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DEMONSTRATION OF ZINC CYANIDE RECOVERY USING REVERSE OSMOSIS AND EVAPORATION
Citation:
McNulty, K. AND J. Kubarewicz. DEMONSTRATION OF ZINC CYANIDE RECOVERY USING REVERSE OSMOSIS AND EVAPORATION. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/2-81/132.
Description:
A field test was conducted to demonstrate closed-loop recovery of zinc cyanide at a job plating facility. Since the zinc cyanide bath operates at room temperature with very little evaporation from the bath, reverse osmosis (RO) treatment of the rinsewater must be supplemented by evaporation in order to achieve the volume reduction necessary for return of a concentrate to the plating bath. The permeate from the RO unit was recycled to the first rinse after plating while the distillate from the evaporator was recycled to the second rinse after plating. Continuous, unattended operation of this system was demonstrated with no adverse effects on plating quality. The economics of the combined RO evaporation system were assessed for a system designed to provide rinsing equivalent to the present two-stage counter-current rinse at the demonstration site. The analysis showed that the total operating cost (including amortization) was somewhat less for the combined RO evaporation system than the evaporation alone. The minimum cost occurred for 90% water recovery in the RO system. However, credits for rinsewater recovery were insufficient to completely off-set the total operating cost of the recovery system.