Wouldn't it be great if there were a way of chasing down waterborne microplastic particles and catching them for removal, as opposed to just passively filtering them out of water bodies? Well, experimental new "microcleaners" can reportedly do that very thing.
By definition, microplastics are fragments of plastic smaller than 5 millimeters in diameter.
Found in waterways around the world, they come from a number of sources. These include chunks of floating plastic waste that break down into smaller pieces; products such as toothpaste which contain plastic microbeads; synthetic clothing that sheds fibers while being washed; and car tires that release bits of rubber which make their way into storm sewers.
Researchers are still trying to understand how people's health may be affected by ingesting the particles in and of themselves. That said, harmful bacteria are often drawn to microplastics, living on or around the particles – and we definitely shouldn't be eating or drinking those microbes.
That's where the microcleaners come in.
Developed by Prof. Orlin Velev and colleagues at North Carolina State University, they take the form of tiny pellets which are in turn composed of multiple particles known as soft dendritic colloids. Such particles have a reputation for being very sticky, and in this case are made of chitosan, which is a biodegradable biopolymer derived from seafood-industry shellfish waste.
One off-center section of each microcleaner pellet is infused with a small amount of a plant-based oil called eugenol. That oil decreases the surface tension on one side of the pellet, thus propelling it sideways as it sinks into the water. As the pellet moves through the water, any microplastic particles it encounters get stuck to its soft dendritic colloid particles.
The fun doesn't stop there, however.
Each microcleaner additionally contains particles of magnesium, plus it's coated in a layer of water-soluble eco-friendly gelatin.
As long as that coating remains intact, the pellet continues to slowly sink. Once the gelatin dissolves enough to allow water to reach the magnesium, however, the magnesium reacts with the water, forming air bubbles. Those attached bubbles cause the microcleaner pellet to float to the surface, carrying its microplastic payload with it.
Lab tests have shown that the pellets can swim around underwater for up to 30 minutes before rising to the surface, where they collectively form a scum. That scum can then be skimmed off the surface for disposal, although Velev does state that the chitosan could be reclaimed from the substance and used to create more microcleaners.
A paper on the research was recently published in the journal Advanced Functional Materials.
Source: North Carolina State University
