The nanoplasticstiny particles arising from degradation of plastic, they are now widespread everywhere and represent a possible risk to human health and the environment. They can accumulate in the organs through the food chain, with possible negative effects on the endocrine and reproductive system. As a result, several have been studied techniques to remove them from the water, like the filtrationthe use of bacteria and the use of special solvents hydrophobic. The latter technique, based on liquid-liquid extraction, has shown promising results in the laboratory and could be applied on a large scale.
Why nanoplastics in water are a problem
Plastic has had an enormous impact on the world, allowing advances in the most disparate fields, from food preservation to transport and, in general, to the production of durable and economical objects for everyday life. Unfortunately, especially since the last century and in particular since the 1950s, the explosive diffusion of plastic products has gone hand in hand with the accumulation of waste, often not adequately recovered or recycled, saturating the environment around us with non-biodegradable substances.
The problems resulting from abandoned artefacts are clear to everyone: just think of the fishing nets, lost or thrown into the sea and often involuntary traps for marine fauna, or the plastic bags often found in the stomachs of these animals. However, the risks due to the smaller plastic particles generated by the very slow degradation of the material.
The particles are divided into microplastics, with dimensions between 5 millimeters and 1 µm (one thousandth of a mm) and nanoplastics, particles with diameter less than 1 µm: they are now widespread throughout the world, from our lakes to the ice of the Arctic.
Due to their size, nanoplastics in particular can pass through the circulatory system during the digestion of food, and then accumulate in organs such as kidneys; this favors the bio-magnificationi.e. the increase in concentration from prey to predators along the food chain.
In this way, nanoplastics can also reach our plates: the dangers to our health are still a source of studies today, but yes hypothesize effects on the endocrine system (regulation of hormones) and on the reproductive one.
How to remove nanoplastics from water
For remove nanoplastics Different approaches have been studied: the first and simplest is certainly the filtration with membranes special ones, which like a tiny “colander” can let the water pass while retaining the plastic particles. However, it is a method that is difficult to apply to large bodies of water such as lakes or seas. Other possibilities are the use of bacteria, fungi or other animals capable of degrading plastic.
Recent studies instead point to the use of special solvents, non-toxic and easily separable from water. The principle used is that of “hydrophobic solvents with deep eutectic point“: this complicated term indicates two components that do not bind to water (they are therefore hydrophobic, like oil) and which see their melting point reduce when mixed (we speak of eutectic mixturesuch as water and salt which freezes at lower temperatures than pure water).
When mixed (emulsified) in water, these solvents can “capture” organic substances such as plastic, in the case of the study polystyrene particles of different sizes. The mixture naturally tends to separate from the water, concentrating and bringing the dispersed nanoparticles to the surface to facilitate their removal.
Laboratory tests showed promising results for some mixturesincluding those of thymol/menthol and or between ammonium salts and organic acids, and work in both salt and fresh water. The objective is now to reproduce, on a larger scale, the mechanisms analyzed in the laboratory, as well as to search for the most effective and easily reusable mixtures.
