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

Abstract

Abstract: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.

Recovery of Gallium from Corundum Flue Dust by Two-Stage Alkali Leaching, Carbonation, Acid Leaching and Solvent Extraction Process

“…Besides, gallium is also recycled from scrap generated in the process of manufacturing GaAs-and GaN-based devices. During the past few decades, studies have been carried out on recovering gallium from various sources, which included Bayer liquor [4][5][6], aluminum industry residues [7], coal fly ash [8,9], industrial zinc or copper processing residues [2,[10][11][12], phosphorus flue dust [13], and corundum slags, among others [14]. In addition, flue dust generated from the process of producing brown corundum was also found to be an important source of gallium, because the gallium content in it was relatively high.…”

Ash Characteristics and Selected Critical Elements (Ga, Sc, V) in Coal and Ash in Polish Deposits

“…A search for alternative sources of gallium began at the start of the 21st century. In the first decade, high Ga contents in coal were recorded in China, Inner Mongolia [74][75][76][77][78][79]. Gallium, which is a rare metal, is anomalously enriched in coal to such an extent that it can be considered an economic resource.…”

Investigation on the Effect of Roasting and Leaching Parameters on Recovery of Gallium from Solid Waste Coal Fly Ash

“…Over the past few decades extraction of gallium from coal and CFA has usually followed three main paths: Direct acid leaching [9,10] or alkali roasting followed by acid leaching [11][12][13] or alkali leaching [14]. However, these methods have a number of disadvantages.…”