| Summary: | In this study, a rare earth composite precipitation (NaREE(SO 4) 2H 2O, REE: Ce, La, Nd, Pr) powder was prepared from spent nickel hydride batteries, and cerium hydroxide was separated from its constituent rare earth elements. As Ce(OH) 3 can be oxidized more easily than other rare earth elements (La, Nd, and Pr), Ce 3+ was converted to Ce 4+ by injecting air into the leachate at 80°C for 4 h. The oxidized powder was leached using sulfuric and hydrochloric acids. Because Ce(OH) 4 has low solubility, it can be separated from other elements. Therefore, the pH of the leaching solution was adjusted for selective precipitation. To determine the crystalline phase, recovery, and grade of the recovered Ce(OH) 4, the powders were analyzed using X-ray diffraction, scanning electron microscopy, and inductively coupled plasma optical emission spectroscopy. The grade and recovery rates of the Ce(OH) 4 powder recovered from the rare earth composite precipitate using sulfuric acid as the solvent were 95% and 97%, respectively, whereas those of the powder recovered using hydrochloric acid were 96% and 95%, respectively.
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