Synthesis and characterization of silica microsphere and their application in removal of uranium and thorium from water

Uranium (U) and thorium (Th) are known to cause acute toxicological effects in human, and their compounds are potential occupational carcinogens. During this work, silica microspheres were used to decontaminate the traces of U and Th in different water sources originated from groundwater and lake water. Ultra-filtration technique was used to isolate the microsphere from the water samples. Silica microspheres were synthesized based on a polyvinylpyrrolidone involved emulsion polymerization and subsequent sol–gel process. The microspheres were characterized for their size by using dynamic light scattering, and presence of silicate structure is verified by recording their attenuated total reflectance-Fourier transform infrared spectrum. The surface morphologies of the prepared silica microspheres were studied by using scanning electron microscope. Water samples collected from the groundwater and lake water were spiked with U and Th in the concentration range of 100–1,000 ng mL^-1. The results of batch sorption experiments suggest that silica microsphere is very effective at pH 3, and sorption is more than 99.9 %. Equilibrium sorption follows Langmuir isotherms and the maximum U, and Th uptake is 30 and 36 mg g^-1, respectively. Major physicochemical characteristics of the water were monitored before and after the decontamination process. Experimental results show no significant variations in any of the measured parameters.

Keywords
Silica microsphere; Groundwater; Lake water; Uranium; Thorium; Decontamination