Influence of the colloid type on the transfer of 60Co and 85Sr in silica sand column under varying physicochemical conditions

The influence of two types of colloids (natural organic matter, NOM), a colloid with high affinity for radionuclides (RN(s)), and hydrophilic synthetic latex (SHL), a colloid with low affinity for RN(s) on the transfer of 60Co and 85Sr in a silica sand column was studied under different physicochemical conditions : pH (4.9), ionic strength (10−3 M and 10−2 M), concentration of colloids (100 mg l−1, 10 mg l−1), flow velocity (12.4 cm h−1 and 3.7 cm h−1), water saturation of the column (100% and 70%). In the absence of colloids, the transfer of 60Co and 85Sr was retarded compared to the transfer of the conservative tracer. In the presence of colloids and according to the specific physicochemical conditions, an acceleration or retardation of 60Co and 85Sr transfer was observed compared to their transfer in the absence of colloids. Our results evidenced that any colloids even with low reactivity could significantly modify the RN transfer. However, the extent to which the transfer was influenced differs according to the colloid type; the NOM exhibiting higher impact than SHL. Batch experiments helped in interpreting of the interactions between the colloids, RN(s) and solid phase observed in column.