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

Abstract

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.