Research On Comprehensive Recovery Of Valued Metal From Spent Nickel-hydrogen Battery

The treatment of NiMH battery electrodes has becoming more and more important, with the growth of production and utilization of NiMH battery. Recycled treatment has a brighter prospect than other treatments, for it not only deals with environmental problems, but also releases the shortage of resources effectively by the recycle and reuse of valued metals from NiMH.This paper created a hydrometallurgical process combining leach by acid and mixed deposition basing on analyzing and comparing pyrometallurgy hydrometallurgy and some other related recycling techniques of NiMH nowadays. The process included three main steps, the first step is leaching of NiMH cathode, and then Rare earth elements can dissolved in the acid solution; the second step is separation of rare earth ions from other ions in the lixivium and then the recycle by separating out and deposition; the third step is depositing nickel and cobalt ions together. With overall recovery of rare earth,nickel and cobalt elements, this experiment applies a favorable condition for entering industrial stage from experimental stage. Compared to organic solvent extraction and ion exchange resin, the method of deposition is an economic and green treat technique friendly to environment. It has many advantages, such as cheap raw materials, simple flow sheet, high rate of recovery, nonpolluting, etc.Leaching of NiMH cathode in sulfuric acid was carried out through orthogonal test. During the test, some factors affecting the leaching rate of Rare earth were analyzed. These factors included concentration of sulfuric acid (C), time of leaching (t), ratio of solid and liquor(S/L), and stirring intensity (I). The highest leaching ration of RE³⁺ was found to be on the condition of C=1.5mol·L^-1, t=60min, S/L=10g·L^-1, S=600r· min^-1. Under the best condition, the leaching ratio of RE was 92.5%, of nickel 98%.Based on the adequate reaction that rare earth sulphate and anhydrous sodium sulphate can combine into rare earth double salt, the rare earth ions in the lixivium will be recovered using deposit method. Through orthogonal test, the highest recovery rate of rare earth elements was 94.6% by atomic absorption spectrometry on the condition of appending rate 1:3, pH=2.0, T=60℃. The purity of rare earth double salt reached 96.6% and appeared crystalline state by XRD analysis.After filtering rare earth double salt and eliminating the foreign ion Mn²⁺,Fe²⁺, Ca²⁺,Mg²⁺, the filtrate is added diluent ammonia to regulate pH, forming complex...