The sorption behavior of CHA-type zeolite for removing radioactive strontium from aqueous solutions

The highly efficient removal of radioactive metal ions (e.g. ¹³⁷Cs, ⁹⁰Sr) remains a challenge from the standpoint of environmental protection and public health. Although adsorption has been proven to be an effective and economical technology to eliminate the radioactive metal ions from aqueous solutions, few adsorption materials have been reported for the efficient removal of ⁹⁰Sr. In this work, an aluminosilicate with CHA-type zeolite framework was synthesized and investigated for the adsorption of Sr²⁺ ions. The CHA aluminosilicate zeolite was hydrothermally synthesized with a cost-effective method by employing N,N,N-dimethylethylcyclohexylamine hydroxide as the structure directing agent. Its structure was confirmed by powder X-ray diffraction and N₂ sorption experiments. Batch scale experiments suggested that the CHA-type zeolite could efficiently remove Sr²⁺ ions from aqueous solutions. The sorption process was kinetically fast with a maximum sorption attained within 60 min, and the high sorption capacity can be maintained at varied pH levels (3–11) and temperatures (298–328 K). Regeneration of the adsorbent showed that more than 96% of the initial capacity remains intact after five cycles. Additionally, the CHA zeolite packed in fixed-bed columns enables a continuous efficient removal of strontium for 60 min. Our results suggested that the CHA zeolite could potentially serve as chromatographic column materials for the removal of radioactive Sr²⁺, prefiguring their great promise for the application in nuclear waste management.