Sorption behavior of europium during alteration of albite

Changes in the sorption characteristics of europium, an analog of trivalent transuranium (TRU) elements, during alteration of albite (NaAlSi3O8) has b een studied. After sliced specimens of albite were contacted with 10 mL of 0.1 mM Eu solutions for 3 to 90 days at 20 to 210 degrees C, depth profiles of Eu, Si, Al and Na were obtained from the specimens by 2.4-MeV He-4 Ruth erford backscattering spectroscopy (RBS). The concentrations of Eu and SiO2 (aq) in the solutions were measured by inductively coupled plasma atomic em ission spectroscopy. A positive peak for Eu was observed in an RES spectrum obtained by subtract ing the spectrum of fresh albite from Eu-doped albite produced at temperatu res above 150 degrees C, but no peak for Eu was obtained with doping at 20 degrees C. The peak height for Eu in the RES spectra of albite and the dept h of Eu penetration into the albite increased with temperature. SEM-EDX ana lysis showed that secondary minerals were present at the surface of albite, corresponding to an Al level comparable to fresh albite, lower levels of S i and Na, and a higher level of Eu. The Eu concentrations in the solutions decreased with increasing SiO2(aq) concentration in the solution. The resul ts indicate that little Eu is sorbed on fresh albite. Rather, most of the s olved Eu is associated with Al oxyhydroxides, such as boehmite or gamma-AlO OH, formed during alteration of the albite. Namely, some of the Eu in solut ion is incorporated with the secondary minerals of the albite.