Constructing flower-like magnesium vanadate for pH-responsive and highly selective separation of Sr(II) and Cs(I) from nuclear wastewater with rapid minute-level rates

Abstract

The effective removal and recovery of 90Sr and 137Cs from nuclear wastewater are crucial for promoting the sustainable development of nuclear energy. However, the current layered materials employed for 90Sr and 137Cs removal exhibit limitations such as low adsorption rate, slight selectivity and prolonged separation time, which compromise their performance. In this study, a pH-responsive and dual-purpose adsorbent, Mg0.17V2O5·0.83H2O (MgVO), with a unique interlayer spacing of 13.6 Å, was developed. MgVO demonstrated highly efficient and selective separation of Sr2+ and Cs+ under acidic conditions. The maximum adsorption capacities of Sr2+ or Cs+ by MgVO were found to be 315.68 mg/g (at pH 2) and 216.45 mg/g (at pH 4), respectively. Meanwhile, MgVO achieved adsorption equilibrium within 120 min for Sr2+ and 2 min for Cs+. Notably, MgVO exhibited the ability to selectively enrich Sr2+ (133.99 mg/g, pH 2) or Cs+ (190.25 mg/g, pH 4) in coexisting systems (containing 300 mg/L Sr2+ and 300 mg/L Cs+), depending on the pH adjustment. The adsorption mechanism involved the replacement of interlayer Mg2+, leading to crystal contraction and distortion. This structural alteration effectively prevented the release of Sr2+ while allowing the reversible interaction of Cs+, resulting in irreversible and reversible interaction mechanisms, respectively. Overall, this work presents a novel strategy utilizing the pH-responsive MgVO adsorbent for rapid and simplified selective separation and enrichment of radionuclides.