RESUMEN
UV-absorbing nanoparticles (NPs) and microparticles (MPs) were prepared by emulsion and dispersion copolymerization of the vinylic monomer 2-(2'-hydroxy-5'-methacryloxyethylphenyl)-2H-benzotriazole (Norbloc (NB)) with the crosslinking monomer divinylbenzene. The effect of the initiator concentration on the size and size distribution of the polyNB (PNB) particles was elucidated. Thin coatings of the formed PNB NPs or MPs of 19 ± 2 and 200 ± 25 nm dry diameter, respectively, onto polypropylene (PP) films were then prepared and characterized. Increasing the concentration or thickness of the PNB NP or MP thin coatings on the PP films decreased their UV transmittance, up to complete UV blocking with just 2 µm of a 4% NP coating. Migration of the UV-absorbing agents from the coated PP films was not observed during three years of storage at room temperature, offering a unique solution to current problems of migration of UV-absorbing additives. The thin coatings obtained by the PNB NPs were superior to those of the PNB MPs, in that no UV transmittance or loss of optical properties of the PP films were observed for the NP coatings, while the coatings produced by the PNB MPs resulted in damaged optical properties, particularly increasing the haze, and achieved incomplete UV blocking.
RESUMEN
In this study, we describe the synthesis and characterization of superparamagnetic core-shell iron oxide (IO)/N-halamine antibacterial nanoparticles (NPs). For this purpose, superparamagnetic IO core NPs were coated with cross-linked polymethacrylamide (PMAA) by surfactant-free dispersion copolymerization of methacrylamide and N,N-methylenebis(acrylamide) in an aqueous continuous phase. The effect of the polymerization process on the chemical composition, size, shape, crystallinity, and magnetic properties of the IO/PMAA NPs was elucidated. Conversion of the core-shell IO/PMAA NPs into their N-halamine form, IO/PMAA-Cl, was accomplished using a chlorination reaction with sodium hypochlorite. The influence of chlorination on the shape, crystallinity, and magnetic properties of the IO/PMAA NPs was studied. The IO/PMAA-Cl NPs demonstrated excellent antibacterial activity against Gram-negative and Gram-positive bacteria. Finally, the chlorination recharging capabilities of the NPs and their potential for use in the purification of water containing bacteria were demonstrated with magnetic columns packed with the IO/PMAA-Cl NPs.
RESUMEN
Magnetic Fe3O4, Fe and Fe/Pd nanoparticles embedded within the pores of activated carbon fabrics (ACF) were prepared by impregnation of the ACF in iron acetylacetanoate (Fe(acac)3) ethanol solution, followed by thermal decomposition of the embedded iron precursor at 200, 400 and 600 °C in an inert atmosphere. The effect of the annealing temperature on the chemical composition, shape, crystallinity, surface area, pore volume, and magnetic properties of the various functionalized ACF was elucidated. The Fe nanoparticles within the ACF were also doped with tinier Pd nanoparticles, by impregnation of the Fe/ACF in palladium acetate ethanol solution. The potential use of the functionalized ACF for removal of a model azo-dye, orange II, was demonstrated. This study illustrated the enhanced removal of the dye from an aqueous solution according to the following order: Fe/Pd/ACF > Fe/ACF > ACF. In addition, the enhanced activity of Fe3O4/ACF in the presence of increasing concentrations of H2O2 (Fenton catalysts) was also illustrated.
RESUMEN
Sorption-desorption behavior of sulfapyridine was studied with three distinct soil types low in organic carbon with or without the introduction of exogenous dissolved organic matter (DOM). Experiments with bulk soils yielded sorption coefficients equivalent to those obtained with soils richer in organic matter, indicating an important sorptive role for soil mineral matrices. Cointroduction of sulfapyridine with DOM significantly reduced sulfapyridine sorption. However, decreasing solution pH from ~9 to ~6 limited the effect of DOM and revealed the effect of ionic speciation of sulfapyridine on the sorption potential. Sulfapyridine sorption to soils precoated with DOM exhibited contrasting trends. Two of the coated soils exhibited decreased sorption of sulfapyridine probably due to blockage of sorption sites by DOM. Conversely, the third soil demonstrated cumulative adsorption of sulfapyridine. Precoating also enhanced sulfapyridine desorption, suggesting that sorption of sulfapyridine to mineral surfaces involves stronger chemisorptive binding as compared with interactions with sorbed DOM. The capacity of soil to sorb DOM as well as the chemical fractionation of DOM during sorption were found to significantly affect binding of sulfapyridine. Competition between preferentially sorbed DOM moieties (e.g., carboxyl, phenol) and sulfapyridine for sorption sites is proposed. This study suggests that the chemical nature of DOM can significantly affect the fate of sulfonamide compounds in soils.