Functionalized membranes for use in applications, such as electrodeionization, can be prepared simply and efficiently by associating a first element of a specific binding pair to a membrane surface and binding a second species comprising the second element of the specific binding pair and at least one functional group to form a complex on the membrane surface. Such membranes may be reversibly modified by disassociating the complex, thereby, providing a fresh surface which may be re-modified according to the preceding methods.