Study of Ni And Cd Bioleaching from Spent Ni-Cd Batteries

Abstract

In the present work the Ni and Cd extraction from the electrode material of spent Ni-Cd batteries by bioleaching using the bacteria Acidithiobacillus ferrooxidans was examined. The possibility of the use of the bacteria for both the Ni and Cd recovery was analyzed. The anode of Ni-Cd batteries contains Ni0, Ni(OH)2, Cd0 and Cd(OH)2. The cathode is covered by nickel hydroxides and nickel oxy-hydroxides. The pH values and content of Ni and Cd in the solution were monitored throughout the experiment (the initial pH was 1.5, the experiment took 28 days). The bioleaching efficiency of Ni and Cd from anode powder reached 5.5% and 98%, respectively. During the cathode powder bioleaching Ni and Cd efficiency reached 45% and 100%, respectively. Throughout the bioleaching process mainly the dissolution of hydroxides occurred meanwhile Ni0 leaching was not observed. The AAS analysis was used to analyze the amount of Ni and Cd in the solutions. The amount of Ni and Cd present in the solid samples before and after bioleaching was examined using X-ray analysis.