Fabrication of highly efficient ZnO-Pt catalysts assisted by biomass-derived carboxymethyl cellulose for the photodegradation of diverse antibiotics

Antibiotic contamination poses a substantial challenge to environmental, thereby necessitating the development of effective strategies for antibiotic elimination. This study utilized a hydrothermal reaction to incorporate the nano platinum (Pt) onto zinc oxide (ZnO), resulting in the formation of an efficient ZnO-Pt powder photocatalyst. Subsequently, biomass-derived carboxymethyl cellulose (CMC), modified via an acid-assisted freeze-thaw process, was employed as a matrix for fabricating the ZnO-Pt@CMC composite. Characterization of the synthesized materials was conducted using X-ray diffraction (XRD), Raman spectra (Raman), Fourier transform infrared spectrometer (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). Afterwards, the photocatalytic performance of both ZnO-Pt and ZnO-Pt@CMC was assessed against a range of simulated antibiotic wastewater including sulfamethoxazole (SMX), ciprofloxacin (CIP), and oxytetracycline (OTC), under various conditions such as solution pH, catalyst dosage, antibiotic concentration, initial solution temperature, and light source. The ZnO-Pt catalyst demonstrated a degradation efficiency of 92.7 % for SMX within 180 min under xenon lamp irradiation, adhering to a pseudo-first-order kinetic model. Otherwise the ZnO-Pt@CMC exhibited degradation efficiencies of 80.6 % and 85.4 % for SMX and OTC over the same duration, while it demonstrated an exceptionally high photodegradation efficiency of 94.9 % for CIP and maintained its activity even after three consecutive cycles of use. Electrochemical impedance spectroscopy (EIS), linear scanning voltammetry (LSV), and radical quenching experiments showed that the introduction of Pt or CMC could increased the transfer and separation rate of ·OH and ·O₂^- during the photocatalytic degradation, along with a reasonable proposed degradation pathway for SMX.