| Summary: | Zirconium oxide nanoparticles (ZrO<sub>2</sub>NPs) were green synthesized for the first time using an aqueous peppermint extract as a precipitating and capping agent. Addition of the extract to Zr<sup>4+</sup> solution was followed by calcination of the resulting precipitate at 570 and 700 °C to form ZrO<sub>2</sub>NPs570 and ZrO<sub>2</sub>NPs700, respectively. These oxides were characterized using X-ray diffraction, transmission electron microscopy, and BET surface area analysis, and used as adsorbents for cobalt ions (Co<sup>2+</sup>) in water. The effects of pH, initial Co<sup>2+</sup> concentration, ZrO<sub>2</sub>NPs mass, and contact time on adsorption efficiency were studied. Characterization results showed formation of cubic ZrO<sub>2</sub> with average crystallite sizes (XRD data) of 6.27 and 7.26 nm for ZrO<sub>2</sub>NPs570 and ZrO<sub>2</sub>NPs700, respectively. TEM images of the two oxides exhibited nearly spherical nanoparticles and BET surface area measurements indicated the formation of mesoporous oxides having surface areas of 94.8 and 62.4 m<sup>2</sup>/g, respectively. The results of the adsorption study confirmed that the synthesized ZrO<sub>2</sub>NPs can be efficiently used for the adsorption of Co<sup>2+</sup> from water. The uptake of Co<sup>2+</sup> from the treated solution is favored at pH values higher than its point of zero charge (6.0). In addition, the adsorption of Co<sup>2+</sup> by ZrO<sub>2</sub> follows a pseudo-second order kinetics (R<sup>2</sup> = 1.0) and can be explained by the Langmuir adsorption isotherm (R<sup>2</sup> = 0.973).
|
|---|
