Hydrothermal Synthesis of Potassium Niobate Powders in Sub/Supercritical Water and Its Cobalt Ion Sorption Properties

摘要

Hydrothermal synthesis of potassium niobate powders was carried out under various subcritical and supercritical water conditions using crystalline Nb{sub}2O{sub}5 powder and aqueous KOH solutions as starting materials. A single phase of K{sub}4Nb{sub}6O{sub}17 was formed under subcritical water conditions, while mixed phases of K{sub}4Nb{sub}6O{sub}17 and KNbO{sub}3 were obtained under supercritical water conditions where KNbO{sub}3 was predominant over K{sub}4Nb{sub}6O{sub}17 as the heating time was increased. The hydrothermally synthesized potassium hexaniobates powders were used for cobalt ion adsorbent under hydrothermal conditions. Co uptake on the hydrothermally synthesized K{sub}4Nb{sub}6O{sub}17 was higher in comparison with the solid state synthesized K{sub}4Nb{sub}6O{sub}17. In addition, Co can be fixed in the niobate matrix under hydrothermal conditions.