Abstract
Antiviral drugs are a major contributor to water pollution because they are persistent and non-biodegradable in the aquatic environment. Antiviral drugs used to treat and suppress viral pandemics have been detected in water bodies because conventional wastewater and drinking water treatment plants are ineffective in removing these drugs. Photocatalyst is regarded as an efficient, environmentally friendly AOPs for the effective removal of antiviral drugs in water.
The n-type tungsten trioxide (WO3) is considered an excellent photocatalyst with a suitable band gap (2.4-2.8 eV) that absorbs light in visible light. However, the high recombination rate of photogenerated charge carriers and low visible light harvesting limit the application of this semiconductor photocatalyst. The study focuses on the developing novel cavitand-MXene photocatalyst (Ce2S3/WO3@TiVC-CB [7]) through an electrostatic self-assembly route to enhance the WO3 photocatalytic activity for photodegradation of nevirapine in water under visible light irradiation.
The spectroscopic and microscopic properties were characterized and confirmed by XRD, Raman, UV-Vis DRS, PL, PC, TEM, SEM, XPS, EIS, PC and BET.
The photocatalytic capability of WO3 was first modified by anchoring the Ce2S3 nanosphere onto WO3 nanocubes to form the S-scheme heterojunction with a strong internal electrical field interface, and band bending, which promotes the migration and separation of the photogenerated charge carriers while maintaining the redox potency.
The photocatalytic activity was further enhanced by incorporating binary composite (CW) with the double transition MXene (TiVC) through ultrasonication and calcination methods. The TiVC exhibits excellent electric conductivity and significant work function corresponding to the lower Fermi level, which is appropriate for the formation of a Schottky junction with photocatalyst, preventing the “backflowing” of electrons, thus aiding the fast separation of electrons and holes, thus enhancing photoactivity of the material.
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The hydrophilic CB [7] was integrated into the CWT composite to form the cavitand-MXene photocatalyst nanocomposite with enhanced photoelectrochemical properties. The CWTC-5 composite exhibited lower charge transfer resistance (96.50 Ω), weak PL intensity and longer electron lifetime (74.89 ms), inferring rapid separation and transfer of the photogenerated electrons and holes. The enhanced photocatalytic activity was attested to the negative carbonyl rim of CB [7], which acted as a trap for the photogenerated holes, improving the separation of photogenerated charge carriers.
The photocatalytic efficiency of prepared photocatalysts was evaluated on the degradation of nevirapine under the visible light lamp. The optimal conditions for NVP degradation were pH 3.5, 10 mg/L working concentration of NVP and 15 mg as catalyst loading. The CWTC exhibited a better degradation with 36.73% compared to WO3 (24.97%), Ce2S3 (20.55%), CW (23.62%), CWC (28.77%), and CWT (30.00%). The better degradation was due to the efficient separation of the photogenerated charge carriers, thus improving the photocatalytic activity. The superoxide (•O2-), and hydroxyl (•OH) radicals were deduced to be the main species for degradation of nevirapine. The possible degradation fragments of nevirapine with m/z=266 were elucidated via LCMS analysis; it exhibited six fragments. The NVP was degraded into six fragments assigned to the m/z= 214, 194, 137, 114, 84, and 74 corresponding to the C12H11N3O, C11H17N2O+, C7H8N2O, C6H14N2, C5H9N, and C4H11N respectively. The last degradation fragment (m/z =74) was less toxic when compared to the NVP compound.