A team of environmentalologists, chemists and chemical engineers from the Autonomous University of Madrid (UAM) and the National University of 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 different 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 particles, adjusting the dose of reagents and prolonging the treatment time.
Based on these findings, the photo-Fenton process has 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 contaminants, 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 SL
The challenge of plastic waste
Thanks to their outstanding properties, plastics are omnipresent 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 over the next two decades.
In this panorama, 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, since these materials can persist for years, taking decades or even centuries to degrade.
Once in the environment, the waste fragments into microplastics (< 5 mm) and nanoplastics (< 1 µm). The dispersion of nanoplastics is especially 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 eliminate more than 90% of plastic pollutants, the amount released into water bodies remains worryingly high. Therefore, it is urgent to develop new water treatment technologies that prevent the emission of micro- and nanoplastics from WWTPs.