Selective transmembrane transport of iodide based on electrochemically induced iodide-trap BiOI/MWCNTs/PVA composite membrane

An electrochemically induced bismuth iodine oxide/multiwalled carbon nanotubes/polyvinyl alcohol (BiOI/MWCNTs/PVA) composite membrane electrode with iodide ion trap (I − -trap) was fabricated by prerelease of I − under reduction potential. The I − -trap BiOI/MWCNTs/PVA composite membrane with unique lattice confinement structures was used for the selective extraction of I − in an electrochemically switched ion permselective (ESIP) process. In the ESIP system, the direct uptake and release of I − were realized by applying a cell voltage-pulse potential (CV-PP) coupling circuit on the membranes to switch the oxidation/reduction state. The I − -trap BiOI/MWCNTs/PVA composite membrane exhibited a maximum flux of 8.32 mg·m −2 ·min −1 and superior electrochemical stability. The separation factors of I − /Br − , I − /Cl − , I − /NO 3 − , and I − /SO 4 2− in the mixed solutions were 2.67, 3.71, 3.82, and 6.70 respectively. Therefore, such a novel I − -trap BiOI/MWCNTs/PVA composite membrane could be used in the ESIP system for the selective extraction of I − ions from low concentration solutions.