One-pot synthesis of pyridine dicarboxamide derivative and its application for uranium separation from acidic medium

Abstract One-pot synthesis of N2,N2,N6,N6-tetrakis(2-ethylhexyl)pyridine-2,6-dicarboxamide (EHPyCA ligand) was done by condensation of pyridine-2,6-dicarboxylic acid and di-(2-ethyl-hexyl) amine using polyphosphoric acid (PPA) as catalyst. The EHPyCA ligand was impregnated on Amberlite XAD-7 to form a chelating EHPyCA-AXAD-7 resin that runs for U6+ ions sorption from G.Gattar leachate solution, North Eastern Desert, Egypt. Experimental measurement parameters were optimized by a batch technique such as contact time, initial U6+ ions concentration, EHPyCA-AXAD-7 dose, pH, interfering ions, and temperature. The maximum uptake of EHPyCA-AXAD-7 ligand was 76.92 mg·g−1 at pH 7. From the gained result, adsorption equilibrium followed well with the Langmuir isotherm model. The thermodynamic parameters (ΔS°, ΔH°, and ΔG°) were also assessed, and they elaborated that the adsorption process was endothermic and spontaneous in nature. The kinetic study clarified that the U6+ ions adsorption on EHPyCA-AXAD-7 obeyed the pseudo-first-order kinetic mechanism. U6+ ions were completely eluted from the loaded EHPyCA-AXAD-7 using 2 M H2SO4. Finally, the optimized parameters were applied for U6+ ions recovery from G.Gattar leachate to prepare sodium diuranate concentrate (Na2U2O7) with a uranium content of 69.88%.