Growth mechanism and uranium extraction from seawater and nuclear waste of densely packed single crystals almond Na2TiOSiO4 with controllable crystallization

Abstract

With the increasing demand for nuclear energy, uranium extraction from seawater and nuclear waste is becoming increasingly important due to the limitations of conventional uranium. Herein, sol-gel and hydrothermal methods prepared almond Na2TiOSiO4 with controllable crystallization. The growth mechanism was that almond Na2TiOSiO4 crystallizes along the {00 l} face parallel to the interlayer sodium ions plane and bottom surface of the TiO5 tetragonal pyramids, growing in all directions while stacking layer by layer, forming almond-shaped crystals composed of densely packed single crystals. Three different morphologic products (Almond, Almond-b, and Walnut) were obtained as uranium adsorbents by changing the acid-base ratio. Due to the higher specific surface area and surface potential, the adsorption capacity of Walnut was 2 times that of Almond, and the equilibrium time was half that of Almond-b. The adsorption mechanism of the adsorbent was proposed and confirmed. At low concentrations, electrostatic adsorption was dominant, and sodium ion exchange was present; at high concentrations, in addition to electrostatic adsorption and sodium ion exchange mechanisms, uranium crystallization was also observed. In addition, adsorbents have great promise for practical applications such as the recovery of uranium from seawater and nuclear wastewater, as well as recycling.