The U.S. Bureau of Mines investigated the use of unsupported liquid emulsion membranes (LEM＇s) for the extraction of copper from heap-leach and mine solutions with the specific objective of developing innovative water purification technology A mobile, continuous circuit used simple equipment designs for all units of the system. The formulation of the emulsion membrane was optimized so that the emulsion had good stability during extraction, but was broken with relatively mild conditions in an electrical coalescer. The recovered organic phase was recycled without apparent problems and the oxime extractant war; regenerated with a hydroxylamine salt solution. Copper was recovered from solution in an electrowinning cell using fairly standard parameters. A 9-day, around-the-clock test was completed at a copper mine in Arizona during which 5,600 gal of solution was processed. Three different solutions were used during the test. They were (1) normal plant pregnant leach liquor (PLS) containing 1.43 g/L Cu, (2) PLS diluted with mine wafer to 500 ppm Cu, and (3) PLS diluted with mine water to 320 ppm Cu. The latter two solutions simulated waste streams that were of interest to the mine operator All three solutions contained suspended solids that did not adversely affect the LEM system. Copper extractions averaged 98.0% for the first solution, 95.7% for the second solution, and 91.6% for the third solution. Membrane swelling averaged less than 8% and membrane leakage less than 0.1% for the test.