Key Laboratory of Geographic Information Science (Ministry of Education), School of Geographical Sciences, East China Normal University, Shanghai 200241, China.
State Key Laboratory of Precision Spectroscopy, Shanghai Key Laboratory of Magnetic Resonance, School of Physics and Electronic Science, East China Normal University, Shanghai 200062, China.
Environ Sci Technol. 2021 Dec 21;55(24):16716-16722. doi: 10.1021/acs.est.1c06658. Epub 2021 Dec 10.
Rare earth elements (REYs) are in increasing global demand, but their mining is costly and environmentally destructive. Coal fly ash (CFA) is a promising alternative source of REYs, but it is necessary to identify CFA with sufficiently high REY concentrations. This study proposes the use of electron paramagnetic resonance (EPR) spectroscopy as part of a simple method to identify CFAs with adequate REY concentrations. The EPR spectra of CFA samples taken from 186 Chinese commercial coal-fired power plants were analyzed. The results suggest that CFAs without evident 6-fold resonances are worth recycling (REY concentrations of 416 ± 108 mg/kg), while those with conspicuous 6-fold resonances are not worth recycling (REY concentrations of 55 ± 26 mg/kg). This is probably due to isomorphic substitution of Ca(II) for Mn(II) and REY(III), resulting in low concentrations of Mn(II) and REY(III) in Ca-rich CFAs. This EPR evaluation method does not require specialized sample preparation, professional skills, or secondary data analysis and has potential global significance in the fast screening of CFAs with REY-recycling potential.
稀土元素（REY）在全球的需求不断增加，但它们的开采成本高且对环境具有破坏性。粉煤灰（CFA）是一种有前途的 REY 替代来源，但需要确定具有足够高 REY 浓度的 CFA。本研究提出了将电子顺磁共振（EPR）光谱用作识别具有足够 REY 浓度的 CFA 的简单方法的一部分。分析了从 186 座中国商业燃煤电厂采集的 CFA 样品的 EPR 光谱。结果表明，没有明显 6 重峰的 CFA 具有回收价值（REY 浓度为 416 ± 108mg/kg），而具有明显 6 重峰的 CFA 没有回收价值（REY 浓度为 55 ± 26mg/kg）。这可能是由于 Ca(II)对 Mn(II)和 REY(III)的同晶取代，导致富含 Ca 的 CFA 中 Mn(II)和 REY(III)浓度较低。这种 EPR 评估方法不需要专门的样品制备、专业技能或二次数据分析，在快速筛选具有 REY 回收潜力的 CFA 方面具有潜在的全球意义。
