"Superparamagnetic" Particles Used to Harvest Phosphorus from Polluted Water

A demonstration of how the phosphorus-laden particles can be removed from water using a magnet.

Phosphorus is a mineral that's widely used in fertilizer, which itself has an unfortunate tendency to leach out of farmers' fields and into our waterways. Now, researchers from Germany's Fraunhofer Institute for Silicate Research have devised a method of retrieving some of that phosphorus from the water – thus both reducing pollution, and providing a source of reclaimed phosphorus.

The Fraunhofer team has been using superparamagnetic particles, which are ordinarily non-magnetic, but that turn magnetic when exposed to a magnetic field. These particles also contain bonding sites for phosphorus, and are added to phosphorus-polluted water. When this happens, the phosphorus anions in the water bond with the particles.

The particles, along with the attached anions, are then removed from the water simply using a magnet. Once the removed particles are in turn removed from the magnetic field, they de-magnetize and release the phosphorus for subsequent re-use. The water, meanwhile, is left phosophorus-free.

Apparently the technology could be tweaked to remove other types of pollutants, such as heavy metals, by applying different types of bonding sites to the particles.

Fraunhofer developed the system in collaboration with the University of Stuttgart.

Source: Fraunhofer