Schwermetall- und chloridhaltige Filterstäube. I. Phasenanalysen und Modellversuche zum Recycling

Flue Dusts Containing Heavy Metal Ions and Chloride.I. Phase Analysis, Model Experiments for Recycling Four flue dusts from a cement factory, an electric-furnace steelmaking plant and a municipal waste plant were analyzed by powder diffraction methods. Chloride combines above all with alkali ions or heavy metal ions, especially yielding PbCl₂ and KPb₂Cl₅. The controlled sublimation of these chloride compounds in open crucibles was developed and optimized in our laboratory. Between 850°C and 1150°C and at reaction times from 30 min up to 12 h, the chloride content decreases to below 0.1 wt-%. The sublimed phase mainly consists of alkali and lead chloride. Zinc is found in the flue dust as oxide and is enriched during this process. Recent investigations with a small waelz kiln give analogous results. With our procedure, the manufacturer by himself is able to exploit flue dusts containing a large amount of heavy metal elements and chloride which cannot be deposited. The remaining product contains mainly zinc oxide which can be recycled in the zinc industry or returned to the production process. The sublimed chloride compounds may be recycled in the potash industry.     

Molecular basis of lipase stereoselectivity

Lipases exhibit specific catalytic properties that make them attractive to biotechnological applications. Most important are the broad substrate specificity and the regio‐ and stereoselectivity of lipases. Despite mechanistic and structural similarities lipases differ significantly with respect to stereoselectivity toward natural and synthetic substrates. Models developed to describe and predict stereoselectivity toward certain types of synthetic substrates, e. g., secondary alcohols cannot be applied to natural acylglycerols, that are hydrolyzed by several animal and microbial lipases in a regioselective or stereoselective manner. Therefore, computer‐aided molecular modeling studies were used in order to predict the stereopreference of lipases toward triradylglycerols. Lipase variants with modified stereoselectivity properties toward triacylglycerols were engineered by re‐designing the recombinant enzyme. To understand the interactions governing lipase stereoselectivity towards natural substrates, knowledge of the structure of enzyme‐substrate complexes at the atomic level is essential. Such information can be obtained by X‐ray or NMR analysis of covalent enzyme‐inhibitor complexes. The crystal structures of enzymes complexed with triacylglycerol analog inhibitors allowed the identification of distinct binding sites for the three hydrophobic chains of the inhibitor.     

Enhancing DPCD in Liquid Products by Mechanical Inactivation Effects: Assessment of Feasibility

The enhancement of standard dense phase carbon dioxide (DPCD) pasteurization by additional mechanical effects was assessed in this work. These effects were induced during pasteurization by the sudden depressurization in a narrow minitube. The high flow velocities, moderate pressures (40–80 bar) and low temperatures (25–45 °C) lead to intense degasification and shear stress. The inactivation of the test microorganism Escherichia coli DH5α (E. coli DH5α) was determined before and after depressurization in the minitube, representing entirely chemical DPCD via dissolved CO₂ and total inactivation comprising the effects of dissolved CO₂ and mechanical effects, respectively. Compared to conventional DPCD pasteurization, which is mostly attributed to chemical effects, the additional mechanical effects increased the inactivation efficiency considerably.     

Kinetische Parameteridentifikation und Modelldiskriminierung am Beispiel der nassen Oxidation von Thiosulfat

Coke technology involves polluted wastewater, which must be treated efficiently in order not to pollute the environment and to comply with legal regulations. This requires a thorough understanding of the process. Due to the large number of possible modifications, sulfur compounds occupy a special position and, thus, knowledge of the reaction pathways and kinetics is essential for the design of apparatuses. By means of parameter estimation and model discrimination, kinetics are determined on the basis of experimental data and reaction schemes of the wet oxidation of thiosulfate are evaluated in order to describe the concentration course of all species with sufficient accuracy.     

Mesostructured Nonwovens with Penguin Downy Feather‐Like Morphology—Top‐Down Combined with Bottom‐Up

Polymer fibers play an important role in nature and technical systems. Fiber morphologies with off‐standing branches, as found in nature, e.g. in penguin downy feathers, provide unique properties but are unknown for man‐made polymer fiber systems. We discovered that it is possible to initiate seeded growth from trisamide seeded polystyrene fibers, prepared by core‐shell electrospinning, to form off‐standing supramolecular trisamide branches similar to penguin downy feathers but in polymer nonwovens and in nanoscale. Resulting mesostructured nonwovens show unique properties. For example, air filtration efficiency of 99.8% for the filtration of 0.3 µm aerosol particles, being significantly higher compared to neat electrospun polystyrene nonwovens as bench‐mark, showing only an efficiency of about 52.6%. Most remarkably, the pressure drop observed in filtration tests and thus, the energy consumption during filtration, did not increase up to a certain content of off‐standing supramolecular fibrils. This is a unique behavior, as higher filtration capabilities are typically connected to higher energy consumptions and pressure drops. Hence, branching electrospun fibers with supramolecular fibrils paves the way to new mesostructured nonwovens with unique morphologies, property profiles and applications in filtration, catalysis, and energy storage/harvesting, exploiting nature's concepts.