Recovery of rare earth elements from spent NiMH batteries using subcritical water extraction with citric acid. Issue 3 (June 2022)

• Record Type: Journal Article
• Authors: Constantine, Jason; Lie, Jenni; Liu, Jhy-Chern
• Is Part Of: Journal of environmental chemical engineering. Volume 10:Issue 3(2022)
• Publication Date: 2022-06
• Subjects: Citric acid -- Nickel metal hydride (NiMH) batteries -- Rare earth elements (REEs) -- Recovery -- Selective precipitation -- Subcritical water extraction (SWE); Chemical engineering -- Environmental aspects -- Periodicals; Environmental engineering -- Periodicals; Chemical engineering -- Environmental aspects; Environmental engineering; Periodicals; 660.0286
• DOI: 10.1016/j.jece.2022.108000
• Languages: English
• ISSNs: 2213-2929

Abstract

Abstract: Spent nickel-metal hydride (NiMH) batteries contain high concentrations of rare earth elements (REEs), nickel (Ni), and cobalt (Co). Subcritical water extraction (SWE) process with citric acid as the leaching reagent was applied to spent NiMH batteries. The effects of acid concentration, solid to liquid ratio (S/L), reaction time, and reaction temperature were examined. Leaching efficiency increased with increasing acid concentration, reaction time and temperature, and decreased as S/L increased. Total of 90.85% of lanthanum (La), 88.84% of cerium (Ce), 90.85% of neodymium (Nd), 90.70% of Ni, and 91.62% of Co were leached out using 2.0 N of citric acid, S/L of 10 g/L, at 150 °C in 5 min. Selective precipitation of REEs was induced by the addition of diluted waste phosphoric acid (H3 PO4 ) to the leaching solutions. At [H3 PO4 ]:[REEs] of 10:1, pH 2.0, and 65 °C, 99.3% of La, 98.8% of Ce, and 99.0% of Nd were precipitated, which correspond to overall recovery of 90.2% of La, 87.8% of Ce, and 89.8% of Nd. The results showed that SWE using citric acid followed by selective precipitation with H3 PO4 could effectively recover REEs from spent NiMH batteries. Graphical Abstract: ga1 Highlights: Effective leaching of REEs, Ni and Co from spent NiMH using SWE. Citric acid performed well due to enough acidity and complex formation. Nearly 90% of REEs were leached out in SWE using 2.0 N citric acid, 150 °C, 5 min. Nearly 99% REEs recovered at [H3 PO4 ]: [REEs] of 10:1, pH 2.0, and 65 °C.