Electrolytic Recovery of Cadmium from Cyanide-ion-containing Rinse Water in Automatic Plating Lines Using Filtering Carbon - based Electrodes

摘要

Effect of dilution of a cyanide cadmium plating solution on pH, conductivity and cathode polarization was studied (Fig.1,2). A conclusion was done on the basis of data obtained that carbon filtering cathodes can be used for the recovery of cadmium from rinse water. The effects of the type of carbon cathodes and conditions of rinsing and electrolysis on the efficiency of the recovery was studied for a number of solutions simulating cadmium-containing rinse water. Concentration of cadmium in the rinse water is maintained constant in the course of electrolysis (Fig.3) and it depends as well as current efficiency on current density (Fig.4), solution circulation rate (Fig.5), type carbon material (Table 1) and on the increasing cadmium concentration in the solution (Fig.6). The latter effect simulates the effect of additional input of cadmium with plated parts transferred from the plating tank Cadmium metal deposited on carbon cathode can be returned into the plating tank by anodic dissolution or even without imposing current due to the operation of a short-circuited cell formed by cadmium anode and carbon cathode. The used of dialysis chambers in the recovery process allows to recycle and return into the plating process also some part of plating solution (Table 2). Simulation of the operation of reclaim tanks with the recovery of cadmium from them for an automatic cadmium plating line demonstrated a possibility to maintain cadmium concentration at a constant level and practically complete recovery of cadmium even in a single-step rinsing (Fig.7). Developed method is recommended for the implementation in industry.