Physico-chemical properties of sol-gel synthesized titanosilicates for the uptake of radionuclides from aqueous solutions

Abstract

Harnessing the power of nuclear reactions has brought huge benefits in terms of nuclear energy, medicine and defence as well as risks including the management of nuclear wastes. One of the main issues for radioactive waste management is liquid radioactive waste (LRW). Different methods have been applied to remediate LRW, thereunder ion exchange and adsorption. Comparative studies have demonstrated that Na2Ti2O3SiO4·2H2O titanosilicate sorption materials are the most promising in terms of Cs+ and Sr2+ retention from LRW. Therefore these TiSi materials became the object of this study. The recently developed in Ukraine sol-gel method of synthesizing these materials was chosen among the other reported approaches since it allows obtaining the TiSi materials in the form of particles with size ≥ 4mm. utilizing inexpensive and bulk stable inorganic precursors and yielded the materials with desirable properties by alteration of the comparatively mild synthesis conditions. The main aim of this study was to investigate the physico-chemical properties of sol-gel synthesized titanosilicates for radionuclide uptake from aqueous solutions. The effect of synthesis conditions on the structural and sorption parameters of TiSi xerogels was planned to determine in order to obtain a highly efficient sorption material. The ability of the obtained TiSis to retain Cs+, Sr2+ and other potentially toxic metal cations from the synthetic and real aqueous solutions was intended to assess. To our expectations, abovementioned studies will illustrate the efficiency and profitability of the chosen synthesis approach, synthesis conditions and the obtained materials. X-ray diffraction, low temperature adsorption/desorption surface area analysis, X-ray photoelectron spectroscopy, infrared spectroscopy and scanning electron microscopy with energy dispersive X-ray spectroscopy was used for xerogels characterization. The sorption capability of the synthesized TiSi gels was studied as a function of pH, adsorbent mass, initial concentration of target ion, contact time, temperature, composition and concentration of the background solution. It was found that the applied sol-gel approach yielded materials with a poorly crystalline sodium titanosilicate structure under relatively mild synthesis conditions. The temperature of HTT has the strongest influence on the structure of the materials and consequently was concluded to be the control factor for the preparation of gels with the desired properties. The obtained materials proved to be effective and selective for both Sr2+ and Cs+ decontamination from synthetic and real aqueous solutions like drinking, ground, sea and mine waters, blood plasma and liquid radioactive wastes.