The team of researchers from the University of Ulm, the Helmholtz Institute in Ulm (Germany), and CISC-Universidad de Zaragoza (Spain) has developed an alternative approach around nanoparticles with a core of magnetic iron oxide and a shell of porous silicon dioxide. The team has introduced the new method in the journal?Angewandte Chemie. The method is based on magnetic nanoparticles coated with a so-called “ionic liquid” that simultaneously remove organic, inorganic, and microbial contaminants, as well as microplastics. The nanoparticles are then easily removed with magnets. This method offers an alternative to rather slow and impractical filtration process (at least when larger volumes of water are concerned).
The ionic liquid used on the surface of nanopartcles is based on polyoxometallates (POMs) — metal atoms bound into a three-dimensional network by oxygen atoms. In this case the metal of choice was tungsten because the polyoxotungstate anions can bind to heavy metals. As counterions, the researchers used bulky tetraalkylammonium cations with antimicrobial properties. The resulting ionic liquids form stable thin layers (supported ionic liquid phases) on the porous silicon dioxide surface of the nanoparticles. Once loaded with contaminants, the nanoparticles can simply be extracted from water with magnets.
In laboratory tests, the nanoparticles reliably removed lead, nickel, copper, chromium, and cobalt ions, as well as a dye called Patent Blue V as a model for organic impurities. The growth of various bacteria was also effectively stopped.
Adjustment of the components of the nanoparticles should allow for further optimization of their properties, making the magnetic nanoparticles a highly promising starting point for both central and decentralized water purification systems. This would allow for easy purification of large amounts of water, even without extensive infrastructure.