Sorption of iodine neptunium, technetium, thorium and uranium on rocks and minerals

Sorption of Tc, I, Th, U and Np were studied using the radionuclides Tc-99, I-125, Th-234, U-233 and Np-237. Samples were selected to represent common rocks and minerals in Finnish bedrock. The determination of Ksub(a)-values for Th, U and Np in porphyric granite, granodiorite, tonalite, mica gneiss, biotite, quartz, hornblende, K-feldspar and plagioclase were performed by the autoradiographic method. To complete the earlier studies the Ksub(d)-values of Tc, I, Th, U and Np for crushed tonalite and mica gneiss samples were determined by the batch method. The order of sorption tendency was Ksub(a)(Np)<Ksub(a)(U)<<Ksub(a)(Th). The range at the Ksub(a)-values were from 0.9x10-4 to 4.9x10-4 m3/m2, 0.7x10-4 to 4.2x10-4 m3/m2, 650x10-4 to 1970x10-4 m3/m2 for Np, U and Th, respectively. For crushed samples the sorption tendency was Ksub(d)(Tc)<Ksub(d)(U)<Ksub(d)(Np)<<Ksub(d)(Th). The Ksub(d) values varied between 0.69-0.74 ml/g for Tc, 0.7-1.6 ml/g for I, 2.3-8.1 ml/g for U, and 8.5-9.2 ml/g for Np. All Ksub(d)-values of Th were greater than 103 ml/g being more than three orders of magnitude higher than those of other elements examined