Adsorption of U(VI) by boron nitride-supported iron phosphotungstate: an experimental and mechanism study

Ultra small (~2 nm) iron phosphotungstate (FePW) nanoparticles were incorporated with boron nitride (BN) to prepare the FePW-BN composites for efficient adsorption of U(VI). The FePW-BNs were characterized by techniques such as scanning electron microscope, transmittance electron microscope, X-ray photoelectron spectroscopy, X-ray diffraction and X-ray fluorescence spectroscopy. Impact of solution pH, adsorbent concentration, ionic strength and initial U(VI) concentration on the U(VI) adsorption by FePW-BN were investigated by static batch techniques. The results demonstrated the pH had great influence on the U(VI) adsorption by FePW-BN and the maximum adsorption was achieved at pH 6. Ionic strength can barely affect the U(VI) adsorption. The adsorption kinetics follow the pseudo-second-order kinetics model and the adsorption isotherms conformed to the Langmuir model. The maximum adsorption capacities of U(VI) adsorbed by pure BN and FePW-BN are 419.44 and 864.10 mg/g, respectively, demonstrating the dramatically enhanced adsorption capacities of the composite materials. The enhanced adsorption properties of the composites may arise from the change of surface potential after FePW incorporation as well as the synergistic adsorption effect between the FePW nanoparticles and BN. The results imply the FePW-BN composites have great application potential in the concentration and separation of U(VI).