Removal of uranium from aqueous solution using montmorillonite-supported nanoscale zero-valent iron

Montmorillonite-supported nanoscale zero-valent iron (M-nZVI) was synthesized by sodium borohydride reduction and characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and field emission scanning electron microscopy (FE-SEM). The interaction of uranium with M-nZVI was studied using batch technique under different experimental conditions such as pH, ionic strength, initial U(VI) concentration, solid-to-liquid ration (m/V), and temperature. The presence of montmorillonite decreased the aggregation while increased the specific surface area (SSA) of the iron nanoparticles. The SSA for as-synthesized M-nZVI was 91.42 m2/g, higher than 26.60 and 10.23 m2/g for nZVI and montmorillonite, respectively. The removal efficiency of U(VI) using M-nZVI was significantly affected by the pH of the aqueous solution, whereas it was slightly affected by ionic strength and temperature. The isoelectric point of M-nZVI was at pH 5.6; however the results indicated that the optimum removal efficiency of U(VI) using M-nZVI was achieved at a pH range 3.0–5.0. The experiments with aqueous solution containing 100 μg/L of U(VI) showed that the removal efficiency of the as-synthesized M-nZVI was about 978 μg/g at pH 3.0. These results show that M-nZVI has a potential as a novel material for removing U(VI) from aqueous solution.