Removal of uranium(VI) from aqueous solutions by magnetic Mg–Al layered double hydroxide intercalated with citrate: Kinetic and thermodynamic investigation

Magnetic Mg–Al layered double hydroxide was modified with citrate acid using a ion-exchange technique. It showed higher adsorption capacity for the uranium(VI) ions compared with magnetic Mg–Al layered double hydroxide without intercalating with citrate. This increasing capacity was mainly attributable to the formation of the citrate–metal complexes in the interlayer of the magnetic citrate·Mg–Al layered double hydroxide. Batch experiments were conducted to study the effects of pH, adsorbent dose, shaking time, and temperature on uranium sorption efficiency. The results reveal that the maximum adsorption capacity is 180.00 mg g−1 when the initial uranium(VI) concentration is kept as 200 mg L−1 at 25 °C, displaying a high efficiency for the removal of uranium(VI) from aqueous solution. The sorption follows Freundlich model and pseudo-second-order kinetics. The thermodynamic parameters such as ΔH°, ΔS° and ΔG° show that the process is endothermic and spontaneous. In addition, the composite can be easily separated from the solution by a magnet after the adsorption process. This work provides an efficient, fast and convenient approach for the removal of uranium(VI) from aqueous solutions.