Synthesis and Characterization of Novel Core–Shell ZnO@SiO2 Nanoparticles and Application in Antibiotic and Bacteria Removal

A novel core–shell nanomaterial, ZnO@SiO2, based on rice husk for antibiotic and bacteria removal, was successfully fabricated. The ZnO@SiO2 nanoparticles were characterized by X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), photoluminescence spectroscopy (PL), Brunauer–Emmett–Teller (BET) method, diffuse reflectance ultraviolet–vis (DR-UV–vis) spectroscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and ζ-potential measurements. β-Lactam antibiotic amoxicillin (AMX) was removed using ZnO@SiO2 nanoparticles with an efficiency greater than 90%, while Escherichia coli removal was higher than 91%. The optimum effective conditions for AMX removal using ZnO@SiO2, including solution pH, adsorption time, and ZnO@SiO2 dosage, were 8, 90 min, and 25 mg/mL, respectively. The maximum adsorption capacity reached 52.1 mg/g, much higher than those for other adsorbents. Adsorption isotherms of AMX on ZnO@SiO2 were more in accordance with the Freundlich model than the Langmuir model. The electrostatic attraction between negative species of AMX and the positively charged ZnO@SiO2 surface induced adsorption, while the removal of E. coli was governed by both electrostatic and hydrophobic interactions. Our study demonstrates that ZnO@SiO2 based on rice husk is a useful core–shell nanomaterial for antibiotic and bacteria removal from water.