| The need to control environmental pollution and conserve important metal resources calls for cost-effective processes to treat streams dilute in metals. The typical metal copper is found in plating rinse waters and in depleted ore tailings from dump leaching. For this study, the available membrane technologies are brought to bear on the copper recovery problem; these include microfiltration, ultrafiltration, reverseosmosis, electrodialysis and water-splitting. Preliminary studies and computations were made. In certain cases the applicability of a given process could be rejected because of the known limitations upon the process, such as the inability of known reverse osmosis membranes to handle acid feed streams. In other cases it was necessary to carry out laboratory feasibility experiments to ascertain whether or not a given process was operable. On these bases it was decided that by a combination of membrane processes employing special ultrafiltration modules for pretreatment, reverse osmosis for concentration and electrodialytic water-splitting to produce a base for neutralization and acid for return to the process, one could effect a closed-loop operation which appears to be feasible for the treatment of many rinse streams, and which can be feasible for dump leaching operations in water-poor regions. On the basis of laboratory studies certain options were either rejected or adopted. A process was designed with a flow diagram for closed-loop process employing a combination of membrane systems. |
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