Papers by Author: Herbert Pöllmann

Abstract: Electrical and electronic equipment (EEE), e.g. printed circuit boards, contain substantial amounts of metals, e.g. Cu, Pb and Sn. The objective of this work was to investigate the bioleaching of a material, originating from a technical waste processing facility, as one possible way of a complete separation of the metals from the polymer carrier. During the leaching experiments the mechanism of the leaching process was investigated, and biofilms and precipitates were analyzed by microscopical (SEM) and spectroscopical methods (EDX, XRF, XRD). The enhanced formation of exopolymer layers seems to promote the precipitation of secondary mineral particles beneath and the sorption of particles from the suspension on the layer surface.

Abstract: Synthetic manganeous Layered Double Hydroxides of the Hydrotalcite- and Shigaite- type were prepared by the coprecipitation method. The thermal behaviour of two compounds, [Mn₆Al₃(OH)₁₈] [(SO₄)₂Na·12H₂O] and [Mn₆Al₃(OH)₁₈] [Cl·4H₂O] was investigated by several experimental techniques. Thermal analysis and in-situ X-ray diffractometry show several dehydration stages of the synthesis products in the temperature range of 25 < T < 170°C followed by decomposition at temperatures above 200°C.

Abstract: Lamellar calciumaluminatehydrates are products of the hydration of ordinary Portland cement and play an important role in its hardening process. Due to the fixation ability of inorganic ions the technical features of this lamellar phases are important as reservoir minerals for pollutants (storage minerals). The lamellar calciumaluminatechromatehydrate Monochromate with the idealized formula C₃A.Al₂O₃.CaCrO₄.Ca(OH)₂.nH₂O has been investigated using a Philips Diffraction System X'Pert with the X'Celerator detector to measure the kinetics of the changes in interlayer dimensions in the lamellar calciumaluminatechromatehydrate at room temperature in air. A certain amount of water is weakly fixed in the interlayer depending on the interlayer anion, temperature and relative humidity of the atmosphere. Processes like ion exchange or water-loss in the interlayer cause a variation of the crystal dimension in c-direction. These "processes" can be very fast, therefore an ultra fast data collection and measurement times less than 2 minutes from 2° 2Θ to 70° 2Θ were essential.