A treated permeable inorganic membrane is disclosed comprising a metal oxide/hydroxide capable of reacting with a phosphoric acid ester. The treated membrane has good chemical stability over a pH range of from 2 to 12. Chemically bonded to the metal oxide/hydroxide surface of the membrane is a monomolecular layer of one or more phosphoric acid esters selected from the class consisting of one or more phosphoric acid monoesters having the formula (RO)PO(OH).sub.2, one or more phosphoric acid diesters having the formula (RO)(R'O)PO(OH), and mixtures of same where R comprises a 1-30 carbon-containing group and R'comprises hydrogen or a 1-30 carbon-containing group. Excess phosphoric acid esters not bonded to the underlying membrane surface is removed to ensure formation of the monomolecular layer of the phosphoric acid esters on the surfaces of the membrane.