"Superparamagnetic" particles used to harvest phosphorus from polluted water


March 27, 2014

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

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. 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

About the Author
Ben Coxworth An experienced freelance writer, videographer and television producer, Ben's interest in all forms of innovation is particularly fanatical when it comes to human-powered transportation, film-making gear, environmentally-friendly technologies and anything that's designed to go underwater. He lives in Edmonton, Alberta, where he spends a lot of time going over the handlebars of his mountain bike, hanging out in off-leash parks, and wishing the Pacific Ocean wasn't so far away. All articles by Ben Coxworth

There is no mention of how scalable this process is, or whether it would be practicable to do so, but, seeing as phosphorus is a finite resource that we are (rapidly) running out of, if it is possible to scale it up, then the sooner we do so, the better.

Mel Tisdale

This is fascinating. I had imagined something similar years ago, but didn't have the knowledge to figure it out. What is not clear is how the "bonding sites" release the phosphorus. Removing the particles with a magnet makes sense, but I assume the connection of the phosphorus to the "bonding sites" on the particles would be chemical.

Bruce H. Anderson

Algae removes nitrates as well.

Separation by applying heat may be the answer. Florida has a big issue with phosphorous runoff from the sugar cane industry. It might help us a lot. Jim Sadler

Wow or you could just use duck weed and get rid of nitrates and heavy metals along with the phosphorous but as that would be cheap and completely self sustaining why should anyone try it when they can spend millions of dollars fiddling with tech that must be continually renewed.

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