A pillared double-wall metal-organic framework adsorption membrane for the efficient removal of iodine from solution

Abstract

• Lac-Zn membrane is prepared and featured with a novel pillared double-wall MOF. • The static adsorption capacity for iodine in cyclohexane is 755 mg·g −1 . • The dynamic adsorption capacity for iodine in aqueous solution is 124.9 μmol·g −1 . • Iodine is captured in lac-Zn membrane by nanochannels and charge-transfer interaction. Effective removal of the radioactive iodine from aqueous solution is imperative but still far from the desired level. Here, a pillared double-wall MOF adsorption membrane comprised of {[Zn 3 (DL-lac) 2 (pybz) 2 ]·2.5DMF} n abbreviated as lac-Zn was reported. The synthesis of the lac-Zn membrane is conducted on the polytetrafluoroethylene (PTFE) support via the seed secondary growth method. A smooth and uniform lac-Zn seed layer can be deposited onto the PTFE support with the combination of the vacuum filtration and spin-coating method, and a continuous and well-intergrown lac-Zn polycrystalline film is formed with a thickness of around 25 μm. Lac-Zn polycrystalline film shows good stabality in the irradiation evironment. The maximum static adsorption capacity of the lac-Zn membrane for iodine ions in cyclohexane solution is 755 mg·g −1 , and corresponding dynamic adsorption capacity in aqueous solution is 31.72 mg·g −1 . In the dynamic adsorption of iodine aqueous solution, the iodine removal efficiency decreases from the initial 92.89% to 78.21% at 216 minutes. The iodine ions were captured by the lac-Zn membrane through the formation of I 3 − anions from the solution. The high iodine capture performance of the lac-Zn membrane can be attributed to the confined nanochannels and considerable pore volume providing enough adsorption sites for iodine ions and the abundant π-electron walls in pybz strengthening the affinity towards iodine.