The emission spectra and the lifetimes of the lasing transition ${}^4{I}_{13/2}{-}^4{I}_{15/2}$ in ${\mathrm{Er}}^{3+}$-doped ${\mathrm{TeO}}_2{-\mathrm{Z}\mathrm{n}\mathrm{O}-\mathrm{N}\mathrm{a}}_2\mathrm{O}$ ternary glasses have been studied. The investigation includes two main studies: The first part discusses the Raman spectroscopic analysis of the host glass structure. In the second part, we explain the dependence of ${\mathrm{Er}}^{3+}$-ion photoluminescence near 1500 nm on ${\mathrm{OH}}^{\mathrm{-}}$-ion concentration. The influence of the concentrations of ${\mathrm{Er}}_2{\mathrm{O}}_3$ and the glass structure modifiers (ZnO, ${\mathrm{Na}}_2\mathrm{O})$ on the lifetimes of ${}^4{I}_{13/2}$ level and line shape of the emission spectra has been analyzed. It was observed that the increasing concentrations of ${\mathrm{Er}}^{3+}$ ions resulted in spectral broadening as a consequence of ${\mathrm{Er}}^{3+}$ being distributed in the glass structure. The measured lifetimes of ${}^4{I}_{13/2}$ emission vary between 4.5 and 7.8 ms and strongly depend on OH-ion concentrations. The structural origin of the spectral broadening of the Er emission line is particularly discussed by analyzing the spectral components in the tellurite, modified silicate, and fluoride glass hosts. The number of spectral components at room temperature in Er-doped ${\mathrm{TeO}}_2,$ silicate, and fluoride glasses are compared, and the dependence of line strengths and site-to-site variation of the rare-earth ions on the structure of each glass is also explained. The unusually large broadening of the ${\mathrm{OH}}^{\mathrm{-}}$ band in the ${\mathrm{TeO}}_2$ family of glasses is analyzed in the context of the tellurite glass structure.

We report the fabrication of single-mode buried channel waveguides for the whole mid-IR transparency range of chalcogenide sulphide glasses ($\lambda \le 11\mathrm{\mu m}$), by means of direct laser writing. We have explored the potential of this technology by fabricating a prototype three-dimensional three-beam combiner for future application in stellar interferometry that delivers a monochromatic interference visibility of 99.89% at 10.6 μm and an ultrahigh bandwidth (3–11 μm) interference visibility of 21.3%. These results demonstrate that it is possible to harness the whole transparency range offered by chalcogenide glasses on a single on-chip instrument by means of direct laser writing, a finding that may be of key significance in future technologies such as astrophotonics and biochemical sensing.

Separation and purification of critical metal ions such as rare-earth elements (REEs), scandium and niobium from their minerals is difficult and often determines if extraction is economically and environmentally feasible. Solvent extraction is a commonly used metal-ion separation process, usually favored because of its simplicity, speed and wide scope, which is why it is often employed for separating trace metals from their minerals. However, the types of solvents widely used for the recovery of metal ions have adverse environmental impact. Alternatives to solvent extraction have been explored and advances in separation technologies have shown commercial establishment of liquid membranes as an alternative to conventional solvent extraction for the recovery of metals and other valuable materials. Liquid membrane transport incorporates solvent extraction and membrane separation in one continuously operating system. Both methods conventionally use solvents that are harmful to the environment, however, the introduction of ionic liquids (ILs) over the last decade is set to minimize the environmental impact of both solvent extraction and liquid membrane separation processes. ILs are a family of organic molten salts with low or negligible vapour pressure which may be formed below 100 °C. Such liquids are also highly thermally stable and less toxic. Their ionic structure makes them thermodynamically favorable solvents for the extraction of metallic ions. The main aim of this article is to review the current achievements in the separation of REE, scandium, niobium and vanadium from their minerals, using ILs in either solvent extraction or liquid membrane processes. The mechanism of separation using ILs is discussed and the engineering constraints to their application are identified.

Extraction of titanium and chromium oxides may be achieved via roasting the respective minerals with alkali at high temperatures, followed by water and organic acid leaching. In this study, sodium and potassium hydroxides are used as alkali for roasting of chromite ores and ilmenite mineral concentrates. The thermodynamic analysis of the roasting process is discussed in terms of designing the process. Samples of chromite and titaniferous minerals were roasted with NaOH and KOH in a temperature range of 400°C–1000°C in an oxidising atmosphere. The roasted chromite and ilmenite samples were further processed in order to extract water-soluble Na2CrO4 from the reacted chromite and purify titanium dioxide from titaniferous minerals, respectively. The TiO2 purity obtained after roasting at 400°C with NaOH and double leaching was 49.2wt.%, whereas when using KOH the purity was 54.5wt.%. The highest TiO2 purity obtained after roasting at 1000°C for 2h and double leaching with water and organic acids was 84wt.%. At low temperature (400°C) the recovery of chromium was higher for chromite roasted with KOH than for chromite roasted with NaOH. However, at high temperatures (700°C and 1000°C) chromium recoveries were similar when roasting with both hydroxides. Around 95% chromium extraction yield was achieved when chromite was roasted with sodium and potassium hydroxides at 1000°C for 2h and water leached