Recycling Of Valued Metal From Spent Metal Hydride-nickel Batteries

The treatment of metal hydride-nickel(MH-Ni) batteries has been becoming more and more important, with the growth of production and utilization of MH-Ni batteries. The recycling of spent MH-Ni batteries which contain about 45% nickel and 10% cobalt and 10% rare earth elements is the most promising treatment, for it not only deals with environmental problems, but also contributes to the preservation of raw materials.This paper has created a hydrometallurgical process of mixed electrodes disposal basing on summarizing and analyzing hydrometallurgy, pyrometallurgy and the technology of recycling positive/negative material separately. The paper has focused on the recovery of nickel and cobalt and rare earth elements from the spent MH-Ni batteries. X-ray fluorescent analysis shows that the batteries used in the experiment are all AB5-type MH-Ni batteries.Leaching of MH-Ni electrodes in sulfuric acid is carried out through orthogonal test. During the test, some factors affecting the leaching ratio of nickel and cobalt have been analyzed. The highest leaching ratio of nickel and cobalt has been found to be in the condition of CH2SO4=6mol·L-1, t=4h, S:L=l:10g·ml-1, T=40℃. Under the best condition, the leaching ratio of nickel is 94.12%, of cobalt 99.67%.Sodium sulfate and oxalic acid are used as precipitant of rare earth ions from lixivium. Sodium sulfate is better to separate rare earth ions. The hightest recovery ratio of rare earth elements is 93.87% at 60℃with the the pH of 1.0 and appending rate 3:1. Rare earth double salt is obtained by precipitation in the best condition. SEM (Scanning Electron Microscopy) examination of rare earth double salt shows the shape is claviform.In order to simplify process and reduce costs, nickel ions and cobalt ions precipitate simultaneously to prepare precursor material Ni0.8Co0.2(OH)2. Through filtration and optimization, the best technics have been found out finally: the concentration of reactants are CNiSO4=0.4mol·L-1, CCoSO4=0.1mol·L-1, CNaOH=1mol·L-1, CNH3·H2O=1mol·L-1, pH is 11.0, mix round speed is 800r·min-1, reaction time is 24h, NH3:(Ni+Co)=1:1, reaction temperature is 50℃, deposit time is 3h, drying temperature is 110℃. The precursor material Ni0.8Co0.2(OH)2 prepared in the optimum condition with spherical morphology provides a good precursor for spherical anode material LiNi0.8Co0.2O2.