Facile fabrication of metakaolin/slag-based zeolite microspheres (M/SZMs) geopolymer for the efficient remediation of Cs+ and Sr2+ from aqueous media.

Herein we report the fabrication of metakaolin/slag-based geopolymer microspheres by dispersion-suspension-solidification technology, and were then transformed into zeolite microspheres by in-situ thermal curing. The rheological properties and mechanical strength of metakaolin/slag-based zeolite microspheres (M/SZMs) were improved by adding slag. The zeolite microspheres were texturally and morphologically characterized by BET, SEM-EDX and XRD techniques. At 20% slag contents of the total mass of M/SZMs, the specific surface area was significantly increased without changing the structure of the zeolite. Rheological properties analysis of slurry revealed pseudoplastic fluid phase and fitted well to Herschel-Bulkley model. The adsorptive removal data of M/SZMs for Cs+ and Sr2+ from wastewater followed pseudo-second-order kinetics. The maximum adsorption capacity of M/SZMs for Cs+ and Sr2+ was 103.74 mg/g and 54.90 mg/g and were best explained by Freundlich and Langmuir isotherm models, respectively. M/SZMs exhibited excellent dynamic separation effect in column-based experimental set up. In addition, M/SZMs also realized outstanding adsorptive removal performance for Cs+ and Sr2+ from different real wastewater samples. Owing to the simplistic fabrication approach, low cost and highly efficacious nature, M/SZMs can be ranked as alternative candidates for the abatement of Cs+ and Sr2+ from wastewater.