Photodegradation of Pharmaceuticals from Aqueous Solutions Using TiO2, Composite Nanofiber PAN-MWCNT/TiO2, and PAN-MWCNT/TiO2–NH2 as Photocatalysts under Ultraviolet and Visible Light

Abstract

The present study investigates the degradation of tetracycline (TCH), amoxicillin (AMX), and diclofenac sodium (DCF) under ultraviolet (UV) and visible light conditions using TiO₂ and two composite nanofibers, PAN-MWCNT/TiO₂−NH₂ and PAN-MWCNT/TiO₂, as photocatalysts. The nanofiber catalysts were prepared by the force-spinning method and characterised by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), Raman spectroscopy and scanning electron microscopy (SEM). Maximum degradation percentage was achieved by optimising various parameters, in particular feed pH (3–11), concentration of feed (50–100 mg/L), and dosing of the catalyst (0.5–1.5 g/L). TiO₂-based nanofiber adjusts the band gap and increase its capability to absorb UV and visible light selectively. The effectiveness of AMX, TCH, and DCF (50 mg/L) degradation was investigated using UV and solar radiation with various photocatalysts (1 g/L) at pH 3 for AMX and DCF and pH 11 for TCH. This study revealed that PAN-MWCNT/TiO₂ was the most efficient catalyst under UV radiation, which showed the maximum degradation percentage of the pollutants, i.e., 97% for AMX, 95% for TCH, and 91% for DCF in 90 min, whereas PAN-MWCNT/TiO₂–NH₂ was highly effective in visible light and resulted in 64% for AMX, 72% for TCH, and 67% for DCF degradation in 6 h. Chemical oxygen demand (COD) analysis was performed before and after the degradation process. 70–80% COD removal efficiencies suggested partial oxidation of the pollutants (AMX/TCH/DCF). To spot the intermediate compounds produced during the degradation process, Liquid chromatography-mass spectrometry (LC-MS) analysis was also performed.