Download - Nanowerk

gas separation. If required, thermal sterilization or cleaning of the structure is possible.
However, further research and development hurdles need to be overcome in order to
enable the cost-effective production of large-area nanoporous membranes of high,
reproducible quality before these membranes can be used extensively.
Figure 3.3 Nickel-based superalloy nanomembrane with E. coli bacterium (source: TU
Braunschweig)
At the Pacific Northwest National Laboratory (PNNL) in the US, chemically modified
nanoceramics with a mesoporous sponge structure have been developed on the basis of
SAMMS technology (Self-Assembled Monolayers on Mesoporous Supports, see Figure
3.4). They can remove hazardous substances from water significantly faster than
conventional filter technologies such as active carbon filters. The nanosponge is produced
using mesoporous silicon dioxide ceramics with pore sizes averaging 6 nm, depending on
the hazardous substance targeted. The pores are filled with a self-assembling capture
layer. Mercury, for example, is removed using modified mercaptan molecules, whereas
chelating ligands are used to neutralize anionic heavy metal compounds such as
chromate. Tests with mercaptan SAMMS showed that with three treatments, 99.9% of
the mercury in contaminated waste water could be removed within 5 minutes. This
technology is also suitable for removing radionuclides and works in non-fluid media. The
PNNL researchers are working towards the integration of the filter system in membrane
and fibrous materials and on marketing the system for purely security-related technical
applications.
Figure 3.4 SAMMS filter technology (source: Pacific Northwest National Laboratory)
26