Synthesis and Characterization of Novel Hybridized CeO2@SiO2 Nanoparticles Based on Rice Husk and Their Application in Antibiotic Removal

This work aims to synthesize a core–shell material of CeO2@SiO2 based on rice husk as a novel hybridized adsorbent for antibiotic removal. The phase structures of CeO2@SiO2 and CeO2 nanoparticles that were fabricated by a simple procedure were examined by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), and Fourier transform infrared (FT-IR) spectroscopy, while their interfacial characterizations were performed by scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), the Brunauer–Emmett–Teller (BET) method, and ζ-potential measurements. The removal efficiency of the antibiotic amoxicillin (AMX) using CeO2@SiO2 nanoparticles was much greater than that using SiO2 and CeO2 materials in solutions of different pH values. The optimum conditions for AMX removal using CeO2@SiO2 including contact time and adsorbent dosage were 120 min and 5 mg/mL, respectively. The maximum AMX removal using CeO2@SiO2 reached 100% and the adsorption capacity was 12.5 mg/g. Adsorption isotherms of AMX onto CeO2@SiO2 were fitted by Langmuir, Freundlich, and two-step adsorption models, while the adsorption kinetics of AMX achieved a better fit by the pseudo-second-order model than the pseudo-first-order model. The electrostatic and nonelectrostatic interactions between the zwitterionic form of AMX and the positively charged CeO2@SiO2 surface were controlled by adsorption. The effects of different organics such as humic acid, ionic surfactants, and pharmaceutical substances on AMX removal using CeO2@SiO2 were also thoroughly investigated. The high AMX removal efficiencies of about 75% after four regenerations and about 70% from an actual water sample demonstrate that CeO2@SiO2-based rice husk is a hybrid nanomaterial for antibiotic removal from water environments.