Short Poster Lecture
Diatom biosilica is a promising material due to its outstanding properties like long-range ordered structure, high specific surface area, high internal pore volume, biocompatibility, high stability, and tailorable surface chemistry. In this study, we used diatom biosilica and carbon replica materials in the adsorption of heavy metals from aqueous solution.
In a first approach, chemical and spectroscopic methods were performed to investigate the interaction processes of Europium(III) with biosilica of two different diatom species (Stephanopyxis turris, Thalassiosira pseudonana), fossilized diatomaceous earth, and a synthetic silica material (mesocellular foam - MCF) which exhibits high porosity. Macroscopic batch sorption experiments demonstrated a strong influence of the used diatom species on sorption success. S. turris and T. pseudonana have a higher retention potential for Eu(III) in comparison to diatomaceous earth and MCF. In addition, time resolved laser induced fluorescence spectroscopy (TRLFS) revealed different surface species for Eu(III) on S. turris and T. pseudonana biosilica, which indicates an influence of silica structure on the sorption behavior. The obtained results provide a basis to understand the mobility of the chosen elements in the environment as well as for the development of process technologies for resource recovery.
In a second approach, a highly porous, biotemplated carbon material was synthesized using a combined nanocasting/carbide-derived carbon (CDC) procedure. The characteristic species-specific macroporous structure is retained during the nanocasting-chlorine treatment process and the resulting materials exhibit very high specific surface areas up to 2300 m2 g-1. Compared to T. pseudonana biosilica and a commercial active coal, the TP-CDC material achieves very high mercury adsorption capacities of almost 1000 mg g-1 from aqueous solution (Hg2+ initial concentration of 100 mg L-1) in combination with rapid uptake. The material shows a linear correlation between mercury uptake and equilibrium concentration over a wide concentration range and its recyclability could be proven. These biotemplated carbon materials have extraordinary properties and may also be promising for other applications like catalysis or in electrochemical devices.