Cyanide Plating with Closed Loop Recovery

Cyanide plating can be an environmental and economically acceptable process through the use of high vacuum, low temperature evaporators employing counterflow rinse tanks with water/water heat pumps to achieve high energy efficiency. The paper presents the airline plating forum with detailed information on the process, particularly as applied to cold bath cadmium plating essential to airline maintenance. An auxiliary chiller provides a method of stabilizing carbonate build-up in closed loop cyanide recovery systems, and can employ the hot end of the heat pump to force bath evaporation or provide hot water for final rinsing. Heat pump evaporators employing auxiliary solar heat and waste heat are also described. These new energy effective systems provide the plating industry with a method of circumventing the escalating costs of hazardous sludge disposal. Recovery of over 99 percent of the plating bath dragout plus savings in destruct chemical costs provides the industry with economical answers to the hazardous waste disposal problem generated by destruct systems.