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Numerous studies expose the catastrophic impact of plastic pollution on a daily basis. The research conducted to assess its impact on global ecology and human health suggests an immediate need for action. In particular, aquatic systems are full off toxic chemicals and small man-made organic debris that irreversibly break down into even smaller fragments through biotic or abiotic processes. Among these are microfibers from synthetic textiles. Within the work, we explored the degradation of polyethylene terephthalate (PET), polypropylene (PP), and polyamide (PA) fibers for the purpose of remediation of wastewater from washing machines. By mimicking natural processes, we investigate the benefits of photodegradation enhanced by the use of a photocatalyst and biodegradation by fungi. In the study, photocatalysis was conducted for 48 hours in a covered quartz beaker. The beaker contained fibers, Milli-Q water, and photocatalyst; we tested TiO2 and ZnO. Reactor systems were irradiated while stirring using a UV-vis simulated sun spectrum (Ultra Vitalux, 300 W, Osram). Biodegradation was performed by two selected species of fungi, Pleurostoma richardsiae and Coniochaeta hoffmannii. Sterilized plastic fibers were transferred to tubes with sterile M9 liquid medium. A cell suspension of each selected strain was added to the tube and incubated at 24°C for 2 and 6 months. Microscopy analysis after the photocatalysis showed that the surface of individual fibers became rough with clear signs of partial degradation, which could not be observed on pristine fibers. We also observed a successful growth of fungi, indicating that their main food source came from fibers. Cross-sectional FIB-SEM analysis revealed details of the damage, and Raman analysis showed structural changes in the plastic material. The kinetics of both degradation processes are relatively slow; however, repetition and proper reactor design could potentially increase the dynamics of microplastics degradation. [ABSTRACT FROM AUTHOR]

Plastic, which was not so long ago considered the material of the future, is today one of the biggest environmental problems. The most common type of primary microplastics that enters the aquatic environment in large numbers are fibers released during the washing of synthetic textiles. Due to their small size, they do not enter the ecosystem only through wastewater, but also through sewage treatment plants. In the present work, we tested a method for the degradation of microplastics from the wastewater of a washing machine, which is based on photocatalysis. In our study, the photocatalytic degradation of polyethylene terephthalate (PET) and polyamide (PA) fibers was carried out for 48 hours in a coved quartz beaker. The beaker contained fibers, 5 mg of TiO2 as a photocatalyst, 5 mL of Milli-Q water and a stirrer. In a photocatalytic reactor, quartz beakers were placed on a magnetic stirrer and irradiated with simulated sunlight (lamp: ULTRA-VITALUX, 230 V, 300 W, Osram). After photocatalysis, plastic samples were taken from the suspension and air-dried in a dust-free chamber. SEM analysis after photocatalytic degradation showed that the surface of the fibers became rough with clear signs of degradation, which could not be observed in the original ones. Cross-sectional FIB-SEM analysis revealed details of the damage. Changes in the chemical structure was analyzed by Raman spectroscopy, and ICP-MS analysis was used to analyze the amount of finer microplastic fiber fragments released into the suspension. In the future work, the presented degradation process will also be tested on real samples, which consist of different types of microplastic (PET, PA) and cotton fibers. [ABSTRACT FROM AUTHOR]

The presence of organic pollutants in the environment and their alarming negative effects on the environment and human health have been described in numerous studies [1]. Various methods have been developed to reduce and degrade organic pollutants with varying effectiveness [1]. Synthetic, heterogeneous, semiconducting, and multidimensional ZnO is utilized in various fields [1,2]. ZnO can act as a photocatalyst in the oxidation of organic pollutants, both in powder and thin film form [3]. The main advantages of ZnO thin films are easier and more efficient reusability and the possibility of using them in continuous processes [3]. Several methods are known for the synthesis of ZnO, among which hydrothermal synthesis is widely used due to its advantages such as low process temperature, low cost, and environmental friendliness [2]. It enables the deposition of ZnO on the substrate and offers the possibility to control and optimize the size and morphology of the resulting ZnO crystals. In this study, the ZnO nanorod arrays were synthesized in two parts. First, a solution of zinc acetate dihydrate (0.50 and 0.25 M) was spin-coated onto glass substrates and annealed at 360 °C for 5 hours. In the second part, the hydrothermal growth method was performed at 90 °C for 3 and 6 hours. The morphology and size of the synthesized particles were characterized by SEM. The photocatalytic activity of the ZnO nanorod arrays was evaluated by studying the degradation of a 5 ppm caffeine solution under simulated solar irradiation using UV-Vis spectrophotometry. The results show that ZnO films are photocatalytically active and that their catalytic performance is affected by the synthesis conditions. The ZnO films can be reused since their photocatalytic efficiency does not change significantly during the cycle. Since the stability of the catalysts is important from both an environmental and economic point of view and the results obtained are promising, it would be useful to further improve the ZnO films (e.g., by doping) and to test the photocatalytic degradation of other pollutants. [ABSTRACT FROM AUTHOR]