Magnetic zeolite hybrid systems have been developed for decontaminating radioactive wastewater from the reactors at Fukushima Daiichi Nuclear Power Plant. Superparamagnetic Fe3O4 and CoFe2O4 (MxOy) nanoparticles were used to make core-shell MxOy/SiO2/zeolite (MSZ) systems. The MSZ were synthesised by 3 steps; preparing MxOy particles by the solgel method firstly, the MxOy particles were coated by SiO2 by the Stöber method, then the MxOy/SiO2 particles were mixed with zeolite seeds of zeolite A, zeolite X or CHA-Na. In addition, MxOy/Chabazite-Na (CHA-Na) was synthesised by a one-pot synthesis using an autoclave by crystallising the nanoparticles on preformed zeolite particles.
The products were characterised by X-ray diffraction, Raman spectroscopy, transmission electron microscopy (TEM) and scanning electron microscopy. The elemental compositions of the cobalt ferrite, the MxOy/CHA-Na and the MSZ were characterised by X-ray fluorescence. The magnetic properties of all products were measured by a magnetic property measurement system or vibrating sample magnetometer. The MxOy particle diameters were calculated from the full width at half maximum of the X-ray peaks, observing by the TEM images, or measured by dynamic light scattering. The Cs or Sr adsorption capacities of the MxOy/CHA-Na and the MSZ were characterised by inductively coupled plasma mass spectrometry