Magnetic zeolite for Cs $^+$ and Sr $^{2+}$ to clean up radioactively contaminated water from the Fukushima Daiichi Nuclear Power Plant

Ito, Azusa (2021). Magnetic zeolite for Cs $^+$ and Sr $^{2+}$ to clean up radioactively contaminated water from the Fukushima Daiichi Nuclear Power Plant. University of Birmingham. Ph.D.

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Abstract

Magnetic zeolite hybrid systems have been developed for decontaminating radioactive wastewater from the reactors at Fukushima Daiichi Nuclear Power Plant. Superparamagnetic Fe $_3$ O $_4$ and CoFe $_2$ O $_4$ (M $_x$ O $_y$ ) nanoparticles were used to make core-shell M $_x$ O $_y$ /SiO $_2$ /zeolite (MSZ) systems. The MSZ were synthesised by 3 steps; preparing M $_x$ O $_y$ particles by the solgel method firstly, the M $_x$ O $_y$ particles were coated by SiO $_2$ by the Stöber method, then the M $_x$ O $_y$ /SiO $_2$ particles were mixed with zeolite seeds of zeolite A, zeolite X or CHA-Na. In addition, M $_x$ O $_y$ /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 M $_x$ O $_y$ /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 M $_x$ O $_y$ 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 M $_x$ O $_y$ /CHA-Na and the MSZ were characterised by inductively coupled plasma mass spectrometry.