Preparation and structure analyses of Sn-bentonite for pertechnetate removal

Abstract

Tin (Sn) -bentonite was prepared by ion exchange method from Ca-bentonite. For the ion exchange process, tin-chloride (SnCl2) solution was prepared from metallic tin, and the tin concentration was determined by Microwave Plasma Atomic Emission Spectroscopy (MP-AES). Sn-bentonite was characterized by X-ray fluorescence spectrometry (XRF), X-ray powder diffraction (XRPD), X-ray photoelectron spectroscopy (XPS) and 119Sn as well as iron-57 (57Fe) Mössbauer spectroscopy. 119Sn Mössbauer spectroscopy and XPS undoubtedly revealed both Sn+2 and Sn+4 ions in Sn-bentonite. SnII was attributed to be incorporated into the interlayer space while SnIV located partly in the octahedral position and in the interlayer space of montmorillonite. The removal of radioactive pertechnetate anion (99mTcO4-) was studied on Sn-bentonite in aqueous and artificial urine media. Based on the measurement results, 99mTcO4- ion can be removed, in case of aqueous media, the equilibrium is reached after 5 mins (x = 99.9 ± 0.01%, k = 4.2 ± 0.83 1/min) (Buzetzky et al., 2019), while in the case of urine media the equilibrium is reached after 30 mins (x = 59.1% ± 2.7, k = 0.18 ± 0.05 1/min). Pertechnetate anoin sorption on tin-bentonite is a (Sn(II/IV)-TcO4-) redox reaction. Thus, Sn-bentonite can be a suitable sorbent for radioactive waste management.