(NHI Nanoblog) What happens to ultra-tiny particles when you throw them — and the products they’re embedded in — away? Swiss researchers examining one type of material found that it didn’t burn up in a waste plant, but did remain, largely intact, in the dregs left behind.
Nature Nanotechnology
Nanoscale cerium oxide before incineration.
The findings, published recently in the journal Nature Nanotechnology, offer some insight into one of the most pressing concerns about ultra-tiny nanomaterials: their fate after the end of their useful life.
Scientists and policymakers are eager to understand how these materials function from birth until death, and the implications for the workers who manufacture them and the consumers who use the finished products, as well as any environmental impact.
The Swiss team added nano-sized cerium oxide particles to the waste moving through an incineration plant, either before the burning or into the gas stream leaving the furnace. Instead of burning, the nano-cerium oxide particles attached themselves to some of the other residue left behind by the furnace.
That means the particles didn’t go into the air, largely because of the filtering process in the flue. But, the authors note, that doesn’t mean they weren’t going to be introduced into the environment, since the slag is typically sent to a landfill or subjected to further treatment.
The nano-cerium oxide after incineration, in the slag.
In addition, they write, waste-plant workers could be exposed to the particles when cleaning the equipment or removing the slag.
“These plants are not an effective end-of-life treatment for highly stable engineered nanoparticles such as nano-CeO2; instead, they shift the disposal problem to subsequent processing steps, landfills and final deposits where the slag and fly ash residues are eventually handled and stored,” the paper says.
Nanotechnology is a broad term that encompasses a wide variety of uses of very small materials. (A nanometer is a billionth of a meter.) These substances can make better batteries or lighter and stronger bike frames, as well as new medical instruments and medicines that can save lives. They’re increasingly common in consumer products, from sunscreens to stain-repellent pants to boat paints that resist algae growth.
Nanomaterials are believed to hold great promise for a wide variety of applications. Their ultra-tiny size often gives them different properties, which is the basis of their appeal; scientists are struggling to figure out whether that can make them dangerous in the process, and how and why it happens.
A big part of solving that puzzle is understanding the so-called life cycle of nanoparticles, and the products to which they’re added. The Swiss paper is a baby step — it looked at one material, with one disposal method, in relatively small-scale experiments — but opens a path for further study. It also bolsters the case, as the authors note, for focusing on nanomaterials that break down more easily, if not disappear altogether.
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