Radionuclide sorption to rocks and minerals: Effects of pH and inorganic anions .1. Sorption of cesium, cobalt, strontium and manganese

Sorption of Cs-137, Sr-85, Mn-54 and Co-60 to rocks (metamorphosed chert and shale, and granodiorite) and minerals (hematite, magnetite and calcite) was investigated in 0.001 N, 0.01 N and 0.1 N solutions of Na2SO4, NaCl, Na2CO3 and NaHCO3. The effects of pH and co-existing anions on the sorption of these radionuclides are discussed in terms of surface complex formation. Increase in the sorption of Cs in the presence of SO42- ions is explained by preferential formation of a ternary complex, such as =M-SO4-Cs. Sorption of Sr increases as the pH increases irrespective of background-anion type at the same electrolyte normality. On the whole, the sorptions of both Co and Mn increase as the pH increases, but sorption in a highly basic Na2CO3 solution sometimes is less than that in a solution of lower pH. Hydrolysis is considered to have occurred in the Na2CO3 solution, thereby generating weakly sorbed species of Mn and Co.