In nuclear industry, liquid radioactive waste coming from reprocessing plant or Fukushima disaster, has to be treated in order to decontaminate these effluents. One way to decontaminate this waste is to synthesize inorganic monolithic sorbent that are less sensitive to radiolysis phenomena than organic ones. Geopolymer cements are good candidates to fulfill these specifications since intrinsically they are mesoporous with high specific surface area and compatible with specific grafting agents which allow to trap selectively radionucleides of interest (especially the cesium). This work aims to synthesize monolithic geopolymer foams (aluminosilicates binders) with high mechanical resistance which can act both as sorbent for decontamination of liquid radioactive waste and containment matrix. The macroporosity has to be connected in order to facilitate the transport of contaminated fluid without drop pressure, and the control of the chemical parameters of the geopolymers allows to tailor the mesoporous network.
In the present study, a sodium geopolymer is studied and hydrogen peroxide is used as blowing agent. The results show that monolithic materials are obtained with a bubble size distribution controlled according to the nature of surfactants, the concentration of H2O2 and chemical composition of the geopolymer. Some X-ray tomography experiments show that the connectivity of the macroporosity (which facilitate the transport of fluid) may be tuned according to the nature of surfactants. In a second part of this work, the precipitation of copper hexacyanoferrate into the porous network has been perform in order to trap selectively the cesium. The results show that monolithic geopolymer is a very good candidate to decontaminate cesium effluent.