Environmental and Applied Mineralogy

Zeolites – Synthesis and Applications

Zeolites contain pores of molecular size (5 – 12 Å) and are used as molecular sieves, ion exchangers and catalysts. Zeolites occur in sedimentary and low-grade metamorphic rocks, but can also be synthesized under hydrothermal conditions. The goal of this project is to investigate processes of zeolite formation under hydrothermal conditions (80 - 150 °C) using precursors like fly ash, perlite and biogenic silica (e.g. diatoms).

Hydrothermal synthesis combined with SEM and XRD studies indicate that amorphous precursor of zeolites precipitates from solution. Assemblage of merlinoite and minor quantities of chabazite and zeolite L was synthesized. Ion exchange experiments demonstrate that the amorphous precursor can reduce the concentration of dissolved heavy metals like Cu, Pb and Zn more efficiently than the subsequently formed zeolite. This is due to its higher specific surface area than crystalline precursor.

Contact: Dietmar Klammer

Soil remediation using Fe⁰-doped bentonite slurries

Trichloroethylene (TCE) has been used as a solvent agent in industrial areas worldwide, especially from the 1920s to 1970s, which resulted in locally severe pollution of subsoils and groundwater with this cancerogenic and non-biodegradable substance. In the course of the HaloCrete project (initiated by the Austrian Institute of Technology and Keller Grundbau Ges.mbH) an experimental set-up was developed in which reductive de-chlorination of TCE was induced by the addition of nanoscale zero-valent iron (Fe⁰) particles mixed with bentonite slurries.

Gas chromatography and advanced electron microscopic, spectroscopic, and X-ray diffraction methods are used to ascertain (i) reaction rate constants for TCE degradation and
(ii) the physicochemical interaction mechanisms between Fe0 particles and bentonite; processes that affect a variety of biogeochemical processes involved in soil environments.

Contact: Andre Baldermann