In-situ leaching is essential for mining rare earth elements (REEs) from ion-adsorption rare earth (RE) ores. The efficiency of RE mining is dependent on the permeabilities of ion-adsorption RE ores, and the permeabilities are controlled by their pore structures. However, the current understanding of the pore structures and permeabilities of the RE ores during leaching is limited, particularly their dynamic variations, the controlling roles of different pore structure parameters on the permeability, the roles of the influencing factors and the mechanisms causing the variations. To investigate the above-mentioned issues, we conducted an experimental study of simulated in-situ leaching on undisturbed ion-adsorption RE ore samples under different conditions via constant waterhead permeability tests. The leaching conditions included leaching time, concentration and waterhead of the (NH)SO solution. Three-dimensional (3-D) pore structures of the RE ores before, during, and after leaching were constructed via X-ray computed tomography, and their pore structure parameters were measured using 3-D image computation. It was observed that the dynamic variations in both the pore structure parameters and permeability coefficients of the RE ores occurred in three distinct stages: rapid reduction, less rapid reduction, and little reduction. The experimental results also revealed that the permeability coefficients of the RE ores were primarily dependent on the average coordination number among the seven pore structure parameters examined, and that the pore throats larger than 30 μm in diameter served as the most effective seepage channels within the RE ores. The waterhead of the leaching solution had a stronger influence on the variations in pore structures and permeabilities compared to that of the concentration. Analysis of the particle/aggregate size distribution and mineralogical compositions of the RE ores before and after leaching indicated that the decreases in the pore structure parameters and permeabilities were largely attributed to clogging of the pore throats and pores by migrated and newly formed clays, as well as swelling of the latter. The newly formed clays were the products of the decomposition of K-feldspar and mica resulting from chemical reactions with the leaching solution. The clays from the two sources occurred in disaggregated and aggregated forms. The results of this study provide an important reference for the mining of RE ores via leaching.

中文翻译：

---

模拟原地浸出过程中离子吸附稀土矿孔隙结构和渗透率的变化：新形成的粘土颗粒及其膨胀的影响


原位浸出对于从离子吸附稀土 (RE) 矿石中开采稀土元素 (REE) 至关重要。稀土开采的效率取决于离子吸附型稀土矿石的渗透率，而渗透率又受其孔隙结构的控制。然而，目前对稀土矿浸出过程中孔隙结构和渗透率的认识还很有限，特别是它们的动态变化、不同孔隙结构参数对渗透率的控制作用、影响因素的作用以及引起变化的机制。为了研究上述问题，我们通过恒定水头渗透率测试，对不同条件下的原状离子吸附稀土矿石样品进行了模拟原位浸出实验研究。浸出条件包括(NH)SO溶液的浸出时间、浓度和水头。通过 X 射线计算机断层扫描构建稀土矿石浸出前、浸出过程中和浸出后的三维 (3-D) 孔隙结构，并使用 3-D 图像计算测量其孔隙结构参数。结果表明，稀土矿石孔隙结构参数和渗透系数的动态变化发生在三个不同的阶段：快速还原、慢速还原和小还原。实验结果还表明，稀土矿石的渗透系数主要取决于所检测的七个孔隙结构参数之间的平均配位数，并且直径大于30μm的孔喉是稀土矿石中最有效的渗流通道。矿石。 与浓度相比，浸出液水头对孔隙结构和渗透率变化的影响更大。对浸出前后稀土矿石的颗粒/骨料粒度分布和矿物组成的分析表明，孔隙结构参数和渗透率的下降很大程度上归因于迁移和新形成的粘土堵塞孔喉和孔隙。作为后者的肿胀。新形成的粘土是钾长石和云母与浸出液发生化学反应分解的产物。这两个来源的粘土以分散和聚集的形式存在。该研究结果为稀土矿浸出开采提供了重要参考。