Sorption Behavior Of Iodine On The Beishan Granite And Beishan Soil

With the rapid development of nuclear energy,the problem of spent fuel post-processing is imminent.At present,the most effective way to deal with this problem is deep geological disposal.After well screened,Beishan area in Gansu is the candidate for disposal repository,Beishan granite has become the key candidate surrounding rock.Batch method was taken to study the sorption behavior of iodate(IO3-)and iodide(I-)onto Beishan granite and Beishan soil as a function of various parameters such as contact time,pH,solid-to-liquid ratio,initial concentration,grain size,ionic strength,humic acid and temperature under atmospheric conditions.The results indicated as follows:?Iodic species made a big difference on the sorption of iodide and iodate,on the one hand,the sorption ability of I' onto Beishan granite and soil were almost 0,on the other hand,the sorption of IO3-was relatively stronger(Kd?1mL/g for Beishan granite and Kd?1.5mL/g for Beishan soil),which indicates that the Beishan granite and Beishan soil are bad retardant for iodine migration.?The thermodynamic parameters calculated from the sorption isotherms indicated that the sorption process of was an exothermic and spontaneous process;their kinetic sorption can be fitted by the pseudo-second-order rate equation quite well(R2>0.99);the sorption can't be improved by increase solid-to-liquid ratio;the ionic strength almost has nothing to do with the sorption process indicating that the sorption mechanism is not ion exchange.?pH plays an important role in the sorption of iodate onto Beishan granite and Beishan soil,under acid condition,the distribution and electricity of the charge on the surface of Beishan granite and Beishan soil will change and the IO3-could partly converse to I-.Under alkaline and neutral conditions,the sorption of iodate on granite may depend on combination of iodate with Beishan granite's surface hydroxyl,while the sorption of iodate on soil is proposed to take place as specific bonding onto Al or Fe sesquioxides or non-crystalline silicates or surface hydroxyl.?PCR solid polymer carries a strong ability to sorb iodate,under alkaline and neutral conditions the Ka is about 14mL/g,so it can be a spare block material to join the Beishan granite fissures or the Beishan soil.The work can provide iodine migration data for the safety evaluation of the repository.