Polyurethane (PU) and PU/multiwalled carbon nanotube (MWCNT) nanocomposite nanofibers, both with diameters of 350 nm, were prepared by an electrospinning process from PU dimethylformamide solutions. The appearance of nanowebs in PU/MWCNT nanofiber structures containing PU fibers with diameters of 20-40 nm was observed. The existence of these structures could have been based on the occurrence of strong secondary electric fields, which were created between individual conducting MWCNTs (distributed in the PU/MWCNT nanocomposites), which started to behave as the local moving nanoelectrodes promoting the creation of additional very fine nanowebs during the electrospinning processes. To our knowledge, this is the first report describing nanowebs from synthetic polymers prepared by an electrospinning process.
For an effective modification of polyalkenes leading to the formation of block and/or graft copolymers, the presence of co-initiating water is absolutely necessary. We have compared two procedures used in the co-initiation of cationic reactions on polymers. Gradually supplied air moisture raises the efficiency of modification of isotactic polypropylene with poly(oxyethylene) several times, compared with a single addition of co-initiating water.
This study emphasizes rapid and simultaneous adsorptive removal of estrogenic hormones (EHs): estrone (E1), 17β-estradiol (E2), 17α-ethinylestradiol (EE2), and estriol (E3) from wastewater using recycled waste cigarette electrospun nanofibers (WCENFs). The nanofibers exhibited a small diameter (196±65 nm) and large surface area (18.05 m 2 /g), along with a strong affinity towards all EHs by adsorption due to abundant hydrogen bonding interactions. A one-step high-performance liquid chromatography technique was developed to detect each EH present in the solution simultaneously. The adsorption kinetics helps select optimum conditions for the large-scale removal process, so experimental data using pseudo-first-order, pseudo-second-order, intra-particle diffusion, Elovich, and fractional power models were fitted. It was found that E1, E2, and EE2 followed pseudo-second-order kinetics while E3 followed pseudo-first-order kinetic models. The total adsorption capacity on WCENFs was determined to be 2.14 mg/g, whereas the individual adsorption capacities of E1, E2, EE2, and E3 were found to be 0.551, 0.532, 0.687, and 0.369 mg/g, respectively. The percentage efficiency of WCENFs was highest with EE2 ~64.3% and least with E3 ~34.6%. Adsorption-desorption studies revealed that WCENFs could repeatedly be used four times. The reported results indicate a significant potential of WCENFs to be an effective sorbent and portable filter for simultaneous estrogenic hormone removal. WCENFs filter is a suitable alternative to commercial Cellulose acetate filters.
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