Selective separation of U(VI) from its solutions using amine modified silica gel produced from leached zircon

A solution of sodium silicate produced from the alkali fusion of Egyptian zircon mineral as a waste was used to prepare silica gel in the pH range 6–7. The surface of the obtained silica was functionalized with diethylenetriamine (DET) and tetraethylenepentamine (TEP) to give triamine modified silica (TAMS) and pentamine modified silica (PAMS), respectively. The success of functionalization process was confirmed by means of FT-IR, energy dispersive X-ray analysis (EDX) and elemental analysis. The surface properties of the modified silica obtained were also investigated. The uptake behavior of the modified silica towards U(VI) ions at different experimental conditions of pH, time, concentration and temperature was studied. The maximum uptake values at 25 °C were found to be 90.3 and 112 mg/g for TAMS and PAMS, respectively. Kinetics and thermodynamics studies showed an endothermic pseudo-second order adsorption process. Regeneration of the loaded silica was performed using 1 M HNO3. The investigated silicas have successfully been applied for extracting of U(VI) obtained from alkaline leaching of Egyptian monazite sand.

► Low-cost silica gel was obtained from silicate wastes of leached zircon.
► The surface of silica gel was modified with different amine chains.
► The modified silicas are effective for separation of U(VI) from thorium.
► Kinetics and thermodynamics showed an endothermic pseudo-second order processes.