Abstract:
Nanoporous track-etched membranes (TeMs) are highly versatile materials that have shown promise in
various applications such as filtration, separation, adsorption, and catalysis due to their mechanical
integrity and high surface area. The performance of TeMs as catalysts for removing toxic pollutants is
greatly influenced by the pore diameter, density, and functionalization of the nanochannels. In this study,
the synthesis of functionalized poly(ethylene terephthalate) (PET) TeMs with Pd nanoparticles (NPs) as
catalysts for the photodegradation of the antibiotic metronidazole (MTZ) was methodically investigated
and their catalytic activity under UV irradiation was compared. Before loading of the Pd NPs, the surface
and nanopore walls of the PET TeMs were grafted by poly(1-vinyl-2-pyrrolidone) (PVP) via UV-initiated
reversible addition fragmentation chain transfer (RAFT)-mediated graft copolymerization. The use of
RAFT polymerization allowed for precise control over the degree of grafting and graft lengths within the
nanochannels of PVP grafted PET TeMs (PVP-g-PET). Pd NPs were then loaded onto PVP-g-PET using
several environmentally friendly reducing agents such as ascorbic acid, sodium borohydride and a plant
extract. In addition, a conventional thermal reduction technique was also applied for the reduction of the
Pd NPs. The grafting process created a surface with high-sorption capacity for MTZ and also high
stabilizing effect for Pd NPs due to the functional PVP chains on the PET substrate. The structure and
composition of the composite membranes were elucidated by scanning electron microscopy (SEM), Xray diffraction (XRD) analysis, thermogravimetry, contact angle measurements and energy dispersive Xray (EDX), X-ray photoelectron (XPS) and Fourier transform infra-red (FTIR) spectroscopies. The effects of
different types of reducing agents, pH, the amount of loaded catalyst and MTZ concentration on the
MTZ catalytic degradation efficiency of the obtained composites were investigated. The efficiency of the
catalyst prepared in the presence of ascorbic acid was superior to the others (89.86% removal at
30 mg L−1 of MTZ). Maximum removal of MTZ was observed at the natural pH (6.5) of the MTZ solution
at a concentration of 30 mg per L MTZ. The removal efficiency was decreased by increasing the catalyst
dosage and the initial MTZ concentration. The reaction rate constant was reduced from 0.0144 to
0.0096 min−1 by increasing the MTZ concentration from 20 to 50 mg L−1
. The photocatalyst revealed
remarkable photocatalytic activity even after 10 consecutive cycles.
