Alkali pretreatment effects on acid leaching recovery of rare earth elements from coal waste of the Western Kentucky No. 13 and Fire Clay seams

Qi Li, Bin Ji, Zhong Xiao, Wencai Zhang
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引用次数: 6

Abstract

The recovery of rare earth elements (REEs) from the Western Kentucky No. 13 and Fire Clay coal wastes was enhanced by alkali pretreatment with concentrated NaOH solutions. The enhancements in the recovery of light REEs (LREEs) are more significant than those of heavy REEs (HREEs). For example, after treating with 5 M NaOH at 90 °C, the recovery of LREEs from the Western Kentucky No. 13 coal waste increased from 26% to 71%, while the recovery of HREEs only increased from 29% to 41%. Based on mineralogical studies through scanning electron microscopy-energy dispersive X-ray spectroscopy and X-ray diffraction analyses, two mechanisms were proposed to explain the positive effect of alkali pretreatment: (1) decomposition of rare earth minerals (primarily crandallite-group minerals) during the alkali pretreatment, and (2) liberation of encapsulated REE-bearing particles due to the enhanced dissolution of clay minerals. The more significant enhancements in the recovery of LREEs were explained by the fact that the REEs comprised in the crandallite-group minerals were mainly LREEs. Compared with zircon, monazite, and xenotime, alkali pretreatment with 5 M NaOH led to a more significant decomposition of crandallite-group minerals. In order to further increase the recovery of REEs, particularly HREEs, harsher alkali treatment conditions are required.
碱预处理对西肯塔基13号和火粘土煤层废煤中稀土元素酸浸回收的影响
采用浓NaOH溶液进行碱预处理,提高了西部肯塔基州13号煤和火煤矸石中稀土元素的回收率。轻稀土(lree)的回收率比重稀土(hree)的提高更为显著。例如,在90℃条件下用5 M NaOH处理后,西肯塔基州13号煤矸石中lree的回收率从26%提高到71%,而hree的回收率仅从29%提高到41%。通过扫描电镜、x射线能谱和x射线衍射分析等矿物学研究,提出碱预处理的积极作用机理:(1)碱预处理过程中稀土矿物(主要是辉钼矿群矿物)的分解作用;(2)粘土矿物的溶解作用增强,使包裹的稀土颗粒析出。重稀土元素回收率显著提高的原因是辉长岩群矿物中稀土元素主要为轻稀土元素。与锆石、独居石和xenotime相比,5 M NaOH碱预处理对辉长石群矿物的分解作用更为显著。为了进一步提高稀土,特别是重稀土的回收率,需要更苛刻的碱处理条件。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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