + Fe²⁺) content (apfu) at this site with R ² = 0.90. An excellent negative correlation exists between the <Y-O> distances and the Al₂O₃ content (R ² = 0.94). The samples at each locality generally show a strong negative correlation between the X-site vacancies and the (MnO + FeO) content. The Mn content in these tourmalines depends on the availability of Mn, on the formation temperature, as well as on stereochemical constraints. Because of a very weak correlation between MnO and CuO we believe that the Cu content in tourmaline is essentially dependent on the availability of Cu and on stereochemical constraints.