A promising method for the degradation of nanoplastics in water

Graphical abstract of the article published in JECE (doi: 10.1016/j.jece.2023.11
Graphical abstract of the article published in JECE (doi: 10.1016/j.jece.2023.110755).

Researchers at the Autonomous University of Madrid (UAM) have developed a process based on the photo-Fenton method that allows the efficient degradation of polystyrene nanoplastics in water. This breakthrough could be key in the fight against plastic pollution, especially in wastewater treatment plants (WWTP).

A team of environmentalists, chemists and chemical engineers from the Universidad Autónoma de Madrid (UAM) and the Universidad Nacional de Mar del Plata (Argentina) has investigated the application of the photo-Fenton treatment method to degrade polystyrene nanoplastics in water.

This method combines a light source (UV-Vis radiation) with low concentrations of iron (as a homogeneous catalyst) to activate the decomposition of hydrogen peroxide (H2O2) into highly oxidizing species. These species can degrade various persistent pollutants into harmless molecules, such as carbon dioxide and water, operating under ambient conditions.

The results, published in the Journal of Environmental Chemical Engineering, reveal that the photo-Fenton process achieves complete and rapid degradation of polystyrene nanoplastics in water, significantly exceeding the removal levels of other photocatalytic processes mentioned in previous studies. Furthermore, this treatment can be adapted to higher concentrations of nanoplastics and larger particle sizes by adjusting the reagent dosage and extending the treatment time.

Based on these findings, the photo-Fenton process presents a high potential as a purification step (tertiary treatment) in WWTP facilities. "This method could be combined with traditional separation processes, such as membrane filtration, to improve the degradation of plastic pollutants, reducing their dispersion and impact, and ensuring the production of high quality reclaimed water," the authors state.

The study was carried out by Jorge Garcia, David Ortiz, Carla di Luca, Macarena Munoz, Jaime Carbajo, Zahara Martínez de Pedro and José Antonio Casas de Pedro, in collaboration with the technology-based company CAPTOPLASTIC S.L.

The challenge of plastic waste

Thanks to their outstanding properties, plastics are ubiquitous in our environment and have become an essential pillar of the "throwaway culture". For context, in 2021, global plastic production reached almost 390 million tons, and this figure is expected to double in the next two decades.

In this scenario, the excessive production and inadequate management of plastic waste emerges as one of the main environmental challenges of the 21st century. The useful life of plastic products varies from one day (single-use plastics) to more than 50 years. When discarded, only 12% is used for energy recovery, 9% is recycled, 8% ends up in landfills and, unfortunately, 71% is dispersed in the environment.

This situation represents a serious threat to ecosystems, as these materials can persist for years, taking decades or even centuries to degrade.

Once in the environment, waste fragments into microplastics (< 5 mm) and nanoplastics (< 1 µm). The dispersion of nanoplastics is particularly alarming since, due to their size, they can penetrate biological membranes and affect cellular functioning, causing damage to living beings.

Water is the main means of transport of micro- and nanoplastics in the environment. Wastewater Treatment Plants (WWTP) have been identified as critical points in the spread of this contamination. Although current WWTP facilities can remove more than 90% of plastic pollutants, the amount released into water bodies is still worryingly high. Therefore, it is urgent to develop new water treatment technologies that prevent the release of micro- and nanoplastics from WWTPs.

Bibliographic reference:

Di Luca, C.; Garcia, J.; Ortiz, D.; Munoz, M.; Carbajo, J.; De Pedro, Z.M.; Casas, J.A. (2023). " Mineralization of polystyrene nanoplastics in water by photo-Fenton oxidation" . Journal of Environmental Chemical Engineering, 11, 110755.

doi: 10.1016/j.jece.2023.110755

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