Prototype membrane electrolysis using a MFI-zeolite-coated ceramic tubular membrane provides in-line generation of two active electron mediators by eliminating active species crossover

Abstract Active ion crossover is a major obstacle in membrane electrolysis, which reduces the efficiency of the active mediator and increases operational cost. Using a prototype tubular cell divided with a MFI-zeolite-coated (shell side) ceramic tubular membrane, two active mediators, Co 3+ (Co 2 (SO 4 ) 3 ) in 5 M H 2 SO 4 at the anodic half-cell and Ni 1+ ([Ni(CN) 4 ] 3- ) in 9 M KOH at the cathodic half-cell, were produced. The rate of Co 3+ production increased from 5.74 × 10 −3  M min −1 to 7.11 × 10 −3  M min −1 when the use of 9 M KOH at the cathodic half-cell instead of 5 M H 2 SO 4 at both half-cells and controlled migration due to the pH change. The absence of a UV–visible spectral peak for cobalt or nickel ions in the other side of the electrolyzed solution supports the lack of active metal ion crossover by the MFI-zeolite-coated ceramic membrane. In high acid and base electrolyte pH, the 5.6 fold higher resistance (5.13 Ω cm −2 ) than in high acid electrolytes in both half-cells (0.91 Ω cm −2 ) prevented proton and active mediator ion crossover. SEM-EDS and XRD data profiles found no cobalt or nickel ions on the membrane, which also supports the lack of migration, whereas the Al ion concentration decreased on the lumen side (9 M KOH containing the cathodic half-cell), demonstrating the dissolution of Al 2 O 3 in the KOH medium (uncoated MFI). The MFI-coated tubular membrane can be a good choice for the effective generation of two mediators by membrane electrolysis using high end pH electrolytes.