Preparation and application of MWCNT-MoO3/ZnO ternary hybrid immobilized PVDF hybrid film photocatalyst

Abstract

This study presents a novel method for immobilizing hybrid catalysts on polyvinylidene fluoride (PVDF) polymeric membranes for solid–liquid separation. A multi-walled carbon nanotube (MWCNT) doped with α-MoO3/ZnO photocatalyst (MWCNT-MoO3/ZnO) was prepared using an ultrasonic-assisted hydrothermal method. The photocatalysts were immobilized into PVDF membranes to prepare PVDF/MWCNT-MoO3/ZnO (IM-C3) via the phase inversion method and evaluated using methylene blue (MB) dye. The bandgap energy and e- - h+ separation potential of the materials was validated using UV–vis diffuse reflectance spectroscopy (UV–vis DRS) and photoluminescence (PL) spectroscopy. The UV–vis DRS results confirmed that the band gap energy of powdered photocatalysts decreased with increasing amounts of MWCNT as C1 (2.7 eV), C2 (2.6 eV), and C3 (2.4 eV). X-ray diffraction (XRD), and field emission scanning electron microscopy (FESEM) validate the structure and morphology of the photocatalysts. The EDX spectra confirm impurity-free samples. The Braeuer-Emmett-Teller (BET) method was used to determine the surface area (m2/g) and porosity of the MWCNT-MoO3/ZnO powdered photocatalyst, which exhibits a mainly mesoporous nature. The specific surface area of C3 was approximately 87.4 m2/g, which is greater than that of C2 and C1 (47.0 m2/g and 18 m2/g, respectively). The atomic force microscopy (AFM) and water contact analysis (WCA) showed that the surface roughness and hydrophilicity of the PVDF film were enhanced upon immobilization of the C3 photocatalyst. This resulted in a better interaction between the MB dye and the prepared IM-C3 hybrid film photocatalyst, thus making it capable of degrading 96 % of the MB dye within 120 min under visible light irradiation. The impact of the operating parameters of the hybrid film photocatalysts, such as the number of films, solution pH, MB concentration, radical scavenger, and recyclability studies, has been prioritized. The degradation percentage decreased as the initial concentration of MB (10–20 mg/L) increased but increased as the number of films increased. The superoxide radical (.O2–) and hydroxyl radical (OH.), were the dominant reactive species for the degradation of MB under visible light irradiation. The IM-C3 film can be reused up to five times without any kind of chemical treatment and without losing its stability or effectiveness.