The method used to purify contaminated water varies based on what the water is actually contaminated with. One method that has become popular is the use of nanoparticles, which are added to the water and go about killing any bacteria they come into contact with or attaching themselves to heavy metals or other types of pollutant that can then be removed.
These so-called nanoscavengers do a good job of purifying the water, but one problem remains: how to remove them from the water after they’ve finished cleaning it. This is achieved by adding a material to each nanoscavenger that is responsive to magnetism. Typically iron oxide is used, but the success rate of recovering the particles is quite low, to the point where the water remains too contaminated to be used.
A team at Stanford University believe they have solved the recovery problem, though. They’ve replaced the iron oxide in each particle with a synthetic material whose two outer layers are magnetic. However, they have opposite magnetic forces.
You’d think that would make the particles even harder to extract from the water, but that’s not the case. When a strong permanent magnet is used, the magnetic layers within each particle turn into alignment, creating a very strong attraction to the magnet. The end result is “virtually all” of the nanoscavengers are removed from the water to the point where it is safe for human use. Compare that to the existing iron oxide nanoscavengers that only saw an extraction success rate of around 20 percent.
In tests carried out at Stanford, water containing the E.coli bacteria was cleaned with a silver version of this new nanoscavengers in just 20 minutes. Afterwards, it was found that 99.9 percent of the bacteria had been killed and all the nanoscavengers removed.
The next stage of the research is to create a nanoscavenger that is capable of clearing lots of different pollutants from water (right now we use different nanoscavengers for different pollutants). That way, it doesn’t matter what contaminants are in the water, this one type of nanoscavenger can be added and sets about cleaning it.