Optimization and Biomass Utilization in Heavy Metal Recycling

Environmental legislation, limited resources as well as high metal prices force the metallurgical industry more and more to make use of secondary materials. For this, also residues from metal production are nowadays considered as a possible resource. Due to their often complex structure and the presence of a multi-metal-system, efficient recycling of such materials is not easy to realize and suffers from various problems. The Christian Doppler Laboratory for Optimization and Biomass Utilization in Heavy Metal Recycling together with its partner companies Befesa R&D, voestalpine Stahl Linz, RHI, and Aurubis investigate alternative strategies and optimization possibilities for the considered residues. The achievements of three years’ activity in the major fields of the CDL, characterization of the complex input materials, upgrade of the product quality of recycling processes, utilization of biomass in the form of charcoal for use as a reducing agent and simultaneous recovery of valuable metals are described in the paper.     

Red wine: a source of potent ligands for peroxisome proliferator-activated receptor γ

Moderate red wine consumption has been correlated with lower incidences of cardiovascular diseases, inflammation, and metabolic diseases such as type 2 diabetes, obesity, and high blood pressure. We studied binding of ligands from different wines to the peroxisome proliferator-activated receptor γ (PPARγ), a key factor in glucose and lipid metabolism. Ellagic acid and epicatechin gallate (ECG) were identified by gas chromatography and mass spectroscopy in the most active wine fractions. They had an affinity to PPARγ similar to that of the standard pharmaceutical agent rosiglitazone, which is used for the treatment of type 2 diabetes. The IC(50) values of ellagic acid and ECG were 5.7 × 10(-7) M and 5.9 × 10(-7) M, respectively. All of the red wines had affinities for PPARγ equivalent to concentrations of rosiglitazone ranging from 52-521 μM. One hundred milliliters of the tested red wines was equivalent to approximately 1.8-18 mg of rosiglitazone. This volume contained an activity equivalent of at least a quarter of (and up to four times) the daily dose of this potent anti-diabetes drug. The ameliorating effects of red wine on metabolic diseases may be partially explained by the presence of PPARγ ligands.     

The missing piece: sediment records in remote Mountain lakes confirm glaciers being secondary sources of persistent organic pollutants

After atmospheric deposition and storage in the ice, glaciers are temporary reservoirs of persistent organic pollutants (POPs). Recently, the hypothesis that melting glaciers represent secondary sources of these pollutants has been introduced by investigations of the historical trend of POPs in a dated sediment core from the proglacial Alpine Lake Oberaar. Here, the hypothesis is further confirmed by the comparison of sediment data gathered from two Alpine lakes with a glaciated and a nonglaciated hydrological catchment. The two lakes (Lake Engstlen and Lake Stein in the Bernese Alps in Switzerland) are situated only 8 km apart at similar altitude and in the same meteorological catchment. In the nonglacial lake sediment of Lake Engstlen, PCBs and DDT (polychlorinated biphenyls and dichlorodiphenyl trichloroethane) levels culminated with the historic usage of these chemicals some 30-50 years ago. In the glacial Lake Stein, this peak was followed by a reincrease in the 1990s, which goes along with the accelerated melting of the adjacent glacier. This study confirms the hypothesis of glaciers being a secondary source of these pollutants and is in accordance with the earlier findings in Lake Oberaar.     

Focused electron beam induced deposition of gold catalyst templates for Si-nanowire synthesis

A new approach using focused electron beam induced deposition (FEBID) to deposit catalyst particles is reported for the synthesis of single crystalline silicon nanowires (SiNWs) grown by low pressure chemical vapor deposition (LPCVD). The FEBID deposited gold dot arrays fabricated from an acac-Au(III)-Me(2) precursor were investigated by AFM and EDX. The depositions were found to form a sharp tip and a surrounding halo and consist of only 10 at.% Au. However, SiNWs could be synthesized on the deposited catalyst using the vapor-liquid-solid (VLS) method with a mixture of 2% SiH(4) in He at 520?°C. NW diameters from 30 nm up to 150 nm were fabricated and the dependency of the NW diameter on the FEBID deposition time was observed. TEM analysis of the SiNWs revealed a [110] growth direction independent of the NW diameter. This new method provides a maskless and resistless approach for generating catalyst templates for SiNW synthesis on arbitrary surfaces.     

Shear-thickening behaviour of concentrated polymer dispersions under steady and oscillatory shear

The rheological behaviour of a 58 vol.% dispersion of styrene/acrylate particles in ethylene glycol was investigated using a plate-on-plate rheometer. Experimental results showed that the concentrated polymer dispersion exhibited a strong shear-thickening transition under both steady shear and dynamic oscillatory conditions. The low-frequency dynamic oscillatory behaviour could be reasonably interpreted in terms of the steady shear behaviour. Accordingly, the critical dynamic shear rate [(g)\dot]_{\textc_d} , \dot{\gamma }_{{{\text{c\_d}}}} , agreed well with the critical shear rate obtained in steady flow [(g)\dot]_{\textc_s} , \dot{\gamma }_{{{\text{c\_s}}}} , where [(g)\dot]_{\textc_d} \dot{\gamma }_{{{\text{c\_d}}}} was calculated as the maximum shear rate by the critical dynamic shear strain γ _c and the frequency ω, i.e. [(g)\dot]_{\textc_d} = wg_\textc . \dot{\gamma }_{{{\text{c\_d}}}} = \omega \gamma_{\text{c}} . However, during high-frequency dynamic oscillation, it was observed that the shear thickening occurred only when an apparent critical shear strain was reached, which could not be fully explained by the wall-slipping effect. Based on freeze fracture microscopic observations, the effect of the micro-sized flocculation of particles on the rheology of concentrated dispersions was also discussed.     

Atypical self-activation of Ga dopant for Ge nanowire devices

In this Letter we report the atypical self-activation of gallium (Ga) implanted by focused ion beam (FIB) into germanium nanowires (Ge-NWs). By FIB implantation of 30 keV Ga(+) ions at room temperature, the Ge-NW conductivity increases up to 3 orders of magnitude with increasing ion fluence. Cu(3)Ge heterostructures were formed by diffusion to ensure well-defined contacts to the NW and enable two point I/V measurements. Additional four point measurements prove that the conductivity enhancement emerges from the modification of the wires themselves and not from contact property modifications. The Ga distribution in the implanted Ge-NWs was measured using atom probe tomography. For high ion fluences, and beginning amorphization of the NWs, the conductivity decreases exponentially. Temperature dependent conductivity measurements show strong evidence for an in situ doping of the Ge-NWs without any further annealing. Finally the feasibility of improving the device performance of top-gated Ge-NW MOSFETs by FIB implantation was shown.     

Recent advancements in ring closing olefin metathesis

A short overview on recent developments in ring closing metathesis (RCM) of 1,ω-dienes to cycloalkenes is provided, with particular emphasis on applications to natural product synthesis and the preparation of olfactory perfume ingredients. These examples show that RCM is becoming a mature tool for the formation of carbo– and heterocycles of any size ⩾ 5, including medium and large ring compounds which are difficult to prepare otherwise. Although the reactivity profile of the standard metathesis (pre)catalysts cannot be reduced to a simplistic picture, their excellent compatibility with an array of functional groups will be outlined. This revised version was published online in June 2006 with corrections to the Cover Date.