Effects of groundwater humic substances on sorption of Np(V) on sandy materials

Nagao, Seiya*; Sakamoto, Yoshiaki ; Rao, R. R.*; Fujitake, Nobuhide*

Sorption behavior of Np(V) onto sandy materials (sand, tuffaceous sand and sandy rock) was studied in the absence and presence of humic substances (HS) using a batch method at pH 5-6 and ionic strength of 0.01M. The effects of shallow land groundwater HS on the Np(V) sorption depend on the mineralogical components of sandy materials. The distribution coefficient (Kd) of Np(V) increased in the presence of HS. The Kd values were in the order of sandtuffaceous sandsandy rock samples. The Np(V) sorption in the presence of HS with different origin for the sandy rock sample was divided into two groups. The Kd values were positively correlated with aliphatic carbon contents of the lake and the shallow groundwater HS, except for the deep saline groundwater HS. These results indicates that the characteristics of the sandy materials and groundwater HS are important factors determining the Np(V) sorption because of the presence of Np(V)-bound HS.