Zwitterionic-surfactant modified Laponites® for removal of ions (Cs+; Sr2+ and Co2+) from aqueous solution as a sustainable recovery of radionuclides from aqueous wastes

International audience; The synthesis of zwitterionic-surfactant modified Laponites® (LAP-CBs) was investigated as a function of the surfactant loading in order to obtain suitable adsorbent for the removal of Co2+, Sr2+ and Cs+ ions from aqueous solutions. The proper adsorption of surfactant was characterized by several techniques allowing to emphasize the modification of the surfactant distribution between the interlayer space and the surface of Laponite® (LAP), with increasing the load of surfactant. The organophilic character of the obtained LAP-CBs strongly affected its affinity with the targeted contaminants. The adsorption of Sr2+ was lowered onto LAP-CBs in comparison to LAP, while the adsorption of Co2+ and Cs+ were strongly improved. The competition between Sr2+ and Cs+ was important onto LAP-CBs, whereas no competition was found when using LAP, indicating different adsorption mechanisms depending on the adsorbent. The desorption of contaminants was performed in various solutions and confirmed these mechanisms. Whereas Cs+ and Sr2+ were adsorbed through cation exchange onto LAP-CBs, as highlighted by a significant desorption in saline solution, the desorption of Co2+ from LAP-CBs was very poor whatever the composition of the solution indicating rather a complexation. Finally, the increase of the load of surfactant decreased the adsorption capacity of all the investigated contaminants. The arrangement of the surfactant, within the interlayer space or on the surface of LAP, was therefore of high concern when considering the potential of this material to durably remove radionuclides from low-level radioactive wastewaters.