Efficient extraction of uranium from environmental samples using phosphoramide functionalized magnetic nanoparticles: Understanding adsorption and binding mechanisms

Phosphoramide functionalized Fe3O4 nanoparticles (NPs) were synthesized by a three step procedure and its application for uranium extraction from different enviornmental matrices has been demonstrated. A maximum adsorption capacity of 95.2 mg of U/g of the sorbent has been achieved which is higher as compared to many reported magnetic NPs. pH dependent adsorption studies were performed at 1 ppm uranium concentrations which suggests more than 80% adsorption in pH range of 4-8 with maximum adsorption at pH 6. Interestingly this is the pH range of most naturally occurring water bodies suggesting the potential of this material to extract uranium from real environmental samples. Adsorption studies were carried out with tap water, drinking water and sea water and more than 90% uranium extraction was observed. Desorption studies were performed with different reagents suggesting that the material can be reused again. EXAFS studies have been carried out which suggests that the uranium binds with oxygens of three P=O group at the surface of phosphoramide functionalized NPs and based on this, binding mode of uranium with the synthesized sorbent is proposed.