This report describes a process for separating and concentrating heavy metals from electroplating rinse waters. Metal ions can be 'chemically pumped' across a coupled transport membrane against large concentration gradients by allowing the counterflow of a coupled ion such as hydrogen ion. The process is carried out within a microporous membrane containing within its pores an organic, water immiscible complexing agent. The complexing agent acts as a shuttle, picking up metal ions on one side of the membrane, carrying them across the membrane as a complex, and preserving electrical neutrality by carrying hydrogen ions in the opposite direction. The importance of coupled transport is its high selectivity and flux. High selectivity derives from the rise of specific complexing agents. High flux is possible because these are actually liquid membranes with diffusivities many times greater than those in solid membranes.

Includes bibliographical references. Prepared by Bend Research, Inc., for U.S. Environmental Protection Agency, Office of Research and Development, Industrial Environmental Research Laboratory, under Grant no. Contract Number: R804682-01.