A New Generation of Catalytic Poly(vinylidene fluoride) Membranes: Coupling Plasma Treatment with Chemical Immobilization of Tungsten‐Based Catalysts

Abstract

A new generation of catalytically active membranes for secondary amine oxidation and phenol degradation has been developed by coupling the advantages of low‐temperature plasma‐modification processes with surface chemical immobilization reactions of catalysts. Poly(vinylidene fluoride) membranes have been modified with NH3 radiofrequency glow discharges in order to graft amino groups at their surface, providing active sites for stable immobilization of tungsten‐based heterogeneous catalysts. Particular attention has been focused on tungstate, WO42–, and decatungstate, W10O324–, which act efficiently as catalysts for the oxidation of secondary amines and as photocatalysts for the degradation of organic pollutants, respectively. Plasma‐modified membranes surface‐tailored with WO42– have been used in catalytic membrane reactors to activate hydrogen peroxide for oxidizing secondary amines to nitrones; membranes modified with W10O324– have been used for the complete degradation of phenol. The obtained results, in terms of amine–nitrone conversion and phenol degradation, respectively, appear extremely promising; these modified membranes can be considered as a pioneering, successful example of heterogenization of W‐based catalysts on plasma‐treated membranes.

Improved functions of human hepatocytes on NH3 plasma-grafted PEEK-WC–PU membranes

“…Beside grafting N-groups (amines, imines, cyano, etc. ), NH 3 plasma-treatments, are known to leave polymer surfaces prone to oxidation upon exposure to air due to long-living free radicals; so, as a general effect, the surface of NH 3 plasma-treated polymers is usually enriched of both N-and O-containing chemical groups [8,20], all responsible for increasing wettability and improving cell adhesion. Such groups likely influence positively the adsorption of proteins (enhanced and/or selective adsorption, favorable conformation of adsorbed proteins, etc.)…”

Self-assembly of rare-earth Anderson polyoxometalates on the surface of imide polymeric hollow fiber membranes potentially for organic pollutant degradation

“…Horan et al [17] prepared a highly proton-conductive membrane based on divinylsilyl-11-silicotungstic acid, butyl acrylate and hexanedioldiacrylate for fuel-cell applications. However, to the best of our knowledge, the exploration of such POMs-functionalized membranes is still in its infancy and very limited reports are available in this area [16][17][18][19][20][21][22].…”

“…Plasma radiation allowed the generation of desired functional groups (e.g. -NH 2 ) on membrane surfaces, which can be used as anchor groups for the immobilization of POMs by protonation and Coulomb interaction [18,20]. The grafting method comprised UV-initiated grafting polymerization of a synthesized ionic liquid monomer for binding POMs by ion exchange [15].…”

“…For those reported POMs-functionalized catalytic membranes [15,[18][19][20], catalytic degradation of organic pollutants in waste water was totally explored in the form of photocatalytic reactors. As long as the artificial light is used, their full-scale applications will be rather limited [27].…”

“…Among the very limited work, the assembly of POMs on the membrane surfaces was mainly realized by the plasma technology [18,20] or complicated grafting method under oxygen-free condition with toxic organic solvent (toluene) [15]. Plasma radiation allowed the generation of desired functional groups (e.g.…”