Fe2O3/TiO2 nanocomposites were fabricated via a facile impregnation/calcination technique employing different amounts iron (III) nitrate onto commercial TiO2 (P25 Aeroxide). The as-prepared Fe2O3/TiO2 nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy (RS), scanning electron microscopy/energy-dispersive spectroscopy (SEM/EDXS), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller analysis (BET), electron impedance spectroscopy (EIS), photoluminescence spectroscopy (PL), and diffuse reflectance spectroscopy (DRS). As a result, 5% (w/w) Fe2O3/TiO2 achieved the highest photocatalytic activity in the slurry system and was successfully immobilized on glass support. Photocatalytic activity under visible-light irradiation was assessed by treating pharmaceutical amoxicillin (AMX) in the presence and absence of additional oxidants: hydrogen peroxide (H2O2) and persulfate salts (PS). The influence of pH and PS concentration on AMX conversion rate was established by means of statistical planning and response surface modeling. Results revealed optimum conditions of [S2O82−] = 1.873 mM and pH = 4.808; these were also utilized in presence of H2O2 instead of PS in long-term tests. The fastest AMX conversion possessing a zero-order rate constant of 1.51 × 10−7 M·min−1 was achieved with the photocatalysis + PS system. The AMX conversion pathway was established, and the evolution/conversion of formed intermediates was correlated with the changes in toxicity toward Vibrio fischeri. Reactive oxygen species (ROS) scavenging was also utilized to investigate the AMX conversion mechanism, revealing the major contribution of photogenerated h+ in all processes.
The presence of pharmaceuticals in the aquatic environment is problematic in many aspects, mainly due to their specific mode of action, and physical and chemical properties that make them highly resistant to degradation. This new group of contaminants is frequently detected in conventional wastewater treatment plants. Removal of pharmaceuticals from water by primary and secondary methods (filtration, sedimentation, biological treatment) is not satisfactory, therefore advanced methods involving membrane and advanced oxidation processes are increasingly being developed. The most significant advantage of membrane technologies is their wide industrial applicability while maintaining the highest water standards. Advanced oxidation processes can effectively decompose complex pollutants into simpler ones, and mineralize organic pollutants in wastewater without generating secondary waste. In order to improve their advantages, but also to eliminate disadvantages, these technologies are increasingly complemented and combined, resulting in higher efficiency in removing pharmaceuticals from water and reducing their toxicity.
Microplastics (MPs) are detected in the water, sediments, as well as biota, mainly as a consequence of the degradation of plastic products/waste under environmental conditions. Due to their potentially harmful effects on ecosystems and organisms, MPs are regarded as emerging pollutants. The highly problematic aspect of MPs is their interaction with organic and inorganic pollutants; MPs can act as vectors for their further transport in the environment. The objective of this study was to investigate the effects of ageing on the changes in physicochemical properties and size distribution of polyethylene terephthalate (PET), as well as to investigate the adsorption capacity of pristine and aged PET MPs, using pharmaceutical diclofenac (DCF) as a model organic pollutant. An ecotoxicity assessment of such samples was performed. Characterization of the PET samples (bottles and films) was carried out to detect the thermooxidative aging effects. The influence of the temperature and MP dosage on the extent of adsorption of DCF was elucidated by employing an empirical modeling approach using the response surface methodology (RSM). Aquatic toxicity was investigated by examining the green microalgae Pseudokirchneriella subcapitata. It was found that the thermooxidative ageing process resulted in mild surface changes in PET MPs, which were reflected in changes in hydrophobicity, the amount of amorphous phase, and the particle size distribution. The fractions of the particle size distribution in the range 100–500 μm for aged PET are higher due to the increase in amorphous phase. The proposed mechanisms of interactions between DCF and PET MPs are hydrophobic and π–π interactions as well as hydrogen bonding. RSM revealed that the adsorption favors low temperatures and low dosages of MP. The combination of MPs and DCF exhibited higher toxicity than the individual components.
The impact of plastic waste on the environment, human health, and ecosystems is one of the most important issues today. Once released into the environment, plastic waste is exposed to various stress factors that can lead to a reduction in its structural integrity and consequently to its fragmentation into smaller pieces. In this work, the effects of simulated UV aging on the surface properties and fragmentation of high-density polyethylene (HDPE) films were studied. HDPE films were prepared from pristine polymer granules, and aged for 14, 28, and 42 days under artificial UV irradiation. The samples were characterised before and after each irradiation period to inspect structural and surface changes. FTIR spectra revealed the appearance of carbonyl (C=O) and carbon-oxygen (C−O, O−C=O, C−O−O−) groups due to photodegradation of HDPE. The change in surface polarity with UV irradiation time was determined by measuring the water contact angle, while the surface morphology was analysed using a SEM microscope. The results revealed a significant increase in carbonyl index, increased hydrophilicity, and increased brittleness resulting from a high degree of photodegradation after 28 and 42 days of UV irradiation. The different particle size distribution yielded upon grinding indicated that aged HDPE films are more prone to fragmentation into micro-sized particles.
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