Nanoplastics, or tiny plastic particles about 100 nanometers in size, are surprisingly reactive towards oxidizing species, a new study found. Transcontinental Times reported that the unexpected reactivity of nanoplastics have significant implication for their environmental impacts and use in industrial and medical applications.
Plastics are used in almost every aspect of everyday life and account for more than 18% of the solid waste in landfills. Many of these plastics also end up in the seas, where it might take hundreds of years to decompose into fragments that can harm aquatic ecosystems and wildlife.
Unexpected Reactivity of Nanoplastics When Exposed to Light
Phys.org reported that Professor Young-Shin Jun of Washington University in St. Louis and his team of researchers examined how light degrades polystyrene, a nonbiodegradable material used to make packing peanuts, DVD cases, and disposable cutlery. They also discovered that nanoplastics could actively participate in environmental systems.
Particularly, the polystyrene-derived nanoplastics surprisingly facilitated the oxidation of aqueous manganese ions and the production of manganese oxide solids under light illumination, which may have an impact on the fate and transport of organic pollutants in engineered and natural water systems.
The study, titled "Oxidative Roles of Polystyrene-Based Nanoplastics in Inducing Manganese Oxide Formation Under Light Illumination," published in the journal ACS Nano, demonstrated how the photochemical interaction of nanoplastics by light absorption produces peroxyl and superoxide radicals on nanoplastic surfaces and starts the oxidation of manganese into manganese oxide solids.
Jun, who leads the Environmental Nanochemistry Laboratory, said there are growing worries about the negative impacts of plastic trash as it builds up in the environment.
In most cases, people have been more concerned about the physical presence of nanoplastics rather than their active roles as reactants. They discovered that such small plastic particles can more easily interact with nearby substances, such as heavy metals and organic contaminants, and can be more reactive than we previously thought.
Surface Functional Groups and Size of Nanoplastics Affect Manganese Oxidation
Zhenwei Gao, Jun's former student and currently a postdoctoral scholar at the University of Chicago, conducted experiments to show that the various surface functional groups on polystyrene nanoplastics affected manganese oxidation rates by affecting the generation of highly reactive radicals, peroxyl and superoxide radicals.
Redox reactions may alter the mobility of the nanoplastics in the environment, which may harm their ability to be removed from the environment. A similar article from Science Daily reports that the generation of these reactive oxygen species from nanoplastics has the potential to threaten human health and marine life.
The researchers used particles with diameters of 30 nanometers, 100 nanometers, and 500 nanometers to examine the effects of polystyrene nanoplastics on manganese oxidation. The two bigger nanoparticles more slowly oxidized manganese than the smaller ones.
Jun explained that the smaller polystyrene nanoplastics might more readily dissolve and release organic materials because of the greater surface area. Manganese oxidation may be aided by the dissolved organic matter's potential to form reactive oxygen species under the light swiftly.
The study also offers significant insights into the heterogeneous nucleation and development of manganese oxide solids on such organic substrates, which helps in understanding manganese oxide occurrences in the environment and the synthesis of designed materials, Jun said.
These manganese solids are superior scavengers of redox-active species and heavy metals, further impacting the mineralization of carbon, biological metabolisms, and elemental redox cycling in the earth's crust.
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