Sorption of Eu(III) at feldspar/water interface: effects of pH, organic matter, counter ions, and temperature

Abstract

Abstract The sorption of Eu(III) on potassium feldspar (K-feldspar) was studied under various physicochemical conditions such as pH, temperature, counter ions and organic matter. The results showed that the sorption of Eu(III) on K-feldspar significantly increased with the increase of pH, and high Eu(III) concentration can inhibit such immobility to some extent. The presence of humic acid (HA) can increase the sorption of Eu(III) on K-feldspar in low pH range; while inhibit to a large extent under alkaline conditions. It is very interesting that at pH ~6.5, high ionic strength can promote the sorption of Eu(III) on K-feldspar in the presence of HA. In contrast, Eu(III) sorption was restricted obviously by NaCl in the absence of HA. The sorption procedure was involved with ion exchange and/or outer-sphere complexation as well as inner-sphere complexation. The presence of F− and PO4 3− dramatically enhanced Eu(III) sorption on K-feldspar, whereas both SO4 2− and CO3 2− had negative effects on Eu(III) sorption. X-ray photoelectron spectroscopy analysis indicated that Eu(III) tended to form hydrolysates at high initial concentration (3×10−4 mol/L) and high temperature (338 K).