Cation exchange hybrid membranes from SPPO and multi-alkoxy silicon copolymer: Preparation, properties and diffusion dialysis performances for sodium hydroxide recovery

Cation exchange hybrid membranes for diffusion dialysis (DD) purpose have been prepared from sol–gel process of multi-alkoxy silicon copolymer (poly(vinyl benzyl chloride-γ-methacryloxypropyl trimethoxy silane)—poly(VBC-co-γ-MPS)) in presence of sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO). The hybrid membranes possess high thermal stability, mechanical strength, strong alkali and swelling resistance. Thermal initial decomposition temperatures are in the range of 233–245 °C. Tensile strength (TS) ranges from 23 MPa to 41 MPa and elongation at break (Eb) is in the range of 11–50%. The swelling behavior of the membranes is better suppressed as poly(VBC-co-γ-MPS) content increases. The hybrid membranes have been successfully applied for DD recovery of sodium hydroxide (NaOH) from the mixture of NaOH and sodium tungstate (Na2WO4). The separation factor (S) of hybrid membranes can reach as high as 301.5 at 25 °C. The pure SPPO membrane, as a comparison membrane, exhibits much lower S value of 36.2.

► Organic–inorganic hybrid membranes are tried for the first time for DD process of base recovery. ► The membranes have high thermal stability and mechanical strength, strong alkali and swelling resistance. ► The diffusivity of the membranes to OH− ions is significantly higher than SPPO base membrane. ► The selectivity to OH− can also reach higher value, especially at lower temperature. ► The separation factor (S) values of hybrid membranes C and D at 25–35 °C are in the range of 54–301.