Poly(4-vinyl pyridine) radiografted PVDF track etched membranes as sensors for monitoring trace mercury in water

International audiencePoly-4-vinyl pyridine chains were radiografted inside the etched-tracks of PVDF nanoporous membrane. P4VP grafting was found to be localized on the solid PVDF surface. Coating of these PVDF-g-P4VP membranes with a very thin layer of gold results in an ASV electrochemical sensor. Functionalized ion track-etched PVDF-g-P4VP sensors were found very selective and highly sensitive for mercury LOD 5 ng/L. a b s t r a c t By a radiation-induced grafting technique, we have functionalized track-etched nanoporous polymer membranes with mercury sensitive poly-4-vinyl pyridine (P4VP). Coating of these membranes with a very thin layer of gold results in an electrochemical sensor that is very selective and highly sensitive for mercury LOD 5 ng/L – well below the norms for water (0.015 mg/L potable water and 0.5 mg/L residual waters-French water norms of 27 October 2011). E-beam irradiation permitted optimization of the radiografting synthesis on PVDF thin films prior to ion-track grafting. Synthesis and characterization by EPR, FESEM and FTIR are described in detail. A comparison between FTIR in ATR and transmission modes enabled us to localize the grafting on the surface of the e-beam irradiated PVDF films allowing us to extrapolate what happens on the etched tracks. Using Square Wave Anodic Stripping Voltammetry (SW-ASV), mercury concentrations of 1 mg/L are detected in 2 h and low ng/L concentrations are detected after 24 h of adsorption. The adsorption is passive so sensors do not require instrumentation and the analysis takes only 3–4 min. Also, the P4VP functionalized sensor appears insensitive to pH variations (pHs 3–9), high salt concentrations (up to 1 g/ L) and the presence of other heavy metals in the same solution.

Unprecedented Scissor Effect of Macromolecular Cross-linkers on the Glass Transition Temperature of Poly(N-vinylimidazole), Crystallinity Suppression of Poly(tetrahydrofuran) and Molecular Mobility by Solid State NMR in Poly(N-vinylimidazole)-l-poly(tetrahydrofuran) Conetworks

Unexpected correlations have been found between structural parameters and glass transition temperatures (Tg) of poly(N-vinylimidazole) (PVIm) and crystallinity of poly(tetrahydrofuran) (PTHF) in a series of novel, unique PVIm-l-PTHF amphiphilic conetworks synthesized in broad composition ranges via free radical copolymerisation of VIm and semicrystalline, methacrylate-telechelic PTHF macromolecular cross-linkers with varying Mn from 2170 to 10 000 g mol−1. Differential scanning calorimetry (DSC) investigations revealed microphase separation between the covalently bonded PVIm and PTHF components, that is two distinct Tgs corresponding to the respective polymers (PVIm and PTHF) were obtained in these optically clear, transparent materials. Complete microphase separation, i.e. absence of mixed phases, was also confirmed by solid state NMR measurements. The Tg of the PVIm phase significantly decreases with increasing PTHF content, and Fox–Flory type correlation was surprisingly found between the Tg of PVIm and its Mc (average molecular weight between cross-links). This striking finding indicates a unique, unpredicted scissor effect of the macromolecular PTHF cross-linker in these materials, i.e. with respect to glass transition, PVIm behaves as individual chains between cross-links. The molecular mobility in the PVIm chain segments obtained by solid state NMR investigations shows a similar trend as a function of Mc. In the DSC thermograms, the semicrystalline PTHF has a sharp endothermic melting peak (Tm) indicating partial crystallisation of this polymer. It was found that the Tm and the crystalline fraction (Xc) of the PTHF phase are suppressed by even a minimal content of PVIm phase in the conetworks. Even complete diminishing of Xc occurs in conetworks with lower than 40 wt% PTHF of the lowest Mn (2170 g mol−1). Unexpectedly, Tm linearly decreases with Mc in conetworks with constant Mn of PTHF. These data indicate that the decrease of both Tm and Xc of PTHF is not only composition dependent, but the MW of the macromolecular PTHF cross-linker and the Mc of the PVIm component also have effects on these parameters. These results also indicate that chemical bonding of polymer chains in conetworks yields novel materials with unprecedented property variation. This provides unique opportunities for fine tuning of the investigated fundamental material properties, i.e. Tg, Tm and Xc, within certain ranges in the novel PVIm-l-PTHF amphiphilic conetworks by selecting the proper synthesis parameters, that is, composition and MW of the telechelic PTHF macromonomer cross-linker

A high-strength polyvinyl alcohol hydrogel membrane crosslinked by sulfosuccinic acid for strontium removal via filtration

This study considered the removal of strontium (Sr2+) from contaminated water using a filtration membrane that exhibits good mechanical strength, high adsorption capacity, and the ability to be regenerated and reused. Polyvinyl alcohol hydrogel membranes were prepared by crosslinking with sulfosuccinic acid in different ratios (2.5, 5, 10 and 20 mol% relative to the PVA monomer), named as PSA2.5, PSA5, PSA10 and PSA20. All PSA membranes showed good Sr2+ adsorption over a wide pH range (pH 2–12), and maintained rapid removal kinetics (> 95% Sr2+ recovered from 5 ppm Sr2+ within 4 h). Furthermore, the Sr2+ adsorption capacities of PSA2.5, PSA5, PSA10 and PSA20 were 27.6, 45.8, 56.3, and 55.3 mg/g, respectively, based on the Langmuir adsorption isotherm. From the four PSA membranes, PSA5 was selected for further filtration studies due to its favorable mechanical and adsorption properties. When filtering 5 ppm Sr2+ and 250 ppm Ca2+, corresponding to the Ca2+ concentration in the wastewater at the Fukushima nuclear plant, 87% Sr2+ was removed using the PSA5 membrane following multiple cycles of regeneration and reuse. Moreover, the tensile strength of the PSA5 membrane remained high (> 100 MPa) following five consecutive uses

Functionalized Nanoporous Membrane Electrodes for ASV Analysis of Water

Abstract not Available.</jats:p

Functionalized Nanoporous Membrane Electrodes for ASV Analysis of Water

Abstract not Available.</jats:p

Functionalized Nanoporous Track-Etched b-PVDF Membrane Electrodes for Heavy Metal Determination by Square-Wave Anodic Stripping Voltammetry

Track-etched functionalized nanoporous β-PVDF membrane electrodes, or functionalized membrane electrodes (FMEs), are electrodes made from track-etched, poly(acrylic acid) (PAA) functionalized nanoporous β-poly(vinylidene fluoride) (β-PVDF) membranes with thin porous Au films sputtered on each side as electrodes. To form the β-PVDF nanoporous membranes, β-PVDF films are irradiated by swift heavy ions. After irradiation, radical tracks are stable in the membranes. Chemical etching removes some of the radical tracks revealing nanopores. Radicals, remaining in the pores, initiate radio grafting of PAA from the pore walls of the nanoporous β-PVDF. PAA is a cation exchange polymer that adsorbs metal ions, such as Pb2+, from aqueous solutions thus concentrating the ions into the membrane. After a calibrated time the FME is transferred to an electrochemical cell for square-wave anodic stripping voltammetry analysis