Recovery of rare earth elements from coal fly ash through sequential chemical roasting, water leaching, and acid leaching processes
Recovery of rare earth elements from coal fly ash through sequential chemical roasting, water leaching, and acid leaching processes
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DOI：
10.1016/j.jclepro.2020.124725
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发表时间：
2021-01-07
影响因子：
11.1
通讯作者：
Pisupati, Sarma V.
中科院分区：
文献类型：
--
作者：
Pan, Jinhe;Hassas, Behzad Vaziri;Pisupati, Sarma V.
粉煤灰（CFA）中的大多数稀土元素（REE）与铝硅酸盐玻璃相结合，阻碍了它们在酸浸过程中的溶解度。采用化学焙烧-水浸-酸浸工艺从CFA中回收稀土元素。首先研究了几种焙烧添加剂对CFA相转化为水溶性或酸溶性相的影响。在热力学分析的基础上，选择了化学焙烧的反应条件。然后通过实验验证了所选择的反应条件。NaOH和Na 2CO 3是将玻璃相破碎成硅酸钠和铝硅酸钠的最有效的添加剂，然后其可以容易地溶解在水或酸中。发现与NaOH的反应在环境温度下是自发的，而与Na 2CO 3的反应在高温下是自发的。水浸出是非常有效的硅酸钠产品的溶解，除去大部分的二氧化硅，并将玻璃相变成多孔结构。因此，传质限制减少，酸可以很容易地扩散到颗粒中，溶解大部分剩余的，并提取稀土沿着与其他元素，如铝。这个过程显着提高了稀土回收率为79%和89%，分别使用NaOH和碳酸钠焙烧，相比20%的稀土回收率在基线酸浸。(C)2020爱思唯尔有限公司版权所有。
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.