Leaching Process of Rare Earth Elements, Gallium and Niobium in a Coal-Bearing Strata-Hosted Rare Metal Deposit—A Case Study from the Late Permian Tuff in the Zhongliangshan Mine, Chongqing

• Published in: Metals (Basel ) 2017-05, Vol.7 (5), p.174
• Main Authors: Zou, Jianhua, Tian, Heming, Wang, Zhen
• Format: Article
• Language: English
• Subjects: Acid leaching; alkaline sintering-water immersion-acid leaching; Alliances; Bearing; Chongqing; Coal mines; Dosage; Enrichment; extractability; Extraction; Gallium; Hot water; Leaching; Materials recovery; Niobium; Rare earth elements; Roasting; Sintering; Strata; Trace elements; Tuff; Water immersion
• ISSN: 2075-4701; 2075-4701
• DOI: 10.3390/met7050174

The tuff, a part of coal-bearing strata, in the Zhongliangshan coal mine, Chongqing, southwestern China, hosts a rare metal deposit enriched in rare earth elements (REE), Ga and Nb. However, the extraction techniques directly related to the recovery of rare metals in coal-bearing strata have been little-studied in the literature. The purpose of this paper is to investigate the extractability of REE, Ga and Nb in the tuff in the Zhongliangshan mine using the alkaline sintering-water immersion-acid leaching (ASWIAL) method. The results show that ASWIAL can separate and extract REE, Ga and Nb effectively under the optimized conditions of calcining at 860 °C for 0.5 h with a sample to sintering agent ratio of 1:1.5, immersing at 90 °C for 2 h with 150 mL hot water dosage, and leaching using 4 mol/L HCl at 40 °C for 2 h with a liquid-solid ratio of 20:1 (mL:g). The final leaching efficiencies of REE and Ga are up to 85.81% and 93.37%, respectively, whereas the leaching efficiency of Nb is less than 1%, suggesting the high concentration of Nb in the leaching residue, which needs further extraction.