Nanocellulose supported ZnWO4/SrTiO3/MoO3 heterojunction: Highly efficient visible light photocatalyst for ciprofloxacin degradation

Abstract

The rationally designed step scheme (S-scheme) heterojunction has advanced to improve the charge separation and provide a high redox potential. Therefore, in the present work, we have synthesized the nanocellulose-based ZnWO₄/SrTiO₃/MoO₃ (NC-ZSM) heterojunction using the ultrasonic-assisted wet impregnation method. Various microscopic and spectroscopic techniques like FE-SEM, HR-TEM, BET, XRD, FTIR, and XPS are used to study the heterojunction composition, structure, surface area, and charge carrier dynamics. BET study shows the high surface area of NC-ZSM (108.6 m²/g) with a large pore volume of 0.95 cm³/g, indicating many active sites. The XPS study confirms the charge migration pathway through S-scheme which is further supported by the trapping experiment. Furthermore, the UV–Vis, PL, and EIS studies revealed increased light absorption and charge separation in NC-ZSM heterojunction. The photodegradation experiment was conducted to evaluate the photoactivity against ciprofloxacin (CIP), a wide and common pharmaceutical pollutant. Here, NC-ZSM heterojunction degraded around 99.2 % of CIP under visible light irradiation within 30 min. To optimize the photoefficiency, photodegradation experiments were conducted at different reaction conditions. Maximum efficiency was achieved at 15 mg/L of photocatalytic dosage that degraded 40 mg/L CIP at pH = 6. Additionally, NC-ZSM showed high stability and retained around 85 % photocatalytic efficiency after performing seven catalytic cycles. Therefore, this work provides a powerful NC-ZSM S-scheme-based heterojunction that can generate hydroxyl and superoxide radical species, established by EPR and trapping experiments, capable of degrading a range of pharmaceutical pollutants.