Fabrication of hierarchically porous CHA-type zeolite composites derived from industrial solid waste for cesium removal

Hierarchically structured CHA-type zeolite composite was fabricated from industrial wastes red mud and coal fly ash via a facile two-step method without the addition of templates. A macro-porous ceramic support was first sintered, then zeolite/ceramic composite was formed through alkaline hydrothermal reaction. The physico-chemical properties of the samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and surface area analyzer (BET). It was found that the as-prepared zeolite/ceramic composite featured micron sized CHA-type zeolite particles (14.1 wt%) on the macro holes and channels of its ceramic support, which developed a hierarchical structure. Compared to the ceramic support, its specific surface area was increased by 2400%. The successfully made zeolite/ceramic composite was tested as an adsorbent for Cs(I) adsorption in batch mode. The results showed that the adsorption of Cs(I) on ZCC can be well described by the pseudo-first-order model and Langmuir model with the maximum adsorption capacity of 34.5 mg/g (25 °C), which is nearly 8 times that of ceramic support. The thermodynamic studies revealed an endothermic and spontaneous process. TCLP results showed that all targeted toxic metals met the regulatory standard. Thus, the reported hierarchically structured zeolite synthesized from industrial solid wastes, exhibiting high adsorption capacity of Cs(I) ions and good environmental compatibility, has the potential to be applied in wastewater treatment. Graphical Abstract Preparation of Ceramic support using fly ash and red mud, then hydrothermal reaction to obtain Zeolite/ceramic composite, followed by cesium ion adsorption experiments to obtain the conclusion that the adsorption performance of zeolite/ceramic composite is much better than that of the Ceramic support.