Perfluorinated sulfonic acid ionomer/poly(N-vinylpyrrolidone) nanofiber membranes: Electrospinning fabrication, water stability, and metal ion removal applications

De Novo Ion-Exchange Membranes Based on Nanofibers

The unique functions of nanofibers (NFs) are based on their nanoscale cross-section, high specific surface area, and high molecular orientation, and/or their confined polymer chains inside the fibers. The introduction of ion-exchange (IEX) groups on the surface and/or inside the NFs provides de novo ion-exchangers. In particular, the combination of large surface areas and ionizable groups in the IEX-NFs improves their performance through indices such as extremely rapid ion-exchange kinetics and high ion-exchange capacities. In reality, the membranes based on ion-exchange NFs exhibit superior properties such as high catalytic efficiency, high ion-exchange and adsorption capacities, and high ionic conductivities. The present review highlights the fundamental aspects of IEX-NFs (i.e., their unique size-dependent properties), scalable production methods, and the recent advancements in their applications in catalysis, separation/adsorption processes, and fuel cells, as well as the future perspectives and endeavors of NF-based IEMs.

A rapid approach for measuring silver nanoparticle concentration and dissolution in seawater by UV-Vis

Detection and quantification of engineered nanoparticles (NPs) in environmental systems is challenging and requires sophisticated analytical equipment. Furthermore, dissolution is an important environmental transformation process for silver nanoparticles (AgNPs) which affects the size, speciation and concentration of AgNPs in natural water systems. Herein, we present a simple approach for the detection, quantification and measurement of dissolution of PVP-coated AgNPs (PVP-AgNPs) based on monitoring their optical properties (extinction spectra) using UV-vis spectroscopy. The dependence of PVP-AgNPs extinction coefficient (ɛ) and maximum absorbance wavelength (λ_max) on NP size was experimentally determined. The concentration, size, and extinction spectra of PVP-AgNPs were characterized during dissolution in 30ppt synthetic seawater. AgNPs concentration was determined as the difference between the total and dissolved Ag concentrations measured by inductively coupled plasma-mass spectroscopy (ICP-MS); extinction spectra of PVP-AgNPs were monitored by UV-vis; and size evolution was monitored by atomic force microscopy (AFM) over a period of 96h. Empirical equations for the dependence of maximum absorbance wavelength (λ_max) and extinction coefficient (ɛ) on NP size were derived. These empirical formulas were then used to calculate the size and concentration of PVP-AgNPs, and dissolved Ag concentration released from PVP-AgNPs in synthetic seawater at variable particle concentrations (i.e. 25-1500μgL^-1) and in natural seawater at particle concentration of 100μgL^-1. These results suggest that UV-vis can be used as an easy and quick approach for detection and quantification (size and concentration) of sterically stabilized PVP-AgNPs from their extinction spectra. This approach can also be used to monitor the release of Ag from PVP-AgNPs and the concurrent NP size change. Finally, in seawater, AgNPs dissolve faster and to a higher extent with the decrease in NP concentration toward environmentally relevant concentrations.

Preparation and characterization of a PFSA–PVDF blend nanofiber membrane and its preliminary application investigation

Herein, electrospinnability of perfluorosulfonic acid (PFSA)–polyvinylidene fluoride (PVDF) blends with different ratios of PVDF were investigated in detail.

Microphase separated sepiolite-based nanocomposite blends of fully sulfonated poly(ether ketone)/non-sulfonated poly(ether sulfone) as proton exchange membranes from dual electrospun mats

In this study, nanocomposite blends of fully sulfonated poly(ether ketone) (PEK) and non-sulfonated poly(ether sulfone) (PES) were prepared from a dual electrospinning process.

Processing-structure-property correlations of polyethersulfone/perfluorosulfonic acid nanofibers fabricated via electrospinning from polymer-nanoparticle suspensions

Polyethersulfone (PES)/perfluorosulfonic acid (PFSA) nanofiber membranes were successfully fabricated via electrospinning method from polymer solutions containing dispersed calcium carbonate (CaCO(3)) nanoparticles. ATR-FTIR spectra indicated that the nanoparticles mainly existed on the external surface of the nanofibers and could be removed completely by acid treatment. Surface roughness of both the nanofibers and the nanofiber membranes increased with the CaCO(3) loading. Although FTIR spectra showed no special interaction between sulfonic acid (-SO(3)) groups and CaCO(3) nanoparticles, XPS measurement demonstrated that the content of -SO(3) groups on external surface of the acid-treated nanofibers was enhanced by increasing CaCO(3) loading in solution. Besides, the acid-treated nanofiber membranes were performed in esterification reactions, and exhibited acceptable catalytic performance due to the activity of -SO(3)H groups on the nanofiber surface. More importantly, this type of membrane was very easy to separate and recover, which made it a potential substitution for traditional liquid acid catalysts.