Applicability of Precipitation-Flotation Method for Differential Separation of Cadmium from Zinc in Synthesized Waste Cyanide Water

Abstract

The removal of heavy metal from synthesized waste cyanide water is achievable by a precipitation-flotation method. However, the differential separation of constituting metals by this method has been thought to be very difficult. The authors found that the addition of some decomposing reagents to the synthesized waste cyanide water of cadmium and zinc can improve the separation characteristics of these metals. The present study deals with the applicability of the precipitation-flotation method for the differential separation of cadmium from zinc in synthesized waste cyanide water. The proposed method was to use sodium sulphide as a decomposing reagent in the first stage of flotation and hydrogen peroxide in the second stage in order to decompose the Cd-CN and Zn-CN complexes, respectively. Furthermore, the use of such a cation flocculant as FC-80 was considerably effective for the removal of the Cd-CN complex. Based on a series of fundamental flotation tests, actual differential flotation tests were made. The separation of cadmium from zinc in synthesized waste cyanide water was found to be satisfactory. This method can be effective for the differential separation of difficult-to-sepa-rate colloidal precipitates from liquids by the sedimentation method.