Magnetic Nanoparticles

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In many parts of the world, access to clean drinking water is far from certain. Filtration of large volumes of water, however, is slow and impractical. As a consequence, scientists have introduced a new water purification method 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. The surfaces of the nanoparticles were coated with a layer of an ionic liquid. An ionic liquid is a salt that is in its molten state at room temperature, making it a liquid without use of a solvent. The ionic liquid used by the researchers were 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.

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.

Additionally, new magnetic nanoparticle recovery devices are being developed such as magNERD was developed and operated to separate, capture, and reuse superparamagnetic Fe3O4 from treated water in-line under continuous flow conditions. Experimental data and computational modeling demonstrate how the MagNERD’s efficiency to recover nanoparticles depends upon reactor configuration, including the integration of stainless-steel wool around permanent magnets, hydraulic flow conditions, and magnetic NP uptake. The MagNERD efficiently removes Fe3O4 in the form of a nanopowder, up to > 95% at high concentrations (500 ppm), under scalable and process-relevant flow rates (1 L/min through a 1.11-L MagNERD reactor), and in varying water matrices (e.g., ultrapure water, brackish water). The captured nanoparticles were recoverable from the device using a simple hydraulic backwashing protocol. Additionally, the MagNERD removed ≥ 94% of arsenic-bound Fe3O4, after contacting As-containing simulated drinking water with the nanopowder. The MagNERD emerges as an efficient, versatile, and robust system that will enable the use of magnetic nanoparticles in larger scale water treatment applications.

Magnetic nanoparticles is a growing technology and it will continue to develop well into the future as we continue our quest to find the best method to treat waste water.


References:

https://www.nanowerk.com/nanotechnology-news2/newsid=54136.php

https://link.springer.com/article/10.1007/s11051-020-4770-4

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