Chemical and electrochemical recycling of the nickel, cobalt, zinc and manganese from the positives electrodes of spent Ni-MH batteries from mobile phones

摘要

Chemical and electrochemical recycling methods for the Ni, Co, Zn and Mn from the positives electrodes of spent Ni-MH batteries were developed. The materials recycled by chemical precipitation have the composition β-Ni(OH)_2, Co(OH)_2, Zn(OH)_2 and Mn_3O_4. The powder retains sulphate, nitrate and carbonate anions from the mother solution as well as adsorbed water. Studies using cyclic voltammetry show that the current density decreases for scan rates greater than 10 mV s~(-1) because of the formation of hydroxide films. The amounts of Ni~(2+), Co~(2+). Zn~(2+) and Mn~(2+) were obtained by analysis of the solution using the inductively coupled plasma with optical emission spectroscopy technique, which demonstrated that the electrodeposition method exhibits anomalous behaviour. The amount of deposited nickel ions is related to the composition of the sulfamate bath. The presence of manganese in the electrode-posits is due to the precipitation of Mn(0H)2. and Zn(OH)_4~(2-) does not undergo reduction in the investigated potential range. The electrodeposited material contains Ni, Co, CoO, Co(OH)_2. and Mn_3O_4. A charge efficiency of 83.7% was attained for the electrodeposits formed by the application of -1.1 V vs. Ag/ AgCl at a charge density of -90 C cm~(-2). The dissolution of the electrodeposits depends on the applied potential.