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Abstract: Track-etched polyethylene terephthalate (TE-PET) membranes, characterized by their well-defined cylindrical pores and narrow pore size distribution, offer advantages in filtration applications but demonstrate a gradual decrease of water flux over time. In this work, we evaluate the performance of track-etched polyethylene terephthalate (TE-PET) membranes as microfilters in low-pressure cross-flow and dead-end filtration systems. Membranes with pore sizes between 0.2 and 2.5 μm and porosities of 0.2–20% were tested at different low pressures (0.02–10 bar). Monitoring water flux over time exhibited a significant reduction. This behaviour is attributed to polymer swelling within the pore walls due to the formation of a sol-gel film. Notably, this swelling is enhanced under dynamic flow conditions, with larger pores exhibiting more rapid and pronounced flux decline. When filtering organic solvents, the flux drop is less pronounced and depends on their viscosity and polarity. Surface characterization by atomic force microscopy further confirmed morphological changes in TE-PET support after water filtration. Additional contributing factors, such as fouling and compaction, are also discussed.
Keywords: track-etched support, polyethylene terephthalate, water filtration, swelling, sol-gel film, carbon nanomembrane
Published in DKUM: 13.06.2025; Views: 0; Downloads: 5
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Abstract: Biocompatible, mechanically stable, highly hydrophilic/swellable and safe antibacterial biomaterials are crucial for wound dressing and other applications in the health sector. Therefore, this study was conducted for the development of bacterial nanocellulose membranes, which were, for the frst time, enriched with bacteriostatic and bactericidal efective avocado seed extracts prepared by diferent extraction techniques (ultrasonic, Soxhlet, high pressure with supercritical carbon dioxide). First, the production process of bacterial nanocellulose membranes from Komagataeibacter hansenii bacteria was optimized related to the fermentation media composition and culture conditions, resulting in bacterial nanocellulose membranes with up to 83% crystallinity and 54.5 g/L yield. The morphological structure of the membranes was varied further by using air- and freeze-drying processes. The Soxhlet and high pressure with supercritical carbon dioxide avocado seed extracts with the most charge negative surface (-33 mV) and smallest hydrodynamic size (0.1 µm) thus resulted in 100% reduction of both Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus with up to log reduction of 2.56 and up to 100% bactericidal efficacy after 24 h of exposure, and at 14 mg/g of avocado seed extracts integrated in the bacterial nanocellulose membranes homogeneously. The high swelling (up to 600%) and water retention ability of avocado seed extracts enriched bacterial nanocellulose membranes, with a biocidal release up to 2.71 mg/mL, shows potential for antibacterial applications in the biomedicine, cosmetics, and pharmaceutical industries.
Keywords: bacterial nanocellulose membrane, avocado seed extracts, extraction, swelling, release, antibacterial activity
Published in DKUM: 23.08.2024; Views: 70; Downloads: 15
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Abstract: Swelling soils can be found in many parts of the world. The state of practice in this area has been changing over recent decades. The design of foundations for expansive soils is an impo rtant challenge facing engineers. The excessive damage is, in part, due to the lack of proper design, resulting in the need for better tools for practitioners in order to assess the impact of swelling soils in typical design applications. A correct measurement of the swelling pressure is required for an accurate prediction of the heave. A theoretical model is proposed to describe the swelling potential of clay soils on the basis of their characteristics obtained from oedometer tests. This paper describes analysis of the behavior of swelling soils when moistened under buildings and structures. The methods and principles currently used for the design of structure foundations on swelling soils involve important problems due to the non-uniform deformations of these soils when subjected to structural loads. The current study was conducted to compute the uplifting of shallow foundations on swelling soils considering the water-content change as well as the contact-pressure distribution under the footing.
Keywords: swelling soil, swelling magnitude, swelling pressure, free-swell oedometer test, loaded-swell oedometer test, shallow foundations
Published in DKUM: 18.06.2018; Views: 1057; Downloads: 110
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Abstract: This contribution is focused on the determination of polymerization and crosslinking mechanism of poly (N-isopropyl- acralymide) hydrogel and its swelling properties. Hydrogels were synthesized by environmental friendly UV polymerization method, from monomer N-isopropylacrylamide (NIPAM) and crosslinker N,N´-methylenebisacrylamide (BIS) of different concentrations. UV polymerization was performed in an UV chamber using UVA light with the wave length 350 nm. Surface morphology and pore structure analysis was carried out using SEM microscopy. The polymerization and crosslinking mechanism was determined by Fourier Transform Infrared spectroscopy (FT-IR). It was confirmed that crosslinker concentration influences the hydrogel structure and swelling properties. By increasing the crosllinker concentration the hydrogel structure changes from homogen to heterogen and the equilibrium degree of swelling decreases.
Keywords: poly (N-isopropylacrylamide) hydrogel, UV polymerization, FTIR, polymerization mechanism, swelling properties, SEM
Published in DKUM: 01.06.2012; Views: 2072; Downloads: 124
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