Adsorption properties of ZrO2 hollow microboxes prepared using CaCO3 cubes as templates

Abstract

Zirconia hollow microboxes were prepared using calcium carbonate cubes as templates. The as-prepared products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen adsorption–desorption isotherms. Adsorption performance of the as-prepared products toward Congo red (CR) aqueous solutions was tested and discussed. Results show that ZrO₂ hollow microboxes copied the morphology of the CaCO₃ template very well with a diameter of ∼1.5 μm and a possible formation mechanism was proposed according to the observed results. The Langmuir surface area and BET specific surface area of ZrO₂ hollow microboxes before calcination are 301.65 m² g⁻¹, 247.88 m² g⁻¹, respectively and the maximum adsorbance was found to be 188.02 mg g⁻¹ which is much higher than that of ZrO₂ hollow microboxes after calcination (90.86 mg g⁻¹) and ZrO₂ nanoparticles (57.86 mg g⁻¹). The adsorption kinetics and isotherms can be well described by the pseudo-second order rate model and Langmuir equation, respectively. These results indicate that ZrO₂ hollow microboxes before calcination have great potential in removing dyes from a water environment.