- Naohito Kawasaki (Faculty of Pharmacy, Kindai University / Antiaging Center, Kindai University / firstname.lastname@example.org)
1) Faculty of Pharmacy, Kindai University , 2) Antiaging Center, Kindai University
We prepared virgin (Lig) and calcined lignin at 200–1000 °C (Lig200, Lig400, Lig600, Lig800, and Lig1000) and evaluated their adsorption capability for zinc ions from the water phase. The properties (morphology, specific surface area, pore volume, mean pore diameter, and functional groups) of adsorbents were characterized by scanning electron microscopy, specific surface area analysis, and FT-IR analysis. The specific surface area and pore volume of Lig800 was greater than those of the other adsorbents. In addition, -OH and -COOH groups were detected on Lig, Lig200, and Lig400, but those functional groups were not confirmed by calcination treatment over 600 °C. Amount of zinc ions adsorbed on Lig800 was greater than that on other adsorbents. We also evaluated the adsorption mechanism of zinc ions with adsorbents. The result showed that the amount of zinc ions adsorbed was related to ion-exchange with proton (correlation coefficient: 0.817) or physical property (mesopore volume; correlation coefficient: 0.867) for Lig, Lig200, and Lig400 or Lig600, Lig800, and Lig1000, respectively. These results indicate that the adsorption mechanism is changed with calcination treatment. Moreover, we elucidated the effect of temperature on the adsorption of zinc ions, and evaluated the adsorbent surface before and after zinc ion adsorption. We confirmed the zinc existed on the adsorbent surface after adsorption. Finally, as per the thermodynamic parameters, the negative value of ΔG indicates the spontaneous nature and feasibility of the zinc ion adsorption. These findings provide significant information that can be useful for removal of zinc ions from aqueous solution.