Influence Factors on Plutonium Sorption in the Soil from a Candidate VLLW Disposal Site

The sorption extent and influencing factors of plutonium (Pu) in the soil, from a candidate site for disposing very low level waste (VLLW) in southwestern China, were studied by batch-type experiments. The equilibrium time of Pu sorption firstly were determined, sample grain size, aqueous pH, and temperature were then studied as the factors to influence Pu sorption. The experimental variables included the following: grain sizes from 0.088 mm to 0.83 mm; pH (4.2, 4.8, 6.2, 7.3, 7.8, 8.5, 8.9 and 9.1); temperature (20degC, 30degC, 40degC, 50degC and 60degC). The results demonstrated that the equilibrium time of Pu sorption was 15 days. The extent of Pu sorption decreased with an increasing grain size that is related to the specific surface area and total pore volume. The results also demonstrated that the sorption of Pu was obviously enhanced within the increasing pH. Besides, the influence of various temperatures on Pu sorption was relatively not as important as the other factors, but it should not be ignored.