Recovery of rare earth elements from coal fly ash through sequential chemical roasting, water leaching, and acid leaching processes

JOURNAL OF CLEANER PRODUCTION

卷:284

Article

Pan, Jinhe^1,2  Hassas, Behzad Vaziri¹  Rezaee, Mohammad¹  Zhou, Changchun²  Pisupati, Sarma V.¹ 

[1] Penn State Univ, Coll Earth & Mineral Sci, Dept Energy & Mineral Engn, EMS Energy Inst,Ctr Crit Minerals, University Pk, PA 16802 USA

[2] China Univ Min & Technol, Sch Chem Engn & Technol, Minist Educ, Key Lab Coal Proc & Efficient Utilizat, Xuzhou 221116, Jiangsu, Peoples R China

关键词: Rare earth elements;    Coal fly ash;    Roasting;    Leaching;    Recovery;    Thermodynamic;   

DOI  :  10.1016/j.jclepro.2020.124725

来源: Elsevier

【 摘 要 】

The majority of rare earth elements (REEs) in coal fly ash (CFA) are associated with the aluminosilicate glassy phase, hindering their solubility in the acid leaching process. In this study, a sequential chemical roasting, water leaching, and acid leaching process was developed for the recovery of REEs from CFA. The effect of several roasting additives on the transformation of CFA phases into water or acid soluble phases was first studied. The reaction conditions for chemical roasting were selected based on a thermodynamic analysis. The selected reaction conditions were then validated experimentally. NaOH and Na2CO3 were the most effective additives to break the glassy phases to sodium silicate and sodium aluminosilicate, which can then be readily dissolved in water or acid. The reactions with NaOH was found to be spontaneous at ambient temperatures, while the reactions with Na2CO3 were spontaneous at elevated temperatures. Water leaching was very effective for the dissolution of the sodium silicate product, removal of the majority of silica, and for turning the glassy phases into a porous structure. As a result, mass transfer limitations were reduced, and acid could easily diffuse into the particles, dissolve the majority of remaining, and extract REEs along with other elements such as Al. This process significantly enhanced the REE recovery to 79% and 89% using NaOH and Na2CO3 roasting, respectively, compared to 20% REE recovery in baseline acid leaching. (C) 2020 Elsevier Ltd. All rights reserved.

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