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Affordable Solution for Removing Micro- and Nanoplastics from Water

A research team from the University of São Paulo (USP) in Brazil has introduced an innovative nanotechnology approach designed to eliminate micro-and nanoplastics from water. The findings appear in Micron.

The Growing Environmental Concern of Microplastics

Ubiquitous tiny plastic particles have emerged as one of the most pressing environmental issues today, second only to the climate and the rapid extinction of species and ecosystems.

Microplastics and Their Ubiquity

Microplastics are present in soil, water, air, and in the bodies of humans and animals. Originating from everyday consumer items and the degradation of larger materials, these particles are found across all environments. A significant source is wastewater from washing synthetic-fiber clothing, which is not yet filtered to remove microplastics, allowing them to enter the soil, groundwater rivers, oceans, and atmosphere.

The Insidious Nature of Nanoplastics

Microplastics, identifiable as fragments up to 1 millimeter, present a visible environmental concern. However, nanoplastics, which are a thousand times smaller, represent a more insidious risk, able to breach biological barriers and enter essential organs. Notably, a recent study detected these particles in the human brain.

Innovative Solution: Magnetic Nanoparticles to Capture Plastics

"Nanoparticles are too small to be seen with the naked eye or conventional microscopes, making them exceptionally challenging to detect and eliminate from water treatment systems," explained Henrique Eisi Toma, professor at the Institute of Chemistry (IQ-USP) and senior author of the Micron article.

Polydopamine-Coated Nanoparticles for Plastic Capture

The USP team developed a process utilizing magnetic ananoparticles coated with polydopamine—a polymer derived from dopamine, a neurotransmitter found in the human body. These nanoparticles attach to micro- and nanoplastic contaminants, which can then be extracted from water by applying a magnetic field.

"Polydopamine mimics the adhesive ability of mussels, which cling strongly to various surfaces," explained Toma. "It adheres tightly to plastic fragments in water, allowing the magnetic nanoparticles to capture them so they can then be extracted with a magnet."

Effectiveness in Water Treatment Facilities

The process has demonstrated effectiveness in removing micro- and nanoplastics from water, particularly in treatment facilities. The research team also aims to degrade these plastics using enzymes like lipase, capable of breaking down polyethylene terephthalate (PET) into its fundamental components. This enzymatic action decomposes PET and other common plastics into smaller molecules, which can then be recycled to create new plastic products.

"We're not only focused on removing plastic from water but also on facilitating its recycling in an environmentally responsible way," Toma explained.

The Challenge of Degrading PET

PET serves as the primary material for plastic bottles and various other products. It is a significant environmental pollutant, primarily due to the toxic byproducts, terephthalic acid (C₆H₄(COOH)₂) and ethylene glycol (C₂H₄(OH)₂), produced during its degradation.

"Lipase decomposes PET into basic monomeric components, which can then be repurposed to synthesize new PET. While our study concentrated on PET, other researchers could apply different enzymes to process various plastics, including polyamide and nylon," he explained.

The Process: Synthesizing Magnetic Nanoparticles

The study, led by Toma, involved synthesizing magnetic nanoparticles of iron (II, III) oxide (Fe₃O₄), also known as black iron oxide, through co-precipitation. These nanoparticles were then coated with polydopamine (PDA) by partially oxidizing dopamine in a mildly alkaline solution to form Fe₃O₄@PDA. Lipase was immobilized on this composite, and hyperspectral Raman microscopy was employed to monitor the sequestration and degradation of the plastic in real-time.

Addressing the Broader Issue of Plastic Pollution

Plastics and Their Environmental Impact

The term 'plastics' encompasses a broad range of synthetic or semi-synthetic polymers, predominantly sourced from fossil fuels. Their malleability, flexibility, lightness, durability, and cost-effectiveness have made them integral to a variety of everyday products. However, the growing concern over the environmental impact of plastics waste has prompted the search for alternatives, including bioplastics. Unlike conventional plastics made from nonrenewable petrochemicals, bioplastics are derived from renewable, biodegradable sources.

The Dangers of Bioplastics

"While bioplastics are a step forward, they too break down into micro- or nanoplastics before fully degrading. Their biocompatibility, however, makes them even more dangerous, as they can interact with biological systems and trigger harmful reactions," Toma explained.

Bioplastic Contamination in Bottled Water

An additional alarming insight shared by Toma is that bottled mineral water could have higher levels of bioplastic contamination compared to the treated drinking water available in households.

"Treated drinking water undergoes processes like filtration, coagulation, and flotation to remove most contaminants, while mineral water—preferred for its lighter texture, higher salt content, and better taste—remains unprocessed to preserve its natural qualities. However, if the source of the mineral water is contaminated by bioplastics, these particles will inevitably reach consumers," he explained.

Conclusion: A Promising but Challenging Path Forward

In conclusion, the challenge is formidable, and clear solutions remain elusive. The nanotechnology introduced by Toma and his team presents a promising approach to a problem whose full scope is still emerging. He encourages fellow researchers to continue their efforts and calls on policymakers to recognize the seriousness of the issue.

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