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

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 {[Zn3(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 I3− 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.