Hybrid membranes are prepared from quaternized poly(2,6-dimethyl-1,4-phenylene oxide) (QPPO), polyvinyl alcohol (PVA), monophenyl triethoxysilane, and tetraethoxysilane through sol–gel process. QPPO contains the anion-exchange groups which can be in the form of –N+(CH3)3OH−, –N+(CH3)3Cl−, or –N+(CH3)3Br−. The OH− ions can combine with PVA–OH groups to form weak interactions such as hydrogen bonds, and thus enhance the compatibility between QPPO and PVA phases and membrane stability. Hybrid membranes with the combination of OH−/−OH are generally homogenous and compact, with the lower water uptake of 57.6–67.4%, methanol content of 38.3–40.2%, and swelling degrees of 223–500% in 65°C water. The ion-exchange capacities are similar in the range of 1.04–1.08 mmol/g. Diffusion dialysis (DD) of HCl/FeCl2 solution shows that as the temperature increases from 15 to 55°C, the dialysis coefficients of HCl (UH) increase from 0.008 m/h to 0.014–0.018 m/h, while the separation factors decrease from 61–67 to 41–50. The UH values are similar to that of commercial membrane DF-120 (0.009 m/h at 25°C), and the separation factors are higher than those of reported membranes (lower than 48). The UH values can remain 87–95% after the erosion of HCl/FeCl2 system, with no significant reduction of selectivity. Hence, the combination of OH− ions and PVA–OH groups is effective to elevate membrane stability and selectivity, and the QPPO/PVA hybrid membranes can be potentially applied in DD process for acid recovery.