Recent efforts have shown that acid mine drainage precipitates (AMDp) may be a promising source of rare earth elements and critical materials (REE/CM). To better understand this resource, several particle characterization studies were conducted on AMDp samples from three AMD treatment sites in Northern and Central Appalachia. This work included the determination of particle size, size distribution, morphology, mineralogy, chemical speciation, and rare earth content. While the particle characteristics and mineralogy varied considerably from site to site, sequential extraction tests showed that the largest portion of REEs (45% to 75%) were found in soluble phases bound to Fe-Mn oxides. Carbonates (5% to 16%) and insoluble residues (4% to 24%) were also found to be significant in some samples, suggesting that different AMD chemistry and AMD treatment approaches can lead to substantial variation in the deportment of REEs to the various chemical phases. Altogether, the results suggest that chemical extraction of REEs from AMDp can be achieved under mild conditions with high recovery values; however, the significant site-by-site variation will necessitate detailed testing of individual samples to determine the overall economic viability.

最近的努力表明，酸性矿山排水沉淀物（AMDp）可能是稀土元素和关键材料（REE / CM）的有前途的来源。为了更好地理解该资源，对来自北部和中部阿巴拉契亚地区三个AMD治疗地点的AMDp样品进行了几项颗粒表征研究。这项工作包括确定粒度，粒度分布，形态，矿物学，化学形态和稀土含量。尽管各地的颗粒特征和矿物学差异很大，但连续萃取试验表明，最大的稀土元素（45％至75％）出现在与铁锰氧化物结合的可溶相中。在某些样品中，碳酸盐（5％至16％）和不溶性残留物（4％至24％）也很重要，这表明，不同的AMD化学和AMD处理方法可能导致REE向各个化学阶段的迁移情况发生实质性变化。总之，结果表明可以在温和条件下以较高的回收率从AMDp中化学提取REE。但是，不同站点之间的显着差异将需要对单个样本进行详细测试，以确定总体经济可行性。