Okeme Ilemona C, Crane Richard A, Nash William M, Ojonimi Theophilus I, Scott Thomas B
School of Physics, University of Bristol, HH Wills Physics Laboratory Bristol BS8 1TL UK
Camborne School of Mines, College of Engineering, Mathematics and Physical Sciences, University of Exeter UK.
RSC Adv. 2022 Jul 1;12(30):19284-19296. doi: 10.1039/d2ra02788g. eCollection 2022 Jun 29.
Due to increasing demand for rare earth elements (REE), growing concerns over their sustainability, and domination of their supply by China, coal fly ash has recently emerged as a viable target for REE recovery. With billions of tonnes in repositories and still more being generated across the globe, it is necessary to develop environmentally friendly and economical extraction technologies for the recovery of the REEs from coal fly ash, and to consider the environmental implications of such a recovery process. This study reports characterisation of Nigerian simulant coal fly ash, and investigates the distribution and leaching of the REEs and U, Th, As, Cr, Cd and Pb from these materials using ethanoic acid. Significant amounts (14% to 31%) of the REEs were recovered in the acid-soluble fraction of a sequential extraction procedure using ethanoic acid. While the greatest amounts of U (53% to 62%) and Th (89% to 96%) were recovered in the stable residual fraction, significant amounts (3% to 13%) of U were recovered in the acid-soluble fraction. As was the most enriched element in the mobile acid-soluble fraction (46% to 60%), followed by Cd (15% to 34%). These results demonstrate that REEs contained within coal fly ash - especially those sourced from coal-fired power plants burning coal at temperatures between 700 °C and 1100 °C - can be recovered through an environmentally friendly procedure using the cost-effective heap leaching method, with ethanoic acid or the more cheaply-available vinegar as lixiviant. These results are also valuable for cost evaluation of rare earths recovery from coal fly ash generated by fluidised bed combustion coal fired power plants, and the development of methodologies for coal fly ash management.
由于对稀土元素（REE）的需求不断增加，对其可持续性的担忧日益加剧，以及中国在其供应方面的主导地位，粉煤灰最近已成为回收稀土元素的一个可行目标。全球粉煤灰储存量达数十亿吨，且仍在不断产生，因此有必要开发环保且经济的提取技术，从粉煤灰中回收稀土元素，并考虑这种回收过程对环境的影响。本研究报告了尼日利亚模拟粉煤灰的特性，并使用乙酸研究了这些材料中稀土元素以及铀、钍、砷、铬、镉和铅的分布与浸出情况。在使用乙酸的连续萃取程序的酸溶部分中回收了大量（14%至31%）的稀土元素。虽然铀（53%至62%）和钍（89%至96%）的最大回收量出现在稳定的残留部分，但在酸溶部分也回收了大量（3%至13%）的铀。砷是可移动酸溶部分中最富集的元素（46%至60%），其次是镉（15%至34%）。这些结果表明，粉煤灰中所含的稀土元素——尤其是那些来自燃烧温度在700℃至1100℃之间煤炭的燃煤电厂的粉煤灰中的稀土元素——可以通过使用具有成本效益的堆浸法，以乙酸或更便宜的醋作为浸出剂，通过环保程序进行回收。这些结果对于评估从流化床燃烧燃煤电厂产生的粉煤灰中回收稀土的成本以及开发粉煤灰管理方法也具有重要价值。
