Emulsion synthetic route of hierarchically porous zeolite-geopolymer composites for Sr2+ decontamination in fixed bed process

The decontamination of wastewater is an important issue for the nuclear industry. The removal of Sr2+, one of the most problematic radioelements, requires hierarchical materials suitable for fixed-bed processes. This article describes a patented emulsion-templating route for the synthesis of Linde Type A (LTA) zeolite-geopolymer composites with a multiscale porosity. By dispersing zeolite particles in an emulsion oil-in-water containing precursors of geopolymer, LTA zeolite–geopolymer composites can be obtained after curing and eliminating the oil phase. The zeolite particles alter the macroporous structure of the materials (replicating the oil droplets) as well as the size of the mesopores of the geopolymer binder. Moreover, zeolite contents higher than 30 wt% induce a crumbling of the material structure. The presence of LTA zeolite particles increases the selectivity of the composites for Sr2+ in very saline media, while the porous network of the material ensures rapid adsorption. The optimal composite prepared here outperformed a commercial sorbent for the Sr2+ decontamination of a saline wastewater through a packed column.