Sorption/desorption of radiozinc on the surface sediments

The comprehension of the behavior of radioactive nuclides in aquifer requires the study of the sorption processes of nuclides in various geochemical conditions. The sorption/desorption of ⁶⁵Zn(II) on surface sediments (0-2 cm) was investigated by batch method in sea water (pH 8.20, 35‰ salinity, filtered by 0.45 μm) at ambient temperature. The surface sediments were obtained from four stations around the Daya Bay of Guangdong Province (China), where the first nuclear power station of China has been running from 1994. The sorption process is fast initially and around 39% average of sorption percentage (SP%) can be quickly obtained in 15 minutes for all the surface sediments. Then, the sorption percentage becomes constant. In 30 days of contact time 79.6% sorption percentage and K_d = 3.9·10³ ml/g distribution coefficient was obtained. The value of K_d became constant, 4.0·10³ ml/g, in contact time more than 120 hours. The distribution coefficient K_d decreases with increasing sediment concentration from 4.0 to 250 mg/l from 1.31·10⁴ to 1.68·10³ ml/g, respectively. Then the value of K_d goes up to 5.38·10³ ml/g with sediment concentration of 3000 mg/l. The desorption experiments suggest that the sorption of Zn(II) is irreversible with a hyteresis coefficient of 66%.