Extraction of rare earth elements from coal fly ash by alkali fusion–acid leaching: Mechanism analysis. Issue 3 (4th March 2022)

• Record Type: Journal Article
• Authors: Tang, Mengcheng; Zhou, Changchun; Zhang, Ningning; Pan, Jinhe; Cao, Shanshan; Hu, Tingting; Ji, Wanshun; Wen, Zhiping; Nie, Tiancheng
• Is Part Of: International journal of coal preparation and utilization. Volume 42:Issue 3(2022)
• Page Start: 536
• Page End: 555
• Publication Date: 2022-03-04
• Subjects: Rare earth elements -- Coal fly ash -- Alkali fusion -- Acid leaching; Coal preparation -- Periodicals; Coal -- Research -- Periodicals; 662.62
• DOI: 10.1080/19392699.2019.1623206
• Languages: English
• ISSNs: 1939-2699

Abstract

ABSTRACT: Coal fly ash (CFA) in some areas contains higher levels of rare earth elements (REEs), which can be seen as a potential substitute for rare earth resources. As an effective method of hydrometallurgy, alkali fusion has been widely used in the recovery of precious metals from secondary resources. In this study, taking a CFA sample and five REEs named Y, La, Ce, Pr, and Nd in the sample as objects, the mechanism of alkali fusion processes of CFA with different alkali fluxes (Na2 CO3, NaCl, Na2 O2, NaOH, KOH, and Ca(OH)2 ) was studied. The results showed that Na2 CO3, Na2 O2, NaOH, and KOH can destroy the structure of CFA to effectively improve the leaching efficiency of REEs from CFA. The total leaching efficiency of the five REEs can reach to 57.45%, 49.25%, 74.23%, and 64.93%, respectively, when these four alkalis were used as fluxs. In addition, with DSC analysis, the non-model fitting dynamics Kissinger method was used to calculate the kinetic parameters of alkali fusion reaction between CFA and Na2 CO3 . The calculated alkali fusion activation energy E was 895.52 kJ·mol −1, the pre-exponential factor A was 3.47 × 10 41 min −1, and the reaction rate constant K was 1.68 min −1 .