Search

The pervasive issue of microplastics in aquatic environments presents a formidable challenge to traditional water treatment methodologies, including those utilizing KMnO 4 . This study pioneers advanced oxidation processes (AOPs) method aimed at improving the degradation of PE microplastics by employing a dual treatment strategy that combines KMnO 4 oxidation with UV irradiation. Detailed analysis of the surface modifications and chemical functional groups of the treated PE microplastics revealed the establishment of Mn-O-Mn linkages on their surfaces. Weight reductions of 3.9%, 4.9%, and 7.5% were observed for the KMnO 4 /UVA, KMnO 4 /UVB, and KMnO 4 /UVC treatments over seven days, respectively. The emergence of carboxyl and hydroxyl groups played a crucial role in accelerating the degradation process. Notably, the combined application of UVC rays and KMnO 4 resulted in the most effective degradation of PE microplastics observed in our study. The process significantly enhanced the formation of MnO 2 particles from KMnO 4 oxidation, with concentrations ranging from 0.036 to 0.070 mM for KMnO 4 /UVA, 0.066-0.097 mM for KMnO 4 /UVB, and 0.086-0.180 mM for KMnO 4 /UVC. Furthermore, the influence of varying pH levels, KMnO 4 concentrations, and different water sources on the degradation efficacy was investigated. The pivotal role of free radicals and reactive manganese species in promoting the degradation of PE microplastics was identified. A comparative evaluation with treatments solely utilizing KMnO 4 or UV light highlighted the enhanced effectiveness of the combined approach, demonstrating its potential as an efficient solution for reducing microplastic contamination in aquatic systems., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 Elsevier Ltd. All rights reserved.)

In this study, total phosphorus (P) and P released forms were measured in core sediments from the areas affected by human settlement and shrimp farming activities and the core zone of the Can Gio Biosphere Reserve, a coastal district in south Vietnam. Furthermore, ecological risk assessment and parameters controlling P release from sediments were investigated, including pH, major elements (Al-Ca-Mg-Fe), and fine fraction. The average total amount of P in the sediments varied from 287 to 669 mg/kg, with significantly lower values being observed in the mangrove biosphere reserve area. According to the results of the correlation analysis, organic matter was the primary source of P in the sediments, but the majority of the P released was inorganic. Positive correlations were found between Fe and non-apatite inorganic P (NAIP) and apatite P (AP), as well as intercorrelations between P fractions (r = 0.40-0.79, p < 0.05), suggesting that Fe might be the controlling factor of P release in the investigated sediments. The rank orders of concentrations of P forms were significantly different between the areas. The range of P forms was AP (35-248 mg/kg) > NAIP (63-201 mg/kg) > LP (labile P) (4-25 mg/kg) in the human settlement and aquaculture areas and NAIP (84-99 mg/kg) > AP (20-38 mg/kg) > LP (7-12 mg/kg) in the mangrove biosphere reserve area. Risk assessment based on the total concentration of P and the availability of P from a single extraction suggested a relatively low risk of P from sediment as an internal load in the studied areas., (© 2022. The Author(s), under exclusive licence to Springer Nature Switzerland AG.)

The adsorption of Pb ions, on high-density polyethylene (PE) microplastics (MPs) with the diameter of 48-500 μm, was examined in this study. According to the Langmuir isotherm, MP of the smallest size, 48 μm, had the greatest adsorption capacity of 0.38 μmol g -1 . The mechanism of Pb ions adsorption onto PE MPs was chemical adsorption, in particular, hydrogen bonding and surface complexation. Pb adsorption onto PE particles was proceeded at a rapid rate, as predicted by the pseudo-second-order rate model (R 2  > 0.99). The PE 48 μm had the maximum adsorption capacity of 0.44 μmol g-1 (or 0.2 mol m -2 ) at pH 5. While humic acid can operate as a bridging agent, boosting heavy metal adsorption on the surface of PE MPs, fulvic acid has the reverse effect. The findings indicated that PE particles may serve as a carrier of heavy metals in the aquatic environment, posing perceived risks to the environment and public health., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

The presence of ultrafine plastics particles and its potential to concentrate and transport organic contaminants in aquatic environments have become a major concern in recent years. Specifically, the uptake of hazardous chemicals by plastics particles may affect the distribution and bioavailability of the chemicals. In this study, the adsorption of tetracycline (TC), an antibiotic frequently found in aquatic environments, on high-density polyethylene (PE) particles with the average size of 45 μm, was investigated. The PE particles were characterized for surface acidity for the first time. Results showed that pH controls the surface charge of PE particles. TC adsorption onto PE particles was rapid as expected following the pseudo-second-order rate law (r 2  > 0.99). Polar forces in addition to specific chemical interactions, such as hydrogen bonding and hydrophophilicity controlled TC adsorption onto PE particles. Parameters, including pH, dissolved organic matter, ionic strength, major cations and anions affected TC adsorption onto PE micro-particles. Results indicated that PE particles can function as a carrier of antibiotics in the aquatic environment, which potentially imposes ecosystem and human health risks., (Copyright © 2021 Elsevier Ltd. All rights reserved.)