Abstract: Provided is a membrane separation method for separating a first component (106) from a second component (108) in a fluid mixture (102). The method is particularly useful for separating a more highly unsaturated organic compound from a less highly unsaturated organic compound of a saturated organic compound, as well as making other separations. A membrane is used that includes first chemical groups, that are ionic and associated with ion exchange sites in the membrane, a second chemical group that modify the electronic environment of the ion exchange sites to enhance facilitated transport through the membrane. An example membrane is a silver (I)-form Nafion™-poly(pyrrole) composite membrane. Also provided are a membrane (112), and apparatus (110) for use with the method.