Test and Evaluation of a Pilot System for Ion Exchange Treatment of Cadmium

摘要

Developmental tests were conducted for an ion exchange process developed to treatrinsewaters generated from cadmium cyanide electroplating operations. Results of previous laboratory studies were used as the basis of design for the construction of a pilot-scale system that was installed at the North Island Naval Aviation Depot, San Diego, CA. In this process, a chelating cationic resin in the sodium form is used to remove Cd(+2) followed by a strong base anionic resin for removal of free cyanide. Tests were conducted using both simulated rinsewaters and actual wastewaters. The results showed that the removal of Cd(+2) was successful in all cases and the effluent concentration was below the Federal Pretreatment Standards in most cases. The success of the cation resin is due to its ability to break the metal cyanide complex and selectively remove Cd(+2) even in the presence of high concentrations of other cations. The removal of CN(-) was not as successful. Effluent concentrations were above Federal discharge standards. The cationic resin was regenerated with sulfuric acid, producing a concentrated solution of cadmium sulfate. Cadmium was recovered from the regenerant solution by electrowinning. The anionic resin was regenerated with sodium hydroxide, producing a concentrated sodium cyanide solution. Ion exchange, cadmium, cyanide, wastewater treatment, metal recovery.