We have performed a detailed structural analysis of several crystals from the Sb2Te3−xSex solid solution (with x = 0–1.55) using a combination of single-crystal and powder X-ray diffraction and high-resolution scanning transmission electron microscope imaging combined with energy-dispersive X-ray spectroscopic mapping. The experimental study was supported by quantum-chemical calculations. All compounds crystallize in the rhombohedral tetradymite structure type in which the atoms occupy three symmetrically independent crystallographic sites; the two chalcogenide sites A1 and A2, and the antimony site Sb. They form quintuple A2–Sb–A1–Sb–A2 layers perpendicular to the [001] direction, held together via A2–A2 chalcogenide-chalcogenide interactions. The results of our experimental study show unambiguously, and in agreement with quantum-chemical calculations, a preferred incorporation of selenium into the A2 position inside the layers. An unexpected increase of the van-der-Waals inter-layer distances is observed for low Se contents (x < 1) and discussed with the help of DFT calculations.

l-Lysine is an essential amino acid of great importance for the pharmaceutical and nutrition industries and is mainly produced by the fermentative conversion of d-glucose. The technological bottleneck for an efficient process is often the development of separation and purification technologies as they can account for 20–50% of the overall operation costs. Liquid-phase adsorption on zeolites is an energy-, resource-, and cost-saving alternative. Zeolites are a well-established and widely available class of adsorbents. In this research, a variety of commercial zeolites of different framework types with varying Si/Al ratios were used to investigate the adsorption of l-lysine from single-component solutions and lysine–glucose mixtures. l-Lysine recovery resulted in adsorption capacities of up to 169 mg g–1 on Hβ-30 in batch experiments. Zeolites showed high l-lysine selectivity in competitive adsorptions from lysine–glucose mixtures, outperforming previously reported adsorbents. Based on the analysis of adsorbent and adsorbate dimensions, a size-exclusion-based separation of l-lysine from d-glucose was proposed, which was found to be primarily responsible for the high l-lysine selectivity. Fourier transform infrared spectroscopy analysis allowed proposing a structure–adsorption relationship for l-lysine on zeolites. The transferability of the batch results to a continuous process was shown. In addition, a high desorption efficiency of up to 90% using water as the desorption solution could be achieved, complemented by successful recyclability tests over five consecutive adsorption–desorption cycles.

Bei Chemieprofessoren in den USA ist der Frauenanteil gestiegen. Allerdings setzen viele Chemikerinnen ihre akademische Karriere nicht fort.

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