Recovery Of Nickel And Rare Earth From Spent Metal Hydride-nickel Batteries

Metal hydride-nickel batteries(MHNB) were used as the power source of portable communication servieces since their industrialization. As the prohibition of heavy metals(such as mercury, lead and cadmium) increased, MHNB can substitue the main market of cadmium-nickel batteries. Spent metal-hydride-nickel batteries, which contain 33-42% nickel and 10% cobalt and 10% rare earth elements are a valueable source for the demanding market of nickel.This paper has focused on the recovery of nickel and rare earths from the spent metal hydride-nickel batteries(SMHB). Batteries used in this paper are all AB5 type nickel hydride batteries.X-ray fluorescent analysis is used to the charaterization of batteries. Hydrometallurgical processe is used to recycle metals as nickel and rare earths. Nickel is choosed as leaching criterion for its retardation kinectics. The best condition for the dissolving of metals in the SMHB is choosed by orthogonal experiments. It is found that the nickel leaching efficiency of mixed electrodes is better than the seperated electrodes. Mixed electrodes of negative and positive electrods are used for the recycling of nickel and rare earths. The leaching efficiency of nickel can reach to 95% in 6mol/L hydrochloric acid with the solid/liquid ratio of 1:100 at 95℃in 6 hours.Saturated oxalate solution is used as precititant of rare earths from the leachate of spent metal hydride-nickel batteries. Rare earth oxalate is abtained by precipitaiton at room temperature with the the pH of 0.5. The granularity of rare earth oxalate(REO)is small. SEM(Scanning Electron Microscopy) examination of REO shows the shape is flat. Cobalt is seperated from the leachate of leaching solution of SMHB by oxidation and precitation processes. Nickel is abtained asα-oxalate salt by precipitaion. The product of nickel oxalate is small and fine. Compared with Ping wei Zhang, et al, the processes used in this paper for the recovery of nickel and rare earths are rather simple, they can be industrializatin processes for the recycle of metal hydride-nickel batteries.