Fabrication of PVDF-based piezocatalytic active membrane with enhanced oxytetracycline degradation efficiency through embedding few-layer E-MoS2 nanosheets

Abstract

A novel piezocatalytic active membrane based on mixed matrix of exfoliated multi-flaw MoS2 (E-MoS2) nanosheets and polyvinylidene fluoride (PVDF) was synthesized by electrospinning technique. The composition and structure of the obtained E-MoS2/PVDF electrospun fiber membranes (EFMs) were characterized via FESEM, HR-TEM, XRD, FTIR and XPS techniques. The piezocatalytic activity of the EFMs was evaluated by the degradation of antibiotic oxytetracycline (OTC) under ultrasonic irradiation in the dark. The 10.0 wt% E-MoS2/PVDF EFMs exhibited superior OTC degradation efficiency of 93.08% within 24 min with pseudo-first-order kinetic constant (k) of 0.09124 min−1, which was 21.1 times higher than that of the pure PVDF EFMs. The superior performance was attributed to the synergetic effect of the embedded E-MoS2 nanosheets and a high proportion of PVDF β-phase (94.1%) to effectively improve the piezoelectric property of composite. In addition, the ultrathin multi-flaw structure of E-MoS2 provided abundant catalytic active edge sites and increased the surface charge density, promoting the generation of more ∙OH and ∙O2– radicals to degrade OTC pollutants. The degradation intermediates of OTC over 10 wt% E-MoS2/PVDF EFMs were detected by HPLC–MS and two main degradation pathways were reasonably proposed. The piezocatalytic activity of 10 wt% E-MoS2/PVDF EFMs remained stable after five consecutive cycles. This study is meaningful for exploring the composite membrane piezocatalysts for largescale applications in wastewater treatment.