The development of acid separation membranes is important. Silica-based reverse osmosis (RO) membranes for sulfuric acid (H2SO4) solution separation were developed by using a counter diffusion chemical vapor deposition (CVD) method. Diphenyldimethoxysilane (DPhDMOS) was used as a silica precursor. The deposited membrane showed the H2SO4 rejection of 81% with a total flux of 5.8 kg m−2 h−1 from the 10−3 mol L−1 of H2SO4. The γ-alumina substrate was damaged by the permeation of the H2SO4 solution. In order to improve acid stability, the silica substrates were developed. The acid stability was checked by the gas permeation tests after immersing in 1 mol L−1 of the H2SO4 solution for 24 h. The N2 permeance decreased by 11% with the acid treatment through the silica substrate, while the permeance decreased to 94% through the γ-alumina substrate. The flux and the rejection through the DPhDMOS-derived membrane on the silica substrate were stable in the 70 wt % H2SO4 solution.
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