Nanotechnology

Removing microplastics and nanoplastics from water in a low-cost way

Overview of the purification process: Water contaminated by microplastics (PET). Addition of magnetic nanoparticles functionalized with polydopamine and lipase. A magnet is used to remove nanoparticles contained in microplastics. Credit: Enrique Eisi Thoma

Researchers at Brazil’s University of SĆ£o Paulo (USP) have developed a new nanotechnology-based solution to remove micro- and nanoplastics from water. Their research is published in the journal Micron.

Tiny plastic particles are ubiquitous around the world today and may be one of the most important environmental challenges of our time, given the climate emergency and accelerated extinction of species and ecosystems.

Microplastics exist in soil, water, air, and even in the bodies of animals and humans. These are caused by everyday consumer products and wear and tear on larger materials. They exist everywhere and in all kinds of environments. The main source is water used to wash clothing made of synthetic fibers. Microplastics cannot currently be filtered out of wastewater and end up in the soil, water table, rivers, oceans and atmosphere.

Microplastics themselves, defined as debris up to 1 millimeter in size, are a well-identified and visible problem. However, it turns out that nanoplastics pose a more insidious danger, as they are 1,000 times smaller and can cross critical biological barriers and reach vital organs. For example, recent research has detected their presence in the human brain.

ā€œNanoparticles are invisible to the naked eye and cannot be detected using conventional microscopes, making it very difficult to identify and remove them from water treatment systems,ā€ said Enrique Eisi of the Institute of Chemistry (IQ-USP). Professor Thoma said. Last author of Micron article.

The method developed at USP uses magnetic nanoparticles functionalized with polydopamine, a polymer derived from dopamine, a neurotransmitter found in the human body. These nanoparticles can bind to micro- and nanoplastic waste, and the bound particles can be removed from water by application of a magnetic field.

“Polydopamine is a substance that mimics the adhesive properties of mussels, which stick very tenaciously to many surfaces. Polydopamine adheres firmly to plastic debris in water, allowing magnetic nanoparticles to capture them. This undesirable substance can then be removed from the water using a magnet,” Thoma said.

This process has already proven to be effective in removing micro- and nanoplastics from water, especially in treatment systems. However, the research group is also aiming to break down polyethylene terephthalate (PET) using specific enzymes such as lipase, which can break down polyethylene terephthalate (PET) into its basic components. Applying enzymes breaks down PET and other widely used plastics into smaller molecules that can be reused in the production of plastic materials.

ā€œOur goal is not only to remove plastic from the water, but also to contribute to the recycling of plastic in a sustainable way,ā€ Thoma said.

PET is the raw material for plastic bottles, etc. In particular, its decomposition produces terephthalic acid (C6H4(COOH)2) and ethylene glycol (C2H4(OH)2), both of which are toxic and are therefore major pollutants.

“Lipase breaks down PET into these initial monomeric forms, which can be reused to synthesize new PET. Although our study focused on PET, other researchers have It can process different plastics, including polyamide and nylon, for example.

In research led by Toma, magnetic nanoparticles of iron oxide (II, III) or black iron oxide (Fe3O4) were synthesized by coprecipitation, and then polydopamine was synthesized by partially oxidizing dopamine in a slightly alkaline solution. coated with (PDA). Forms Fe3O4@PDA. Lipase was immobilized on this substrate. Hyperspectral Raman microscopy was used to monitor plastic sequestration and degradation in real time.

complex problem

The term “plastic” refers to a wide range of synthetic or semi-synthetic polymers, most of which are derived from fossil fuels. Malleability, flexibility, light weight, durability and low cost ensure its presence in numerous products used in everyday life. Concerns about the residue and waste produced by this highly intensive use have led to the search for alternatives such as bioplastics. Instead of non-renewable petrochemicals, bioplastics are derived from renewable and biodegradable resources.

ā€œWhile that is a good idea, bioplastics also fragment to form micro- or nanoplastics before they fully degrade. Because they are biocompatible, they interact more directly with living organisms and stimulate biological responses. It’s even more dangerous because it can cause it,” Thoma said.

Another troubling piece of information provided by Toma is that bottled mineral water may be even more contaminated with bioplastics than the treated drinking water we consume at home.

ā€œWhile treated drinking water undergoes processes such as filtration, coagulation, and flotation to remove most residues, mineral water is superior in several ways, including being lighter and less salty. “It tastes great, but none of these treatments are done,” because if the environment in which it is collected is contaminated with bioplastics, these particles can reach consumers. Because it will,ā€ he said.

In short, the challenge is daunting, and there are no clear answers. The nanotechnology presented by Toma and his collaborators offers a promising solution to a problem whose full extent is only beginning to be understood. He urges other researchers to persevere in their search for solutions, and urges authorities to take the problem seriously.

Further information: Ana LCP de Brito et al, Direct monitoring of enzymatic sequestration and degradation of PET microplastics using hyperspectral Raman microscopy, Micron (2024). DOI: 10.1016/j.micron.2024.103722

Citation: A low-cost method to remove micro- and nanoplastics from water (November 12, 2024) from https://phys.org/news/2024-11-method-micro-nano Plastics.html November 2024 Retrieved on 12th

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