Study On Recovery Process For Nickel And Cobalt From Spent Ni-MH Batteries

Since Ni-MH batteries comprise a variety of valuable mineral resources like nickel, cobalt and rare earths, etc, it is well worth to be recovered from the point of view of the economic incentive. However, contents of elements in electrodes have little difference and the electrodes contain many impurities, leading to the difficulty in separation and recovery, thus recover and reuse the metals from Ni-MH electrodes efficiently is one of the urgent problems needs to resolve.The purpose of this research was to develop an effective hydrometallurgical process for the separation and recovery of metals such as nickel, cobalt and rare earths from spent Ni-MH secondary batteries. The overall experimental approach used was to leach the internal components in sulfuric acid followed by metal recovery using different techniques including solvent extraction and precipitation.In the present work, we first studied the optimized process of acid leaching of anode materials. Based on this, we used P204 as extractant to extract and purify the leach liquor. The best operating conditions were as follows:at room temperature; the concentration of P204,30%; the saponification rate of P204,65%; the pH,3.5; extraction time,10 minute; the phase ratio,1:1; the extraction level,3. Under these conditions, the overall recovery of nickel and cobalt was more than 95%.In addition, we also investigated the optimal process of acid leaching of cathode materials. Conditions for removement of rare earth, iron and aluminium elements by precipitation were worked out, other impurities were removed by P204 extraction. The best condition for extraction were obtained:at room temperature; the concentration of P204,10%; the saponification rate of P204,65%; the pH,3.5; extraction time,10 minute; the phase ratio, 1:1; the extraction level,3. In this way, the overall recovery of nickel and cobalt recovery was more than 90%.The results shew that the recovery process was simple, economical and rational. In this process, nickel, cobalt and rare earths contained in the electrodes of Ni-MH battery can be separated and recovered effectively.