Effect of Humic Acid on Re(Ⅶ) Diffusion in GMZ Bentonite

Humic acid, a kind of organic matter, is ubiquitous in environment, which may affect the migration of radionuclides by complexation and redox reaction. The effect of humic acid on the diffusion of Re(Ⅶ) in GMZ bentonite was investigated at different bentonite dry densities and humic acid contact time through diffusion method. The effective diffusion coefficient D_e and capacity factor α were obtained. The D_e decreases from 1.8×10^-11 m²/s to 0.59×10^-11 m²/s with the dry density increasing from 1600 kg/m³ to 1 800 kg/m³. The D_e increases from 0.59×10^-11 m²/s to 0.83×10^-11 m²/s with the humic acid contact time increasing from 0 day to 60 days. All the α values are less than the total porosities, which implies that Re(Ⅶ) may be still the anion species in diffusion in compacted bentonite in presence of humic acid.