In many parts of the world, access to clean drinking water is uncertain. However, the filtration of large amounts of water is slow and impractical. In the magazine Angewandte Chemie, scientists introduced a new method of water purification based on magnetic nanoparticles coated with so-called “ionic liquids” that simultaneously remove organic, inorganic and microbial contaminants and microplastics. The nanoparticles are then easily removed with a magnet.
Under the leadership of Carsten Streb, Robert Güttel and Scott G. Mitchell, Ulm University, Ulm The (Helmholtz) Institute (Germany) and the CISC University of Zaragoza (Spain) in Spain have jointly developed an alternative method around a nanoparticle iron oxide with a magnetic core and a porous silica shell. The surface of the nanoparticles is coated with an ionic liquid layer. Ionic liquids are salts that are molten at room temperature and can be made liquid without the use of solvents. The ionic liquids used by researchers are based on polyoxometalates (POMs)-metal atoms are combined by oxygen atoms into a three-dimensional network. In this case, the metal of choice is tungsten because the polyoxytungstate anion can be combined with heavy metals. As counter ions, the researchers used large volumes of tetraalkylammonium cations with antibacterial properties. The resulting ionic liquid forms a stable thin layer (supported ionic liquid phase) on the surface of the porous silica of the nanoparticles. Once loaded with contaminants, nanoparticles can be simply extracted from the water using 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 is also effectively prevented. In addition, the nanoparticles attach themselves to the surface of a polystyrene sphere with a diameter of 1 to 10 m (this is a model of microplastics), which can then be removed quantitatively.
Adjusting the composition of the nanoparticles should allow further optimization of their performance, thus making magnetic nanoparticles a highly promising starting point for centralized and decentralized water purification systems. This makes it easy to purify large amounts of water even without extensive infrastructure.
