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-gamma-methacryloxypropyl trimethoxy silane)-poly(VBC-co-gamma-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 degrees C. Tensile strength (TS) ranges from 23 MPa to 41 MPa and elongation at break (E(b)) is in the range of 11-50%. The swelling behavior of the membranes is better suppressed as poly(VBC-co-gamma-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 (Na(2)WO(4)). The separation factor (S) of hybrid membranes can reach as high as 301.5 at 25 degrees C. The pure SPPO membrane, as a comparison membrane, exhibits much lower S value of 36.2. (C) 2011 Elsevier B.V. All rights reserved.