The diffusion of 75Se(IV) in Beishan granite – temperature, oxygen condition and ionic strength effects

Abstract To explore the diffusion behavior of 75 Se(IV) in Beishan granite (BsG), the influences of temperature, oxygen condition and ionic strength were investigated using the through-diffusion experimental method. The effective diffusion coefficient D e of 75 Se(IV) in BsG varied from 4.21×10 −14 m 2 /s to 3.19×10 −13 m 2 /s in our experimental conditions, increased with increasing temperature. The formation factor F f of BsG was calculated to be nearly constant in the range of temperatures investigated, suggesting that the inner structure of BsG had no significant change in the temperature range of 20–55°C. Meanwhile, the D e values of 75 Se(IV) in BsG under anaerobic condition was significantly larger than that under aerobic condition, which may be attributed to the difference in the sorption characteristics and species distribution of Se and pH values. Moreover, the diffusion of 75 Se(IV) was promoted with ionic strength increased from 0.01 M to 0.1 M, and then decreased at 0.5 M, mainly due to the combined effects of reduced double layers with increased ionic strength and increase of the solution viscosity at higher ionic strength.