Rapid synthesis of phosphomolybdic acid encapsulated ZIF-8 for efficient uranium(<scp>vi</scp>) capture from alkaline solution

Phosphomolybdic acid hydrate (PMA) encapsulated within a ZIF-8 framework (PMA@ZIF-8) was synthesized and utilized for U(vi) adsorption from the alkaline leach liquor of dolostone material collected from SW Sinai. The prepared PMA@ZIF-8 composite was characterized by FT-IR, XRD, XPS, and SEM techniques to confirm its structural and morphological properties. To estimate the optimum conditions for the removal of U(vi), various parameters including pH, contact time, solid/liquid ratio, initial U(vi) concentration, and temperature were examined in a batch adsorption technique. The maximum adsorption capacity of the PMA@ZIF-8 composite toward U(vi) was achieved at pH 10.5 after 90 min at room temperature. The kinetic study demonstrated that the adsorption of U(vi) onto the PMA@ZIF-8 composite fitted well with the pseudo-second-order model, and adsorption isotherm results indicated that the U(vi) adsorption fitted the Langmuir model. Thermodynamic analysis suggested that the adsorption is an exothermic process. This study reveals the potential use of the PMA@ZIF-8 adsorbent for the removal of U(vi) from alkaline leach liquor solutions of dolostone ore.