The Study On The Sorption Behavior Of Americium On Granite

In this paper, the sorption behavior of Am on granite and its rock-forming minerals inBeiShan groundwater under the aerobic and anoxic conditions was studied by batchexperiment. The equilibrium time was determined firstly and effects of some factors suchas ratio between aqueous phase and solid phase, concentration of the Am, pH value ofaqueous and the presence of humic acid, SO₄^2- etc. were investigated, and the K_d valueswere gotten under various conditions mentioned above. Desorption experiment of somesamples in the sorption test was carried out for further understanding of the adsorptionmechanism of Am on granite. Sorption experiment in the distilled water was done also forsample system of sorption. The different species of Am in the sorption system undervarious experimental conditions were simulated by EQ3/6 software.The results of the experiment show that granite has great adsorptive capacity of Am,and the K_d values are 2.4×10⁴mL/g under aerobic condition and 1.4×10⁵ mL/g underanoxic condition. K_d values of feldspar+ quartz, mica, hornblende, clay minerals and pyrite,the rock-forming minerals of granite, are 6.0×10²,2.5×10³,1.8×10³,1.1×l0⁴ and 2.6×10⁴mL/g under aerobic condition. Their desorption ratio are 70.0%,84.7%,74.9%,91.2%and 76.8 %. Pyrite plays an important part in the sorption of Am on granite, which adsorbsAm well and has lower desorption ratio than other rock-forming minerals of granite. Effectof granite granularity on the adsorption behavior is not obvious and K_d value increasedwith the increasing of granularity slightly. Effect of pH on adsorption is obvious in 3-8, andK_d value increases suddenly with the increasing of pH. The presence of humic acid, SO₄^2-and CO₃^2- in the distilled water system could weaken the adsorption of Am on the granite,and along with the increasing of their concentration, the K_d value reduced gradually in testscope. The simulated results of EQ3/6 as follows: the main species of Am were AmCO₃⁺,AmSO₄⁺,Am³⁺,Am(CO₃)₂^-,AmOH²⁺,AmF²⁺ and Am(SO₄)₂^- etc. in BeiShan groundwatersystem under experimental condition. With the increasing of pH value or the concentrationof CO₃^2-, the proportion of the complexation species of Am and CO₃^2- will be increased.When the pH value increased further, Am(OH)₃ would appear and the proportion ofcomplexation species of Am and CO₃^2- will be reduced. The proportion of complexationspecies of Am and SO₄^2- would be increased with the increase of the concentration of SO₄^2-.The simulated results are coincident with the results of the experiment well.