原地浸出体系稀土离子运移过程再吸附行为机理研究

The in-situ leaching process has been widely used in ion-absorbed rare earth mines in recent years because of its outstanding advantages in production cost, processing capacity and environmental protection. However, rare earth ion can be re-adsorbed during the leaching process, leads to the low resource recovery rate and long leaching period, and has a serious affection on eco-friendly, economical and efficient recovery of rare earth resources. By consulting the relevant research literatures at home and abroad, it is found that few basic theoretical researches on rare earth ion re-adsorption in leaching process have been carried out. Based on this engineering background, the study of the influence factors of rare earth ion re-adsorption behavior is conduct firstly in this project, reveal the law of rare earth ion re-adsorption under the different concentrations of leaching agents, analyze the effect of the particle size grading of ore sample and the permeability of leaching system on the re-adsorption of rare earth ion. Secondly, the column leaching test is carried out to simulate the in-situ leaching process, the variation of solution leaching agent concentration and rare earth ion concentration in the leaching process is tested, analyze the variation of pore structure parameter characteristics and the variation of leaching system permeability, reveal spatiotemporal evolution of rare earth ion re-adsorption behavior during ion exchange, porosity evolution and solution flow process. Based on the experimental results, investigate the triggering mechanism and dynamic response mechanism of rare earth ion re-adsorption behavior during dynamic leaching process, and reveal the behavior mechanism of rare earth ion re-adsorption during in-situ leaching process.

原地浸出工艺因其在生产成本、处理能力、保护环境等方面的突出优势，近年来在离子型稀土矿山得到积极推广应用，但浸出过程存在稀土离子再吸附问题，导致资源回收率低、浸出周期长，严重影响稀土资源绿色经济高效回收，通过查阅国内外相关研究文献发现针对浸出过程稀土离子再吸附问题的基础理论研究报道较少。基于此工程背景，本项目首先开展稀土离子再吸附行为的影响因素研究，分析浸出液中不同浸出剂浓度下稀土离子再吸附规律，探讨矿样粒径级配与浸出体系渗透性能对稀土离子再吸附的影响；其次，开展室内柱浸试验模拟原地浸出过程，测试浸出过程溶液浸出剂浓度与稀土离子浓度变化规律，研究浸出体系孔隙结构参数变化特征，分析浸出体系渗透性能变化规律，揭示离子交换、孔隙演化与溶液渗流过程稀土离子再吸附行为时空演变规律；基于以上研究结果，探明动态浸出过程稀土离子再吸附行为的触发机制与动态响应机制，揭示原地浸出过程稀土离子再吸附行为机理。

离子型稀土矿原地浸出过程存在稀土离子再吸附问题，导致资源回收率低、浸出周期长，严重影响稀土资源绿色高效回收。本项目通过现场调研、室内试验、机理分析等手段，研究了静态与动态条件下不同因素对稀土离子再吸附的影响，分析了浸出体系孔隙结构对稀土离子再吸附的影响机制，考察了离子交换与孔隙演化过程稀土离子再吸附行为特征，阐明了多因素耦合作用下稀土离子再吸附行为机理。研究结果表明，在相同条件下，动态过程稀土离子稀土再吸附量普遍高于静态试验过程，溶液流动促进稀土离子更广泛与矿物接触，流动状态下，硫酸铵对于稀土离子再吸附的抑制作用较静止状态更强；溶液在矿柱内停留时间越久，稀土离子再吸附越显著，改善渗流、减少溶液停留时间有助于抑制稀土离子的再吸附行为，浸出体系持水能力相当时，在细颗粒区域停留稀土离子越容易再吸附；浸出过程，矿体孔隙结构由大孔隙向中小孔隙转化，浸出后期再次由中小孔隙向大孔隙转化，孔隙结构在微观上的变化对于体系渗透性能影响较小，其持水能力基本保持不变；浸出反应中，矿样核磁反演图像出现明显的黑色区域，其出现时间与注入硫酸铵溶液时间一致；随浸出溶液的持续注入，核磁图像中的黑色区域不断向下迁移，直至矿体底部，黑色区域可作为大量稀土离子聚集向下迁移流动的证据。浸出过程中，当铵根离子浓度较低时，黑色区域出现并缓慢向下移动，前期浸出过程中，铵根离子持续维持在较低浓度，此过程即使溶液中铵根离子浓度不断升高，依旧无法有效抑制高浓度稀土离子的再吸附行为；随着持续溶液注入，铵根离子浓度存在快速提升阶段，稀土离子浓度同步大幅上升，随后铵根离子浓度继续升高，稀土离子浓度不断下降，此阶段稀土离子再吸附行为基本被抑制，当铵根离子浓度上升至1g/L以上时稀土离子被大量浸出。项目研究在一定程度上揭示了浸出过程稀土离子再吸附行为机理，为解决工程实际中稀土离子再吸附问题提供一定依据，促进稀土资源绿色经济高效回收。