Se(Ⅳ)在伊利石-蒙脱石混合物中的扩散行为

Se(Ⅳ)Diffusion Behavior in Illite-Montmorillonite Mixture

采用贯穿扩散法研究了Se(Ⅳ)(代替79Se(Ⅳ))在伊利石-蒙脱石混合物中的扩散行为。结果表明,蒙脱石的伊利石化对Se(Ⅳ)的迁移行为有明显影响,Se(Ⅳ)的有效扩散系数De从3.89×10-11 m2/s增加至18.1×10-11 m2/s。伊利石-蒙脱石混合物比例为1∶9~5∶5时,De的变化不明显,伊利石-蒙脱石混合物比例为6∶4时,De明显增大,表明矿物的优势组分对Se(Ⅳ)的扩散行为起主导作用。随着伊利石-蒙脱石混合物比例从1∶9增大至6∶4,Se(Ⅳ)的岩石容量因子由4.07降低至0.75,分配系数由22.7×10-4 m3/kg降低至1.95×10-4 m3/kg,它们均随伊利石含量的增加而降低,这表明由于伊利石对Se(Ⅳ)的吸附能力较蒙脱石弱,导致伊利石-蒙脱石混合物对Se(Ⅳ)的阻滞能力变弱,从而增大了Se(Ⅳ)的迁移能力。

The diffusion behavior of Se（Ⅳ）（surrogate to 79Se（Ⅳ））in illite-montmorillonite mixture was investigated by through-diffusion method.The results show that the migration of Se（Ⅳ）is altered significantly by the illitization of montmorillonite.The effective diffusion coefficient of Se（Ⅳ）increases from 3.89×10-11 m2/s to 18.1×10-11 m2/s.When the illite-montmorillonite ratio is in the range of 1∶9and 5∶5,De values have no obvious change. Whereas,Devalues increase significantly at illitemontmorillonite ratio of 6∶4,indicating that the predominant composition of the mineral clay plays a leading role in Se（Ⅳ）diffusion.When the illite-montmorillonite ratio increases from 1∶9to 6∶4,the rock capacity and distribution coefficient ofSe（Ⅳ）decrease from 4.07 to 0.75 and from 22.7×10-4 m3/kg to 1.95×10-4 m3/kg,respectively.Both of them decrease with the increase of illite content.It demonstrates that the hindrance of illite-montmorillonite mixture turns worse due to the weaker sorption of Se（Ⅳ）on illite,leading the increase of Se（Ⅳ）migration in illite-montmorillonite mixture.