Tackling microplastics and water pollution with magnetic "rust" - Advanced Science News

Beyond the problem of greenhouse gas emissions and their contribution to the climate crisis, the widespread use of hydrocarbons, the fundamental components of fossil fuels, presents significant environmental challenges.

“Hydrocarbons represent the most abundant class of organic pollutants on Earth,” said Marcus Halik, professor in the Department of Materials Science and Engineering at Friedrich-Alexander-Universität. “Almost all organic pollutants originate from crude oil, and the simplest components of oil, with structures of (-(CH2)n-), are widely used as fuels for cars and airplanes, household heating fuels, or as polymer materials (which we all know as plastic).”

Despite the alarms being raised over the devastating impacts of climate change — many of which are already unfolding — the problem remains that fossil fuels still drive the global economy.

“The world production of crude oil as main source of liquid fuels still exceeds 4200 million tons (Mt) added by >4000 billion m3 of natural gas in 2021,” wrote Halik and his team in a paper recently published in  Advanced Science .

Besides the staggering volumes of greenhouse gases released into the atmosphere, the pervasive presence of microplastic pollution derived from hydrocarbons has also raised alarm. Scientists have recently discovered microplastics in the most remote corners of our planet, such as the Arctic, and more recently, even within clouds.

“Hydrocarbons are chemically very stable and have a low tendency to degrade in the environment — this is called persistence,” added Halik. “[They] accumulate in the soil and are taken up by plants and animals but the major transportation pathway to distribute them around the world is water.”

Cleaning up plastic pollution is imperative

While the transition away from fossil fuels and the exploration of alternative options for plastic products are gaining momentum, the removal of the multitude of plastic pollution currently plaguing our environment requires an urgent solution.

“This means a simple, reliable method to remove all kind of hydrocarbons from water,” wrote the team. But options for removing micro- and nano-plastics are limited so far. “It is possible to remove portions of the microplastics by skimming and flocculation [the clumping together of small particles],” they continued. “However, the smaller pieces are still a huge challenge for today’s wastewater treatment plants.”

When mechanical and trapping methods proved unfeasible, Halik and his team took a different approach. They developed a universal remediation method to eliminate a variety of hydrocarbons, ranging from C15 to C∞, by employing superparamagnetic iron oxide nanoparticles, abbreviated as SPIONs.

“SPIONs are basically ‘rust’ of very small size (approximately 10 nm) with huge active surfaces,” explained Halik. “The superparamagnetism, as a size-related effect of the material, ensures that the particles do not attract each other but they can be [collected using] an external magnet.”

Halik also explained that the SPION are inexpensive and non-toxic, and their surface chemistry can be tuned, making it possible to capture a range of different hydrocarbons. For example, for low-weight, liquid hydrocarbons that are hydrophobic, meaning they don’t mix well or dissolve in water, the iron particles surfaces were fitted with similar carbon-based molecules that interact favorably with them.

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Taxonomy

• plastic debris
• microplastics